Notes

Outline

Comparing Erosion Risks from Forest Operations to Wildfire Bill Elliot and Pete Robichaud Soil and Water Engineering Rocky Mountain Research Station Moscow, Idaho

Forest Management Goals 19th Century:  Ample source of fuel, food, and building material 20th Century:  Large corporate logging and fire suppression  Multiple use and ecosystem management Current conditions: Excessive fuels, fires, roads and erosion

Forest Management Goals 19th Century:  Ample source of fuel, food, and building material 20th Century:  Large corporate logging and fire suppression  Multiple use and ecosystem management Current conditions: Excessive fuels, fires, roads and erosion This paper compares erosion rates following harvest to following fire

Forest Erosion Processes Erosion occurs when forests are disturbed Roads Timber Harvest Fire Soil erodibility depends more on soil surface condition than on texture Roads > Wildfire > Skid Trails > Rx fire > Forest

Forest Recovery After wildfire or harvesting, forests recover quickly More available light, nutrients, and water for low-growing vegetation Erosion rates drop 90 percent in first year, and another 90 percent the second.

Erosion Rates are Variable Vary Spatially, within soil, and with weather Sites recover quickly Erosion is NOT average.  It will either be above or below average, and may be zero! Sediments may spend years in a stream system, moving during flood flows only

Erosion Prediction We use the Water Erosion Prediction Project (WEPP) model Interfaced to run on our web server with any browser, anywhere in the world Requires calibration to ensure “cover” is correct Interface allows inclusion of a buffer of any length

Model Performance

Management Strategies Modeled Considered steep Oregon site, and less steep Montana site Compared erosion rates Harvest + (Rx fire or Thinning) Wildfire

Oregon Results

Montana Results

Comparing Results

Confounding Factors We modeled for “average” conditions Weather is never average With such a variation in erosion rates due to recovery, should we consider the “average” erosion rate over the fire or harvest cycle?

Precipitation Results

Sediment Yield after Harvest

Sediment Yield after Wildfire

Average Erosion over the Cycle

Questions to Ponder Wildfire is natural Shaped our ecosystems and our watersheds

Questions to Ponder Wildfire is natural Shaped our ecosystems and our watersheds We have “Smokey Beared” our ecosystems! Will we “Smokey Bear” our watersheds if we manage fuels to prevent wildfires and wildfire erosion?????

Questions to Ponder Wildfire is natural Shaped our ecosystems and our watersheds We have “Smokey Beared” our ecosystems Will we “Smokey Bear” our watersheds if we manage fuels to prevent wildfires and wildfire erosion? What about roads? Likely more sediment than harvesting and less than wildfire, but eroding EVERY YEAR.

More Questions to Ponder Should we be using “average” erosion rates to support our management decisions? Where do TMDLs come into the plan First year only? Average over cycle? Hillslope or watershed scale?

Conclusions We can predict erosion from forest operations with confidence Sediment delivery following fuel reduction is a magnitude lower than following wildfire Average sediment delivery over the harvesting cycle is less than wildfire We do not know the long term effects of managing for minimal sedimentation

Questions & Comments?