Predicting natural channel types in the Columbia River basin

Hiroo Imaki1, Tim Beechie1, John Buffington2

1. NOAA, Northwest Fisheries Science Center, 2. USFS, Rocky Mountain Research Station

2010.10.28

Questions

• Where are we now?– How much habitat we used to have?

• Where are we going?– Restore or not?– Where?– How much we can gain?– How much do we have to pay?

Columbia River Basin Historical Ecology Project

Channel Type

Riparian Vegetation

SalmonDistribution

Project Objectives

• Establish a guideline to restore stream processes for endangered salmon and biodiversity

• Our methods and products can be used as…– Natural channel type template for restoration– Restoration prioritization tool

Columbia River BasinArea　 668,000km2

Total stream length 444,121 km

Our common perspective

Why Channel Types?

• Process-based channel classification– Natural or potential channel types

• Restoration potential or target

• Large geographic scale– Map presentation of physical channel type

• Prioritization tool

• Simplicity– Easy to explain and communicate!

Floodplain Channel Types

Straight Meandering BraidedIsland-braided

Beechie et al. (2006)

Mountain Channel Types

Montgomery and Buffington (1997)

Cascade

Step-pool

Plane-bed

Pool-riffle

Channel Type System

Pool-riffle

Step-pool

Plane-bed

Cascade

Slope < 0.015

Slope < 0.03

Slope < 0.065

BFW< 8 m *

Meandering

Island-braided

Braided

Straight

Reach

Prediction Model *

Mountain Channels Floodplain Channels

Yes

No

Montgomery and Buffington (1997)

* Hall et al. (2007)

Confined

Confined

Beechie and Imaki (in review)

* Support Vector Machine

Biophysical Floodplain Channel Type Model

Methods

Establish channel type reference reaches

Calculate geomorphic characteristics

GIS data preparation(DEM, stream, etc.)

Build a model and predict channel types(Support Vector Machine)

Field measurements

1. Slope2. Bankfull width3. Floodplain width4. Relative shear stress (RSS)5. Fine sediment supply

• Fine sediment• Alpine sediment

6. Root strength / Wood supply

ABC

Flow direction

Pro

file

Reach

RSS+-

Relative shear stress

Braided Island-braided

Meandering Straight

0.00

0.02

0.04

0.06

Slope

Slo

pe(m

/m)

Braided Island-braided

Meandering Straight

0e+0

04e

+06

8e+0

6 Accumulated Precipitation (BFW)

Acc

umm

ulat

ed p

reci

pita

tion

(mm

)

Braided Island-braided

Meandering Straight

050

100

150

Confinement

Cha

nnel

con

finem

ent (

fpw

/bfw

)

Braided Island-braided

Meandering Straight

-200

-100

010

020

0

Relative Shear Stress

Rel

ativ

e sh

ear s

tress

(N/m

2)

Braided Island-braided

Meandering Straight

020

4060

8010

0 Fine Sediment

Fine

sed

imen

t sup

ply

area

(%)

Braided Island-braided

Meandering Straight

05

1015

2025

Alpine SedimentA

lpin

e se

dim

ent s

uppl

y ar

ea (%

)

Columbia River

Grand Ronde

Snake River

N

0 50 km

Prediction accuracy and errorObserved channel type

Pre

dic

ted

cha

nne

l

typ

e

BraidedIsland-

braidedMeandering Straight Total Accuracy

Braided 20 4 0 1 25 80%

Island-braided 1 18 4 4 27 67%

Meandering 1 2 22 2 27 81%

Straight 4 2 0 19 25 76%

Total 26 26 26 26 104

Accuracy 77% 69% 85% 73%

Channel type ~ Slope + acc_precip + r_stress + fine_sediment + alpine_sedimentOverall accuracy = 76% Kappa = 0.69

Coming Soon!