Mokelumne Avoided Cost Analysis Technical Committee Meeting: GeoWEPP modeling 1/9/2013 Mary Ellen Miller Michigan Tech Research Institute Bill Elliot, USDA Forest Service

Modeling Overview Disturbed WEPP soil parameters Erosion maps GeoWEPP Climate forecast DEM Burn severity from Flame Length predictions Climate data Cligen Rock:Clime Land Cover Data Landfire EVT Disturbed WEPP Land use/management Soils Landfire STATSGO

Batch Processing: The Cookie Cutter Approach For each batch file: – TOPAZ carries out channel delineation – Outlet point based on elevation (iterate if needed) – TOPAZ watershed delineation – Select Cligen station closest to the outlet or for Mokelumne selection based on climate zone using a LUT – TopWEPP2 converts files into WEPP inputs and runs WEPP Post-processing scripts – Mosaic the results Create a polygon watershed delineation based upon input DEM – I use ESRI watershed tools. Sub-watersheds are then used to cut out smaller raster inputs for batch files.

Climate Forecasts 50 years of weather modeled 3 local Cligen stations (Twin Lakes, Calaveras Big Tree, and Tiger Creek) Rock:Clime used to generate 5 additional climates in order to account for the impact of elevation. The average elevation of the initial sub-watersheds were used to select appropriate climate file.

Inputs: Climate forecasts from Cligen stations and Rock:Clime

Inputs: Landcover Existing Vegetation Cover reclassified for Disturbed WEPP

Inputs: Flame length predictions reclassified to burn severity For the Mokelumne Basin 12% of the area predicted not to burn 41% predicted to burn at low severity 29% moderate severity 18% high severity

Inputs: Soils modified by burn severity and land cover

Inputs: Hillshade derived from National Elevation Dataset 30m

Results: Hillslope scale first year post-fire erosion predictions

Results: Erosion Predictions x Burn Probability averaged by AU unit

Results: Erosion Predictions Our mean hillslope scale predicted erosion rate is 32 Mg/(ha yr -1 ) with a standard deviation of 73 Mg/(ha yr -1 ) the range is 0 - 2,955 Mg/(ha yr -1 ) Average annual erosion values observed by Pete Robichuad in California: – Mixing fire were 6-13 Mg/(ha yr -1 ) – Cannon Fire were Mg/(ha yr -1 ) – Cedar Fire Mg/(ha yr -1 ) In all cases, the climates were drier than most of the Mokelumne Basin (604 mm, 669 mm, and 464 mm respectively). These were all from high severity fires, and compare reasonably well with our predictions. Our predictions are also comparable to published sediment yields for the Pacific Medium rainfall regime with a reported range from – 490 Mg/(ha yr -1 ) and a mean value of 97 Mg/(ha yr -1 ) for hillslope measurements. (Moody and Martin 2009) Moody JA, Martin DA (2009) Synthesis of sediment yields after wildland fire in different rainfall regimes in the western United States. International Journal of Wildland Fire 18, 96– 115.