in-stream habitat survey. modified from odfw entory/methods.html quantitative method for assessing...
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In-Stream Habitat Survey
In-Stream Habitat Survey
Modified from ODFW http://oregonstate.edu/Dept/ODFW/freshwater/
inventory/methods.html Quantitative method for assessing habitat for
fish 2 steps to survey:
Data collection Summary
Measurements are made at the “unit type” level
Habitat Units~~~~~~
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1
2
3
Unit Number
Unit Type
1 R
2 P
3 G
Unit Number Sequential # starting
downstream
Unit Type Riffle, glide, or pool
Unit Types – Riffle
RI Riffle: Fast, turbulent, shallow flow over gravel or cobble substrate.
Unit Types – Riffle
Unit Types – Glide
GL Glide: Fairly uniform depth and flow with no surface turbulence.
Deeper than riffle, but not deep enough to be a pool.
Unit Types – Glide
Unit Types – Pool
Unit Measurements
Length Width and Depth
Wetted Surface Active Channel
Depth at Pool Tail Crest (pools only) Channel Shade (left and right side) Percent Actively Eroding Bank Percent Undercut Bank
Pool Tail Crest
Place where water leaks out of pool (measure at deepest spot)
Measure for POOL units only
Max Depth
PTC Depth
FLOW
Shade
Measure using clinometer
90°80°
Substrate
Percent (within each unit) Silt/Organics Sand Gravel Cobble Boulder Bedrock
Large Boulder Count (>1.5 ft diameter)
Substrate Fine Sediments Coarse sediments Solid
Clay Silt Sand Gravel Cobble Boulder Bedrock
0.002 mm 0.05 mm 2 mm 6 cm 25 cm (0.25 in.) (2.5 in.) (10 in.) pea tennis ball bowling ball
1 2
3
Determining intermediate axis: 1 = Longest Axis (Length) 2 = Intermediate Axis (Width) 3 = Shortest Axis (Thickness)
Large Boulders
Large boulders create “pocket water”
Large Woody Debris
Large Woody Debris
LWD Type Diameter Length
Root Wad >6” -
Small >6” >10’
Medium >12” >20’
Large >20” >35’
Must be DEAD
Overhanging or in channel
Diameter = Circumference (approx. 3.14)
Diameter
Circumference
Habitat Summary
Why did we take all those measurements?
The Summary allows us to see whether our stream has desirable habitat for fish
Percent Pool Area
Percent Pool Area = Pool Area/Reach Area Pool Area = Length x Width for pool units Reach Area = Length x Width for ALL units
Pool PoolRiffle
Percent of stream area which is pool
Percent Pool Area
Pool Area = (10 x 10) + (10 x 10) = 200 Reach Area = (5 x 20) + 200 = 300 Percent Pool Area = 200/300 = 67%
Pool
W = 10’ L = 10’
Riffle
W = 5’, L = 20’
Pool
W = 10’ L = 10’
Percent Pool Area
Percent Pool Area = 200/300 = 67%
Habitat Benchmarks
Undesirable Between Desirable
Pool Area (%)
< 10 10-35 > 35
67% > 35%, so Pool Area = Desirable
Pool Frequency
Pool Frequency = Distance Between Pools / Channel Width Channel Width = Average width for all units
between pools
Pool PoolRiffle
Length/Width = distance btwn pools relative to stream width
Pool Frequency
Pool Frequency = Distance Between Pools / Channel Width
Pool Frequency = 20 / 5 = 4
Pool PoolRiffle
W = 5’, L = 20’
Pool Frequency
Pool Frequency = 20 / 5 = 4
Habitat Benchmarks
Undesirable Between Desirable
Pool Frequency
> 20 9 - 20 < 8
4 < 8, so Pool Frequency = Desirable
Residual Pool Depth
Residual Pool Depth = Max Depth – Pool Tail Crest Depth Important for low to no flow conditions
Max Depth
PTC Depth
Residual Pool Depth
Residual Pool Depth = Max Depth – Pool Tail Crest Depth
Example: Pool Depth = 3’ Pool Tail Crest = 1’ Residual Pool Depth = 2’
Residual Pool Depth
Habitat Benchmarks
Undesirable Between Desirable
Small Streams (<23 feet wide)
< 0.5 0.5 – 1.5 > 1.5
2’ > 1.5’ , so Residual Pool Depth = Desirable
Residual Pool Depth = 2’
Habitat Summary – Riffles
Width to Depth RatioPercent GravelPercent Sand-Silt-Organics
Riffle – Width to Depth
Width / Depth = 5 / 0.5 = 10
Pool PoolRiffle
W = 5’, D = 0.5’
Habitat Benchmarks
Undesirable Between Desirable
Width to Depth
> 30 15 - 30 < 15
Riffle – % Gravel
If % Gravel = 25%, Rating is Between
Habitat Benchmarks
Undes Btwn Desir
Percent Gravel
< 15 15 - 35 > 35
Riffle – % Sand-Silt-Organics
If % Sand-Silt-Organics = 10%, Rating is Between
Habitat Benchmarks
Undes Btwn Desir
Percent Sand-Silt-Organics
> 15 8 - 15 < 8
Values for streams with Volcanic Parent Material
Habitat Summary - LWD
Number of Pieces / 300’ Stream Reach Large LWD Pieces / 300’ Stream Reach
>20” Diameter and 35’ Length
Habitat Benchmarks
Undesirable Between Desirable
Number of Pieces < 10 10 – 20 > 20
Large Pieces < 1 1 – 3 > 3
Habitat Summary
90°80°
Shade (average for entire reach) Left + Right Bank Shade (degrees) / 180 Final Shade in %
90° + 80° = 170° 170 / 180 = 94%
Habitat BenchmarksSHADE (REACH AVERAGE %) U B D
Stream Width <40 feet
West Side <60 60 – 70 >70
Northeast <50 50 – 60 >60
Central-Southeast <40 40 – 50 >50
Stream Width >40 feet
West Side <50 50 – 60 >60
Northeast <40 40 – 50 >50
Central-Southeast <30 30 – 40 >40
94% > 70%