The Automated Geospatial Watershed Assessment Tool (AGWA): Developing Post-Fire Model Parameters Using Precipitation and Runoff Records from Gauged Watersheds

Abstract:

New tools and functionality have been incorporated into the Automated Geospatial Watershed Assessment Tool (AGWA) to assess the impacts of wildfire on runoff and erosion. AGWA (see: www.tucson.ars.ag.gov/agwa or http://www.epa.gov/esd/land-sci/agwa/) is a GIS interface jointly developed by the USDA-Agricultural Research Service, the U.S. Environmental Protection Agency, the University of Arizona, and the University of Wyoming to automate the parameterization and execution of a suite of hydrologic and erosion models (RHEM, WEPP, KINEROS2 and SWAT). Through an intuitive interface the user selects an outlet from which AGWA delineates and discretizes the watershed using a Digital Elevation Model (DEM). The watershed model elements are then intersected with terrain, soils, and land cover data layers to derive the requisite model input parameters. With the addition of a burn severity map AGWA can be used to model post wildfire changes to a catchment. By applying the same design storm to burned and unburned conditions a rapid assessment of the watershed can be made and areas that are the most prone to flooding can be identified.

Post-fire precipitation and runoff records from gauged forested watersheds are now being used to make improvements to post fire model input parameters. Rainfall and runoff pairs have been selected from these records in order to calibrate parameter values for surface roughness and saturated hydraulic conductivity used in the KINEROS2 model. Several objective functions will be tried in the calibration process. Results will be validated. Currently Department of Interior Burn Area Emergency Response (DOI BAER) teams are using the AGWA-KINEROS2 modeling interface to assess hydrologically imposed risk immediately following wild fire. These parameter refinements are being made to further improve the quality of these assessments.