Expanding the WEPPcloud Toolbox: WEPPcloud – TREE, Timber Recovery Erosion Estimator

Abstract. The effects of a warming climate have increased the number, size, severity, and cost of wildfires. Salvage logging to recover the value of burnt timber is often undertaken after wildfires; yet predicting the sediment disturbance and impact to streams is challenging to quantify. Major advancements in our knowledge of post-fire salvage logging effects, mitigation treatments, and stream buffer management have improved our ability to predict the impacts of salvage operations on sediment delivery. Our watershed-scale decision support tools have incorporated cloud computing technology and allow for automating the acquisition and processing of climate, soil, management, and topographic inputs for the WEPP (Water Erosion Prediction Project) model from publicly available datasets with national and international (European Union countries and Australia) coverage. WEPPcloud users with limited GIS experience now have the ability to do watershed analysis with a process-based spatially-distributed hydrology and erosion model. We have expanded the WEPPcloud capabilities to predict the impact of ground-based salvage logging activities on stream sedimentation with a new interface, TREE (Timber Recovery Erosion Estimator). The interface is available on the WEPPcloud platform (https://forest.moscowfsl.wsu.edu/fswepp or https://wepp.cloud/weppcloud/) after the user uploads the soil burn severity map and, if available, a salvage logging plan with proposed logging equipment track layout and targeted stream buffer widths. Alternatively, a 2-m resolution WorldView imagery can be used to map logging equipment tracks spatially using the Normal Difference Vegetation Index (NDVI) by detecting disturbed bare soil from the logging equipment tracks and can even differentiate when logging wood slash was added to the track. Once a scenario is defined, the logging equipment tracks are modified to provide defined flow paths for runoff down the tracks until a water bar is encountered or the slope changes enough for the runoff to return to overland flow downslope. Logging equipment tracks can be designated as high traffic, low traffic, or treated with mulch (logging wood slash or straw mulch). Stream buffers widths and effectiveness are modeled with parameters based on field experiments. The effectiveness of the buffers is a function of soil burn severity (low, high, or unburned) and timing of salvage operations after the fire (i.e., 2-, 12-, 24-months) aligned with post-fire vegetation recovery. The ability to apply a process-based spatially-distributed hydrology and erosion model make this a unique and powerful tool for watershed assessment and management planning.