CE 513

Erosion in the Fall Creek Watershed Rick Faber

Erosion in the Fall Creek Watershed following the Clark Fire: Implications for the Hehe Timbersale  Clark Fire destroyed 5000 acres of undisturbed forest land in late 2003  Fall Creek is home to genetically diverse population of anadromous fish  Current proposals are for a 2500 acre timber sale in the neighboring Hehe Creek basin.

The universal soil loss equation is: A = R K L S C P  A is soil loss (tons/acre/year)  R is the rainfall/runoff erosivity factor  K is the soil erodibility factor (tons/acre/year)  L is the slope length factor  S is the slope steepness factor  C is the cover management factor  P is the support practice factor

Isoerodent Map of Oregon R = 50

K-factor from STATSGO soil coverage from the USDA.

L & S: Length & Steepness Now combined and expressed as a single factor. (Moore and Burch 1986) Spatial AnalystArcHydro

C-Factor Land Cover TypeC-Factor Agriculture0.09 Developed0.24 Disturbed0.24 Forest0.004 Grasslands0.06 Open Water0.00 Riparian0.004 Unvegetated0.24 Woodland LARSE DATA

C-Factor Rasters

Calculate the Erosion

Soil Erosion

The loss of one inch of soil due to erosion is equivalent to 150 tons of soil per acre. Mean Soil Loss for Fall Creek Watershed

Limitations  Sedimentation vs erosion  Truncate the Flow accumulation grid for LS factor  Land cover & time  Systematic error?