River Restoration and Climate Change: Some ReflectionsMatt KondolfUniversity 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

Uvas Creek, California Jan 1996, 2 mo post-construction (Are we in Denmark?)

This means our attempts to mimic humid climate forms, such asundertaken on Uvas Ck in Gilroy, are even less likely to succeedthan they have to date

Uvas Ck (same view as last photo) July 1997 Channel failed Feb 1996, 3 months after construction

Design for the Climate/hydrologyCultural 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

Deer Creek

Using river restoration to (partially) mitigate effects of climate change: 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 analysisshowed that the conditions of large gravel and lack ofvegetation along low-flowchannel were consequencesof 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 channelNo 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

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Figure 3.2‑2: Longitudinal profile of thalweg in a geomorphically complex reach of lower Deer Creek near RM 9.

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Figure 3.2‑1: Longitudinal profile of thalweg in a geomorphically simple reach of lower Deer near RM 1.

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upwelling hyporheic water

cobble bar or island

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.

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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.

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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.

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Figure 3.4‑16: Hyporheic exchange sensors near RM 5.0 for a 6 day period in August, 2005.

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Figure 3.4‑22: Hyporheic exchange sensors near RM 6.9 for a 6 day period in August, 2005.

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/restorationin terms of connectivity and flow variability

We see restoration trajectories rarely parallel degradation trajectories

Streamflow variabilitylow high

Long

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spring fed snowmelt rainfall ephemeral/intermittent

DeschutesRiver, Oregon

Butte Ck California

Isar River, Germany

Crow Creek, Tennessee

Torrens River,South Australia

Condamine-Balanne, Queensland

flow

reg

ulat

ion

(dam

)

perennialization by urbanization,

weirs, and wastewater

channelization

off-stream storages

divert base flow

rehabilitation

rehabilitation

reha

bilit

atio

n

Clear Creek, California

flow

regu

latio

n (d

am)

Kondolf et al. in review

The road ahead for river restoration:

Let’s avoid building SUVs!