Potential Effects of Wildfire on Watershed Hydrologic Response: Sabino Creek Basin, Arizona

Wildfires and their hydrologic consequences, such as flash floods and mudslides, pose serious hazards in the southwestern United States. As a result of the present drought and decades of fire suppression, wildfires are occurring with greater frequency and intensity. Preservation or rehabilitation zones can be identified in a watershed to minimize the severity of secondary-order fire effects, such as erosion, increased flow peaks and landslides. Distributed hydrological models can be a useful tool to locate these zones. In this study, a distributed watershed model was used to evaluate the effects of pre- and post-fire land use scenarios on watershed hydrologic response in the Sabino Creek watershed north of Tucson, Arizona. During the summer of 2003, the Aspen fire burned in excess of 34 thousand hectares in the Santa Catalina Mountains, including a large part of the study basin. To model the watershed, field and laboratory measurements of soil permeability in burned and unburned areas were used, together with fifteen years of climatological data from NOAA, USGS and Pima County. To investigate the hydrologic effects of wildfire, model simulations using pre- and post-fire soil and vegetation parameters, in particular soil permeability and leaf area index, were compared to each other as well as to field observations.