Download Shoreline Erosion Site Inspection Report: Sherwood Forest Property

Shoreline Erosion Site Inspection Report:
Sherwood Forest Property
Maryland Department of Natural Resources
Chesapeake and Coastal Service
Shoreline Conservation Service
Inspection Date:
July 20, 2016
Point of Contact:
Bill Chandler
(410) 624-6957
[email protected]
Site Location:
842 Beach Dr.
Sherwood Forest, MD 21405
Cottage 842
Severn River
Anne Arundel County
Site Inspectors:
Bhaskar Subramanian
Shoreline Conservation Service
Program Manager
(410) 260-8786 / (443) 454-1638
[email protected]
Rebecca Swerida
Shoreline Conservation Service
Project Manager, Biologist
(410) 353-7003
[email protected]
Further Program Information:
http://dnr2.maryland.gov/ccs/Pages/livingshorelines.aspx
Purpose of Inspection:
To inspect eroding shoreline areas of concern and to provide
technical assistance and recommendations.
Tawes State Office Building – 580 Taylor Avenue – Annapolis, Maryland 21401
410-260-8DNR or toll free in Maryland 877-620-8DNR – dnr.maryland.gov – TTY Users Call via the Maryland Relay
Fetch:
Direction
Northwest
North
Northeast
East
Distance (Miles)
2.11
0.52
0.52
0.59
Site fetch distances.
Approximate Shoreline Length:
750 feet
Approximate Distance to
Infrastructure:
75 feet
Approximate Water Depth:
3 feet depth 20 feet from the shore
Historic Rate of Erosion (Mean):
0.36 feet per year (Slight Erosion)
Line Color
Purple
Green
Yellow
Basemap
Year
1845
1965
1994
2014
Increment Distance (ft)
61.5
22.5
-
Note: Historical shorelines are most accurate in areas of open water.
Description of Shoreline:
The shoreline of concern is approximately 750 feet in length and faces northeast along the
Severn River near Round Bay. The shoreline shows historical evidence (based on Maryland
Coastal Atlas historical shoreline data) of active erosion at a mean rate of less than one foot per
year, a rate classified as slight erosion. The historical shoreline data also indicated that the
shoreline hardening in place has slowed erosion sometime between 1965 and 1994, although
erosion has since continued behind the structure. The shoreline consists of a low, eroding bank
backed by some area of vegetated buffer, including native species such as three square rush
(Scirpus americanus), marsh hibiscus (Hibiscus moscheutos) and mowed grass lawn. Some
invasive phragmites (Phragmites australis) was also noted. A low riprap/revetment structure
constructed of loosely placed small stone is currently in place along most of the shoreline with
areas of erosion and depressions on the landward side. Above the bank there is a fairly flat
landscaped grass lawn and a paved road approximately 75 feet from the shoreline and a higher
elevation residential area beyond. A wooden finger pier, boat ramp and kayak rack is located on
the western edge of the shoreline. The water depth to approximately 20 feet off shore is very
shallow, estimated to only 3 feet and the substrate appears sandy. A dense bed of submerged
aquatic vegetation (SAV), specifically widgeon grass (Ruppia maritima), sago pondweed
(Stuckenia pectinata) and perfoliated pondweed (Potamogeton perfoliatus) was observed and has
been aerially mapped 37 to 165 feet from the shoreline. Neighboring areas have also been
hardened with bulkheads, stone revetments and groins. An effective living shoreline project has
been installed on the eastern side of the property. Overland flow runoff was identified as a
problem, particularly in areas where the vegetated buffer is fairly thin. Stone lined drainage
swales also flood regularly.
Wide view of portion of shoreline, note limited buffer,
Example of eroded area behind riprap.
Previously installed bulkhead, stone revetment and groins.
Newly installed stone revetment.
Portion of effective, in place living shoreline.
Stone lined drainage swale.
Recommendations:
A combination of over land flow and storm event wave activity is most likely the cause of
erosion at this shoreline. It was determined that the site’s erosion could be controlled with a
Living Shoreline project while creating habitat and maintaining natural processes.
Fill and Vegetation Plan
The erosion immediately behind the stone rip rap structures can be temporarily controlled
by filling the existing holes and vegetating the area with stabilizing native plants. The depressed
eroded areas should be lined with woven, 70 sieve filter cloth (available at hardware and
landscaping stores). More shallow depressed areas can then be filled with layers of mulch and
sand. Deeper areas should be filled with segments of coir coconut fiber bio-logs, staked in place.
A layer of mulch and sand should be filled behind the coir log. The coir logs are designed to hold
that sand in place for 4 to 5 years until the logs naturally biodegrade and the root mats of growing
vegetation will stabilize the sediment. Bio-logs, as well as many shoreline plants, are available
from the Pinelands Nursery in Columbus, NJ (609-291-9486), among other vendors. Locally, the
Providence Center in Arnold is an excellent source of many shoreline plants, 410-766-2212 ext.
411.
The area (at least 3 to 4 feet) behind the stone riprap or coir logs should be vegetated with
native stabilizing plants. Switchgrass (Panicum vigatum) is the most highly recommended species
for a situation like this. It has very strong fibrous roots that grow seven times as long as the above
ground material. These grasses very effectively stabilize shoreline sediments and are attractive,
often used decoratively, and provide the environmental functions listed above. Plugs can be
purchased from most nurseries, including those listed below, and should be planted in 2 to 3
offset rows every 3 feet in spring or early summer. The plants will grow quickly and natural fill
in the rows most likely within one growing season. Switchgrass can grow quite tall, up to 7 feet,
but can be trimmed to as short a height as 3 feet. Feel free to design the planted area to your
desired aesthetics including features like walking paths etc. There are many more appropriate
grass and shrub species for shoreline stabilization that could be incorporated into the planted area
if more species diversity is desired: Little bluestem (Schizachyrium scoparium), deertongue
(Dichanthelium clandestinum), big bluestem (Andropogon gerardii), coastal pepper bush
(Clethra alnifolia), buttonbush (Cephalanthus occidentalis), partridge pea (Chamaecrista
fasciculata) and wild indigo (Baptisia tinctoria). Before any work is done on the shoreline, it is a
good idea to notify the county Critical Area Program (410-222-7485).
Upland Stabilization Plan
The upland run off and drainage portion of the shoreline erosion problem can be managed
through strategic vegetation and the installation of drainage control structures. The existing
vegetation on the sloping bank has clearly helped to provide a buffer that has slowed run off and
increased percolation of water through the soil. The buffer can be enhanced with the addition of
plant species with especially extensive and strong root systems that will help to stabilize the
sediment and hold the bank together, such as those listed above. If dead or dying trees must be
removed on the slope, the tree should be cut so that the stump and root system remain in place.
The upland run off can further be controlled through vegetated bioswales and/or rain
gardens. These structures consist of small raised areas that will route runoff water to a designated
area where it can flow into layers of sand, mulch and soil, or sometimes cobbles and stones.
Those biorention area are specially designed to absorb water and should be vegetated by moisture
tolerant plants. There is a huge amount of diversity in native Maryland plants suitable for rain
gardens and vegetated bio-swales. Here are a few suggested species: northern lady fern (Athyrium
filix-femina), broomsedge (Andropogon virginicus), white turtlehead (Chelone glabra), joe pye
weed (Eupatorium fistulosum), mist flower (Conoclinium coelestinum), swamp azalea
(Rhododendron viscosum), spicebush (Lindera benzoin) and winterberry (Ilex verticillata). A
publicly available technical guide to rain garden installation called “Rain Gardens Across
Maryland” produced by the Maryland Coastal Bays Program is an excellent resource. The Anne
Arundel county Soil Conservation District are experts in the field of upland run off control and
should be contacted for further information. Please contact
John Czajkowski
District Manager
[email protected]
410-571-6757 ex 114
Low Profile Stone Sill
Although the stone riprap revetment structure has reduced overall erosion of the shoreline,
it has been clearly overtopped by storm event and boat wake waves and impacted by over land
flow. Erosion can be more effectively controlled, valuable habitat created and more of a buffer to
shoreline flooding created through the installation of a low profile stone sill living shoreline
design. This design option would include the installation of a segmented stone sill structure built
parallel to the shoreline approximately 35 feet channelward from the shoreline. These structures
would be trapezoidal in cross section and only about as high as the mean high tide level. A wedge
of sand (made up of material with a low fine particle content) would be placed at a 10 to 1 slope
on the landward side of the stone structures. The sand wedge would then be vegetated to create
and low and high marsh habitat and stabilize the sediment. Salt meadow hay (Spartina patens)
would be planted above the high tide line where the plants would only be inundated occasionally
to form high marsh habitat and smooth cord grass (Spartina alterniflora) would be planted
between the high and mid tide lines to form low marsh habitat. Plugs of each plant would be
planted in the spring or early summer in offset rows at 18 inch intervals. If desired, biodiversity
could be increased in the marsh habitat by taking advantage of the salinity of the area and some
of the following brackish mars plants: annual wildrice (Zizania aquatica), arrow arum (Peltandra
virginica), river bank wildrye (Elymus riparius) and common rush (Juncus effusus). Upon
request, I can recommend many more appropriate species to enhance the marsh habitat or create a
“shoreline garden”. Costs can be controlled by reusing the stone making up the existing riprap
structures, although larger stone would be necessary to cap off an effective structure. The
estimated cost of this design is $300 to $400 per linear foot, for 750 feet resulting in a
conservative total estimated cost of $300,000. The marsh habitat created and enhance would be
protected by the stone sills while remaining accessible by wildlife (ex. Horseshoe crabs, turtles,
or kayaks!) through the “windows” between the structures.
Invasive Phragmites Control
Information concerning the invasive wetland grass species Phragmites australis can be
found at the following website:
http://dnr2.maryland.gov/wildlife/Pages/plants_wildlife/Phragmites.aspx
This is a very aggressive species and is not native to Maryland and is considered noxious
due to its ability to quickly out compete native species and create dense, single species stands.
Phragmites are considered inferior to native marsh grasses as they do not provide effective
wildlife habitat, biodiversity, sediment stabilization or many of the other ecological services
comparable to native species.
A combination of chemical and physical control methods are recommended to remove the
phragmites present on your shoreline and prevent future reestablishment. The two most
commonly used phragmites management herbicides are glyphosate (Rodeo®, Aquamaster® and
others) and imazapyr (Habitat®). Imazapyr is considered more effective overall, however, it may
negatively impact all other plants in the area of application and remains active in the soil for an
extended period of time. Glyphosate products are often less expensive and do not persist in the
soil, but must be strategically applied in the late summer or fall to the seed heads of the plant.
For further information, please contact:
Waterfowl Habitat Specialist – Donald Webster
MD DNR – Wildlife and Heritage Service
828B Airpax Road, Suite 500
Cambridge MD 21613
410-221-8838(ext.103)
[email protected]
Funding Options
Some grant options may be available through the MD DNR Chesapeake and Atlantic
Coastal Bays Trust Fund. This grant opportunity greatly emphasizes nutrient and sediment
reductions to the Chesapeake Bay watershed and public benefit to shoreline ecosystems. Often,
living shoreline projects are very beneficial to shoreline ecosystems, but may not reduce a large
enough portion of nutrient additions to the watershed compared to other best management
practices to be competitive. Details can be found here:
http://dnr2.maryland.gov/ccs/Pages/funding/trust-fund.aspx. The Chesapeake Bay Trust Fund
non-profit organization also offers a restoration and outreach grant program that has been
successfully applied to community living shoreline projects in the past. Details can be found here:
http://www.cbtrust.org/site/c.miJPKXPCJnH/b.5457271/k.C58E/Grants.htm.
Also, the MD DNR Shoreline Conservation Service offers a 0 interest loan program for
living shoreline projects which may be used independently or in conjunction with one of the
above grants. The 0 interest loan program would work with Sherwood Forest as a targeted
community and create a Shoreline Erosion Control Special Tax District with the help of Anne
Arundel County. For more information, see the following website:
http://dnr2.maryland.gov/ccs/Pages/livingshorelines.aspx.
Additional Comments
Submersed aquatic vegetation (SAV) beds are considered high priority habitat in the
Chesapeake Bay because of the extremely valuable ecosystem services that they provide for the
health of the Bay at large. As a result, shoreline construction or disturbance is restricted in areas
that have had aerially mapped SAV beds during the past 5 years. The presence of mapped SAV
beds in the area of the Sherwood Forest shoreline does not exclude the possibility of a living
shoreline project, however it will impact the potential design options and should be kept in mind.
It is important to avoid direct disturbance to the SAV habitat during potential living shoreline
design and construction to maintain their ecosystem health.
Design images:
Example image of switchgrass (Panicum virgatum)
Figure illustrated by Dede Christopher, Tennesee Valley Authority, Benefits of Riparian Zones
Example image of salt meadow hay (Spartina patens)
Example image of smooth cordgrass (Spartina alterniflora)
Example image of phragmites (Phragmites australis)
Shoreline Plant Nurseries:
Pinelands Nursery
Don and Suzanne Knezick
323 Island Road
Columbus, NJ 088022
(609) 291-9486
Shore Solutions Nursery
Connie Zinter
P.O. Box 487
Cordova, MD 21625
(410) 820-6868
Environmental Concern, Inc.
Suzanne Pittenger-Slear
P.O. Box P
St. Michaels, MD 21663
(410) 745-9620
Wicklein’s Aquatic Farm & Nursery
Erik Wicklein
1820 Cromwell Bridge Road
Baltimore, MD 21234
(410) 823-1335
Water’s Edge Nursery Co.
Scott Haschen
6526 Dion Road
Federalsburg, MD 21632
(410) 829-3723
Providence Center Inc.
Laurie Collins
370 Shore Acres Road
Arnold, MD 21012
(410) 544-2664
Angelica Nurseries Inc.
11129 Locust Grove Road
Kennedyville, MD 21645
Lilypons Water Garden
Margaret Koogle
6800 Lily Pons Road
(410) 928-3111
Adamstown, MD 21710
(800) 999-5459
Shoreline Contractors:
Waterfront Preservation Inc.
Donny Burgess
1110 Old County Rd.
Severna Park, MD 21146
(410) 703-7211
Dissen & Juhn LLC
Gilbert Dissen
101 Log Canoe Circle, Ste J
Stevensville, MD 21666
Phone: (410) 604-1802
Atlantic Shoreline
Doug Jordan
25515 Golt Farm Lane
Goldsboro, MD 21636
(410) 490-1981
Shoreline Design, LLC
Wes Matheu
637 Shore Drive
Edgewater, MD 21037
(410) 956-4662
Heinsohn Contracting, Inc.
Gerd Heinsohn
222 Severn Ave., Suite 45, Building 10-8
Annapolis, MD 21403
(410) 263-1852
Envirens. Inc.
Michael Hollins
21221 Mikules Manor Lane
Freeland, MD 21053
(410) 299-6898
Corman Marine Construction
Sean MacNeal
711 East Ordnance Road Suite 715
Baltimore, MD 21226
(410) 439-9700
Edwin A. & John O. Crandell Inc.
David Harris
733 Crandell Road
West River, MD 20778
(410) 867-0200