Regional patterns of postwildfire streamflow response in the Western United States: The importance of scale‐specific connectivity |
| |
| Authors: | Dennis W Hallema Ge Sun Kevin D Bladon Steven P Norman Peter V Caldwell Yongqiang Liu Steven G McNulty |
| |
| Institution: | 1. U.S. Department of Agriculture Forest Service, Southern Research Station, Eastern Forest Environmental Threat Assessment Center, Raleigh, NC, USA;2. U.S. Department of Energy, Oak Ridge Institute for Science and Education, Oak Ridge, TN, USA;3. Department of Forest Engineering, Resources, and Management, Oregon State University, Corvallis, OR, USA;4. U.S. Department of Agriculture Forest Service, Southern Research Station, Eastern Forest Environmental Threat Assessment Center, Asheville, NC, USA;5. Coweeta Hydrologic Laboratory, Southern Research Station, U.S. Department of Agriculture Forest Service, Otto, NC, USA;6. U.S. Department of Agriculture Forest Service, Southern Research Station, Center for Forest Disturbance Science, Athens, GA, USA |
| |
| Abstract: | Wildfires can impact streamflow by modifying net precipitation, infiltration, evapotranspiration, snowmelt, and hillslope run‐off pathways. Regional differences in fire trends and postwildfire streamflow responses across the conterminous United States have spurred concerns about the impact on streamflow in forests that serve as water resource areas. This is notably the case for the Western United States, where fire activity and burn severity have increased in conjunction with climate change and increased forest density due to human fire suppression. In this review, we discuss the effects of wildfire on hydrological processes with a special focus on regional differences in postwildfire streamflow responses in forests. Postwildfire peak flows and annual water yields are generally higher in regions with a Mediterranean or semi‐arid climate (Southern California and the Southwest) compared to the highlands (Rocky Mountains and the Pacific Northwest), where fire‐induced changes in hydraulic connectivity along the hillslope results in the delivery of more water, more rapidly to streams. No clear streamflow response patterns have been identified in the humid subtropical Southeastern United States, where most fires are prescribed fires with a low burn severity, and more research is needed in that region. Improved assessment of postwildfire streamflow relies on quantitative spatial knowledge of landscape variables such as prestorm soil moisture, burn severity and correlations with soil surface sealing, water repellency, and ash deposition. The latest studies furthermore emphasize that understanding the effects of hydrological processes on postwildfire dynamic hydraulic connectivity, notably at the hillslope and watershed scales, and the relationship between overlapping disturbances including those other than wildfire is necessary for the development of risk assessment tools. |
| |
| Keywords: | climate change hydraulic connectivity streamflow watershed wildfire wildland– urban interface |
|
|
