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Pajaro Compass Case Study five

Pajaro River Bench Excavation

Levees are designed to protect people, homes, and livelihoods from the effects of flooding. Stakeholders in the Pajaro River watershed have been working with the Army Corps for decades to develop a flood risk reduction project to improve upon the current levee system which is inadequate to withstand a major flood event. This was demonstrated in 1995, when the levee broke during a catastrophic flood event, leaving many homeless and jobless. While delayed at the federal level, partners in the region mobilized to deliver a project in the interim to reduce the harmful effects that another flood could have in the Pajaro River floodplain.

The Pajaro River Bench Excavation Project is designed to relieve the magnitude and severity of potential future flooding of the Pajaro River. The excavation removes excess sediment from the riverbed and creates benches to improve the flood carrying capacity of the levee system, and provide critical, low-flow habitat for fish, particularly steelhead trout. Bench excavation will eventually become self-maintaining and will help the river regain its natural ability to move sediment through the river channel system by natural geomorphic processes, as it did originally.

The project has had positive benefits outside of the immediate project area as well. Over 300,000 cubic yards of sediment was removed in the excavation process, which The Elkhorn Slough Foundation used to raise the elevation of over 100-acres of tidal marshland in Elkhorn Slough. This restored the slough to its original, shallow and properly-functioning depth to benefit the many animals that rely on this habitat, such as sea otters. Santa Cruz County Flood Control and Water Conservation District Zone 7 also used some of the sediment to improve a levee along Salsipuedes Creek.

The project provides many benefits to the Pajaro River watershed—the floodplain area in particular—including a lowered risk of flood inundation of agricultural fields and residential areas, improved habitat within the existing levee system, as well as improved habitat as a result of sediment relocation offsite.