Download Supplemental Carmel River Watershed Action Plan

March 2007
Supplemental Carmel River
Watershed Action Plan
Prepared for
The Planning and Conservation League Foundation
In Partnership with
The Carmel River Watershed Conservancy
PWA
PHILIP WILLIAMS & ASSOCIATES, LTD
ENVIRONMENTAL HYDROLOGY
Prepared by
Philip Williams & Associates, Ltd.
with
Ecosystem Management International
Philip Williams & Associates, Ltd. | 550 Kearny Street, Suite 900 | San Francisco CA 95108 | t: 415.262-2300 | www.pwa-ltd.com
PWA Ref. # 1879
SUPPLEMENTAL CARMEL RIVER WATERSHED ACTION PLAN Prepared for
The Planning and Conservation League Foundation In partnership with the Carmel River Watershed Conservancy Prepared by
Philip Williams & Associates, Ltd.
with
Ecosystem Management International March, 2007 PWA REF. # 1806.00 This report has been produced by the Planning and Conservation League
Foundation in partnership with the Carmel River Watershed
Conservancy. Funds were provided in part by the State Water Resources
Control Board (Proposition 13) and by the State Coastal Conservancy.
In this effort, the Planning and Conservation League Foundation has
engaged with local residents, community-based nonprofit organizations,
regional and state agencies to support efforts to develop a watershed
action plan for the Carmel River Watershed that benefits the communities
of the Carmel Valley as well as the residents of the State of California.
Services provided pursuant to this Agreement are intended for the use
and benefit of the Planning and Conservation League Foundation, the
State Water Resources Control Board and the State Coastal
Conservancy.
TABLE OF CONTENTS
Page No.
EXECUTIVE SUMMARY E-1
1.
INTRODUCTION
1.1
OVERVIEW OF DOCUMENT STRUCTURE
1.2
THE CARMEL RIVER WATERSHED
1.2.1
Groundwater Pumping and Diversions
1.2.2
Dams on the Carmel River
1.2.3
Carmel River Estuary
1.2.4
Water Quality in the Carmel River and Estuary
1.2.5
Existing Human Infrastructure
1.3
PREVIOUS PLANNING AND RESTORATION EFFORTS
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2.
KEY ISSUES AND ASSOCIATED IMPACTS
2.1
RIPARIAN AQUIFER WITHDRAWALS
2.2
SAN CLEMENTE DAM 2.2.1
Risk to Public Safety
2.2.2
Altered Sediment Transport and Channel Geomorphology
2.2.3
Disconnected Floodplain and Reduced Flow
2.2.4
Disruption of Ecological Integrity
2.3
SEDIMENT TRANSPORT AND RIVER MANAGEMENT 2.3.1
Current Disruptions to Physical Processes and
Geomorphology of the Carmel River
2.3.2
Potential Impacts of Renewed Sediment Supply
2.4
RESTORATION NEEDS
2.4.1
Ecological Functions and Processes
2.4.1.1 Loss of Streamside Vegetation
2.4.1.2 Increased Invasion by Non-native Species
2.4.1.3 Modified Aquatic Food Chains
2.4.1.4 Loss of Coastal Salt Marsh Habitats
2.4.1.5 Reduced Water Quality in Estuary
2.4.1.6 Discontinuity of Habitats
2.4.2
Effects on Key Species
2.4.2.1 Steelhead Trout
2.4.2.2 California Red-legged Frog
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3.
PRINCIPLES FOR A FUNCTIONALLY RESTORED WATERSHED
3.1
INTEGRATING HUMAN INFRASTRUCTURE WITH ECOSYSTEMS
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4.
RECOMMENDED ACTIONS
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4.1
REDUCE PUMPING FROM THE RIPARIAN AQUIFER 52
4.1.1
State Water Resources Control Board Order WR 95-10 and CAW Pumping 53
i
4.2
4.3
4.4
4.1.2
Private Pumping
4.1.3
Benefits of Discontinuing Riparian Groundwater Pumping
REMOVE SAN CLEMENTE DAM
4.2.1
Essential Components for Post-Dam Site Design and Management
4.2.1.1 Criteria for On-site Restoration – An Eco-Geomorphic
Approach
4.2.1.2 On-site Sediment Storage
4.2.1.3 By-pass Channel Design
4.2.1.4 Monitoring and Adaptive Management
4.2.2
Benefits of Dam Removal with Eco-Geomorphic Restoration
DEVELOP A SEDIMENT MANAGEMENT STRATEGY FOR POST-DAM
CONDITIONS
4.3.1
Evaluating Impacts from Changing Sediment Supplies
4.3.2
An Integrated System of Sediment and Runoff Management Controls
4.3.3
Benefits of Sediment Management Actions
INTEGRATE SOLUTIONS INTO A CARMEL RIVER WATERSHED
RESTORATION PROGRAM
4.4.1
Purpose
4.4.2
Key Objectives and Work Plan
4.4.3
Structure and Funding Ideas
4.4.4
Scientific Research on Dam Removal
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5.
REFERENCES
80
6.
LIST OF PREPARERS
85
LIST OF APPENDICES
Appendix A.
Appendix B.
Appendix C.
Appendix D.
Key Species List
Frequently Asked Questions
Eco-Geomorphic Conceptual Model
Adaptive Management
ii
LIST OF TABLES
Table 1.
Table 2.
Table 3.
Total Available Spawning and Rearing Habitat (NOAA, 2005)
Potential Rearing Habitat for Steelhead Trout (NOAA 2001)
Total Steelhead Rearing Habitat Carrying Capacity
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43
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LIST OF FIGURES
Figure 1-1.
Figure 1-2.
Figure 1-3.
Figure 1-4.
Figure 1-5.
Figure 2-1.
Figure 2-2.
Figure 2-3.
Figure 2-4.
Figure 2-5.
Figure 2-6.
Figure 2-7.
Figure 2-8.
Figure 2-9.
Figure 2-10.
Figure 2-11.
Figure 2-12.
Figure 2-13.
Figure 4-1.
Figure 4-2.
Figure 4-3.
Figure 4-4.
Figure 4-5.
Figure 4-6.
Figure 4-7.
Figure 4-8.
Figure 4-9.
Carmel River Watershed
Groundwater Pumping Station along the Carmel River
San Clemente Dam
Carmel Lagoon Following Construction
Restored Carmel Lagoon
Carmel River Aquifer
Typical Summertime River Conditions Along Pumping Zone
Flood Conditions at San Clemente Dam
San Clemente Dam and Reservoir
Incised Reach of the Carmel River
Residential Homes Along the Carmel River
Longitudinal and Lateral Channel Responses to the San Clemente Dam
Typical Response of the Downstream Riparian Community to Dam Removal
Typical Responses to Dam Removal with Associated Timeframes
Cumulative Effects of Dams
Key Landscape Drivers of Cumulative Impacts
Land-use Distribution in the Lower Carmel River
California Red-legged Frog
Stored Alluvial Sediment Integrated with Eco-geomorphically Functional Conditions
Example of Functional Geomorphic Channel Design
Eco-geomorphic Design Incorporates Channel, Floodplain, and
Vegetation Components
Existing Floodplain Functions
In-channel Structures Designed to Hold Channel Integrity and
Provide Sediment Storage
Linkages between Key Watershed Processes Supports the Need for an Integrated
Management Solution
Components of an Integrated Watershed Restoration Program
Inputs and Outcomes Associated with the Integrated Watershed Restoration Program
Landscape Functions for the lower Carmel River
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EXECUTIVE SUMMARY
The Carmel River presents one of the most significant opportunities for river restoration
on California’s Central Coast. Flowing through the Ventana Wilderness and the Los Padres
National Forest, the Carmel River provides essential wildlife habitat for important species,
including the state and federally listed steelhead trout and California red-legged frog.
Since 1921, the San Clemente Dam has impacted the Carmel River and its wildlife
resources. As a result, the Carmel River suffers accelerated erosion, its once vibrant steelhead run
has dramatically decreased, and lives and property below the dam are threatened with potential
dam collapse and inundation by sediment currently trapped behind the dam. In addition,
groundwater pumping in the lower river basin seasonally dewaters the Carmel River channel in
many years further impacting sensitive habitat and wildlife.
This report, the Supplemental Carmel River Watershed Action Plan, analyzes the
extraordinary opportunities that now exist to remove the antiquated dam, reduce downstream
groundwater pumping, and implement an integrated watershed restoration and sediment
management strategy that will bring this river back to life. This Supplemental Action Plan focuses
on opportunities to provide benefits to the downstream community and the public through
restoration of the Carmel River Watershed. The following paragraphs outline these opportunities
and benefits.
A Public Safety Risk Will Be Eliminated
The San Clemente Dam poses a significant threat to lives and property. The State has
determined that this dam could fail during a magnitude 6.5 or greater earthquake, releasing over
2.1 million cubic yards of sediment trapped above the dam. Removal of San Clemente Dam
would expedite resolution of the seismic safety issue that now threatens 1500 homes,
infrastructures, vineyards and commercial buildings downstream of the dam. Allowing the dam
structure to remain in place would require long-term management of associated impacts to the
river ecosystem, including significant costs, to assure sediment management problems and
challenges posed by the existence of a dam structure are fully addressed.
Threatened Species Will be Restored
San Clemente Dam is a barrier to threatened south central population of steelhead trout.
Nearly half of the natural spawning habitat and three-quarters of the potential rearing habitat is
located above the dam. The existing 85-foot fish ladder prevents many adult fish from accessing
upstream habitat areas while no provision exists to guide downstream migrating juvenile trout
and smolts. The Carmel River once boasted an estimated steelhead run of 10,000 to 20,000 fish,
and now, less than 700 fish return to the Carmel River each year. Though small, the Carmel River
E-1
steelhead population is genetically important. The National Oceanic and Atmospheric
Administration has determined that the Carmel River steelhead run is a critical foundation and
source population that is essential for the recovery of steelhead on the Central Coast. Removal of
San Clemente Dam would contribute to recovery of this important trout population and restore
access to seven miles of river habitat now blocked by the dam.
The California red-legged frog is a threatened amphibian found in the Carmel River
Watershed. Impacts related to development and changes in the dynamics of sediment and water
regimes have impacted its habitats. San Clemente and Los Padres dams and downstream
groundwater pumping have changed the hydrologic regime of the Carmel River and resulted in a
disconnecting of the river from the floodplain and wetlands. Restoring the Carmel River physical
and hydrologic processes will provide and opportunity to restore habitats for the frog and prevent
its extirpation in the watershed.
Sediment Transport Will be Re-Established
The San Clemente Dam has captured sediment from the upper half of the 255 square-mile
Carmel River Watershed. The loss of a natural sediment regime in the lower river has resulted in
channel incision and coarsening of the riverbed. This in turn has degraded the habitat in the
Carmel River and decreased the production of macroinvertebrates, the primary food of
endangered steelhead trout. Lack of seasonal sediment regime has contributed to accelerated
erosion of the Carmel River channel, lagoon and beach habitats. Erosion threatens to destabilize
homes and roads adjacent to the Carmel River lagoon. Removal of San Clemente Dam would
establish a new natural sediment regime on the Carmel River. This would help restore natural
channel processes in the River’s lower reaches and contribute to improved habitat in the river
channel.
Working Toward Restoration
This Supplemental Carmel River Watershed Action Plan has been developed by the
Planning and Conservation League Foundation in partnership with the Carmel River Watershed
Conservancy. The Plan focuses on two primary activities as key components of a restoration
strategy: removal of San Clemente Dam and cessation of downstream groundwater pumping.
The Supplemental Carmel River Watershed Action Plan builds on existing research,
management and restoration work being done in the watershed. It is based upon understanding
that complex ecological and geomorphic processes affect watersheds. It presents information that
describes how human actions at one location have influences throughout the watershed. The
cumulative effect of these actions has led to a disrupting of the ecological processes in the
watershed. Resolving these problems cannot be accomplished by independent actions. Instead a
coordinated approach to watershed restoration must be employed that focuses on specific actions
that cumulatively work together to support ecological restoration. This Plan outlines how to
manage those human and natural influences and strategically accomplish tasks to achieve a
E-2
sustainable, self-maintaining watershed that supports fish, wildlife, protects water quality, and
provides for human needs.
The Supplemental Action Plan presents several key recommendations, including
establishing a coordinated Carmel River Watershed Restoration Program. By integrating the
information and recommendations provided in this report, implementation of a Restoration
Program can link current opportunities with the potential benefits of future restoration needs that
will occur as resolution to the dam seismic problem goes forward, and as a solution is identified
for State Water Board Order 95-10. A key objective of the Carmel River Watershed Restoration
Program is to provide the organizational structure necessary to achieve these and other goals
articulated in this report. Recommended actions for implementation of the Restoration Program
will:
ƒ
Provide an integrated scientific and management organization that can identify
problems, set priorities, find solutions, and track progress. The program can take a lead
role in identifying lead agencies for various projects, establishing funding, provide
staffing and other resources, and ensure effective accountability.
ƒ
Facilitate collaboration and coordination among stakeholders. The success of the
program will depend on the cooperation of many agencies, entities, landowners, and
other stakeholders. The program will promote an integrated approach throughout the
watershed that can act to remove existing barriers to cooperation.
ƒ
Establish and maintain a working conceptual model for the interactions between the
various geomorphic, ecological, biological, social and political systems within the
watershed. This will provide a common basis for management actions that can be used
by all agencies, landowners, and managers within the watershed to prioritize actions and
serve as a roadmap for restoration.
A Vision for a Restored Carmel River Watershed
The vision of a restored Carmel River Watershed described in this document is based on
the understanding that management actions should encourage the river to restore itself through
natural processes that result in a more resilient and sustainable watershed ecosystem. Restoring a
fully functional watershed will contribute to numerous valuable environmental services and
functions that will meet both human and ecosystem needs. A functioning watershed ecosystem
can minimize flood risks, recycle nutrients, purify water, augment and maintain stream flow,
recharge groundwater, provide habitat for fish and wildlife, and provide recreation for people.
Achieving these benefits will require collaboration among many stakeholders including
landowners, local nonprofit organizations, state and federal agencies. Through their collective
efforts, actions to prioritize and implement restoration on a watershed scale will promote
successful outcomes from the headwaters to the coastal estuary and lagoon, and assure a healthy
future for the Carmel River Watershed.
E-3
1. INTRODUCTION The Carmel River Watershed exhibits the effects of changes to the natural environment that have
occurred through time, as well as human impacts that have occurred in the last 150 years. Natural
environmental processes are influenced by geology, climate, vegetation, and topography. Key
natural processes include fire, floods, landslides, vegetation succession, and wind. Human
impacts in the watershed are typically related to development, water management, land
management, forestry practices, and infrastructure, including the construction of dams on the
river.
The Carmel River Watershed has significant long-term physical and biological problems that
require watershed-based solutions. The impact of upstream San Clemente and Los Padres dams,
groundwater withdrawals along the lower Carmel River, and current management of the Carmel
River Estuary have negatively impacted the ecological and physical character of the river and the
aquatic, avian, amphibian and terrestrial wildlife that it supports.
The vision of a restored Carmel River Watershed described in this document is based on the
understanding that management actions should provide the river with the physical processes to
restore itself through natural actions. As the physical processes are restored, the biological
processes will occur. These actions will ultimately lead to a more resilient and sustainable
watershed ecosystem. Restoring a fully functional watershed will contribute to numerous
valuable services and functions that will meet both human and ecosystem needs. A functional
watershed can minimize flood risks, recycle nutrients, purify water, augment and maintain stream
flow, recharge groundwater, provide habitat for fish and wildlife, and provide recreation for
people.
This report entitled, The Supplemental Carmel River Watershed Action Plan, was funded by the
State of California Coastal Conservancy and the California State Water Quality Resources
Control Board. This report augments the Carmel River Watershed Assessment and Action Plan
(Carmel River Watershed Conservancy 2005), which identified and summarized many of
the major issues facing the Carmel River Watershed based on numerous technical and scientific
documents that have been developed specifically for the Carmel River. This report also
synthesizes information from reports developed by NOAA (2002, 2001), USFWS (2002), the
Environmental and Biological Assessment of portions of the Carmel River Watershed (MPWMD
2004), and the Physical and Hydrological Assessment of the Carmel River Watershed (Smith, et al.
2004). The goal of the Supplemental Plan is to provide recommendations for restoring the Carmel
River Watershed ecosystem under a scenario of: a) discontinued riparian aquifer/groundwater
withdrawals, and b) removal of the San Clemente Dam..
1
1.1
OVERVIEW OF DOCUMENT STRUCTURE
Information presented in the following chapters describes key issues and recommended actions
for restoring and managing the Carmel River Watershed focused on the following:
1. Discontinuing groundwater pumping from the Carmel Aquifer.
2. Removing San Clemente Dam while protecting habitats and river channel functions
within the existing dam site.
3. Developing a strategic sediment management plan to address the change in sediment
supply associated with removal of the San Clemente Dam, and resultant effects on the
Carmel River, floodplain and estuary.
4. Establishing a Carmel Watershed River Restoration Program that manages the
complex information and implementation requirements needed to functionally restore
and protect habitats throughout the watershed.
Natural and human processes in the Carmel River Watershed have become inherently
intermingled. The four actions identified above, and discussed in detail throughout this report,
will together yield a more comprehensive understanding of the natural and human-induced
processes that control the qualities of the Carmel River Watershed. Finding solutions that meet
the needs of both humans and the greater ecosystem will require an integrated, watershed-scale
approach that develops sufficient knowledge of the watershed ecosystem, develops sustainable
designs, and implements projects in a structured and coherent restoration strategy.
1.2
THE CARMEL RIVER WATERSHED
The Carmel River Watershed is the northernmost of a series of northwest-southwest trending
valleys that dissect the Santa Lucia Mountains of the California coastal ranges (Smith, et. al.
2004). The drainage area of the watershed is 256 square miles and ranges in elevation from
slightly greater than 4,000 feet to sea level, over a length of approximately 26 miles with an
average slope of 3 percent. The aquatic and terrestrial habitats along the Carmel River mainstem
and tributaries have evolved through the interaction of hydrologic, geological, and sediment
processes with the biochemical processes driven by the climate and local weather conditions.
Historically, the watershed landscape was a continuum of small and large scale habitats stretching
from the mountain peaks to the Pacific Ocean (Figure 1-1). Pre-development, there was
significant habitat complexity and connectivity that seasonally responded to hydrologic,
meteorological and ocean conditions and supported a diverse ecological assemblage.
Surface water in the Carmel River comes from four main sources: (1) direct runoff from rainfall,
(2) planned releases from upstream dams, (3) seeps and springs of groundwater, and (4) return
flow from urban uses including irrigation, septic systems, and waste-water treatment plants
2
(Smith, et al. 2004). Water flowing through the Carmel Valley consists of the flow in the surface
river channel of the mainstem, a subsurface flow (hyporheic water), and a shallow sub-stream
3
Source: Monterey Peninsula Water Management
District
f i g u r e 1-1
Supplemental Carmel River Watershed Action Plan
Carmel River Watershed
4
aquifer in the sand beneath the river channel (Kondolf and Curry 1982; Maloney 1984). The
shallow Carmel River aquifer is over-pumped by approximately 11,000 acre-feet per year
(SWRCB 1995). The riparian zone of the lower Carmel Valley is partially supported by return
flows from irrigation. The existing water budget for the Carmel River can be allocated as 64%
for evaporation and plant use, 23% for stream runoff, and 13% for groundwater recharge (Smith,
et al. 2004). Historically the riparian forest along the river corridor would have been much
larger. It has been noted in historic documents that summer conditions could lead to low water
conditions in the lower river due to a larger river channel and extensive riparian zone
evapotranspiration (Larry Hampson, MPWMD personal communications).
The Carmel River Watershed evolved as a highly dynamic system, experiencing large seasonal
variability in flow levels with subsequent variation in sediment transport from the upper
watershed to the estuary and ocean. This evolution maintained a connected complex of
terrestrial, riparian, freshwater aquatic, and coastal estuarine habitats that supported native
steelhead trout; California red-legged frogs; seasonal and resident obligate riparian birds,
shorebirds, and waterfowl; and an aquatic insect assemblage that represents a dynamic coastal
California ecosystem. The steelhead trout (Oncorhynchus mykiss) and California red-legged frog
(Rana aurora draytonii) are currently listed as threatened at both the federal and state levels. The
decline of these key species is indicative of the overall decline in ecosystem viability within the
Carmel River Watershed.
Vegetation in the Carmel River Watershed is dominated by California chaparral, grasslands, and
oak woodlands. At higher elevations, conifer and redwood forests are most dominant. Along the
riparian zone, willows, cattails, sedges, and grasses predominate. An inventory of aquatic,
riparian, and terrestrial species found in Carmel River Watershed is listed in Appendix A.
Any plan to restore ecological sustainability to the Carmel River must be developed at a
watershed scale because responses to restoration activities often vary across the watershed. An
effective Carmel River restoration approach must acknowledge these differences and embrace a
collaborative and coordinated strategy that supports development of an adaptive management
design and implementation program.
Previous studies (Carmel River Watershed Conservancy 2004; Smith, et al. 2004; Monterey
Peninsula Water Management District 2004) have evaluated the functional condition of portions
of the Carmel River Watershed. These studies suggest that the majority of reaches upstream of
river mile 10 (the Narrows) are capable of providing functional habitats. However, from the
Narrows downstream to the Carmel River Estuary, the aquatic habitat is considered “functional
at-risk” and moving towards becoming non-functional (MPWMD 2004). The reduced physical
and ecological functioning of the lower Carmel River and estuary are the result of the cumulative
effects of several factors, including:
5
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Groundwater pumping from the riparian aquifer by California American Water Company
and private wells and associated Carmel River water diversions
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The existence of San Clemente Dam (river mile 18.6) and Los Padres Dam (river mile
27) that influence downstream river conditions and affect the connectivity of habitats
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Seasonal breeching of the Carmel River Estuary sand bar
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Erosion and polluted runoff from developed landscapes
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Constraints on the natural river processes by levees, river control walls, bridges, roads,
and other human infrastructure that reduce the ability for river to geomorphically function
resulting in a reduction in the ecological and physical resiliency of the river ecosystem
1.2.1
Groundwater Pumping and Diversions
California American Water Company (CAW) is responsible for approximately 85% of the total
water diversions from the Carmel River system and its associated aquifer (MPWMD 2004). The
remaining diversions are due to a group of water users, including 14 non-CAW entities that are
responsible for an additional 12-13% of the total water withdrawn from the Carmel River (NOAA
2002). In addition to CAW's eighteen groundwater wells (Figure 1-2) which produced a total of
11,076 acre-feet of water (MPWMD 2004), an additional 561 private wells draw water out of the
aquifer (MPWMD 2004). Approximately 14,000 acre-feet of water has been annually diverted
from the Carmel River by CAW in recent years. Of this amount, 3,376 acre-feet are appropriated
through legal pre-1914, riparian and appropriative water rights; the remainder is diverted without
a basis of water right (SWRCB Order 95-10).
1.2.2
Dams on the Carmel River
The San Clemente and Los Padres dams were originally constructed as the two primary water
supply facilities in the Carmel River Watershed. San Clemente Dam is an 85-foot tall, concrete
thin-arch dam completed in 1921 (Figure 1-3). The original reservoir had an impoundment area
of 2,100 acre-feet. Subsequent sediment inflow to the reservoir has reduced the storage area to
less than 150 acre-feet. The dam does not have any functional fish passage capability and
completely blocks the upstream movement of steelhead trout into the upper portions of the
Carmel River Watershed. Hand netting of adults below the dam and transport upstream is the
only viable means to move spawning adults above the dam. No effort is made to capture and
transport downstream migrating young smolts or kelts (post-spawning adults). The dam does
seasonally provide the opportunity for CAW to divert water during high flow periods to their
Carmel Valley Filter Plant. The dam has known safety issues associated with its location near a
major earthquake fault and the volume of sediment trapped above the dam. The State of
California has required CAW, the dam owner and operator, to address these safety issues. One
alternative under consideration by federal and state agencies and CAW is removing the dam and
sequestering the existing reservoir sediments in place.
6
fi g u r e 1-2
Source: Monterey Peninsula Water Management District
Supplemental Carmel River Watershed Action Plan
Groundwater Pumping Station along the Carmel River
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Source: PWA (Mike Liquori)
f i g u r e 1-3
Supplemental Carmel River Watershed Action Plan
San Clemente Dam
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Los Padres Dam, a rock-and-earth fill dam also owned by CAW, is located approximately nine
miles above the San Clemente Dam. The original 3,130 acre-foot capacity of Los Padres
Reservoir has been reduced by approximately 50% since it was constructed in 1948 (Entrix
2000). Los Padres Dam has two fish trap facilities located at the base of the structure. Both
facilities require CAW personnel to employ a “trap and truck” process that captures (with nets or
pumps) upstream migrating steelhead adults and transports them above the reservoir. Current
estimates for Los Padres Dam suggest that it has a useful life of about 40-50 years before
sedimentation fills the reservoir (MPWMD 2004). No facilities exist to guide the downstream
movement of juvenile steelhead to the estuary or rearing habitats located below the dam. Los
Padres Dam constrains upstream steelhead migration, downstream juvenile movement, restricts
the natural movement of water and sediment in the Carmel River, modifies the water quality of
the Carmel River, and alters the natural geomorphic processes of the watershed.
The watershed above Los Padres reservoir is relatively unimpacted from human induced changes,
however, it is highly susceptible to a naturally high level of bedload sediment yield which
increases substantially immediately after wildfires (Smith, et al. 2004).
1.2.3
Carmel River Estuary
The Carmel River Estuary, publicly owned and managed by the California Department of Parks
and Recreation (DPR), represents the interface between the river/watershed and the Pacific
Ocean. Most of the estuary and present wetlands lie within the Carmel River Lagoon (Figure 1
4) and Wetland Natural Preserve, part of the Carmel River State Beach (Figure 1-5). Watershed
and ocean processes, and the seasonal relationship between the quantity and quality of water,
sediment and physical energy dynamics provided by the Carmel River control the estuary
hydrology and morphology.
The estuary has been altered historically, primarily by the farming activities west of Highway 1,
where levees were constructed to reduce the size of the estuary and control flood flows to
accommodate artichoke farming, which occurred for about a century. The estuary is generally
physically closed off from the Pacific Ocean from approximately May through October,
during which time water levels are sustained by the groundwater migrating down the river valley
to the ocean. During winter high flows, an opening to the ocean is made through the barrier
beach by the Monterey County Department of Public Works to prevent flooding of homes and
infrastructure in low-lying areas to the north. The estuary supports an abundant wildlife, coastal
bird and fishery populations, and is recognized as one of the most important ecological sites along
the Central Coast. In particular, the estuary habitat is critical to a significant population of native
steelhead, and also supports the California red-legged frog (both listed as threatened species). A
number of estuary enhancement projects have been implemented in the State Park in recent years,
funded by the California Department of Transportation, the State Coastal Conservancy, and
9
f i g u r e 1-4
Source: Carmel Pine Cone (Paul Miller)
Supplemental Carmel River Watershed Action Plan
Carmel Lagoon Following Construction
10
f i g u r e 1-5
Source: Ecosystem Management International, Inc.
Supplemental Carmel River Watershed Action Plan
Restored Carmel Lagoon
11
supported by DPR staff. Descriptions of the estuary morphology and function are provided in
several reports developed to support the enhancement projects: (PWA 1992; PWA 1999).
1.2.4
Water Quality in the Carmel River and Estuary
The Carmel River is not known for having high levels of contaminants, but herbicides and
pesticides have entered the waterway from golf course ponds, sediment catch basins, adjacent
agricultural areas, and from urban development (USFWS 2002; Reis 2003, 2002). Water
temperature and dissolved oxygen in the Carmel River can seasonally be a limiting factor for
steelhead trout. Water quality in the Carmel River Estuary is influenced by freshwater inflow
from the Carmel River, tidal levels, and ocean waters over topping the sandbar from the Pacific
Ocean (MPWMD 2004). Water quality often declines during the late summer, fall and early
winter months when Carmel River flows are reduced due to upstream groundwater pumping and
storage.
1.2.5
Existing Human Infrastructure
A large array of human infrastructure features exists within the Carmel River Watershed,
including roads, bridges, levees, culverts, diversions, dams, and armored stream banks. Many of
these features are designed to control erosion or flooding, while others are designed to support
various human needs (e.g., transportation). River and ecosystem processes have often not been
adequately accommodated in the design and construction process of infrastructure features.
The overall sustainability of human uses within the watershed depends in part on the long-term
function of the river and supporting ecosystem. Significant changes in the river environment can
undermine the integrity of many structures, increasing the risk of failure. Often, failure of the
existing structures increases the risk to other structures (e.g., homes, roads, pipelines, and
utilities).
1.3
PREVIOUS PLANNING AND RESTORATION EFFORTS
This report builds on previous studies from the Carmel River Watershed, including:
ƒ
Watershed Assessment and Action Plan (CRWC 2004)
ƒ
Physical and Hydrologic Assessment of the Carmel River Watershed (CSUMB 2004)
ƒ
Steelhead habitat studies (Dettman 1989)
ƒ
Riparian habitat studies (Kondolf and Curry 1984; Kondolf and Smeltzer 1999; Smith
and Huntington 2004)
ƒ
Sediment supply and transport modeling studies (Mussetter Engineering 2002a and
2002b; Mussetter Engineering 2003; Kleinfelder 2003)
ƒ
Carmel River Estuary and lagoon studies (Oliver 1989; Williams and Josselyn 1987)
12
ƒ
Federal and state government reports on species recovery for the steelhead trout (Snider
1983; NOAA 2001) and California red-legged frog (USFWS 2002).
ƒ
Instream flow requirements for steelhead trout (NOAA 2002)
The Carmel River Watershed Assessment and Action Plan (CRWC 2005) used qualitative and
quantitative methods and defined indicators to assess the health and resiliency of the Carmel
River mainstem. The majority of the data used in the Assessment was compiled from Monterey
Peninsula Water Management District (MPWMD) records and other publicly available
documents (CRWC 2005). Parameters used in the Assessment included information on stream
functionality (37 sites), riparian vegetation, population size and distribution of California redlegged frog and steelhead, distribution of large woody debris, water quality, and benthic
macroinvertebrates.
The Carmel River Watershed Assessment and Action Plan (2005) concluded that:
ƒ
Many reaches of the Carmel River can provide high quality, productive habitat for
steelhead trout. However the current population numbers and distribution of steelhead are
reduced due to fragmented and degraded habitat, introduced non-native predator species,
impaired fish passage, impacts to the aquatic food base, and water diversions that alter
natural stream flows.
ƒ
The river corridor upstream of Los Padres Reservoir is the least impacted by human
influences and remains naturally sustainable.
ƒ
The 15 miles of river corridor between Los Padres Dam and the Narrows (river mile 10)
appear to be in reasonably good condition, although channel degradation has occurred
immediately downstream of both Los Padres and San Clemente Dams.
ƒ
The lack of appropriately sized gravels for spawning in the river corridor below the dams
inhibits successful mainstem spawning of steelhead trout.
ƒ
The majority of the river corridor in the 10 miles downstream from the Narrows is
functionally impaired due to ground water extraction (pumping) and development
adjacent to the stream channel.
The Carmel River Watershed reflects the combined effects of both natural and human processes.
Natural processes are influenced by geology, climate, vegetation, and topography. Key natural
processes include fire, floods, landslides, vegetation succession, and wind. Anthropogenic
changes are usually related to development, water management, forestry practices, land
management, and constructed infrastructure. In the Carmel River Watershed the largest human
related impacts include:
ƒ
San Clemente and Los Padres dams;
ƒ
Pumping of groundwater;
13
ƒ
Unnatural control of the water level within the Carmel River Estuary; and,
ƒ
Constraint of natural river processes due to construction of levees, dikes, bridges,
armored streambanks and placement of materials in the river.
The cumulative effects of these human influences have resulted in a fragmented and ecologically
disrupted river environment in the 27 miles of the Carmel River system below Los Padres Dam.
Surveys conducted during the Carmel River Watershed assessment identified that of the ten creeks
that were surveyed, one (Las Garzas Creek) was properly functioning while six were classified as
Functioning but at Risk and three were classified as Non-functional (CRWC 2004). The majority
of the creeks in the watershed lacked adequate vegetation and stabilizing large woody debris.
Natural rates of erosion and stream migration help to sustain normal ecological process.
However, urban, rural and agricultural development can lead to unsustainable degradation and
erosion, and eventually to loss of aquatic, riparian and wetland stability. Key problem areas
identified in the CRWC (2004) study include:
ƒ
Lack of adequate vegetative cover or mature, deeply rooted trees to stabilize banks and
reduce bank erosion.
ƒ
Excessive sediment deposits in most creeks due to increased bank erosion as a result of
dirt-cut roads, cattle trails, grading activities associated with clearing land for
construction, and consequences from cumulative actions.
ƒ
Degraded fish spawning and rearing habitat due to pool filling and degraded spawning
gravels.
ƒ
Negative impacts from cattle grazing including manure in creeks, increased bank erosion
from trailing, bare floodplains, inaccessible floodplains, and lack of vegetation
recruitment.
ƒ
Failing bank stabilization features
ƒ
Lack of canopy cover provided by large trees needed to support greater terrestrial
biodiversity and water temperature necessary for proper fish habitats.
ƒ
Impediments to fish migration in the form of undercut bridges, retired summer dams,
undercut abutments and culverts and other structures laid in the creek bed that act as
barriers to fish passage.
ƒ
Lack of large woody debris, rocks, or boulders to aid in dissipating high energy flows.
ƒ
Lack of water (seasonally) in many of the creeks, and signs of overpumping in many
creeks (as indicated by the signs of stress exhibited by many streamside trees and shrubs)
Addressing these issues in the watershed will improve the functionality of the creeks, enhance
biodiversity and help to ensure the stability of the creek banks of local landowners and
homeowners. However, many of these symptoms are associated with larger, watershed-scale
problems. Simple fixes that only address local symptoms are unlikely to provide sustainable or
14
lasting solutions. This report advocates an integrated strategy that identifies problems and applies
solutions in an integrated manner across the entire watershed.
The CRWC report (2004) recommended 57 actions that can form the basis for a watershed
management plan. The logical next step is to prioritize these actions by synthesizing existing
information into a spatially explicit plan that recognizes the interactions among and between the
existing conditions, eco-geomorphic processes, and restoration activities. The success of a
watershed restoration plan depends on reducing riparian groundwater withdrawals and removing
San Clemente Dam.
15
2. KEY ISSUES AND ASSOCIATED IMPACTS
The Carmel River, like most coastal California waterways, exhibits the effects of environmental
and human impacts over the last two centuries. Restoring a fully functional watershed will
contribute numerous valuable services and functions that will meet both human and ecosystem
needs. A functional watershed can minimize flood risks, recycle nutrients, purify water, augment
and maintain stream flow, recharge groundwater, provide habitat for fish and wildlife, and
provide recreation for people. Development within the Carmel River Watershed has modified
many natural features and processes resulting in a fragmented and ecologically dysfunctional
ecosystem. This chapter details the impacts related to four key issues:
1.
2.
3.
4.
2.1
Riparian Aquifer Withdrawals
San Clemente Dam
Sediment Transport and River Management
Ecological Function and Habitat Quality
RIPARIAN AQUIFER WITHDRAWALS
A significant opportunity for restoring a healthy Carmel River can be achieved by discontinuing
riparian pumping from CAW groundwater wells immediately adjacent to the Carmel River
(Figure 2-1). Currently more than 60% of the water supply for the Monterey Peninsula comes
from these wells located in the lower Carmel River basin. In 1995 the State Water Resources
Control Board ordered CAW to find an alternative water supply in order to stop pumping from
these wells. Ongoing pumping has prevented the restoration of a more natural seasonal flow
regime and groundwater levels in the lower river.
The SWRCB Order WR 95-10 identified the impacts from groundwater withdrawal activities.
These impacts include loss of streamside vegetation communities, loss of coastal salt marsh
habitats, declines of fish, amphibian and reptile populations, and the loss of recreational and
aesthetic values along the lower Carmel River. Other impacts include declines in water quality,
depletion of aquatic food chains, and declining circulation within the lower Carmel River and
lagoon. This section describes both the physical functions and processes that are affected by
excessive groundwater withdrawals. Streamside pumping has produced a number of negative
effects, which include:
ƒ
Lowered water table – pumping artificially lowers the water table along the lower river,
imposing a number of negative impacts on water supply, water quality, fish and wildlife
habitat, and streamside vegetation.
16
ƒ
Effects on streamside vegetation and wetlands – the lower water table causes drought
stress on streamside vegetation, resulting in the mortality of important species (especially
tree species such as cottonwoods and willows). A lowering of the river channel also
17
f i g u r e 2-1
Notes: Carmel river aquifer shown as yellow zone along the Lower
Carmel River.
Supplemental Carmel River Watershed Action Plan
Carmel River Aquifer (shown as yellow zone along the Lower Carmel River)
18
leads to a disconnection between the river and the floodplain, negatively affecting
wetlands and seeps important to amphibian species. (Curry and Kondolf 1983)
ƒ
Loss of channel stability – when streamside cottonwoods and willows die, the roots that
support the banks also die, resulting in structurally weakened river banks. During large
storms, the river erodes these weakened banks, causing river channels to carve new
pathways through the valley floor. (Kondolf and Curry 1986)
ƒ
Disconnected river flows (dewatering) – the lowering of the water table causes river
flows to infiltrate into the channel bed (Figure 2-2). This channel infiltration changes the
river's flow regime, and may even lead to a dry river channel for an extended period of
time. Particularly impacted are the character of flows in the early winter, persistence of
flows in the spring, and lowered quantity of flows in the dry season.
ƒ
Loss of rearing habitats for steelhead – under the present aquifer pumping regime, the
river below approximately river mile 7 is dewatered by July of each year, resulting in the
loss of habitat for an estimated 45,000 juvenile steelhead.
ƒ
Reduced ability for steelhead to migrate – water withdrawals from the Carmel River
and the resultant lack of water in the river channel can delay the movement of steelhead
smolts downstream from the upper watershed to the lagoon by up to 6 weeks. Reduced
flows in the river can delay the natural hydrologic breaching of the lagoon.
ƒ
Negative impacts to the Carmel River Lagoon - the lagoon receives little to no inflow
during the summer season, reducing its water exchange, circulation and available useable
aquatic habitats. The result is poor water quality and significantly reduced habitat area
for juvenile steelhead and other species. The limited habitat leads to increased predation
and physiological stress, reduced growth, and subsequent mortality.
2.2
SAN CLEMENTE DAM
Since San Clemente Dam was constructed in 1921, it has trapped sediment that would previously
have been conveyed down the river to the ocean. By 2003, approximately 1,375 ac-ft (2.2 million
cubic yards) of sediment had filled a design reservoir volume of 1,425 ac-ft (2.3 million cubic
yards). The reservoir is now so filled by this sediment that it no longer functions as a reliable
water supply reservoir. Due to high costs, few disposal options, traffic impacts, and other
engineering challenges, it is not feasible to remove the sediment and re-establish the original
reservoir function.
The San Clemente Dam has imposed a number of significant negative impacts on the Carmel
River Watershed for the past 86 years. In its present condition, the dam's negative impacts
outweigh any public benefit that it may provide. Current dam impacts include:
ƒ
Risk to public safety
ƒ
Altered sediment transport and channel geomorphology
ƒ
Disconnected floodplain and reduced flow
ƒ
Disruption of ecological integrity
19
Source: PWA (Mike Liquori)
f i g u r e 2-2
Supplemental Carmel River Watershed Action Plan
Typical Summertime River Conditions Along Pumping Zone
20
2.2.1
Risk to Public Safety
The California Division of Safety of Dams and the dam owner, CAW, have identified structural
deficiencies in the dam that could cause it to fail in a strong earthquake or extreme flood event
(Figure 2-3). Dam failure would endanger the lives and property of downstream residents.
Under California law this risk must be eliminated.
Recent studies conducted by California American Water are being evaluated by the California
Department of Water Resources to assess the viability of dam removal as a means to protect
public safety (Entrix/CAW 2006). Dam removal would have the additional environmental
benefits of allowing fish to migrate upstream and downstream as a part of their natural lifecycle,
and restoring habitats for amphibians, birds, and other species along the river corridor below San
Clemente Dam. Dam removal provides a unique opportunity to restore ecological, hydrological
and geomorphic processes that are necessary to naturally sustain a high-quality river ecosystem.
2.2.2
Altered Sediment Transport and Channel Geomorphology
San Clemente Dam traps most sediment upstream of the dam in the reservoir basin (Figure 2-4).
As a result, the channel below the dam has been depleted of the sediment that, under pre-dam
conditions, defined the geomorphic character of the river. Due to the lack of sediment supply the
dam controlled Carmel River has incised (downcut), resulting in an isolated channel and
increased bank instability. In other places, the seasonal sediment regime of sand and gravel has
been replaced by coarse cobbles and boulders and a hardening of the downstream river channel.
The loss of natural sediment supplies from the headwater areas reduces the availability of
spawning gravels below the dams. Hardening of the channel that results from the diminished
sediment supply creates lower flushing hydraulic conditions that are less able to maintain
spawning gravels. Both effects reduce the actual amount of spawning habitat available for fish
reproduction below the dams. Over time, the coarsened and hardened channel bed becomes less
mobile during large flows, and the more static and incised river bed loses much of its habitatforming capacity.
Even if left in place, San Clemente Dam has a rapidly diminishing potential to retain future
sediment supply from the area between Los Padres and San Clemente. As the reservoir fills, the
ability to store sediment will decline significantly. Within 4 to 14 years of complete reservoir
filling (depending on storm conditions), less than 5 ac-ft of the 16.4 ac-ft of average annual
sediment inputs will be retained by the dam (Mussetter Engineering 2003). Eventually, all the
background sediment will bypass the dam site and will either be deposited in the channel,
along channel floodplains, in the estuary, or in the Pacific Ocean.
21
f i g u r e 2-3
Source: Courtesy of Division of Dam Safety
Supplemental Carmel River Watershed Action Plan
Flood Conditions at San Clemente Dam
22
f i g u r e 2-4
Notes: San Clemente Dam and Reservoir - note extent of
sedimentation.
Supplemental Carmel River Watershed Action Plan
San Clemente Dam and Reservoir
23
As sediment supply is returned to these locations, it will affect the patterns and response of the
Carmel River in some locations. The river will respond to the increases in sediment supply and
storage by regaining some of the dynamic channel characteristics that existed prior to the dam’s
construction. While this will help to restore some beneficial channel characteristics, increased
sediment supply and storage can increase the risk of localized flooding, bank erosion, channel
migration, and other geomorphic responses. These factors will need to be considered in the postdam management of both the San Clemente site, as well as downstream infrastructure.
Recommended solutions are discussed in Section 4.3.
2.2.3
Disconnected Floodplain and Reduced Flow
The cumulative effects of channel incision and reduced flow levels in the Carmel River
downstream of Los Padres and San Clemente dams have resulted in a physical separation
between the river channel and the seasonal ponds and wetlands in the historic floodplain along
the river corridor, and a draining of the connected wetlands into the Carmel River. The loss of
connectivity and water exchange between the river, floodplain and wetlands reduces the amount
of available habitat for fish, aquatic macroinvertebrates, amphibians, insects, and avifauna.
The coastal marshes and wetlands at the Carmel River Estuary have been reduced in size and
ecological viability as the flow and sediment regime has been modified. Additional impacts
include the encroachment on historic marsh lands by development of houses, roads, bridges and
water management infrastructure. Tidal influences interact with upstream freshwater inflow to
determine the water and salinity levels in the estuary. These processes create a dynamic and
continually changing environment that supports species in transition from freshwater to saltwater
habitats, including migrating adult and juvenile steelhead, California red-legged frogs (tadpoles,
eggs, and adults), shorebirds (migrating and resident), waterfowl (migrating), aquatic
macroinvertebrates and the benthic community. Reduced freshwater inflows to the coastal
estuary periodically lead to poor water quality conditions (low dissolved oxygen, high
temperatures) during the late summer and fall months that reduce the amount of area available for
habitat.
2.2.4
Disruption of Ecological Integrity
The dam disrupts processes that are important to sustain many ecosystem functions throughout
the watershed. The dam significantly blocks the movement of the federally listed south central
population of steelhead trout (Oncorhyncus mykiss) to historic spawning and rearing areas in the
upper portions of the watershed.
Fragmenting the Carmel River has resulted in loss of seasonally important habitats for many
aquatic, terrestrial and vegetation species, primarily due to changes in the river and floodplain
24
condition. Such habitat losses impact the ability for many species of fish, amphibians, birds and
their food base (insects, plants) to complete their full life cycles.
Dam-induced changes in Carmel River hydrology have impacted the transfer and cycling of
natural minerals and nutrients downstream. The result has been modification of the bio-chemical
cycling and biological uptake of nutrients by the aquatic and terrestrial ecosystem components.
2.3
SEDIMENT TRANSPORT AND RIVER MANAGEMENT
Rivers are natural corridors that transport water, sediment, nutrients, debris and organic material
from the headwaters to the ocean. Since 1921, San Clemente Dam has captured all natural
sources of sediment between San Clemente and Los Padres dams, except during extreme
hydrologic events. The loss of a natural sediment regime has degraded the natural river form and
ecological functions and resulted in channel downcutting, increased erosion, and loss of habitatforming processes (Figure 2-5). Over time, the river environment has adjusted to this depleted
sediment load, creating a simplified and unsustainable channel condition.
Under existing conditions, estimates for the background bedload sediment at San Clemente
average about 16.4 ac-ft/year, and range from a low of 5.0 ac-ft/year to a high of 21.1 ac-ft/year
(Mussetter Engineering 2003; Matthews 1983). Within the next few years, this background
sediment will be delivered to the lower Carmel River, regardless of the fate of the San Clemente
Dam. Some may be trapped by various structures associated with the San Clemente Dam
removal or retrofit, but most of this sediment will be routed to the lower river.
The historical rate of sedimentation observed behind the dam structure suggests that about 820
ac-ft of sediment will be routed to the lower river over the next 50 years. Most of this sediment
will likely be medium to coarse sand, although about 15% (123 ac-ft) will be gravel, based on
composites developed from analysis of the existing sediments behind San Clemente Dam
(Mussetter Engineering 2003). No estimates for the fate of these sediment are currently available,
and would require detailed hydraulic and sediment transport modeling.
Modifying downstream sediment transport along the river and floodplain corridor can cause a
number of physical changes to the river over the course of the next several years to decades.
Even if the majority of new sediment is fine-grained silts and sand, a number of hydraulic studies
have shown that rapid influx of fine sediment to a coarse, armored gravel channel bed condition
(as currently exists) can increase the overall bed mobility (e.g., Curran & Wilcock 2005). Such
changes could result in changing the local elevation of the Carmel River channel bed, modifying
channel morphology, creating new channels, changing water quality characteristics, increasing
sediment transport, changing habitats, and others. Additionally, these changes have the potential
to change the location and frequency of flooding, decrease channel stability, and alter the spatial
habitat characteristics in the channel.
25
f i g u r e 2-5
Supplemental Carmel River Watershed Action Plan
Incised Reach of the Carmel River
26
In addition to the risks to human infrastructure (Figure 2-6), changes in sediment supplies can
affect ecosystem functions as well. The biological and physical structure of the Carmel River is
the result of a suite of environmental processes that influence its evolution, and restored
background sediment supply will improve certain ecosystem functions. The integrity of the
system helps to provide a sustainable ecological character that affects both the ecological
response, as well as the impacts to human infrastructures. The historic sediment depletion below
San Clemente Dam, and the pending return of natural sediment supplies to the river channel as
the dam fills (or is removed), has had (and will have) a number of impacts on the Carmel River
Watershed, as described below.
Many of these potential impacts can be managed and mitigated with proper analysis and
planning. Section 4.3 of this report outlines the steps necessary to properly identify and manage
sediment issues associated with the obsolescence of San Clemente Dam.
2.3.1
Current Disruptions to Physical Processes and Geomorphology of the Carmel River
Since 1921, the artificially-depleted sediment regime of the lower Carmel River has caused direct
physical changes in the waterway that have impacted the aquatic community through effects on
habitat distribution, extent, and quality. These physical changes include:
ƒ
Decreased amounts of spawning gravels. Steelhead trout depend on coarse gravels for
spawning. These gravels typically are supplied from headwater sources, and have been
trapped behind the dam. The depletion of gravels from the lower river has reduced the
available spawning sites for key fish species.
ƒ
Increased armoring of the Carmel River bed. In any waterway, channel substrate tends
to be moved downstream. Without replenishment of sediment from upstream, all
smaller substrate materials become mobilized and transported until the only substrate
materials remaining are those that are not capable of movement under normal river flow
conditions. The result is an “armoring” of the bed that reduces the habitat availability
and results in lower overall fish production.
ƒ
Simplified Carmel River channel morphology. The loss of natural sediment supply has
resulted in downcutting and localized narrowing of the channel, and a reduced
distribution and ratio of pool and riffle areas (Figure 2-7). The result is a more uniform
stream channel and important loss of habitat complexity and diversity.
ƒ
Narrowed active stream vegetation corridor. The loss of sedimentation bedforms like
bars and flood deposits reduces available substrate for pioneer species such as
cottonwoods, willows and other riparian species. When combined with channel incision,
the result is a narrowing of the riparian corridor and reduction in the terrestrial riparian
habitat complexity and diversity. The result is impaired habitat for many terrestrial and
semi-aquatic species and life history stages, a shift from native vegetation species toward
exotic invasive plant species, and an overall reduction in the integrity (stability) of the
watershed ecosystem.
27
Source: Carmel River Steelhead Association (Clive Sanders)
f i g u r e 2-6
Supplemental Carmel River Watershed Action Plan
Residential Homes Along the Carmel River
28
f i g u r e 2-7
Notes: Primary and secondary knickpoints following dam removal
have the potential to affect downstream channel conditions. Proper
management can minimize risks to downstream landscapes (from
Pizzuto 2002).
Supplemental Carmel River Watershed Action Plan
Longitudinal and Lateral Channel Responses to the San Clemente Dam
29
ƒ 2.3.2
Altered beach and estuary dynamics. Beaches are dependent on river sediments to
replace sands that are washed off-shore. Since the San Clemente Dam was built in 1921,
the beach has been eroded and is now threatening homes and roads built near the ocean.
The estuary dynamics are also influenced strongly by the supply of sediment from river
sources. Without its natural sediment supply, the Carmel River Estuary has a reduction
in nutrients and substrates to support seasonal habitats.
Potential Impacts of Renewed Sediment Supply
The specific impacts associated with the return of natural sediment supplies from the area
between San Clemente Dam and Los Padres Dam to the lower Carmel River are difficult to
assess. At the time of this report, there is an incomplete evaluation of potential conditions as the
post-dam configuration is still uncertain. Many of these changes may take decades to fully
evolve (Figure 2-8). A comprehensive analysis of sedimentation conditions has not been
completed, although several analysis components are available from existing reports (e.g., Smith,
et al. 2004; Moffatt and Nichol Engineers 1996; Mussetter Engineering 2002; Mussetter
Engineering 2003). In the absence of a sediment management plan (see Section 4.2.2), some of
the potential impacts that may develop include:
™
™
™
™
™
Unsustainable development along the Carmel River. The dam has provided a false sense
of security that has encouraged an unsustainable level of development adjacent to some
sections of the river. Some of these areas may be difficult to protect once the natural
sediment supply is conveyed to the lower river reaches, and natural river processes are
restored. Much of the landscape below the Narrows (river mile 10) was created by natural
sediment deposition during floods. Historic reduction in natural sediment has potentially
increased the apparent stability of the channel. As background sediment is supplied to the
lower river, channel changes are likely to occur that could impact development practices and
infrastructure along the channel margins (Figure 2-9).
Increased flood risks. Increased sedimentation in portions of the lower Carmel River can
result in increased flooding conditions by reducing the capacity of the channel during large
storms.
Channel changes. Channels are constantly adjusting to the supply of sediment, water and
debris. Increasing sediment supplies can result in channel widening, new bar-forms,
increased sinuosity, and increased channel migration.
Increased erosion and land losses. Channel changes may impact adjacent landowners, who
may have limited ability to control the river behavior at a site scale. More effective strategies
usually require a watershed-scale understanding combined with reach-scale restoration
designs. Previously hardened sites (bridges, revetments, culverts, roads) will also become
locations of potential concern.
Steelhead spawning impacts. Excessive sedimentation buries steelhead egg nests (redds),
causing young fish to die before they can hatch. Localized portions of the lower Carmel
River may experience reductions in egg survival rates.
30
f i g u r e 2-8
Source: Shafroth 2002
Supplemental Carmel River Watershed Action Plan
Typical Response of the Downstream Riparian Community to Dam Removal
31
f i g u r e 2-9
Source: Shafroth 2002
Supplemental Carmel River Watershed Action Plan
Notes: Note that responses will occur in both upstream and
downstream directions, and that changes will likely occur over the
course of decades.
Typical Responses to Dam Removal
32
2.4
RESTORATION NEEDS
The Carmel River Watershed historically provided seasonally important habitats for the federally
listed steelhead trout and California red-legged frog. The river was one of the most productive
steelhead rivers along the California Coast (NOAA 2002) and today is included as an element of
the south central steelhead trout evolutionarily significant unit (ESU). Considering the
diminished number of watersheds in California that support anadromous fisheries (McEwan and
Jackson 1996), the restoration of the Carmel River Watershed is ecologically important.
The Carmel River Watershed is the northernmost of a series of valleys that dissect the Santa Lucia
Mountains of the California Coastal Ranges (Smith, et al. 2004). Mainstem and tributary habitats
appropriate for steelhead trout are formed by hydrological and sediment regimes, which are
controlled by the local geology, topography and water supply conditions (Figure 2-10). High
sediment bedload coupled with variable seasonal hydrologic conditions led to the development of
a dynamic assemblage of aquatic, riparian, and estuarine habitats that supported a diverse
assemblage of terrestrial and aquatic species. The majority of these species occupied habitats that
are not found in other locations in California and along the West Coast of the United States.
Several of these species, including the steelhead trout (Oncorhynchus mykiss) and California redlegged frog (Rana aurora draytonii), are listed as federally and state threatened species, meaning
that their potential for extinction is high. Throughout their range, these two species are limited by
a lack of available habitat required to meet their life history needs. The Carmel River Watershed
provides needed habitat, however various human impacts within the watershed have limited the
quality and extent of required habitats necessary for these species to sustain themselves. Thus,
restoring the watershed not only helps an ecosystem to recover, but also helps California meet its
legal requirement to protect threatened species.
2.4.1
Ecological Functions and Processes
Ecosystem functions within the Carmel River Watershed are controlled by a number of drivers
(e.g., water management or land-use patterns). Such drivers each influence dominant ecological
and geomorphic processes, which ultimately control the conditions and trends observed in the
watershed (Figure 2-11). The sections below describe some of these relationships.
2.4.1.1
Loss of Streamside Vegetation
A variety of vegetation communities exist in the Carmel River Watershed. These communities
range from headwater terrestrial habitats composed of a mix of oak-grassland and forestgrassland, to lower elevation communities dominated by coastal shrubs, sedges, grasses and
wetland vegetation. The riparian vegetation community found along the mainstem and tributaries
includes willows, alders, buckeyes, coastal shrubs, and grasses.
33
f i g u r e 2-10
Source: Poff and Hart 2002
Supplemental Carmel River Watershed Action Plan
Cumulative Effects of Dams
34
f i g u r e 2-11
Supplemental Carmel River Watershed Action Plan
Key Landscape Drivers of Cumulative Impacts
35
The San Clemente Dam and pumping from the riparian aquifer have negatively impacted the
diversity and extent of the riparian streamside vegetation community along the Carmel River
through four mechanisms:
ƒ
Disruption of the natural flow regimes due to the construction and operation of San
Clemente and Los Padres dams. This disruption of natural flow regimes and
distribution of sediments has reduced the overbank flows, modified seasonal timing of
flows, and modified the reproductive processes of some vegetation species, including
patterns of seed dispersal.
ƒ
Incisement of the Carmel River mainstem channel below Los Padres and San
Clemente dams. The cutting down of the stream channel results in disconnecting the
river with the historic floodplain, and reduces the ability of the Carmel River to
seasonally distribute sediments and associated nutrients.
ƒ
Confinement of the Carmel River channel due to infrastructure constraints.
Seasonally, the Carmel River channel meandered within the Carmel Valley. The levees,
bridges, channel constraints, and roads associated with development in the valley has
restricted the Carmel River to a limited area resulting in confinement of the channel and
disconnection from the floodplain and wetlands.
ƒ
Reduction of the surface and subsurface Carmel River water flow due to pumping
from the Carmel River aquifer. Pumping results in reduced water available for
supporting the riparian vegetation and aquatic insect community and leads to seasonal
physiological stress on these communities.
2.4.1.2
Increased Invasion by Non-native Species
Native species have evolved in a particular environment and have adapted to the temporal and
spatial variability of the ecosystem. Non-native species are frequently opportunists that take
advantage of a disturbed ecosystem or unoccupied habitat. Disturbances (both natural and
anthropogenic) that have occurred in the Carmel River Watershed provide opportunities for non
native species to invade the native community. Examples of non-native species that may impact
and out-compete native species in the Carmel River Watershed include [non-native cyprinids and
bass, bull frogs, cowbirds, rodents, and vegetation such as gorsch, scotch thistle, tamarisk and
cheat grass.
Non-native plants threaten the integrity of aquatic ecosystems in diverse ways. For example,
species such as tamarisk (Tamarix sp.), giant reed (Arundo donax), and cape ivy (Delaria
odorata) have invaded native willow-cottonwood-sycamore communities in many Central
California watersheds. Because these non-native species have higher transpiration rates than the
native species complex, their presence may lead to a net loss of surface water (USFWS 2002).
Biologists have noted that California red-legged frogs avoid streams dominated by Eucalyptus
(Eucalyptus sp.), perhaps due to the secretion of toxic chemicals from the eucalyptus leaves as
they decompose (USFWS 2002).
36
2.4.1.3
Modified Aquatic Food Chains
Aquatic food chains are sensitive to the hydrologic regime and water quality of the watershed.
The macroinvertebrates, benthic community, aquatic vegetation, phytoplankton, zooplankton, and
bacteria that comprise the food chain typically show seasonal variations in biomass and species
composition that are related to the life cycle of the species as well as to seasonal changes in
temperature and hydrologic conditions. Modifications to the Carmel River Watershed have
resulted in the following changes to the aquatic food chain:
ƒ
Reduced species richness of benthic macroinvertebrates (i.e., fewer species)
ƒ
Reduced functional diversity of benthic macroinvertebrates (i.e., fewer distinct functional
types)
ƒ
Increased algal productivity in the lower Carmel River and Estuary
ƒ
Reduced streamside riparian vegetation due to channel incisement
Due to their short life spans (relative to aquatic vertebrates), and relative position in the food web,
and sensitivity to a suite of characteristics (substrate composition, current velocity, flow regime
pattern, food availability, water temperature, dissolved oxygen, and water chemistry), aquatic
macroinvertebrates are frequently used as an indicator of the health of an aquatic ecosystem.
Stanford and Ward (1979) showed that altered hydrographs impact benthic fauna that are
dependent upon cyclic thermal and flow cues for their development.
Studies which have
evaluated the composition and abundance of macroinvertebrate communities in the Carmel River
Watershed, summarized in the Carmel River Bioassessment (MPWMD 2004), have concluded
that:
ƒ
Higher quality benthic macroinvertebrate assemblages were found in the mid-Carmel
River valley.
ƒ
Sites located immediately below Los Padres and San Clemente dams had relatively poor
benthic macroinvertebrate assemblages due to large substrate and the quantity, timing
and quality of water releases from the dam.
ƒ
Higher elevation sites at Cachagua had lower quality macroinvertebrate assemblages
ƒ
Macroinvertebrate assemblages decreased in diversity over time
ƒ
Fewer macroinvertebrate numbers and reduced assemblage diversity occurred in large
substrate (boulder, cobble) than in gravels.
2.4.1.4
Loss of Coastal Salt Marsh Habitats
Modification of the natural flow dynamics and geomorphic constraints has restricted the ability of
the Carmel River to sustain the coastal marshes of the estuary. The physiography of the estuary
37
area is the product of fluvial deposition and coastal erosion. In the Carmel River Estuary an
assemblage of habitats exists including open water areas, wetlands, open sand flats, and an area of
tidal inflow. This assemblage of habitats is maintained by the surface and subsurface mixing and
movement of fresh and salt water within the confines of the lower Carmel River. Historically, the
extent of the Carmel River Estuary varied in response to tidal and sea storm influences, seasonal
flow patterns of the Carmel River, changes in sea level, and formation of the river mouth bar.
Excessive groundwater withdrawals have reduced the extent and quality of coastal salt marsh
habitats, resulting in less area available for fish, amphibians, shore birds and waterfowl. Specific
issues include:
ƒ
Modified seasonal freshwater flows due to pumping and upstream dam operations has
allowed increased salt-water intrusion with subsequent impacts to estuary dynamics that
directly effect the vegetation distribution.
ƒ
Physical constraint of the wetland area by roads, homes, channel restriction,, and levees.
ƒ
Decreased water quality due to reduced quantity and quality of incoming freshwater and
runoff from residential areas and roads.
ƒ
Reduced vegetation diversity due to increased disturbance and loss of ecosystem
integrity.
ƒ
Reduced sediment and nutrient inflow from the upstream watershed, resulting in reduced
substrates for vegetation and modified nutrient dynamics.
ƒ
Reduced open water holding and transition aquatic habitats for steelhead smolts and for
the staging of adult steelheads migrating from the ocean to spawning areas.
ƒ
Artificial breaching of the bar at the mouth of the Carmel River Estuary results in
disrupted seasonal flow dynamics in the estuary which directly impacts the ability of the
estuary marshes to sustain themselves.
2.4.1.5
Reduced Water Quality in Estuary
An estuary is defined as being a semi-enclosed coastal body of water that has a free connection
with the open sea and within which seawater is measurably diluted with fresh water derived from
land drainage (Lauff 1967). The mixing of seawater with fresh water in the estuary produces
density gradients of salinity which drive estuarine circulation patterns. These circulation patterns
and inherent water quality conditions define the useable habitat for aquatic species. The Carmel
River supports the maintenance and sustainability of the aquatic and riparian ecosystems based on
delivery of fresh surface and subsurface flows to the estuary.
Prior to the construction of San Clemente and Los Padres dams and before groundwater pumping
seriously modified and depleted the water flow levels of the Carmel River, the estuary had a
seasonally defined flow regime and water quality that supported adult and juvenile steelhead trout
38
and an assemblage of other aquatic species, including California red-legged frogs, insects, and
aquatic vegetation. The resulting estuary environment included both wetland and open water
characteristics.
Human development within the Carmel River Watershed has significantly modified the natural
flow pattern, volumes, and seasonal quality of the mainstem river. The changes associated with
human development include increased summer water temperatures, reduced summer dissolved
oxygen, modified productivity and nutrient transport, and reduced biological diversity. The
Carmel River Estuary, being at the bottom of the watershed, is the recipient of impacts from
upstream sources. The changes in water quality occur as a result of:
ƒ
Modified flow dynamics (timing and quantity) due to the modification of flow regime
due to San Clemente and Los Padres release patterns.
ƒ
Modified water quality dynamics (temperature, dissolved oxygen, nutrient cycling) due to
bio-chemical changes in the water stored behind the two dams.
ƒ
Seasonally reduced quantities of water in the lower Carmel River due to groundwater
pumping, at times drying up the lower Carmel River.
ƒ
Incised Carmel River channel below Los Padres and San Clemente dams resulting in
modified groundwater and hyporheic flow in the lower Carmel River.
ƒ
Encroachment on the boundaries of the Carmel River Estuary associated with home and
infrastructure development.
ƒ
Seasonally modified flow dynamics of the Carmel River Estuary due to artificial
breaching of the bar at the mouth of the river.
2.4.1.6
Discontinuity of Habitats
Riverine ecosystems and their watersheds are multidimensional. Ward (1989) described four
primary dimensions of riverine systems and a landscape connection for each: longitudinal
(upstream to downstream), lateral (floodplains to uplands), vertical (subsurface of stream to
canopy of riparian vegetation), and temporal (over the riverine system through time). In the
Carmel River Watershed, human disturbance has disrupted and modified many connections within
the watershed (Figure 2-12).
The cumulative effects of fragmenting and disconnecting the Carmel River mainstem and
supporting tributaries are an overall ecosystem decline and loss of biological integrity and
complexity. Specific effects include:
ƒ
The dry channel seasonally creates a barrier to the longitudinal movement of juvenile
steelhead and kelts (post-spawning adults who return to the ocean) downstream to the
estuary.
39
f i g u r e 2-12
Source: Big Sur Land Trust
Supplemental Carmel River Watershed Action Plan
Land-use Distribution in the Lower Carmel River
40
The entire water system in the Carmel River Watershed is connected. Pumping of the
shallow aquifer draws water from the hyporheic zone that can lead to an increase in
lateral flows, which can drain riparian wetlands and other wetland habitats important for
California red-legged frogs and other species.
ƒ
2.4.2
Gaps in canopy cover along the riparian corridor can limit migration and movement of
terrestrial species and avifauna and lead to increases in water temperature in the river.
Effects on Key Species
The steelhead trout and California red-legged frog are two species of particular interest in the
Carmel River Watershed. Each of these species is threatened by the degradation and loss of
habitat caused at least in part by human activities related to water development (dams and
diversions), urbanization, agriculture, flood control, and recreation.
Dams have fragmented migration pathways and habitats along the Carmel River. For steelhead,
this habitat fragmentation not only reduces access to important spawning and rearing areas, but
also limits downstream dispersal opportunities and may preclude genetic mixing with other
coastal steelhead subpopulations. For the California red-legged frog, habitat fragmentation limits
movement between wetland areas and, as with steelhead, can affect metapopulation structure.
For both species, isolated populations are vulnerable to extinction through random adverse
environmental events and human-caused impacts.
Urbanization and agricultural development directly affect the quantity, quality, and connectivity
of wildlife habitat. Roads and poorly designed bridges and culverts form barriers to movement
and lead to fragmented populations. Modified runoff patterns, drainage, irrigation activities, and
other actions change the pattern of water delivery within the watershed and especially the
mainstem river; pesticides and fertilizers in runoff can affect the quality of water delivered to the
river. These disturbances may create environments that are less suitable for the native steelhead
and California red-legged frog, and more suitable for predators and non-native species.
Channelization and flood control activities which typically include vegetation control and
removal, herbicide spraying, shaping and armoring of stream banks to control erosion, and flow
control in channels, can result in degraded habitats. Besides direct changes to habitat structure,
these measures often cause velocity to increase in mainstem currents, further reducing the
suitability of mainstem low velocity habitats for young steelhead. Stream channel and floodplain
disturbances often create opportunities for the proliferation of non-native aquatic species.
Recreational activities can degrade aquatic habitat if not properly managed. Unmanaged off-road
vehicles in the watershed can damage riparian vegetation, increase sediment runoff into pools and
spawning areas, compact soils, and disturb the water in stream channels. Additional impacts on
steelhead include compaction of spawning gravels and potential crushing of eggs that have been
41
spawned in redds. Recreational activities such as angling can result in the introduction of non
native species either intentionally through the illegal stocking of streams, lakes or ponds, or
unintentionally by the transfer of non-native species (e.g., the New Zealand mud snail) on waders
or other equipment.
Predation by introduced, non-native species is another significant factor in the decline of the
steelhead trout and California red-legged frog. Of specific concern in the Carmel River
Watershed are bullfrog, crayfish, mosquito fish (Gambusia affinis) and centrarchids. Changes in
quantity and quality of habitat tend to be favorable to a suite of introduced non-native aquatic
predators. The interaction between native species and predatory non-native species may be
exacerbated when crowded into smaller habitats that lack habitat complexity. Bull frogs in the
Carmel River Watershed are likely to cause the greatest problems to California red-legged frog
tadpoles and adults (CRWC 2004). The combined effect of non-native frogs and non-native fish
often leads to extirpation of red-legged frogs (Kiesecker and Blaustein 1998; Lawler, et al. 1999).
While these general impacts have similar effects on both species, other characteristics of the
watershed have consequences specific to steelhead trout or California red-legged frog discussed
in sections 2.4.2.1 and 2.4.2.2.
2.4.2.1
Steelhead Trout
In the short-term, the cumulative impacts to habitats for the steelhead trout will occur in the reach
of the Carmel River from Los Padres and San Clemente dams downstream to the estuary. Table 1,
below, presents habitat assessment information for steelhead in the Carmel River Watershed
(NOAA 2005) and shows that nearly 50% of the available rearing habitat (48.2%) and spawning
habitat (49.2%) occurs above San Clemente Dam.
Table 1.
Total Available Spawning and Rearing Habitat (NOAA 2005)
Below San
Between San
Above Los
Clemente
Clemente Dam and
Padres Dam
Dam
Los Padres Dam
(miles)
(miles)
(miles)
Totals
(% above San
Clemente Dam)
Mainstem spawning
15.4
6.9
3.2
25.5 (39.6%)
Tributary spawning
29.1
18.2
14.9
62.2 (53.2%)
Total spawning
44.5
25.1
18.1
87.7 (49.2%)
Mainstem rearing
18.6
6.9
4.5
30 (38.0%)
Tributary rearing
29.1
18.2
14.9
62.2 (53.2%)
Total rearing
47.7
25.1
19.4
92.2 (48.2%)
42
Access to useable habitat is an issue at the scale of the Carmel River Watershed, including
mainstem and tributaries. Table 2 shows that 73.5% of the potential rearing habitat for the
steelhead of the Carmel River occurs above San Clemente Dam (NOAA 2001).
Table 2.
Potential Rearing Habitat for Steelhead Trout (NOAA 2001)
Total Carmel River
Habitat
Below San Clemente
Dam
Above San Clemente Dam
(% of total)
Tributary rearing
29.1 miles
5.2 miles
23.9 miles (82.1%)
Mainstem rearing
20 miles
7.8 miles
12.2 miles (61.0%)
49.1 miles
13 miles
36.1 miles (73.5%)
Total rearing
Juvenile rearing habitat in the mainstem has been divided into three reaches based on physical
character of the channel, availability of spawning substrate, primary migration impediments and
summer flow regimes (NOAA 2001):
ƒ
Upper Mainstem – above Los Padres Dam and within the Ventana Wilderness area.
ƒ
Middle Mainstem – between Los Padres Dam and San Clemente Dam. Limited gravel
substrate due to trapping of sediments in Los Padres Reservoir. Minimum flow of 5 cfs
exists below Los Padres Dam.
ƒ
Lower Mainstem – below San Clemente Dam. River character controlled by bedrock
outcrops near Paso Hondo Road, with limited gravel substrate due to upstream trapping at
San Clemente and Los Padres.
Surveys of over three million square feet of steelhead rearing habitat completed by MPWMD
(2004) have been used to estimate the following carrying capacities and are summarized in
Table 3.
Table 3.
Total Steelhead Rearing Habitat Carrying Capacity
Downstream of SCD
Between SCD and
LPD
Above LPD
Estimated Total
Carrying Capacity
25%
(61,250 YOY*)
33%
(80,850 YOY*)
42%
(102,900 YOY*)
Mainstem River
Carrying Capacity
34%
(60,200 YOY*)
30%
(52,000 YOY*)
36%
(62,400 YOY*)
1,300,000 square feet
seasonally limited use
based on a 5cfs release
from San Clemente Dam
to Schulte Bridge
763,000 square feet with
seasonally limited use
due to water quality
problems
400,000 square feet =
97% of total stream area
High Quality Rearing
Habitat
* young of year steelhead
43
The majority of quality habitat available for steelhead spawning and rearing occurs above San
Clemente Dam. Sediment accumulation in San Clemente reservoir basin and the current
restrictions on the functional usability of the fish ladder limits access to these areas. Limited flow
releases from Los Padres Dam and large substrate restrict the amount and viability of spawning
habitat and consequently the carrying capacity of the mainstem of the Carmel River.
After emergence from the spawning gravels, steelhead fry collect in small schools and utilize the
margins of streams until they become stronger swimmers. As they grow larger the fry disperse to
other habitat with cover and establish individual territories for feeding and resting. Most
steelhead during their first year of life live in riffles, moving to pools or deep fast runs as they get
larger. Instream cover is important as it provides protection from predators.
The mortality rate for steelhead is highest during the first few months after emergence from the
spawning gravels. The length of time steelhead juveniles remain in freshwater before they
migrate to the ocean varies within and between genetic stocks. Steelhead trout typically spend
between two to three years in freshwater before smolting and migrating to the ocean (Behnke
2002). Studies have shown that development of the smolt stage and seaward migration are
stimulated by environmental factors. Downstream migration is not necessarily related to
smolting. In some streams, steelhead fry are forced to migrate as stream flow and available
habitat decreases. Depending on the environmental conditions, the young juveniles may migrate
to the estuary and live there for some time before entering the ocean The larger the smolt when
it enters the ocean, the better its potential for survival to adulthood.
A concern with the dams upstream has been the reduction in large woody debris moving down
the watershed to the coastal estuary. Large woody debris performs essential ecological functions
for watersheds – they provide organic carbon for cycling into the aquatic food base, they provide
cover for migrating and resident fish, and they provide areas for sediment accumulation and
habitat development. The dams and reservoir seasonally trap this woody material and do not
allow it to migrate downstream. Efforts have been made recently to physically place large woody
debris into the lower Carmel River in order to restore essential habitat and biochemical benefits
(C. Sanders personal communication 2006)
The Southern steelhead stocks found in the Carmel River are winter-run steelhead and typically
spawn from December to May, with peak spawning occurring during the period of January
through March. Some steelheads enter the river fully mature and spawn relatively soon after they
migrate up the river. Other steelheads mature as they enter the Carmel River and do not become
biologically ready to spawn for several months (McEwan and Jackson 1996).
Steelhead that enter the river later tend to spawn in smaller tributaries and further upstream than
do earlier arriving fish. The timing of upstream migrations is often correlated with the occurrence
44
of freshets, with steelhead moving upstream during both the rising and falling stream levels and
ceasing movement during flood peaks. The entry of steelhead into the Carmel River Estuary is
often in association with high tides. Several actions currently limit the successful spawning of
steelhead trout in the Carmel River:
ƒ
Existence of San Clemente and Los Padres dams – fragmenting the river
ƒ
Operation of San Clemente and Los Padres dams – reduced flows for migration and
attraction flows (flows to stimulate upstream migration for spawning)
ƒ
Limited fish passage capability at both dams – poor biological design and limited
capacity to trap and haul fish above the barriers
ƒ
Pumping of the lower Carmel River and seasonal drying up of the lower Carmel River
channel
ƒ
Disrupting the flow and sediment dynamics of the Carmel River Estuary including the
periodic breaching of the bar
ƒ
Barriers to fish passage in tributaries associated with improperly placed culverts and
roads
Based on 1989 surveys, the amount of spawning habitat in the mainstem Carmel River upstream
from the Narrows (river mile 10) totals approximately 120,000 square feet, including 50,000
square feet in the reach from the Narrows upstream to the San Clemente Dam (41% of total),
11,000 square feet from the San Clemente Reservoir to Los Padres Dam (9% of total), and 60,000
square feet above Los Padres Reservoir (50% of total) (MPWMD 2004). Limited returns of adult
steelhead to Los Padres Dam indicate that the issue is not habitat related, but more likely passage
related.
Passage over San Clemente Dam currently is supported by a poorly designed, 68 foot elevation
gain, fish ladder. The ladder is estimated to pass 55% of the adult steelhead population in the
Carmel River (Duffy and Associates, Inc. 2000) however no accuracy assessment has been
done on this estimate. Numerous structural and operational problems exist with the fish ladder,
the primary one being that it is only useable during a very narrow range of river flows. Ladder
flow control, exit conditions at the top of the ladder, periodic sediment clogging, limited
attraction flow capability, and no ability to pass juvenile or adult steelhead downstream renders
the existing fish ladder essentially useless. Modifications to San Clemente Dam in 2006 have
not been in place long enough to evaluate whether improvements will provide more downstream
migration survival of steelhead and subsequent returning adults.
Passage at Los Padres Dam consists of two fish collection station ladders at the base of the dam.
One fish ladder terminates in a holding tank from which adult fish are netted out and transported
above the dam. The second station ladder deposits adult steelhead into a holding tank from which
the fish are moved via a pipe to a truck and subsequently transported above the dam. Neither fish
45
collection station was adequately designed to handle attraction flows. CAW is currently working
on a settlement agreement with NOAA to address Endangered Species Act steelhead ‘take’ issues
at Los Padres Dam (personal communication J. Ambrosius, NMFS 2006). No effort is made to
collect and transport the downstream migrating juveniles.
Juvenile steelhead trout generally remain in freshwater and estuary habitats for 1-3 years in
California and then spend 2-5 years in the ocean. Depending on the flow and water quality
conditions in the Carmel River, juveniles may spend less time in the mainstem and tributaries,
either migrating directly to the ocean or spending additional time in the Carmel River Estuary.
Limited freshwater inflowing to the Carmel River Estuary has lead to fewer cool, deep habitats
preferred by steelhead smolts (personal communication C. Sanders, 2006).
NOAA Fisheries in 2002 proposed a set of bypass instream flow recommendations for steelhead
in the Carmel River. They identified three key seasons for the steelhead:
ƒ
Winter season (December 15-April 14) for adult steelhead attraction, migration and
spawning
ƒ
Spring season (April 15-May 31) for smolt outmigration
ƒ
Summer-Fall season (June 1-December 15) for low flow maintenance
The intent of the NOAA (2002) recommended hydrologic regime is to provide a more natural
flow sequence to attract adults to the Carmel River, provide habitat protection, provide adult and
smolt migration flows, and to protect refugium habitats for holding young steelhead trout in the
mainstem river.
2.4.2.2
California Red-legged Frog
California red-legged frogs (Figure 2-13) have been observed in backwater and off-channel pools
along the Carmel River and its tributaries (EIP Assoc. 1993; Reis 2002, 2003). The preferred
breeding habitats require still water and emergent vegetation (USFWS 2002). Seasonally, the
adult frog moves from the backwaters and pools to riparian and upland areas (USFWS 2002).
The Carmel River Watershed has been identified as an important area for this species. Factors in
the Carmel River Watershed which may limit the population and distribution of California redlegged frogs include:
ƒ
Loss of habitat due to pumping of groundwater
ƒ
Loss of habitat due to channel incision
ƒ
Loss of habitat due to urbanization and development
ƒ
Loss of coastal wetlands due to encroachment of development
46
f i g u r e 2-13
Source: Wildlife Research Photography (B. "Moose" Peterson)
Supplemental Carmel River Watershed Action Plan
California Red-legged Frog
47
ƒ Degraded water quality impacts due to reduced flow regimes on the Carmel River
ƒ Increased non-native predators and loss of native plant species
California red-legged frog habitat has been fragmented in the Carmel River Watershed by both
San Clemente and Los Padres dams. San Clemente Dam is a partial barrier to movement by the
frog resulting in an isolated population existing upstream in the reservoir delta and braided
channel areas. San Clemente Dam effectively prevents tadpoles and adults from dispersing
downstream from upstream locations. While the distribution of California red-legged frogs in
and around Los Padres Reservoir has not been well documented, individuals have been
observed at the upstream end of the reservoir inundation zone (EIP Assoc. 1993; Reis 2002;
Reis 2003). Currently the San Clemente Dam reservoir is drawn down by order of the Division
of Safety of Dams during the spring of each year for safety reasons, which impacts habitats and
likely has negative impacts on any juvenile and adult frogs in the impacted areas. Mitigation
measures include relocating tadpoles and adults to areas where they will not be desiccated
or preyed upon as easily by bullfrogs. CAW is currently working with the USFWS on a
Habitat Conservation Plan to address impacts of dam operations on California red-legged frog
habitat.
Water diversions and pumping in the lower Carmel River can rapidly dewater reaches and
backwaters. Excessive pumping by CAW (18 wells) and private individuals (561 wells) can
dewater important habitats for the frog during the critical summer (August-September) months.
Development of the Carmel River Watershed has resulted in a loss of connection between the
river and its floodplain, and thereby limiting off-channel pool and frog habitat development.
Incising the Carmel River due to limited sediment and reduced flow dynamics, in combination
with bank hardening, has resulted in increased mainstem water velocities in certain reaches and
prevents the use of these areas by California red-legged frogs for egg laying (CRWC 2004).
Amphibians have complex life cycles, which subject them to multiple routes of exposure to
contaminants (USFWS 2002). The Carmel River experiences small, periodic contaminant
inflows of pesticides and herbicides from golf course ponds, sediment catch basins, adjacent
agricultural areas, parking lots, housing developments and other urbanization. In addition to
herbicides and pesticides, mineral fertilizers used on crops, lawns, and golf courses can also
directly impact the frog’s development or survival.
Non-native species can negatively impact native frog populations through direct predation,
occupying habitats, and competition for food. In the Carmel River Watershed bull frogs are
likely to cause the greatest problems to native California red-legged frog tadpoles and adults
(CRWC 2004). Examples of additional non-native, introduced, predators in the Carmel River
48
watershed include crayfish, bass, and mosquito fish.
necessary component of any species recovery plan.
Management of these predators is a
Predation by introduced, non-native, species is a significant factor in the decline of the California
red-legged frog. Of specific concern in the Carmel River Watershed are bullfrog, crayfish, and
fish including mosquito fish (Gambusia affinis) and centrarchids. Changes in quantity and
quality of habitat that are unfavorable to California red-legged frogs tend to be favorable to a
suite of introduced non-native aquatic predators. The interaction between the California redlegged frogs and predatory non-native species may be exacerbated when they are crowded into
smaller habitats that lack habitat complexity. The combined effect of non-native frogs and non
native fish often leads to extirpation of red-legged frogs (Kiesecker and Blaustein 1998, Lawler, et
al. 1999).
In addition to non-native animals, non-native plants threaten the integrity of aquatic ecosystem by
out-competing and replacing native plants, reducing plant diversity. For example, species such as
tamarisk, giant reed, and cape ivy have impacted the viability of native willow-cottonwood
sycamore communities in Central California watersheds. The result is a change in the structure
and function of the riparian corridor and may lead to a loss of surface water due to their increased
transpiration rates (USFWS 2002). Biologists have noted that California red-legged frogs avoid
streams dominated by Eucalyptus (Eucalyptus sp.), possibly due to the release of toxic chemicals
from eucalyptus leaf decomposition (USFWS 2002).
Amphibians are susceptible to pathogens and diseases. Of particular concern to California redlegged frogs is infection from the yeast Candida humicola and chytrid fungus. These pathogens
can be introduced to a watershed from stocked fish and non-native bull frogs and have been
implicated in amphibian die-offs in other parts of the country (Blaustein and Wake 1995).
The level of effects of human induced impacts to the Carmel River Watershed may be exacerbated
by natural factors such as drought, fire and manmade factors associated with mine runoff, runoff
contaminants (pesticides, fertilizers, herbicides, airborne pollutants), and runoff associated with
roads and transportation vehicles (oil, tar, petrochemical products).
49
3. PRINCIPLES FOR A FUNCTIONALLY RESTORED WATERSHED Restoration is defined as reestablishing core aquatic, riparian and upland functions and related
physical, chemical, and biological processes (Cairns 1988; Magnuson, et al. 1979; Lewis 1996).
Restoration differs from habitat creation, reclamation, and rehabilitation in that restoration is an
integral process that goes beyond the isolated manipulation of individual elements (NRC 1992).
Effective restoration requires managing key physical conditions; encouraging biochemical
adjustments to the soil and water; and reestablishing community assemblages and diversity by the
reintroduction of native flora and fauna harmed by human-induced disturbances. Restoration is
most effective when considered at a watershed scale with an understanding of how core
components interact on a regional basis.
The Carmel River Watershed has been manipulated and disturbed by numerous human related
activities, many of which have resulted in large cumulative effects that have significantly altered
the environment. Restoring the Carmel River Watershed requires an understanding of complex
watershed processes and functions, including both human and natural influences and responses.
The vision of a restored Carmel River Watershed described in this document is based on the
understanding that management actions should encourage the river to restore itself through
natural processes. Such actions will lead to a more resilient and sustainable watershed ecosystem.
From a long-term perspective, such a system will impose fewer impacts on human infrastructures,
while benefiting key environmental functions including fish production, wildlife habitat, water
quality, aesthetic values, and recreation.
The key principles essential for restoring a functional watershed include:
ƒ
Watersheds are dynamic, evolving systems comprised of complex physical and
biological interactions. Functional ecosystems depend on maintaining these interactions
so that the processes that regulate desired attributes continue to operate in beneficial
ways. Therefore, restoring key processes, and reconnecting the linkages between key
processes, is an effective method to restore overall watershed functions.
ƒ
The watershed at any time is an expression of its historic processes and
disturbances. As such, future conditions will depend on current conditions and
processes. Restoring critical processes today will ensure a resilient watershed ecosystem
for current and future generations.
ƒ
Natural processes and functions are key contributors to effective watershed
restoration. Management actions that seek to control or force natural processes often
alter the effectiveness of natural processes, and can create unintended negative
consequences to other watershed functions and increases risks. By contrast, those actions
that support natural processes are more effective, and often less costly over time.
50
3.1
ƒ
Watershed components have self-reinforcing functions that maintain certain
“states” until critical thresholds are crossed, at which point they evolve to a new
state. For example, a river channel can sustain a meandering profile over time. If
sufficient amounts of sediment are delivered to the channel, it can transition to a braided
river without meanders, a structure it can retain long after the sediment supply is reduced
to pre-disturbance levels. Typically, there is a range of tolerances for watershed
functions that support a sustainable ecosystem as well as a sustainable human
infrastructure. Restoration is more achievable with less intervention before threshold
responses occur. New states may result in watershed responses that are no longer
compatible with human needs. Maintaining and restoring key processes can maintain
existing stabile states, which support human and ecosystem needs. Ultimately, when the
range of conditions exceeds the capacity of the watershed for a prolonged period,
watershed integrity begins to degrade, resulting in increased costs (and risks) to human
infrastructure.
ƒ
Watershed processes occur in four dimensions: the longitudinal (upstream to
downstream), lateral (hillslope to floodplain to channel) and vertical (groundwater
to surface water), and temporal. Given the dynamic connectedness of a watershed,
poor management practices and other activities can fragment and disconnect riparian and
aquatic habitats and the species that they support. Instream conditions are largely
determined by processes that occur within the watershed and cannot be isolated or
manipulated independently without other consequences.
INTEGRATING HUMAN INFRASTRUCTURE WITH ECOSYSTEMS
A functional Carmel River Watershed requires that the human infrastructure be aligned with
ecosystem processes and functions. Such alignment can reduce maintenance costs, avoid failure,
and improve function. The existing human infrastructure is a major component of the watershed,
and improvements to the design, function and location of such features can have major benefits.
Homes may be located in flood-prone or erosional landscapes. Bridges and culverts may be
designed for flow conditions that are altered due to development (or are likely to change in the
future in response to climate changes). Static flood management features (levees, barriers,
revetments) gradually degrade over time, or fail to respond to natural watershed change. These
are all examples of infrastructure that directly interact with natural ecosystem processes.
When the human infrastructure is designed and managed in alignment with natural ecosystem
processes and functions, it can be maintained with lower costs, greater benefit, and fewer
resources. This report recommends key infrastructure improvements (see Section 4) that can
provide significant public benefits and reduce adverse impacts. The primary objective is to
improve the compatibility of human infrastructure with natural processes and functions. This will
better support a resilient and sustainable ecosystem that in turn provides a resilient and
sustainable human presence.
51
4. RECOMMENDED ACTIONS
Restoring and maintaining the Carmel River Watershed and habitats will best be accomplished
using a long-term, watershed-scale, ecosystem-based approach and strategy. Years of ecosystem
impacts from dams, groundwater pumping, riparian area encroachment and increased watershed
erosion have produced major impacts. Restoring ecosystem function will occur over a period of
years to decades. Successful watershed restoration will require that all stakeholders and groups
collaborate on a watershed basis to identify and prioritize activities and actions.
Ecosystem-based management integrates an understanding of watershed dynamics, ecosystem
and species seasonal requirements, management opportunities and constraints, infrastructure
constraints and administrative/legal (regulatory) obligations. The river habitat exists as an
ecological continuum from headwaters to the coastal estuary, even though the land-use is divided
into distinct units. Protection, management and restoration of important ecosystem functions and
habitats require a strategically coordinated and prioritized plan for the future.
The authors of this report have identified four major Action Items that need to be addressed to
restore the function of the Carmel River Watershed:
I.
II.
III.
IV.
Reduce Pumping from the Riparian Aquifer
Remove San Clemente Dam
Develop a Sediment Management Strategy for Post-Dam Conditions
Integrate Solutions into a Carmel River Watershed Restoration Program
These are each discussed in detail below.
4.1
REDUCE PUMPING FROM THE RIPARIAN AQUIFER
Groundwater pumping of the streamside aquifer by CAW and many private landowners has
affected the channel environment between about river mile 3 and river mile 15. Impacts of
pumping activities have been well-documented (Kondolf and Curry 1986; SWRCB 1995).
Pumping lowers the subsurface water table near the river, resulting in a dry channel during the
summer, dead streamside vegetation, stream banks prone to erosion, and disruption of the fresh
water flow regime to the estuary. Noticeable loss of streamside vegetation began in the 1960s,
and has intensified during drought periods since that time.
Recent efforts by local landowners have tried to mitigate for subsurface water withdrawals by
irrigating streamside vegetation during the dry season. This can provide short-term support to
streamside vegetation communities, however, the loss of natural draw-down processes can affect
germination and regeneration of individual tree and shrub species (Malanson 1993), limiting the
52
long-term success of this strategy. Groundwater withdrawals reduce flows to all downstream
habitats, including the estuary.
4.1.1
State Water Resources Control Board Order WR 95-10 and CAW Pumping
Recommended Action: Discontinue riparian groundwater withdrawals in accordance with
State Water Resources Control Board Order WR 95-10.
The negative impacts of CAW groundwater extraction from the streamside aquifer are
considerable, and have been recognized by regulatory agencies. In 1995 the State Water
Resources Control Board (SWRCB) issued Order WR 95-10. This order requires CAW to reduce
pumping from the streamside aquifer by 10,730 acre feet per year and to find alternative supplies
of water.
4.1.2
Private Pumping
Recommended Action: Compile a complete inventory and assessment of pumping impacts
of the private wells to determine the restoration potential of the Carmel River aquifer.
A growing concern is the increasing impacts associated with groundwater withdrawal from
private wells. In recent years, riparian groundwater pumping by private parties adjacent to the
river has begun to approach or exceed the volume of groundwater extracted by CAW. This has
amplified the problem, and suggests the need for a more collaborative solution. If substantial
withdrawals are affecting the recharge rate of the aquifer, additional watershed management
actions may need to be developed.
4.1.3
Benefits of Discontinuing Riparian Groundwater Pumping
Recovery of the Carmel River aquifer will lead to an increase in the volume of water in the sub
surface (hyporheic) and surface Carmel River system. Increasing the volume of water flows
during the summer months coupled with restoring the physical processes of the Carmel River as
described in this report will restore the dynamic nature of the river ecosystem and improve the
function of the riparian, wetland, and aquatic systems to be self-sustaining. Specific benefits
include:
Restored riparian ecology and channel bank stability. Improved riparian and riverine
integrity will allow the Carmel River ecosystem to recover and sustain itself. Functional riparian
habitats are a combination of soil, grasses, nutrients, shrubs, leaf litter, and many other
components that support the more visible vegetation, aquatic species, and wildlife. An
appropriate seasonal flow regime is critical to the survival and sustenance of the streamside zone.
Increasing summer water flows in the river in a timely manner and with the proper constituents
53
(sediments, nutrients, minerals) will begin to transform the streamside to become more complex,
increasing its productivity, function and ability to withstand and recover from extreme events. A
healthy streamside community supports insects, amphibians, reptiles, avifauna, and mammals,
and through riparian shading and nutrient cycling, the streamside community provides critical
energy input to the aquatic ecosystem.
Increased instream flows. Reduced groundwater pumping in the Carmel River aquifer will
restore the low flow regime in the river during the dry summer months. Instream flows provide
essential water for fish, amphibians, and the insects that they feed on. Instream flows also
maintain a water table near the surface which supports riparian vegetation that stabilizes channel
banks. Optimizing instream flows must consider the timing of flows, frequency and duration of
high and low flows, and the channel shaping flows that define the river channel and associated
habitats.
Restored subsurface flows. Restoring surface flows and ground water levels will allow the
subsurface (hyporheic) zone to stabilize and provide escape and development habitat for insects
and small fish, capture and cycle nutrients, and improve ecological stability of the Carmel River
aquatic system.
Insect productivity. Many insects spend a significant portion of their lives in stream
environments, and provide an essential food source for fish, amphibians, birds, and other species.
Without flows, insect communities decline in diversity and may be completely lost. Improving
water flows, decreasing water temperatures, and improvement of water table conditions will
support a larger diversity and abundance of insects. This will benefit steelhead, aquatic species,
birds and overall ecosystem dynamics.
Estuary water supply and quality. Restoring flows during the summer months in the Carmel
River will provide more freshwater to the estuary. Increased freshwater dilutes the effects of salt
water intrusion during the low flow months and improves the overall aquatic conditions for
steelhead, California red-legged frogs and associated species. Improving the flow of water to the
estuary will aid in providing more biologically acceptable water quality conditions that will
benefit the ecosystem.
4.2
REMOVE SAN CLEMENTE DAM
San Clemente Dam is functionally obsolete, and seismically unstable according to the California
Division of Safety of Dams. Environmental studies have concluded that the dam negatively
impacts both upstream and downstream habitats for a variety of species. Alternatives to address
the dam have been discussed over the past decade. This report describes some of the benefits of dam
removal and recommends important strategies for restoration of the watershed. Assessments regarding
54
retaining or removing the existing sediment stored behind the dam should be accomplished
before any action is undertaken..
Recent evaluations by the H. John Heinz Center (2002), the Aspen Institute (2002), and the
World Commission on Dams (2000) have identified dam removal as an effective strategy for
restoring a functional river system when carefully designed and managed. The dam structure can
and should be removed in a manner and sequence that supports both ecosystem and human needs.
Large dam removal is a relatively new undertaking (but one that is eventually inevitable for
virtually all dams), and a number of key questions must be addressed during detailed technical
studies and design for post-dam mitigation. Despite the questions however, it is clear that there
are many public benefits that will occur with dam removal. These include:
ƒ
More sustainable hydrological and sediment functions and processes
ƒ
Eliminate hazard of dam failure
ƒ
Eliminate long-term management/maintenance of the dam structure
ƒ
Recovery of steelhead access to habitats below Los Padres Dam
ƒ
Fish and wildlife habitat improvements
ƒ
Restored connectivity between the lower Carmel River and floodplain
Failure to remove the dam will require a commitment to maintain an obsolete, damaging and
dangerous facility in perpetuity. A proper evaluation of project costs must recognize the benefits
of removal versus the initial costs and implications of burdening all future generations with
management and maintenance of this obsolete facility.
4.2.1
Essential Components for Post-Dam Site Design and Management
Recommended Action: Focus on alternatives for removing San Clemente Dam that
sequester the large amount of sediment stored behind the dam structure and provides
sustainable solutions to long-term river channel effects.
The draft EIS/EIR (Entrix/CAW 2006) river re-route alternative offers several compelling advantages
that are both cost-effective and can support a good eco-geomorphic recovery of the dam site.
There are two primary areas that will be affected by removal of San Clemente Dam:
1. The dam site, associated reservoir and delta deposits. Removing the dam will require
a restoration design plan that accommodates a sustainable, safe and resilient
55
reconfiguration of the river and associated habitats. Approaches to address this issue will
be discussed in Section 4.2.
2. Downstream river channel effects. The return of natural sediment supplies downstream
of the dam will require careful analysis and design to ensure proper river management
that will minimize risks to downstream human infrastructure, maintain important aquatic
and riparian habitats, and preserve water quality. Approaches to address this issue will be
discussed in Section 4.3.
Dam removal requires a planned and strategic approach that protects both the downstream human
infrastructure and the natural environment. A comprehensive dam removal plan provides the
opportunity to restore aquatic habitats, create a dynamic, productive streamside corridor and
reduce the long-term risk from flooding and infrastructure failure.
The removal of San Clemente Dam is expected to increase sediment transport downstream both
immediately following dam removal (when some of the sediment behind the dam will likely be
mobilized and transported downstream) and under longer term (equilibrium) conditions, when the
expected sediment load will be higher. Some filling of the Carmel River Estuary with sediment
could occur. However if the natural flow regime of the river is maintained, it would be expected
that the estuary morphology would remain in dynamic equilibrium consistent with its likely
performance pre-dam.
4.2.1.1
Criteria for On-site Restoration – An Eco-Geomorphic Approach
A proper design for restoring the Carmel River and San Clemente Creek upon removal of the dam
will be a major component of the watershed restoration plan. Dam removal will require that the
channels immediately above the dam are reconfigured to provide a stable and functional river
environment for many decades following removal of the dam structure.
Any design for restoring the dam site should meet the following criteria:
ƒ Safety. The design should ensure that the risk of catastrophic failure is low, either
through fail-safe designs (those that resist failure), or safe-fail design (those that
accommodate small changes over time so that impacts are functionally invisible).
ƒ Resilient. The design will need to function in perpetuity, with little or no management or
maintenance requirements. Designs that can persist for thousands of years are more
desirable than those that will need to be maintained by future generations.
ƒ Cost-Effective. The design should be consistent with economic and social costs of more
structural solutions.
ƒ Robust Technical Basis for Design. Large dam removal projects are a relatively new
undertaking, and few models exist to guide proper designs. Therefore, the technical basis
for design must be based on a detailed and thorough analysis of existing science and
56
engineering strategies to reduce the risk of design failure, and anticipate necessary
management actions.
ƒ Geomorphically Stable. The design must ensure that natural channel adjustments that
will inevitably follow dam removal can be accommodated by the river network without
imposing risks to downstream resources or to the ecological and geomorphic integrity of
the restored design. The design must address long-term (e.g., decadal to century-scale)
changes associated with channel grade adjustments, lateral channel migration potential,
sediment entrainment, bank stability, groundwater conditions, habitat establishment and
maintenance, and the return of natural sediment supply conditions. Given the timescale,
such designs must rely more on natural river processes and less on structural controls.
The design should anticipate landscape-scale changes that are likely to occur in the area
impacted by the dam, including both immediately downstream, as well as the upstream
extent of the existing sediment delta above the dam.
ƒ Biologically Rich Habitat. The design should ensure that a biologically rich habitat
landscape exists at the site, both upstream and downstream. There are opportunities to
integrate habitat complexes within the restoration design while also meeting the other
objectives outlined. By providing rich habitat features, the design can meet regulatory
mitigation requirements, and aid in long-term recovery of the site.
ƒ Ecologically Dynamic. The design should establish varied micro-habitat features that
support the ability for the site to respond to changing conditions over decades to
centuries. Such dynamic responses will help to regulate changes over time, minimizing
long-term impacts while ensuring that natural recovery can be supported.
ƒ Encourages Natural Recovery. The design must ensure that important factors that
support natural recovery are provided. For example, water should be routed to wetlands,
floodplains and groundwater areas so that they can support long-term recovery processes.
Sediments should be distributed (not concentrated) over the landscape in a manner that
creates ecological diversity, reduced risk of erosion, and dynamic (e.g., responsive)
landforms.
Together, these criteria help to describe an eco-geomorphic approach to restoration that can
improve ecological values of the site, provide a more functional river environment, retain existing
sediments behind the dam, and mitigate negative impacts associated with the return of natural
sediment supplies. The design for the dam site should incorporate these types of strategies that
provide significant improvements over purely structural approaches.
4.2.1.2
On-site Sediment Storage
Recommended Action: Develop conceptual eco-geomorphic approaches for
sequestering reservoir sediments that can be incorporated early in the design
process.
An eco-geomorphic design approach works by encouraging ecological and geomorphic processes
to manage the river response to dam removal. It can be done within a rigorously designed
57
engineering framework. An eco-geomorphic approach provides sustainable and ecologically
resilient strategies to control sediment in a sustainable manner (see, e.g., Figure 4-1).
Removing San Clemente Dam and retaining the sediments in place offers many benefits to human
infrastructure and the river environment. When combined with a design for restoration that is
ecologically and geomorphically robust, an on-site sediment management strategy provides
habitats for fish and wildlife, helps control the natural channel evolution following dam removal,
and regulates the natural supply of sediment reaching the lower river. Such benefits can be
designed to reduce risk and be cost-effective.
Physical, biological and ecological processes strongly influence the trend of landscape patterns
over a period of decades to centuries. An eco-geomorphic approach to restoration design
recognizes and supports these processes so that they can naturally sustain channel and riparian
evolution in ways that serve human needs and natural communities.
An eco-geomorphic approach seeks the right balance between ecological and structural resilience.
Structural resilience is defined as the time it takes to return to a stable state following natural
disturbances. Designs that rely on structural resilience tend to resist change, so failures tend to be
large and potentially catastrophic. Ecological resilience is defined as the amount of disturbance
that a system can tolerate without changing the natural, self-organized processes and structures
that maintain its natural state. Ecological resilience recognizes that many naturally stable states
are possible, and designs can support more than one stable condition. Designs that rely on
ecological resilience tend to change often, but changes tend to be small, and are absorbed by the
system. Such frequent but small changes actually improve the long-term stability of the system
while creating diversity and connectivity among micro-habitats.
For example, one approach to store some sediment could be to use a series of small flood terraces
integrated into existing landforms along the Carmel River and/or San Clemente Creek. The
landforms could be stabilized using biotechnical stabilization techniques, combined with risk
strategies that consider the location of the river relative to storage sites. The shape, size and
distribution of the landforms would be consistent with natural river terrace deposits that often
persist for thousands of years in undisturbed environments.
4.2.1.3
By-pass Channel Design
Recommended Action: Develop conceptual eco-geomorphic approaches for re
routing the river channel that can be incorporated early in the design process.
Channel instabilities can significantly increase the risk to downstream landowners by entraining
large amounts of sediment currently stored in the reservoir’s delta deposits. The San Clemente
Creek branch of the river re-route alternative poses design challenges that will need to be
58
Notes: Functional floodplain traps and stores sediments at rates
similar to natural vegetation succession, allowing the vegetation
community to provide dynamic sediment storage functions that can
respond to natural channel adjustments and changes over time.
f i g u r e 4-1
Supplemental Carmel River Watershed Action Plan
Stored Alluvial Sediment Integrated with Eco-geomorphically Functional Conditions
59
addressed to reduce the risk of channel instability. For example, San Clemente Creek has
evolved to accommodate a smaller supporting watershed than existed historically. River
adjustment to a larger watershed, with increased flows and sediment while retaining some
ecological and geomorphic stability of a smaller channel, will be critical to the long-term stability
of the design. This will require correctly sizing the channel width, depth, slope, bed materials,
and shape to ensure both stability of the channel and long-term fish passage capacity (Figure 4-2).
For example, headcuts are common responses to dam removal. Headcuts are upstream-migrating
knickpoints in the longitudinal river profile that form in response to hydraulic or geomorphic
instabilities in the river profile. Headcuts can cause channels to incise, resulting in bank
instability, increased sediment supply, and increased flood impacts. Headcut responses in
reservoir deposits can be designed using a combination of hydraulic design parameters,
geomorphic structures, and planform configuration features that are designed to sustain a viable
low-flow channel and a large flood condition.
4.2.1.4
Monitoring and Adaptive Management
Recommended Action: Implement a well-designed adaptive management strategy
that monitors and manages the response to key watershed actions.
Currently available computer models cannot accurately predict the sediment transport conditions
following dam removal. Complex interactions exist between gravel transport, transport of fines,
infiltration of fines into the channel bed, changes in local sediment size distributions, channel
depositional patterns, and other factors that affect the fate of sediment in the channel following
dam removal. It is therefore essential that a long-term monitoring and adaptive management
program be developed that can respond in real-time to changes in the channel profile that may
cause undesired impacts. The adaptive management program should develop working scientific
hypotheses and models that can be tested, calibrated, and validated by detailed monitoring data.
This will not only provide the opportunity to better manage the Carmel River, but will also be
essential to improve the science for future dam removal projects at other sites. More information
about implementing effective adaptive management systems is discussed in Appendix D.
4.2.2
Benefits of Dam Removal with Eco-Geomorphic Restoration
The benefits of removing San Clemente Dam are numerous. The list described below focuses on
benefits that support ecosystem and natural river functions that are important to the Carmel River
Watershed. We recognize that there are many other potential benefits affecting social, economic
and political interests, but these are beyond the scope of this report. Some of the more important
ecosystem benefits include:
60
f i g u r e 4-2
Source: PWA
Supplemental Carmel River Watershed Action Plan
Example of Functional Geomorphic Channel Design
61
ƒ
Sediments are naturally released back into the watershed over the course of centuries, at
a rate that supports natural rates of channel adjustment, geomorphic response, management of
downstream flood risks and provides benefits for the channel integrity and habitat
complexity.
ƒ Preserve existing high-quality California red-legged frog habitats.
Existing
California red-legged frog habitats above San Clemente Dam provide an excellent refuge
that has allowed the federally threatened frog to prosper in recent years. Removing San
Clemente Dam will help restore historic amphibian populations downstream by allowing
the processes that naturally form and maintain wetland and floodplain habitats. Removal
of San Clemente Dam will impact upstream red-legged frog habitats that have formed on
the sediment delta of the reservoir unless an eco-geomorphic approach is used to ensure
that their habitats can be protected until other habitats can be reestablished downstream
following dam removal.
ƒ Dam site maintenance decreases over time. An eco-geomorphic design approach to
manage the existing sediment behind the dam structure would minimize the use of
hardened engineered structures to hold back sediment, focusing such structures to those
locations / conditions where other measures are not feasible. Hard structures create
additional (and often unintended) impacts, and require long-term maintenance as
weathering processes and natural disturbances act to degrade the structural integrity over
time.
ƒ Restore steelhead access and habitats. Removing San Clemente Dam will immediately
allow steelhead access to watershed habitats above the dam, expanding the total amount
of habitat available for spawning, rearing, and over wintering by 9 times. A diversity of
habitat types is essential to the long-term survival and maintenance of the genetic
integrity of the species. Access to the continuum of habitats from headwaters to the
ocean will support individual fish to be healthier, resulting in improved survival and
reproduction. Dam removal will improve other efforts to restore steelhead habitats by
restoring the function, form and process that supports the creation and maintenance of
natural habitats.
ƒ Restore connectivity of habitats. Removing the dam will restore the connectivity of the
lower Carmel River to tributaries and headwater streams for the benefit of many other
species. The existing dam structure acts as a barrier to passage for a number of species of
plant and animals. Existing habitats have been fragmented and their functionality
reduced by the presence of the dam. Restoring the dynamic nature of the Carmel River
will allow the natural riverine and geomorphic processes to restore and support the
continual presence of important ecological and geomorphic processes that are affected by
the existence of the dam (Figure 4-3).
ƒ Restore the resilience of the Carmel River. Restoring a more natural hydrologic and
sediment regime in the Carmel River will provide the physical and ecological processes
that naturally create and sustain viable habitats and species throughout the river corridor,
including the estuary. For example, streamside vegetation communities along the Carmel
River will be revitalized by processes that encourage germination of seeds, distribution of
nutrients and sedimentary substrates, and distributed water.
62
f i g u r e 4-3
Source: PWA
Supplemental Carmel River Watershed Action Plan
Eco-geomorphic Design Incorporates Channel, Floodplain, and Vegetation Components
63
4.3
ƒ
Sediment supply to rivers and beaches. Removal of San Clemente Dam will restore
delivery of sand to the beaches served by the Carmel River. Beach sands are constantly
moved by ocean waves. Over time, waves and other processes move sand from the
beaches into the deep offshore shelf. Without a regular supply of new sand from rivers,
beach sands can be depleted, increasing erosion along coastal bluffs and reducing the size
and protective ability of the beach.
ƒ
Failure risk. Potential dam failure imposes risks on downstream communities. Leaving
San Clemente Dam in place only delays the need to ultimately remove the structure, and
may shift responsibility for removal onto the local community. Long-term ownership of
liabilities like a non-functional San Clemente Dam is a major consideration. We
recommend resolving this issue now, rather than leaving it to future generations.
DEVELOP A SEDIMENT MANAGEMENT STRATEGY FOR POST-DAM
CONDITIONS
Sediment management along the Carmel River will be crucial over the next few decades.
Whether the dam is removed or strengthened, natural sediment supply to the river downstream of
the dam will be restored for the first time in over 85 years. Most of the human development in
the lower Carmel River has occurred under a river regime where virtually all the natural sediment
supply between San Clemente and Los Padres dams was trapped by San Clemente Dam. The
Carmel River channel, floodplain and estuary environment have adjusted to this artificially low
sediment supply. As natural supplies of sediment return, the watershed will respond in various
ways, including potentially adjusting the shape of the channel and its connection to the
floodplain.
Estimates of the long-term annual sediment supply between Los Padres and San Clemente range
from 5 to 21 ac-ft/year (Moffatt & Nichol Engineers 1996; Matthews 1989). Sediment
supplies during infrequent events (e.g., fires and landslides) have delivered an average of 90
ac-ft/year for several years following these events. Increasing sand loads to armored gravel
river channels like the lower Carmel River can significantly increase the sand content of the
river bed and the mobility of gravel fractions which can lead to bed degradation and
preferential evacuation of these sediments from the river. These effects of dam removal
deserve detailed study for the Carmel River.
River and floodplain changes can impact human infrastructures unless actions are taken to
manage the return of a natural sediment supply. Sediment management is a watershed-scale
issue, and watershed-scale solutions will be needed to manage changes and avoid undesired
impacts. Because the indirect sediment impacts of dam removal are likely to fall outside any
direct regulatory responsibility by CAW, responsibility for managing the downstream effects will
need to be managed by other entities or agencies.
64
Elements of an effective sediment management plan will:
ƒ Integrate the on-site design into management of downstream sediment impacts in a
manner that supports a sustainable, resilient river channel that is functional and
ecologically beneficial.
ƒ Identify the impacts and risks from sediment increases on flood hazards, and develop
appropriate response strategies.
ƒ Establish an integrated system of eco-geomorphic and structural controls throughout the
watershed that help manage the supply and distribution of sediment.
ƒ Identify and design appropriate wetland stabilization above San Clemente Dam to protect
existing high-quality California red-legged frog habitats.
4.3.1
Evaluating Impacts from Changing Sediment Supplies
Recommended Action: Evaluate the downstream hydraulic and geomorphic impacts
from a range of possible future post-dam conditions so that risks and solutions can
be appropriately identified and managed.
The existing infrastructure in the lower Carmel River Watershed has been built during a period of
artificially low and unsustainable sediment supply. Regardless of the approach to dam
stabilization, higher rates of sediment will be delivered below San Clemente over the next several
decades. Understanding how the river system will recover from the return of a natural sediment
supply will help ensure that appropriate infrastructure improvements and/or mitigations for San
Clemente Dam removal are developed. This task should build on existing studies by evaluating
the areas of potential downstream impacts, and developing strategies to address these impacts.
Natural background sediment transport rates are higher than what has been experienced since the
dam was constructed. The historical record describes infrequent, but large sedimentation events
upstream of the dam. Some of the most severe events were associated with fire impacts. Similar
events will reoccur in the future, and will deliver large amounts of sediment to the lower Carmel
River, even if the existing sediments are sequestered. Significant downstream changes to the
river system may occur over time as natural background sedimentation returns to the lower
watershed (Figure 4-4). It is important to understand how and where these changes will occur so
that appropriate actions can be developed.
For example, during the winter storms of 1983, approximately 150,000 cubic yards of sediment
were trapped behind San Clemente Dam. During this same year, a similar amount of sediment
entered the river from Tularcitos Creek, causing significant changes in the river morphology,
including damage to over two miles of steelhead habitat (Matthews 1983). Had the sediment not
been trapped above the dam, it would have been delivered to the lower Carmel River, where it
65
f i g u r e 4-4
Source: Big Sur Land Trust
Supplemental Carmel River Watershed Action Plan
Notes: Existing floodplain functions must be managed to address
likely river response to dam removal and cessation of pumping.
Existing Floodplain Functions
66
would have increased the sediment load by approximately 79%, greatly increasing the impacts in
the lower river. When a similar event occurs in the future (e.g., after the dam is removed or after
the reservoir is filled), the sediment load is likely to result in a significant geomorphic response to
the channel and surrounding streamside areas. Evidence from similar natural processes in other
landscapes, suggests that the possible geomorphic response could include channel filling, re
routing the existing channel, additional flooding, a long-term sediment wave, or formation of new
channels.
Sediment transport models developed to address dam removal alternatives cannot adequately
characterize the downstream geomorphic response of the river. Prior sediment transport models
below San Clemente Dam (e.g., Mussetter Engineering 2003) were focused on evaluating the
alternatives for various forms of sediment releases associated with the reservoir sediments. These
models necessarily made simplifying assumptions that addressed comparisons between dam
removal alternatives. However, these modeling efforts did not evaluate the full range of potential
impacts associated with increased background sedimentation. Alternative models or model
modifications, combined with a detailed geomorphic analysis, will identify potential responses to
the new watershed configurations and possible solutions.
This study should build on existing modeling efforts with a focus on evaluating likely and worstcase scenarios that support flood management, infrastructure improvements, and land-use
considerations. The study is necessary to develop solutions for the return of natural sediment
supplies, and is necessary regardless of the decision related to San Clemente Dam. Some of the
questions this effort should address include:
ƒ Descriptions of how sediment will move through the reconfigured delta and by-pass
channel (assuming the dam is removed)
ƒ Long-term sediment transport conditions in the downstream reaches
ƒ Worst-case scenarios associated with flooding
ƒ Potential alternatives for in-channel storage sites (see, e.g., Figure 4-5)
ƒ Potential alternatives for integrated flood management approaches to mitigate potential
channel changes
4.3.2
An Integrated System of Sediment and Runoff Management Controls
Recommended Action: Key agencies and land-use managers should develop and
implement an Integrated River Management Plan that integrates sediment
management controls and flood management strategies.
67
fi g u r e 4-5
Supplemental Carmel River Watershed Action Plan
In-channel Structures Designed to Hold Channel Integrity and Provide Sediment Storage
68
Managing the changing river environment will require detailed attention to the changes the
Carmel River will experience, and the effects on existing human infrastructure and land-use
practices. It will involve developing design approaches at a watershed-scale, using the strategies
described in this report. We envision a strategy that manages sediment and runoff processes
throughout the watershed, including sources (e.g., hillslopes and floodplains), transport corridors
(channels, culverts and pipes), and sinks (ponds, wetlands, floodplains, estuary, ocean, reservoirs,
channel bed, etc).
Modern strategies to manage flood risks along river corridors utilize integrated management
strategies. Unlike prior methods that focused on flood management using in-stream structural
approaches, integrated management strategies combine in-stream structures, land-use controls,
runoff management, river restoration and erosion control systems. Integrated strategies consider
the complete water cycle and natural river processes. These include water quality, water quantity
and the processes that control erosion, deposition and river function. Such strategies recognize
that water and sediment sources come from both upstream and upslope sources. By integrating
hillslope runoff controls, in-stream structures, watershed stabilization and other features,
watershed managers can more effectively manage river and flood impacts.
The ability to accurately predict channel changes is limited. Uncertainty associated with storm
timing, climate effects, global climate changes, major disturbances (e.g., fires), and other factors
limit the ability to forecast sediment supply and associated channel changes. Therefore, it is
necessary to actively manage river conditions during the period of adjustment associated with
recovery of natural sediment supplies from above San Clemente Dam. Strategies that utilize
adaptive management can be especially beneficial.
A strategy that integrates management of these areas will be more effective than managing the
river in isolation. Elements of an integrated sediment management strategy should include:
ƒ
Sediment Source Controls – the volume of sediment deposition in the lower river is
directly related to the supply of sediment delivered to the river. Where sediment supplies
are high relative to the river’s transport capacity, channel adjustments can result in
increased flooding. Therefore, managing the supply of sediment can reduce river impacts
in the lower Carmel River. Examples include best management practice strategies,
sediment traps, road sediment management, etc.
ƒ
Transport Controls – sediment delivered to the river environment becomes part of the
river channel and floodplain. Rivers naturally process sediment by creating floodplains
and sand/gravel bars. Sediment is transported through the river network based on the size
of sediment and the characteristics of river flows. Geomorphic investigations, hydraulic
models, and source investigations can help to identify the likely fate of sediment in the
river environment. A sediment management plan and an integrated system of sediment
controls can help to regulate the transport through critical channel reaches. Controls
69
could include managing the channel shape, improving connectivity between the channel
and floodplain, and managed flows.
ƒ
Deposition Controls – sediment deposition occurs in response to physical processes that
occur in the channel during storms. River management actions can be taken to help
encourage deposition in preferred landscapes. Controls could therefore include targeting
depositional landscapes along the river corridor that support deposition without risking
existing infrastructure.
ƒ
Runoff Management – directing flows to store rainfall on hillslopes and floodplains can
reduce the transport capacity of the river during floods, and can affect the length of time
that rivers can transport sediment. Strategies that encourage infiltration are preferred
over strategies that route the water off the slopes as fast as possible.
This Integrated River Management Plan can be part of the overall Watershed Restoration
Program (see Section 4.4), but would focus on coordinating specific sediment and runoff
management controls. It would evaluate sources, depositional areas and transport zones for
sediment to effectively manage sediment supply and deposition as it affects flood risks and river
functions. This will assist resource managers in determining appropriate actions that will be
necessary to protect and restore specific habitats for aquatic and riparian species. The Carmel River
Watershed Assessment and Action Plan (2004) identified a number of sources and treatment
opportunities, and could provide key information for the Integrated River Management Plan.
4.3.3
Benefits of Sediment Management Actions
The approach outlined above will have a number of significant benefits to the Carmel River
Watershed. Some of these include:
ƒ
Flood risks are properly managed; The changes that will occur in the river over time
will be well understood and can be anticipated more effectively, providing managers the
opportunity to respond effectively to minimize impacts and to strategically address
infrastructures concerns such as home/property protection, bridges, roads, and culverts.
ƒ
Existing infrastructure functions are retained; Much of the existing infrastructure
was designed using historical channel patterns and processes. As these river processes
and patterns change, the existing infrastructure may need to be modified to retain full
function. The sediment management actions described here are intended to provide
timely information needed to maintain the function of these systems.
ƒ
Ecological productivity throughout the river corridor is greatly enhanced, providing
habitat for frogs, fish, birds and plants, while natural restoration processes are evolving.
The loss of existing habitats will be monitored and minimized until new habitats are
developed and available. Short-term impacts to steelhead spawning and rearing habitats
may occur but under proper management, the risks can be reduced and impacts
minimized.
70
4.4
INTEGRATE SOLUTIONS INTO A CARMEL RIVER WATERSHED
RESTORATION PROGRAM
Sustainable river ecosystems are dependent on maintaining and supporting a complex suite of
habitats for species. Many habitats are formed by the processes that scour, move and deposit
river sediments (Figure 4-6). Presently the Carmel River is ecologically compromised by the
combined effects of San Clemente Dam, Los Padres Dam, water diversions, road culverts,
bridges, channel migration constraints, groundwater pumping in the lower Carmel River, and the
management of the sand bar at the mouth of the river.
The Watershed Restoration Program (Figure 4-7) will identify and manage significant changes to
the river that can be expected to occur in response to the actions described in this report. Aquifer
management will change flows and riparian conditions in the lower river. Removing San
Clemente Dam will result in an adjustment period that may last several years to decades. The
return of natural sediment supplies to the river below San Clemente will have impacts on the
Carmel River, not all of which can be accurately anticipated. Various direct and indirect habitat
restoration actions also have the potential to change river functions. Program will address dam
impacts of Los Padres dam and identify key issues that could be addressed in a watershed
restoration plan.
Many of these changes are complex, and accurately addressing impacts will require careful
management. Effective management will benefit by specific and detailed knowledge, a wellstructured scientific understanding of the watershed, and integrated collaboration with agencies
and landowners. With a strong program of monitoring and response (adaptive management),
issues can be resolved in advance and the risk of failures will be significantly reduced.
Successful watershed-scale management efforts use scientific methods and principles to gather
the critical information and knowledge that support good decisions.
A Watershed
Restoration Program would provide the analysis and management systems necessary to
effectively manage the Carmel River at a watershed scale. The program should bring scientific
understanding of watershed and ecosystem processes into effective watershed-scale management
of the Carmel River.
The Watershed Restoration Program will build on several existing efforts, including the Carmel
River Watershed Assessment and Action Plan (CWRC 2005), the existing and future water
supply constraints, existing scientific studies, constraints associated with aquifer withdrawals,
and the decisions associated with San Clemente Dam removal and management of Los Padres
Dam. It will integrate these and other efforts to develop strategic approaches that guide
management as watershed conditions change in the coming years and decades.
71
f i g u r e 4-6
Supplemental Carmel River Watershed Action Plan
Linkages between Key Watershed Processes Supports
the Need for an Integrated Management Solution
72
f i g u r e 4-7
Supplemental Carmel River Watershed Action Plan
Components of an Integrated Watershed Restoration Program
73
4.4.1
Purpose
The purpose of the Watershed Restoration Program is to provide the implementation structure
needed to achieve several of the goals articulated in this report. The Watershed Restoration
Program will:
™ ™ ™ Provide an integrated scientific and management organization that can identify
problems, set priorities, find solutions, and track progress. The program can take a lead role
in identifying lead agencies for various projects, establishing funding, provide staffing and
other resources, and ensure effective accountability.
Facilitate collaboration and coordination among stakeholders. The success of the
program will depend on the cooperation of many agencies, entities, landowners, and other
stakeholders. The program will promote an integrated approach throughout the watershed
that can act to remove existing barriers to cooperation.
Establish and maintain a working conceptual model for the interactions between the
various geomorphic, ecological, biological, social and political systems within the
watershed. This will provide a common basis for management actions that can be used by
all agencies, landowners, and managers within the watershed to prioritize actions and serve
as a roadmap for restoration.
4.4.2
Key Objectives and Work Plan
The overall goal of this restoration program is to develop a systematic, watershed-scale
coordination structure that can bring together managers, landowners, scientists, agencies and the
general public for the benefit of the entire community. The plan will be organized to develop an
adaptive management strategy that will benefit from an approach that allows for updates,
revisions, and modifications as conditions and initial results are evaluated.
Implementing an effective watershed management approach requires efforts that efficiently
integrate science, analysis, collaboration, restoration oversight, funding, and political will. Much
information has already been gathered about the Carmel River Watershed. These efforts have
identified a range of issues currently affecting the watershed and have outlined actions that can be
taken to address these impacts. The Watershed Restoration Program forms the structure from
which a coordinated and successful approach can be developed to implement these actions, to
achieve watershed restoration (Figure 4-8).
To achieve this goal, the authors of this report have identified a number of more detailed
objectives and preliminary work tasks that support each objective. The Watershed Restoration
Program should build on other ongoing and planned efforts within the watershed including those
that are directed at evaluating watershed functions, addressing water supply concerns or
74
f i g u r e 4-8
Supplemental Carmel River Watershed Action Plan
Inputs and Outcomes Associated with the Integrated Watershed Restoration Program
75
developing approaches to restoring essential components of the watershed. It may be ideal to
build on these efforts to jump-start the Restoration Program. The key objectives include:
1. Developing a working eco-geomorphic conceptual model for the watershed,
including both natural and human influences (Appendix C). Components could
include:
o An integrated Geographic Information System database containing all relevant
spatial datasets
o A systematic synthesis of existing studies and data that characterize watershed
processes and functions
o Simple box diagrams showing the relationship between key infrastructure
parameters and associated watershed systems
2. Managing the long-term watershed response to Removing San Clemente Dam,
including:
o A study to develop eco-geomorphic approaches to long-term storage of
sediments currently stored behind San Clemente Dam as described in Section
4.2.1.2, and that meets the criteria described in Section 4.2.1.1
o A study to evaluate likely downstream hydraulic and geomorphic impacts from a
range of possible future conditions so that risks and solutions can be
appropriately identified
o A watershed-scale river management plan that integrates eco-geomorphic and
structural sediment management controls, along with an integrated flood
management approach
o Apply the information and knowledge gained from San Clemente and utilize it to
effectively plan other actions within the watershed, including Los Padres Dam
operation, engineering and management
3. Strategically managing impacts from the Water Supply Infrastructure within the
watershed, including:
o Implementing alternatives to riparian groundwater supplies, including an
associated water supply plan
o Completing and implementing the Integrated Water Management Strategy Program
(IRWMP) for the entire watershed
4. Prioritizing and implementing actions that restore and protect functional habitats,
processes and conditions to the watershed, including:
o Consolidate and complete an integrated list of current human caused impacts
within the Carmel River Watershed, utilizing efforts already completed (e.g.,
Figure 4-9)
o Consolidate this information into a watershed and geographically based data set.
This data set will be shared with stakeholders and the public via a website
dedicated to sharing information
76
f i g u r e 4-9
Source: Big Sur Land Trust
Supplemental Carmel River Watershed Action Plan
Notes: Landscape Functions for the Lower Carmel River. Many of
these are dependent on existing ecological and geomorphic functions.
Managing future landscape functions requires an integrated approach
as described in this report.
Landscape Functions for the Lower Carmel River
77
Overlay this information with known life history requirements of indicator aquatic,
wetland, riparian and upland species
o Develop a matrix for each indicator species and life stage, and prioritize actions
as related to specific existing species/habitat impacts
o Identify the appropriate sequence for actions within the watershed to restore
functional habitats
5. Establish a functional adaptive management program (Appendix D), including:
o A systematic method to obtain and evaluate data
o Measurable performance targets and reference conditions that define thresholds
for management action
o Development of a facilitated public process that will allow the public and
stakeholders to remain engaged in watershed restoration
4.4.3
Structure and Funding Ideas
Implementing the restoration program requires collaboration among key stakeholders. Many of
the action items will need appropriate funding, and lines of responsibility and authority need to be
established so that action items are properly managed. An implementation plan that outlines
organizational structures, authorities, funding mechanisms, program goals, and other aspects
should be developed collaboratively among a coordinating committee of key stakeholders.
Potential Sources of Funding include:
ƒ
State agencies and programs directed at integrated water resource management
ƒ
Current and future state bond propositions that support protecting water resources
ƒ
Federal appropriations
ƒ
National Science Foundation
ƒ
Private foundations (for example: Moore Foundation, Packard Foundation, and others)
ƒ
NOAA, EPA, and USACE Federal Restoration Programs
ƒ
California American Water Company
The costs and scope for this program depend on many factors. Generally, we anticipate that the
program will require expertise in hydrology, geomorphology, biology, ecology, botany, planning,
and stakeholder coordination. It will require managerial expertise in developing watershed-scale
science and management. It will also require data collection, data management and may require
outside experts to assist with more complex issues (e.g., hydraulic modeling, detailed restoration
engineering, etc). The program will benefit from a coordinating committee of local agencies and
scientists who can assist in developing and guiding the Restoration program.
78
The program will remain active for at least 10-15 years after sediments begin to pass the San
Clemente Dam site, at which time the value of the program can be re-evaluated and modified as
appropriate. This will provide a sufficient period to monitor changes in the river system that
accompany the return of natural sediment supplies and any adjustments associated with the dam
removal and collaborate with local conservation and resource management agencies.
The Carmel Watershed Restoration Program can be housed at one or more existing agencies or
institutions. Suitable organizations include academic institutions (e.g., the California State
University Monterey Bay Watershed Institute, the University of California Hasting Biological
Field Station), existing agencies (e.g., Monterey Peninsula Water Management District, Monterey
County Resource Conservation District), or other community organizations (e.g., Carmel River
Watershed Conservancy, Big Sur Land Trust).
4.4.4
Scientific Research on Dam Removal
Recommended Action: Coordinate dam removal programs with the scientific research
community.
There is considerable interest within the scientific and dam management communities to study
the effects of large dam removals to better understand the implications for dam removal, and to
improve removal techniques and methods. Developing a rigorous scientific approach to dam
removal is critical to developing sound scientific knowledge for future applications. Effective
monitoring strategies will also provide the public with data that can be used to plan and
implement additional restoration and infrastructure improvement efforts. Removing the San
Clemente Dam will provide scientists and managers with an unprecedented national and
international opportunity to study and evaluate dam removal strategies and the associated
ecological, biological and geomorphic response. This can also be an important source of funding
and scientific expertise for the Carmel River Watershed Restoration Program.
Restoring a functional watershed ecosystem will provide a unique and unprecedented opportunity
to study the requirements of conservation-reliant species and their response to specific actions.
The lessons learned are important to other landscapes where dam removal may be required in
coming decades. We also view this as an opportunity to identify funding options for various local
river management and adaptive management tasks.
79
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84
6. LIST OF PREPARERS
This report was prepared by the following:
Phil Williams and Associates
Mike Liquori
Jeff Haltiner
Setenay Bozkurt
Ecosystem Management International
David Wegner
Planning and Conservation League Foundation
Jonas Minton
Monica Hunter
Mindy McIntyre
Barbara Byrne
85
Appendix A
Key Species List Appendix A - Key Species List This list includes species found in the Carmel River Watershed that are considered to be
“special” by the California Natural Diversity Database, or “threatened” or “endangered” by the State of
California or the federal government.
PLANTS
Gambel's water cress (Nasturtium gambelii) Marsh sandwort (Arenaria paludicola) INVERTEBRATES
California freshwater shrimp (Syncaris pacifica) Tomales asellid (Caecidotea tomalensis) FISH
Steelhead trout (Oncorhynchus mykiss)
Tidewater goby (Eucyclogobius newberryi) Unarmored threespine stickleback (Gasterosteus aculeatus williamsoni) AMPHIBIANS
California tiger salamander (Ambystoma californiense) Santa Cruz long-toed salamander (Ambystoma macrodactylum croceum) California red-legged frog (Rana aurora draytonii)
Foothill yellow-legged frog (Rana boylii) Mountain yellow-legged frog (Rana muscosa) Arroyo southwestern toad (Bufo microscaphus californicus) Western spadefoot toad (Scaphiopus hammondii) REPTILES
Alameda whipsnake (Masticophis lateralis euryxanthus) San Francisco garter snake (Thamnophis sirtalis tetrataenia) Two-striped garter snake (Thamnophis hammondii) Western pond turtle (Emys marmorata) BIRDS
Brown pelican (Pelecanus occidentalis) Snowy plover (Charadrius alexandrinus) Little willow flycatcher (Empidonax traillii brewsteri) Southwestern willow flycatcher (Empidonax traillii extimus) Least Bell's vireo (Vireo bellii pusillus) Saltmarsh common yellowthroat (Geothlypis trichas sinuosa) Tricolored blackbird (Agelaius tricolor) A-1
Appendix B
Frequently Asked Questions
Appendix B - Frequently Asked Questions
This document describes the benefits and strategies for achieving the broader goal of watershed-scale
restoration. However, many public concerns and questions have been raised regarding the potential
impacts of river restoration and dam removal. The answers to many of these questions depend in large
part on the approach taken to restore key watershed processes and functions.
The recommended approaches and strategies would provide many beneficial improvements to both the
ecological structure of the watershed, and its human infrastructures. While there are uncertainties, we
believe that dam removal and discontinued CAW pumping represent a unique opportunity to create major
ecosystem improvement. Planning should be focused on establishing the strategic and ecological context
for effective restoration.
Q. How will the sediment behind San Clemente Dam be managed?
A. There are three options for the sediment currently trapped behind the dam: 1) the sediment may
be sequestered in place; 2) The sediment could be excavated and removed to another location; or 3)
the sediment could be gradually released downstream. At present, it appears that alternative 1 would
have the most benefits. Alternative 2 has been analyzed in earlier studies that identified significant
problems associated with removal and transportation of sediment from the dam site. Problems include
significant traffic impacts from truck transport of excavated sediment to a disposal site. Also, it has
been difficult to identify a disposal site or use for the removed sediment under Alternative 2.
Concerns about the possible increase in flood risks that might occur if the released sediment decreases
the channel capacity downstream are associated with Alternative 3.
Q. Will flooding risk increase because of the removal of San Clemente Dam?
A. San Clemente Dam currently provides minimal flood management benefits. Removal is not
expected to increase flood hazard as a result of any decrease in upstream reservoir water storage
capacity.
Q. Will the movement of sediment downstream from San Clemente Dam lead to increased
potential for flooding?
A. Earlier studies conducted by CAW suggest that increased sediment released from the Reservoir
could reduce river channel flow conveyance downstream until that sediment passes through to the
ocean. Under all future scenarios currently being considered (dam stabilized in place; dam removed),
the current sediment stored behind the dam will not be released downstream. However, some
increase in sediment supply will occur whether the dam is removed (and there is no barrier to new
sediment supply) or stabilized in place (in which case an increasing portion of new sediment supply
will begin to be released downstream as the capacity of the dam to continue to trap upstream sediment
is exhausted). A program to manage flood risks in the lower river reaches is an important component
of future river planning.
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Appendix B - Frequently Asked Questions
Q. How will dam removal affect wetlands and red-legged frog habitats presently located in the
reservoir basin?
A. Dam removal could potentially dewater the sediments trapped behind the dam which currently
provide seasonal red-legged frog habitat. Dam removal may require continued discharge or trapping
of some flow into these sediments to conserve red-legged frog habitat. As watershed restoration
occurs, it may be feasible to sustain red-legged frog populations in additional locations in the
watershed. It is likely that red-legged frog habitats will be reestablished as the Carmel River channel,
floodplain, and wetlands are reconnected.
Q. How will restoration affect the estuary and beaches?
A. Prior to the construction of San Clemente and Los Padres dams, the estuary and beaches were in
balance with the upstream sediment supply from the watershed. As a result of the reservoir
construction, as well as numerous other watershed changes, the sediment regime has been altered.
The response of the downstream ecosystems to changes in the sediment supply will depend greatly on
the magnitude and timing of changes. A large temporary increase in sediment supply could reduce
the volume of the estuary for some period of time. Over time, it would be expected that the excess
sediment would be removed by periodic high flow events. Alternatives that restore the supply of
sediment from upstream of San Clemente will benefit the beaches that receive sand supply from the
river. This sand supply is an important component of the capacity of the beaches to act as a buffer
during periods of large coastal storm events and increased sea level rise.
Q. Will restoring sediment supply to the ocean protect the homes located along the estuary?
A. If increased sediment from the watershed reduced the holding capacity of the estuary, the reduced
water storage capacity could result in a slight increase in flood hazards. However, the estuary volume
is currently relatively small, and does not play a major role in the current flood management
approach. Instead, flood management is accomplished by breaching the barrier beach and allowing
the river to discharge directly to the ocean. It is anticipated that the barrier beach breaching program
will continue until some alternative flood management project (e.g., flood wall to protect the homes)
is developed. Current efforts to develop a long-term management strategy for the lagoon have gained
in support from the community, signaling a renewed effort to develop a collaborative process for
establishing an improved lagoon management program.
Q. Will traffic increase in the area?
A. Traffic impacts will be related to the final alternatives selected. All of the alternatives will result
in minor and temporary increased traffic during the construction period. The actual traffic impacts
(traffic volume, types of vehicles, duration of impact, etc.) will vary depending on the scale of
construction work required.
Q. Will the Carmel Aquifer recharge itself quickly?
A. It is expected that the aquifer would respond relatively quickly (within a few years) to
discontinued CAW pumping. The timing will be dependent on regional hydrologic conditions and
the extent of the effect of continued pumping from private wells.
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Appendix B - Frequently Asked Questions
Q. Will water quality change in the Carmel River?
A. Construction related activities may increase the turbidity and sediment transport in the river for
short periods of time. Fine-grained sediment release may result in increased turbidity until the
channel adjusts to the new sediment transport regime. Such impacts are likely to be short-term, and
will likely receive considerable attention from regulating agencies. Water quality in the Carmel River
will improve as a natural seasonal flow regime is restored, riparian vegetation along the river corridor
increases, and increased flow to the estuary occurs. Thermal conditions will immediately improve
with other changes occurring in proportion to sediment transport, reconnection of the river with the
floodplain and other ecological responses occur.
Q. Will the steelhead and red-legged frog populations improve with dam removal?
A. Removal of the dam will eliminate the need for the challenging fish ladder that fish are currently
required to navigate to move upstream. Dam removal will also reduce the need for active human
involvement (e.g., trapping and transporting fish around the dam) currently required to help maintain
steelhead populations. Dam removal will allow access to habitat areas between San Clemente and
Los Padres dams, allowing access to seven miles of usable fish habitat.
Red-legged frog habitats currently exist in the reservoir sediment delta above San Clemente Dam.
Dam removal will likely drain these sediments of water and on a short-term basis negatively impact
the habitat for the listed frog species. Habitats may be protected on a short-term basis from
dewatering by employing engineering techniques. Natural habitats will begin developing as the water
levels behind the reservoir drop and the river begins to reconnect and develop new wetland areas in
the reservoir basin and downstream. Overall, with the reconnection of the Carmel River to the
floodplain and wetlands, historic and new wetland habitats will be established for the red-legged
frogs.
Q. How much will all this cost ratepayers and/or local governments?
A. The exact costs from local sources are uncertain at this time. Alternative water supply sources are
already being pursued by CAW, and will be subject to new supply costs. Public funding for a portion
of the costs to restore the Carmel River Watershed could be available due to the public benefit from a
coordinated Watershed Restoration Program that includes dam removal. Discussion of costs must
also recognize the trade-off between short-term costs (dam removal) and long-term costs (required
dam maintenance and future strengthening in perpetuity).
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Appendix C
Eco-Geomorphic Conceptual Model
Appendix C - Eco-Geomorphic Conceptual Model
A scientifically-based conceptual model of watershed processes provides the scientific context for
evaluating, designing and prioritizing actions. It requires a set of working hypotheses that describe key
watershed functions, and outlines the linkages between these functions. It establishes the context for
integrating science into management decisions and provides the framework for effective monitoring,
research and management. Ultimately, the model helps to develop predictions of watershed responses
that allow managers to identify impacts before they occur, so that solutions can be designed and
implemented.
A conceptual model integrates detailed understanding of the physical, biological and ecological processes,
functions, and interactions within the watershed. It is based on relevant literature and scientific
disciplines, as well as research and analysis specific to the Carmel River Watershed. It will integrate
knowledge of hydrology, geomorphology, hydraulics, riparian ecology, fisheries, aquatic ecology, and
terrestrial biology.
The working conceptual model should be supported by Geographic Information System inventories,
spatial and temporal analyses, and appropriate databases. It should encourage collecting and evaluating
data to validate working hypotheses and measure changes that can potentially impact human
infrastructures. It will be supported by collaborative research that addresses management uncertainties
and provides predictive ability to evaluate future conditions.
The working hypotheses and assumptions should also be coordinated with the monitoring and adaptive
management elements of the Watershed Restoration Program.
Examples of watershed restoration programs:
ƒ Watershed Restoration Program for Upper Salem River Watershed (2005)
ƒ Watershed Restoration Plan for the Mud Creek Watershed (2003)
ƒ Chesapeake 2000: A Watershed Partnership (2000)
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Appendix D Adaptive Management Appendix D - Adaptive Management
Adaptive management is an important concept in modern environmental management. It describes an
approach to land-use management that integrates monitoring with a management framework to provide
feedback on the effectiveness of various actions and appropriate responses. It guides future actions by
examining the successes and failures of past actions.
Adaptive management provides an opportunity for scientists, the public, decision-makers, interested
groups, and managers to discuss and learn from actions, especially when all the information required for a
decision is not initially available. Adaptive management provides a strategy for action that will build on
new knowledge and ecosystem responses. Adaptive management provides an opportunity to act when
uncertainties may otherwise stall decisions.
Implementing an effective adaptive management program requires significant efforts to establish and
commit to a long-term resource monitoring and management plan. However, it provides opportunities for
collaboration among stakeholders and emphasizes transparent decision-making that is grounded in both
science and policy. The core components of an adaptive management program include:
Working Hypotheses – set the context for establishing monitoring protocols and actions.
Actions – designed to improve elements of the watershed that no longer function as desired.
Resource Objectives – specific goals established to drive actions and monitoring. For example,
specific targets for restoring adult steelhead populations.
Performance Measures – measurable variables for assessing success. For example, number of
spawning sites (redds) per restored reach. Performance measures should be supported by
working hypotheses. Performance measures are developed for those parameters that will likely
show response to changes in the physical dynamics of the Carmel River Watershed.
Success Criteria – criteria necessary for revising actions, changing performance measures, or
revising resource objectives. These include identifying threshold criteria and levels for
action. Examples of threshold criteria may include:
ƒ
State or federal water quality standards violated
ƒ
Listed species populations or habitats reach levels where they cannot biologically or
genetically support the species.
ƒ Sediment transport does not occur as predicted in terms of volumes, movement or distribution
Effectiveness Monitoring –designed to collect and evaluate data to evaluate the effectiveness of
restoration actions. The monitoring plan should be based on detailed working hypotheses, and
scientific methodologies.
Validation Monitoring –designed to verify working assumptions or hypotheses of the
watershed. It may or may not be tied to specific actions.
Management Feedback – decision loops that allow managers to respond to monitoring
information without interfering with the scientific integrity of the monitoring and research
protocols.
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Appendix D - Adaptive Management
An effective adaptive management program requires: (1) an effective design, (2) a commitment to
communicate and work together, (3) defined thresholds for action, (4) committed funding, (5) a facilitated
management process, and (6) an integrated decision-management-science articulated plan. Adaptive
management on complex restoration efforts requires a lot of work and an understanding that success is
incremental, and cumulative.
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