Horizontal Levee

Sea levels are rising around the globe, caused by burning of fossil fuels since the beginning of the industrial age. San Francisco Bay has one of the oldest tidal gauges in the nation at the Golden Gate, installed in the 1850s. It measured a rise in sea level of over seven inches between 1900 and 2000, consistent with readings from tide gauges around the world. But the rate of rise is increasing and scientists forecast that levels could rise and additional sixteen inches by 2050. The State of California has instructed its agencies to plan for a rise of fifty-five inches by 2100. Restoration of the marshlands of San Francisco Bay can play a major role in protecting the shoreline from flooding. In collaboration with other organizations, The Bay Institute has found a green infrastructure solution to sea level rise in the Bay Area, the Horizontal Levee.

The Horizontal Levee, a coastal storm-surge barrier is a new concept that can be applied during the current era of sea level rise. It uses the natural flood protection benefits of coastal tidal marshes to reduce the destructive forces of storms. The levee incorporates brackish marsh at the landward edge of typical tidal marsh restoration designs. It would function as a self-maintaining levee, building in elevation as plant root systems expand.

The first horizontal levee storm-surge barrier in the nation is being built at the Oro Loma Sanitary District treatment plant just south of Oakland International Airport. If successful, it will point the way to strategy that could be applied to hundreds of coastal cities around the nation that are threatened by rising seas.