Horizontal levees get attention as sea level rise looms

Mark Prado

The benefits of horizontal levees to stem rising seas have drawn attention in an editorial this week co-authored by the San Francisco Estuary Partnership against the backdrop of king tides across the Bay Area.

With the arrival of king tides this week, some in the Bay Area may see roads and shorelines go under water, albeit temporarily. But there is concern that as sea levels rise in future years, roads, other infrastructure and tidal habitats could succumb to the ocean. 

Horizontal levees would help prevent that. Horizontal levees utilize a gently vegetated slope to provide multiple benefits including wave mitigation, enhancement of transitional habitat between tidal wetlands and terrestrial uplands, and filtering treated wastewater. And they they can protect communities from sea level rise.

A first-of-its-kind horizontal levee project — led by the Partnership and the city of Palo Alto — has received $2.1 million from the U.S. Environmental Protection Agency for construction this fall. 

The project will use highly treated wastewater from the Regional Water Quality Control Plant in Palo Alto to irrigate a vegetated horizontal levee prior to release into San Francisco Bay. The project will be the first in the region to receive treated wastewater for irrigation prior to discharge via shallow surface/subsurface seepage to the bay.


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