Effective January 1, 2020, A.B. 825 (C.A., 2019) amended the San Mateo County Flood Control District Act to expand the San Mateo County Flood Control District's responsibilities, create an independent governing board for the District, and rename the District the San Mateo County Flood and Sea Level Rise Resiliency District (https://oneshoreline.org/). The flood control zones (Colma Creek, San Bruno Creek, San Francisquito Creek, and Ravenswood Slough) formerly administered by the County of San Mateo Department of Public Works are now being managed by the new District.

The San Mateo County Flood Control District is a Countywide Special District that was created by State legislation in order to provide a mechanism to finance flood control projects. The legislation requires that a flood control zone be formed over an entire watershed and a proposed funding source be determined before a flood control project is undertaken.  Recent changes in the State Constitution require an election if a flood control zone is to be financed with property assessments or taxes.  There are currently three active flood control zones:

Colma Creek

The Colma Creek Flood Control Zone was created in 1964 to construct flood control facilities in Colma Creek to alleviate flooding in the City of South San Francisco. Originally the project extended from Mission Road in South San Francisco approximately three miles to San Francisco Bay. Several channel improvements were constructed and four bridges replaced before Proposition 13 curtailed the project's funding source (property taxes) in 1978. The plan to improve the Colma Creek Flood Control Channel was re-vitalized in the mid 1990’s by the financing of improvements by the BART Airport Extension Project and a financial contribution from the State Department of Transportation (CALTRANS) for drainage improvements in El Camino Real in Colma and Daly City. The scope of the project was extended upstream from Mission Road to the vicinity of “A” Street in Daly City.

The BART and CalTrans projects were combined with bond financing in the amount of $15.7 million to provide funding for additional flood control facilities within the expanded project limits. Culvert improvements have been made in Old Mission Road and El Camino Real and the South Airport Boulevard Bridge has been replaced.  A collaborative project with the Peninsula Joint Powers Board to replace the Mainline Railroad Bridge over Colma Creek was completed in 2004.  A project that includes channel improvements from Spruce Avenue to San Mateo Avenue and the raising of the San Mateo Avenue Bridge is near completion.  The Colma Creek Flood Control Zone has issued additional bonds to finance and complete the remainder of the planned projects.

Construction between Spruce and San Mateo Avenues on Colma Creek resulted in the filling of half an acre of salt marsh wetlands within the original earthen channel of Colma Creek. Federal and State permits for the current construction require that the District mitigate for these lost wetlands. Therefore the District is constructing 1.5 acres of salt marsh wetlands and 2.0 acres of "native" upland habitat. This project, known as the Colma Creek Flood Control Habitat Mitigation Project, is located along the mouth of Colma Creek where it enters San Francisco Bay, below Utah Avenue. When complete, this habitat is expected to be used by the endangered California Clapper Rail, which has been observed in the area.

San Bruno Creek

The San Bruno Creek Flood Control Zone was established in 1967 to finance the construction of channel and culvert improvements in the lower reach of San Bruno Creek.  The Zone also contributed to the financing of drainage improvements in the City of San Bruno below El Camino Real.  The Zone finances the maintenance of the channels and contracts with the City of San Bruno for pump station maintenance.  The Zone recently removed accumulated silt and vegetation from the open channel area known as “Cupid Row” located between the CalTrain tracks and U.S. 101. Complex Federal and State permits are required to maintain this channel as the area is habitat for the California Red Legged Frog and the San Francisco Garter Snake, both listed as Federal Endangered Species.

San Francisquito Creek

San Francisquito Creek is the boundary between San Mateo and Santa Clara Counties. The San Francisquito Creek Flood Control Zone finances creek improvements in cooperation with the Santa Clara County Water District. The Zone's source of revenue is property taxes, which are limited by Article XIII of the State Constitution. The Creek overtopped its banks in 1998 and flooded portions of the Cities of Palo Alto, East Palo Alto and Menlo Park. The San Francisquito Creek Joint Powers Authority (SFCJPA) was created as a result to develop solutions to the flooding problem and provide for a coordinated approach to planning in the San Francisquito Creek Watershed. The SFCJPA members include the cities of Palo Alto, East Palo Alto, Menlo Park and the Santa Clara Valley Water District and San Mateo County Flood Control District. Stanford University and the San Francisquito Creek Watershed Council are Associate Members. The SFCJPA is currently pursuing a major flood control project with the Army Corps of Engineers to prevent a repetition of the 1998 flood.


Each day, a variety of toxic pollutants could be washed from streets and parking lots into storm drains via stormwater that ultimately run into one of the County’s maintained Flood Control Zones mentioned above. Stormwater is runoff from rain, snowmelt, and irrigation water that travels over impermeable surfaces like roads, sidewalks, and parking lots and doesn’t soak into the ground. This water enters storm drains and is piped underground where it flows into creeks and streams and eventually into the San Francisco Bay or the Pacific Ocean. Stormwater isn’t treated, so any pollutants left on the ground like trash, oil and dog waste are picked up and deposited into the Bay and Ocean. These pollutants can degrade water quality and harm aquatic and human life.

Stormwater Pollution Prevention

Through city and county stormwater programs in the Bay Area, the water quality of our local creeks, the Bay, and the Ocean can improve. With improved water quality, the marine ecosystem will become healthier, which will enhance the quality of life for all Bay Area residents.

In San Mateo County, there are several programs aimed to reduce stormwater pollution and manage stormwater quality:

  • The Municipal Regional Permit is issued by the State and requires San Mateo County and its municipalities to enact stormwater pollution prevention measures related to construction activities, industrial sites, new development, trash management, and more. The Office of Sustainability is responsible for overseeing the Municipal Regional Permit.
  • The San Mateo Countywide Water Pollution Prevention Program is a partnership between the City/County Association of Governments, the County of San Mateo, and every incorporated city and town in the county to conduct coordinated stormwater management.

Report Stormwater Pollution

Only stormwater is allowed to enter the storm drain system. Potential pollutants and other materials such as washwaters, sewage, automotive fluids, construction materials, paint, sediment, silt, and food wastes are not allowed to enter the storm drain system. Reporting incidents of water pollution problems such as illegal dumping, spills or illicit discharges helps keep our local creeks, San Francisco Bay, and the Pacific Ocean clean.

When Should You Make A Report?

  • When you find dumped waste in or near the storm drain
  • When you notice unusual odors in or near the storm drain
  • When the drainage system has unusually large flows during dry periods
  • When you see someone illegally dumping anything into a storm drain

How Can You Make A Report?

Note: If you are reporting an emergency situation that could result in imminent or substantial danger to the health and safety of persons, call 911.