FEMA Flood Zone History & Overview


The National Flood Insurance Act of 1968 allows the Federal Emergency Management Agency (FEMA) to make flood insurance available to communities that adopt floodplain management regulations. The City of San Mateo has been a regular member of the National Flood Insurance Program since 1981. Historically, the City was not considered flood prone, but studies completed in the 1980s revised this assessment. In response, FEMA conducted a flood insurance study that designated areas north of Highway 92 for inclusion in a special flood hazard area. This designation became part of a Flood Insurance Rate Map (FIRM) that went into effect in 2001 and made flood insurance mandatory for properties within the special flood hazard area and optional for those in other areas. Since then, the City has undertaken a number of steps to modify FEMA’s designation and reduce residents’ insurance premiums.

City’s Efforts to Revise FIRM

FEMA requires communities to address tidal flooding (from the Bay) and residual flooding (from interior sources like creeks) to remove areas designated as flood prone from the FIRM. In response, the City adopted a flood ordinance that meets federal standards for regulating development and improvements to properties in special flood hazard areas. The City also completed a comprehensive study of tidal and residual flood risks, flood protection measures to address these risks, and estimated costs and funding sources to implement improvements. In 2003, the City requested revision of the FIRM and provided FEMA information on planned or in-progress flood improvement measures. FEMA has approved the design concept for projects and issued a Conditional Letter of Map Revision (CLOMR) to the City. The CLOMR provides assurance that FEMA will revise the floodmap upon completion of the levee improvements. The City needs to secure funding for detailed design and construction. The amount of time needed to complete a project and the length of construction is dependent upon a multitude of factors, including whether permits from outside agencies must be secured, availability of materials, and the complexity of the design.

To date, the City has:

  • Completed construction of the southern levee wall along San Mateo Creek (2001)
  • Completed construction of the Norfolk Bridge over San Mateo Creek (2002)
  • Completed construction of the northern levee wall along San Mateo Creek (2004)
  • Enlargement of the box culvert under Highway 101 at 3rd Ave was completed by Caltrans (2004)
  • Completed construction of the O'Neill Slough Tide Gate and Levee Improvements (2007)
  • Approved formation of an Assessment District to fund the South Bayfront Levee Improvement Project (2009)
  • Completed construction of the South Bayfront Levee Improvement Project (2011) which resulted in the removal of approximately 4,000 properties from the FIRM and prevented an additional 4,000 from being placed on the FIRM
  • Completed 95% design of the North Bayfront Levee and Coyote Point and Poplar Pump Stations required to remove North Shoreview and North Central homes out of the High-Risk Zone AE. Began working with a consultant to start a study to evaluate the interest of an Assessment District to help fund the construction of those projects (2014-2016).

Remaining projects to address Tidal Flooding include:

  • Raising the North Levee at Coyote Point Beach ($7.5 million cost estimate)

Steps to Address Residual Flooding

There are several sources of residual flooding in San Mateo:

  • Spill from San Mateo Creek near El Camino Real
  • Local runoff to Coyote Point and Poplar Avenue Pump Stations
  • Capacity restrictions and local drainage at the 19th Avenue Channel
  • Capacity restrictions and local drainage at Laurel Creek

Remaining projects include:

  • Constructing an inboard levee and rehabilitating existing Coyote Point and Poplar pump stations ($8 million cost estimate)
  • Capacity and drainage improvements to Laurel Creek in the vicinity of the San Mateo/Glendale Village neighborhood ($27.5 million cost estimate)
For more information about federal insurance requirements, please visit the Federal Emergency Management Agency Web site.

For questions or information about the City’s flood protection activities, please contact Gary Heap in the San Mateo Public Works Department via email or (650) 522-7307.