Sediment Delivery, Flood Control, and Physical Ecosystem Services in Southern California Chaparral Landscapes

Abstract

Southern California chaparral environments, with steep mountain slopes, semi-arid climate, and non-cohesive soils, are very erosive landscapes. Wildfire is the dominant ecological disturbance event in chaparral and it greatly accelerates flooding and erosion, which are directly and/or indirectly related to the loss of the protective vegetation. Since the 1920s, dams and debris basins have been constructed by public works agencies to protect the growing population and infrastructure of southern California by intercepting and impounding flows of water and debris. Dams also capture stream runoff for supplying water to downstream agriculture and urban populations. Major sediment inflows into dams and debris basins following fire can reduce capacity and threaten the ability to provide flood control and water supply. Chaparral provides physical ecosystem services that aid in flood hazard reduction, sediment retention, and the supply of water as well as protecting habitat for endangered species and soil quality.