Colma Creek: How does sediment removal from a flood control channel affect nearby tidal wetlands and habitats? 

Client: Horizon Water & Evironment / San Mateo County Department of Public Works
Location: South San Francisco, California
Dates: 2013

walls land+water was contracted by Horizon Water & Environment to assist in a sedimentation and habitat study of Colma Creek, a tributary to San Francisco Bay, drains urban and undeveloped portions of the northern San Francisco Peninsula including portions of San Bruno Mountain. A period of rapid urbanization in 1960s and early 1970s led to engineered flood control channels, whose sediment management challenges persist today. Horizon Water and Environment is working with the San Mateo County Flood Control District/County of San Mateo Public Works Department (County) to develop a flood control channel maintenance strategy that addresses numerous natural resource management challenges that are common throughout the San Francisco Bay. Key issues addressed through this data collection and planning effort include calculating and mapping sediment volumes and deposition patterns in the flood control channel; evaluating sediment supply to tidal marshes near the mouth of Colma Creek (downstream of the flood control channel); characterizing habitat conditions for endangered species; and assessing potential effects of sea-level rise scenarios. Colma Creek provides a useful microcosm of many of the resource management challenges facing San Francisco Bay watersheds and tributaries. The results will help guide the County to develop a sustainable flood control and maintenance strategy for Colma Creek.