AN INTEGRATED APPROACH TO EVALUATING WATERSHED RESPONSE TO WILDFIRE: SANTA ANA RIVER CASE STUDY

In semi-arid and arid regions of the United States, understanding watershed recovery after wildfire is a necessary tool for protecting water resources and their constituents. The negative effects of wildfire are well documented, including accelerated erosion, decreased soil productivity, and flooding. However, little quantitative information is available concerning the ability of stream networks to naturally respond to and recover from wildfire impacts. Our project fills this knowledge gap by examining fire response within waterways on a basin-wide scale. We have selected over 40 stream sites within the headwaters of the Santa Ana River in southern California, an area that is highly susceptible to wildfire due to prolonged drought and high vegetation mortality. Sites were selected by stream order and watershed position, and data collected regarding stream morphology, sedimentology, riparian characteristics, and water quality. Hydrologic information documenting large-scale sedimentation and runoff rates within the watershed is available from multiple public agencies that monitor gaging stations, sediment basins, and water diversion structures along the main stem of the Santa Ana River. The integration of our data with this longer-term public information provides a basic framework to begin addressing difficult questions about the benefits and limitations of using point measurements to predict watershed-scale response to disturbance, as well as the spatial and temporal distribution of wildfire impacts within the watershed.