1

Floodplains, Fish Habitat, and Climate Change Resilience

Tim Beechie NOAA Fisheries, Northwest Fisheries Science Center, Seattle, WA

2

What is resilience?

•  Ability of an ecosystem to maintain its structure and functions despite environmental change

•  For salmon, resilience more commonly means persistence of the species despite climate change

•  Floodplains confer climate change resilience through: •  Habitat diversity

•  Thermal diversity

•  Species diversity

3

1970-1999

Seattle

Portland

Boise

Banff

Data source: http://www.hydro.washington.edu/2860/report/

Rainfall

Snowmelt 2070-2099

Seattle

Portland

Boise

Banff

Rainfall

Snowmelt

Transitional

Transitional

Change in flow regime

4

Increased water temperature

1970-1999 >30 26-30 22-26 18-22 14-18 10-14 <10

2070-2099 >30 26-30 22-26 18-22 14-18 10-14 <10

Beechie et al. 2013 Beechie et al. 2013

bkw pool

scr pool

glide

lg riffle

hg riffle

Young scroll bar channel

Riffle dominated

Higher habitat diversity

bkw pool scr pool glide lg riffle hg riffle

Young abandoned main stem

Mixed riffle and pool

Higher habitat diversity

pool glide lg riffle hg riffle

Old abandoned main stem

Pool / pond dominated

Higher habitat diversity

8

Surface water temperature patterns in the Sauk River floodplain

Thermal diversity

9

Longer hyporheic flow paths regulate stream temperature

Poole et al. 2008

10

Longer hyporheic flow paths regulate stream temperature

955 m 955 m

955 m

175 m

175 m

175 m

SW SW

SW

Poole et al. 2008

Higher invertebrate diversity

•  Young channels dominated by gatherers

•  Older channels dominated by scrapers

Main channel <5 years 5-25 years 25-75 years >75 years

12

Higher growth rate

Mainchannel Floodplain

Jeffresetal.2008Enclosedexperiment,sameageChinook

13

More salmonids in side channels

mainstem

floodplain

Bellmore et al. 2013, Pess et al. 2008

MC CSC DSC

Elwha River Methow River

14

What can floodplains do for climate change resilience?

Restoration action Temperature increase

Low flow decrease

Peak flow increase

Increase resilience

Longitudinal connectivity Y Y N Y

Floodplain connectivity Y N Y Y

Restore incised channel Y Y Y Y

Restore in-stream flow Y Y N N/Y

Riparian rehabilitation Y N/Y N N

Sediment reduction N N N N

In-stream habitat N N N N

Nutrient enrichment N N N N

15

Reducing climate change effects through restoration

Levee

Mainstemhabitatsonly

Mainstem

Pond

Floodrefuge

Groundwaterchannel

Side-channel

Waples et al. 2008

16

Reducing climate change effects through restoration

Levee

Mainstemhabitatsonly

Mainstem

Pond

Floodrefuge

Groundwaterchannel

Side-channel

Waples et al. 2008

And restoring incised channels

Reduce temperature Increase low flow Decrease peak flow (or its effect) John Day

River basin

18

Summary •  Connected or restored floodplains confer

resilience through • Habitat diversity • Thermal diversity • Species diversity

•  They also can ameliorate peak flow and high temperature effects through • Flood attenuation and refugia • Thermal refugia