Stormwater

Stormwater management systems consist of drains that collect urban runoff and underground pipes that convey flows either by gravity or by pumping to a discharge location (outfall).

1_BCDC StormwaterDischarge

Photo credit: BCDC

In the ART Subregional Project area stormwater from all cities, except the City of Alameda, is collected and conveyed by city-owned systems and discharged to infrastructure owned and maintained by the Alameda County Flood Control and Water Conservation District (ACFCWCD). The county has nine flood zones, seven of which are in the project area. These zones are treated as separate financial entities for the purposes of maintenance, construction, levying assessments, planning and budgeting for capital improvements. The City of Alameda manages its own stormwater and flood control infrastructure. Within the city there are eight drainage management sub-areas, each containing pipes, pumps, culverts, outlets and lagoons that collect and convey stormwater to the Bay.

Key findings

2_Eddy_SWPumpStation

Photo credit: BCDC

The vulnerability of stormwater management systems to sea level rise and storm events depends on their current storage and flow capacity, the elevation and location of their outfalls, and whether they are gravity drained or pumped. It is difficult to fully assess the vulnerability of stormwater systems to sea level rise and storm events because of gaps in critical data (e.g., elevation of inlets and outfalls) and understanding of current and future capacity.

In general, stormwater and flood management systems share a number of vulnerabilities with other types of utilities, for example, a reliance on uninterrupted power, and water and salt sensitive components. The capacity to collect, convey and discharge flows to the Bay will be reduced by higher Bay water levels. Outfalls that are below the new high tide or storm event levels may need to be elevated, have check valves installed to prevent backups, and be pumped rather than gravity drained. Reduced discharge capacity and/or failures of pump stations could cause flooding of adjoining properties and, in neighborhoods served, disrupt access to homes, jobs, and recreation areas leading to potentially significant consequences.

3_Chesapeake Bay Program_street flooding

Photo credit: Chesapeake Bay Program

Improvements to the stormwater system as a whole will require collaboration and coordination among cities, property owners, and flood control managers. However, there is no framework in place for comprehensive, watershed-based stormwater and flood control management. Sea level rise and future storm event impacts will only increase the need for this kind of shared decision making. In addition, the limited ability of cities, counties and districts to raise revenues for spending on stormwater and flood management systems will continue to prevent improvements – many of which are needed today to address systems that are currently undersized or have had maintenance deferred.

Project Findings and Materials

For more information:

  • Lindy Lowe
  • Lindy.Lowe@bcdc.ca.gov
  • 415-352-3642