Download Matt Kondolf, University of California, Berkeley

River Restoration and Climate Change:
Some Reflections
Matt Kondolf
University of California
Berkeley
NBWA, Petaluma, April 2008
We can consider both
-How climate change will affect our efforts to
restore rivers
-How river restoration could be used to mitigate
effects of climate change
Consider our favorite charismatic megafauna,
anadromous Pacific salmon
First: Northern California will become more like
southern Calif: more episodic
This means our attempts to mimic humid climate forms, such as
undertaken on Uvas Ck in Gilroy, are even less likely to succeed
than they have to date
Uvas Creek, California Jan 1996, 2 mo post-construction
(Are we in Denmark?)
Uvas Ck (same view as last photo) July 1997
Channel failed Feb 1996, 3 months after construction
Design for the Climate/hydrology
Cultural preference for single-thread meandering
channels – like green lawns – probably inherited
from Atlantic climates
-18th-19thC English landscape theory, more
recent research
Anticipating higher Temps: Using Butte Creek spring run
to re-populate a restored San Joaquin
Using river restoration to
(partially) mitigate effects of
climate change: Deer Creek
Deer Creek
Restoration planning documents for salmon in the
Sacramento River system identified the need for smaller
gravels and more riparian trees in Lower Deer Ck.
Recommended: add spawning gravel, plant trees
But a geomorphic analysis
showed that the conditions
of large gravel and lack of
vegetation along low-flow
channel were consequences
of a 1949 flood control project
Pre-1949 channel:
multi-threaded,
complex, shaded,
frequent pool-riffle
alternations,
hydraulically rough
Post-1949 channel:
simplified, wider,
hydraulically smooth
High shear stress in
floods, gravels and
trees would scour
Confinement by levees increases bed shear stress
during high flows
Deer Ck Strategy:
Allow overbank flow to relieve excess shear stress
in channel
No channel maintenance
Because watershed is largely unaltered, flow and
sediment load should lead to re-establishing
channel complexity
Complex channel induces more hyporheic exchange,
buffering water temperatures
Elevation (ft)
395
Station (feet upstream of Sacramento River Confluence)
51500
50500
49500
Head of Riffle
Tail of Riffle
Head of Run
Head of Run
390
Head of Riffle
Figure 3.2-2: Longitudinal profile of thalweg in a geomorphically complex reach of lower Deer Creek near RM 9.
Head of Run
385
Head of Riffle
Head of Run
Head of Riffle
Head of Run
Head of Riffle
380
48500
47500
Head of Run
Head of Riffle
Head of Pool
Head of Riffle
Head of Run
Head Riffle
375
Head of Riffle
Head of Run
Middle of Run
365
46500
345
45500
Head of Riffle
Head of Chute
Head of Riffle
Head of RifflePool
370
Head of Riffle
355
Tail of Riffle
360
Flow
Head of Riffle
400
350
190
Flow
Elevation (ft)
Head of Pool
Head of Riffle
175
Run US of Beaver Dam
180
Beaver Dam Pool
Top of Beaver Dam
Head of Riffle
185
170
165
160
155
6700
6900
7100
7300
7500
7700
7900
8100
Station (feet upstream of Sacramento River Confluence)
Figure 3.2-1: Longitudinal profile of thalweg in a geomorphically simple reach of lower Deer near RM 1.
8300
8500
8700
Q
main channel (low elevation)
Q
side channel (high elevation)
Q
cobble bar or island
downwelling “source” water
upwelling hyporheic water
Figure 3.3-6: Schematic of typical hyporheic exchange temperature study site in lower Deer Creek.
Figure 3.3-5: Upwelling hyporheic water identified by tracer dye test.
Downwelling source water “pod”
Upwelling hyporheic water piezometers
Figure 3.3-7: Picture of typical hyporheic exchange study site in lower Deer Creek near RM 5.0. Flow direction is from top to bottom of picture.
10000
30
25
Flow (cfs)
20
100
15
10
Temperature (°C)
1000
10
5
September-05
August-05
July-05
June-05
May-05
April-05
March-05
February-05
0
January-05
1
Date
Flow at USGS Gage (cfs)
Flow at SVID (cfs)
Temperature (°C)
Figure 3.4-4: Comparison of mean daily streamflow at USGS gage (approximately RM 10.5), streamflow downstream of the SVID dam (approximately RM 2.4), and water temperature at the USGS
gage.
Figure 3.3-9: Typical downwelling (left) and upwelling (right) temperature sensor installations in lower Deer Creek.
32
Downwelling Peak
30
Peak Reduction
Temperature (°C)
Upwelling Peak
Downwelling
Amplitude
28
Upwelling
Amplitude
Lag
Time
Between
Peaks
26
24
22
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
Time (hours)
Downwelling Water
Upwelling Water
Figure 3.4-10: Illustration of peak water temperature reduction, water temperature amplitude fluctuation reduction, and lag time between peaks measured at downwelling and upwelling hyporheic
exchange sites. Data from hyporheic exchange site at RM 5.0 for August 1, 2005.
30
29
28
Temperature (°C)
27
26
25
24
23
22
Time (days)
Downwelling Water Temperature (°C)
Figure 3.4-16: Hyporheic exchange sensors near RM 5.0 for a 6 day period in August, 2005.
Upwelling Water Temperature (°C)
8/18/2005
8/17/2005
8/16/2005
8/15/2005
8/14/2005
8/13/2005
8/12/2005
21
30
29
28
Temperature (°C)
27
26
25
24
23
22
Time (days)
Downwelling Water Temperature (°C)
Figure 3.4-22: Hyporheic exchange sensors near RM 6.9 for a 6 day period in August, 2005.
Upwelling Water Temperature (°C)
8/18/2005
8/17/2005
8/16/2005
8/15/2005
8/14/2005
8/13/2005
8/12/2005
21
Salmonid juvenile at upwelling site in July when surrounding water temps reach 30+ C!
Often: irrevocable changes to the system,
restoration of only some functions possible
Viewing directions of anthropic change/restoration
in terms of connectivity and flow variability
We see restoration trajectories rarely parallel
degradation trajectories
Crow Creek, Tennessee
Butte Ck
California
rehabilitation
flow regulation (dam)
high
Longitudinal connectivity
Deschutes
River, Oregon
Isar River,
Germany
channelization
rehabilitation
Clear Creek,
California
CondamineBalanne,
Queensland
low
Torrens River,
South Australia
spring fed
low
snowmelt
rainfall
Streamflow variability
ephemeral/
intermittent
high
Kondolf et al. in review
The road ahead for river
restoration:
Let’s avoid building
SUVs!