Lanterna Rally

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Published: 2000

Total Pages: 96

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The U. S. Army Engineer Committee on Channel Stabilization participated with the U.S. Army Engineer San Francisco District to provide guidance, insights, and/or recommendations regarding the District's rehabilitation work on the Corps of Engineer Pajaro River Flood Control Project. This project, located in both Santa Cruz and Monterey Counties, California, consists of levees on both sides of the river's main channel. The project protects valuable agricultural lands and the cities of Watsonville and Pajaro. The project levees were overtopped during floods in both March 1995 and February 1998 causing extensive property damage as well as damage to the flood control project itself. Both floods exceeded the project's design discharge. Vegetation that had become established in the flood control channel prior to March 1995 had been removed before February 1998. It was the consensus of the Committee that the original design concept was a good one in that it had operated successfully for almost 50 years. Project overtopping occurred when the discharge exceeded design values and extensive erosion occurred when protective vegetation was removed from the benches and the banks of the main channel. The Committee recommended that rehabilitation efforts focus on restoring the original set-back levee configuration, using reliable bank protection measures where appropriate and vegetative protection as much as possible. Allowing vegetative growth in the flood conveyance channel introduces the requirement for a detailed maintenance plan that is both technically and economically feasible. This will require that sponsors and resource agencies work together to develop a feasible monitoring and maintenance plan. It should be recognized that the vegetative features associated with this project may increase the design uncertainty.