stream sediment
DESCRIPTION
Stream Sediment. Sediment - particles transported or deposited in stream channels Sediment levels - good indicator of effectiveness of watershed mangement. Erosion is a natural process. Clearwater River, Idaho. The name says what the watershed management goal is. Clearwater River, Idaho. - PowerPoint PPT PresentationTRANSCRIPT
Stream Sediment
• Sediment - particles transported or deposited in stream channels
• Sediment levels - good indicator of effectiveness of watershed mangement
Erosion is a natural process
Clearwater River, Idaho
The name says what the watershed management goal is.
Clearwater River, Idaho
Clean gravel beds for spawning
Erosion Process
• Detachment• Transport• Deposition
Eroded skid trail
Watershed Gross Erosion
• Components of gross erosion– Interrills– Rills– Ephemeral gullies– Channels– Landslides or slumping
Interril Erosion
Raindrops striking exposed soil detach the soil particles and splash them into the air and into shallow overland flows. Raindrops striking these shallow flows enhance the flows's turbulence and help to transport more of the detached sediment to a nearby rill or flow concentration
Rill Erosion
Gully Erosion
Channel Erosion
Landslides
Grand Ditch, Rocky Mountain National Park
Estimates of rill erosion
• Universal soil loss equation– Developed by US Dept. Agriculture– Oldest and most accepted estimator– Over-estimates for forest land– Use as a starting point only
Universal Soil Loss Equation
A = R K LS C PA = tons/acre/yearR = rainfall energy factorK = soil erodibility factorsLS = effect of topographyC = ratio of soil loss with specified cover and with
continuous tillageP = conservation practice factor
R factor
R = [∑ ∑ (E I30)] / 100 n)
E = storm kinetic energy, ft-t/acre/inch of rainfallI = maximum 30 minute storm intensity, in./hr.n = total number of yearsm = number of storms in each year
R = 150 to 200 for Indiana
n m
K factor
Describes soil detachability and transport-ability due to soil texture, structure, organic matter, density, compaction, and biological characteristics
K = A / (RLSCP)K is given in NRCS soil survey reports
K factor
100 K = 2.1M1.14(10-4)(12-a) + 3.25(b-2) + 2.5 (c-3)
M = (%silt + %very fine sand) (100 - % clay)a = % organic matterb = soil structure code used in soil classificationc = profile permeability class
LS factor
LS = (λ/22.13)a (0.065 + 0.0454 S + 0.0065 S2
λ = slope lengtha = 0.5 for slope ≥ 5%, and 0.3 for 1 to 3% slopeS = slope steepness in %
C factorC = A (with treatment) / A (with clean tillage)
Undisturbed mature forest
Thinned to 50%
density
Clearcut, no site
preparation
Clearcut, roller
chopped
Clearcut, complete site prep.
Clearcut, site prep., fallowed
0.0001- 0.001
0.002 -0.004
0.003 -0.009
0.03 NA 0.11- 0.17
0.001 – 0.0034
NA 0.0003 – 0.01
0.001 – 0.022
0.004 – 0.028
0.023 – 0.068
0.00014 0.00019 0.00165 0.00325 0.0242 0.097
C values reported in 3 studies of forested site conditions
P factor
P = A (with conservation practice) / A (up-and-down hill cultivation)
P = 1 if no conservation practices
P < with conservation practices
Recommended Values for P Factor
Land slope %
ContouringContour
stripcroppingTerrace and
stripcropping
1 to 2 0.60 0.45 0.30
3 to 5 0.50 0.38 0.25
6 to 8 0.50 0.38 0.25
9 to 12 0.60 0.45 0.30
13 to 16 0.70 0.52 0.3517 to 20 0.80 0.60 0.40
21 to 25 0.90 0.68 0.45
Drum chopper for site preparation Windrow of logging slash
Burning piles of logging slash
Erosion rates for clear cuttings in SE USTreatment Recovery time Annual erosion
(t/ha)Natural NA 0.00 – 0.05
Logged and roaded 3 0.10 – 0.50
Burned 2 0.05 – 0.7
Chopped 3 0.05 – 0.25
Chopped and burned 4 0.15 – 0.40
Windrowed 4 0.20 – 0.24
Disked 4 2.50 – 10.0