Water Resources Research Act Program

Details for Project ID 2016CA364B

Debris flow and debris basin management impacts on water quality

Institute: California
Year Established: 2016 Start Date: 2016-03-01 End Date: 2018-02-28
Total Federal Funds: $24,378 Total Non-Federal Funds: $5,274

Principal Investigators: Andrew Gray

Project Summary: Debris flows in the mountains of southern California pose acute hazards to local populations, and potentially far reaching water quality effects. Although debris flows in urban areas are contained in part by many debris basins constructed for sediment impoundment, fine sediments are routinely discharged from debris basins. As suspended sediments are not routinely monitored from debris basins, little is known about the impact of debris flows on downstream water bodies. This study proposes the enhancement of work currently addressing the causality of debris flow generation on the steep slopes extending down from Glendora Ridge to the City of Glendora, CA. While this work will lead to further understanding of how debris flows occur, it does not address the water quality implications of debris flows. Monitoring of water and sediment discharge from the waterway draining the instrumented debris basin will allow for the quantification of suspended sediment impacts coupled to high resolution information on debris flow production and debris basin management. It is expected that suspended sediment flux from debris basins will depend on the magnitude and timing of debris flow generation in relation to debris basin management activities. The trapping efficiency of debris basins is reduced as they fill, and sediment flux quantities and qualities are expected to change with debris basin filling during and between debris flow events. The results of this study will then be used to inform the City of Glendora and LA County Flood Control on aspects of debris basin management in terms of water quality.