Evaluating Increased Erosion Potential due to Wildfires

Evaluating Increased Erosion Potential due to Wildfires

Brian DrakeCE394K – Fall 2005

Term Project Presentation

Study Area

Cedar Wildfire

• Duration: 10/25/03 – 11/3/03• Size = 280,000 acres• 2,232 homes destroyed• 15 human deaths• Suppression Cost: >$31 Mil

Major Factors Affecting Soil Losses

• Vegetative Cover• Soil Characteristics• Topography• Intensity of Storms

Modeling Erosion

• USDA Universal Soil Loss Equation (USLE)

• A = R∙K∙LS∙C∙P– A = Soil loss per unit area– R = Rainfall-Runoff Erosivity– K = Soil Erodibility– LS = Slope Length/Steepness Factor– C = Land Cover Factor– P = Conservation Practice Factor

Rainfall-Runoff Erosivity (R)

• Reflects rainfall intensity and storm energy

Soil Erodibility (K)

• Represents susceptibility of soil to erosion

Legend0.100000002 - 0.136666669

0.136666669 - 0.173333336

0.173333336 - 0.210000003

0.210000003 - 0.246666671

0.246666671 - 0.283333338

0.283333338 - 0.320000005

0.320000005 - 0.356666673

0.356666673 - 0.393333340

0.393333340 - 0.430000007

Slope Length/Steepness (LS)

LS = (a/22.13)0.4 (s/0.0896)1.3

DEM

Land Cover Factor (C)• Ratio of soil loss based on vegetative cover

Conservation Practice Factor (P)

• Reflects impact of erosion-reduction practices

Total Sediment Potential (A)

Aave = 30.7 ton/acre/yr

Aave = 1,295 ton/acre/yr

Remaining Tasks

• Adjustments to current pre-fire calculation– Check for unit consistency– Search for more representative R-Factor– Ensure that LS value is accurate

• Modify factors to model post-fire conditions– Increase C-Factor

Resources

• DEM: http://seamless.usgs.gov/

• NHD: http://nhd.usgs.gov/data.html

• USDA Soils: http://www.ncgc.nrcs.usda.gov/products/datasets/statsgo/

• Fire Info: http://map.sdsu.edu/fireweb/

Questions?