Text / San Clemente and Matilija Dam Removal: Alternative Sediment Management Scenarios

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Title: San Clemente and Matilija Dam Removal: Alternative Sediment Management Scenarios
Creator: Mark H. Capelli
Date Created and/or Issued: 3/8/07
Contributing Institution: UC Riverside, Library, Water Resources Collections and Archives
Collection: Clearinghouse for Dam Removal Information (CDRI)
Rights Information: Copyrighted
Transmission or reproduction of materials protected by copyright beyond that allowed by fair use requires the written permission of the copyright owners. Works not in the public domain cannot be commercially exploited without permission of the copyright owner. Responsibility for any use rests exclusively with the user.
Description: Scope/Content: Abstract: San Clemente Dam on the Carmel River and Matilija Dam on Matilija Creek are located in coastal California watersheds comprised of highly erosive soils. Both dams are thin arch concrete structures constructed in 1921 and 1948 respectively, and both reservoirs have been filled with sediments, thereby eliminating their water storage capacity and any incidental flood control function. As a result, the removal of both dams is under consideration. A major challenge to the removal of the San Clemente and Matilija Dams is the management of the approximately 2.5 and 6 million cubic yards of sediment impounded in their respective reservoirs. Mechanical removal of impounded sediments entails large economic and societal costs because of restricted access, distance to disposal sites, and the length of time to excavate and transport material. Natural flushing of sediments through the river system could adversely impact aquatic habitat, including their estuaries, as well as cause potential impacts to water supply systems and flooding of floodplain situated properties. The San Clemente and Matilija Dam projects illustrate two basic approaches to the management of impounded sediments: (1) permanent stabilization of sediments off-site,or permanent stabilization of sediment within the reservoir behind San Clemente Dam and by-passing a short reach of the Carmel River through San Clemente Creek; and (2)controlled flushing of sediments through Matilija Creek and the Ventura River by temporary stabilization of coarse materials impounded behind the Matilija Dam and slurrying finer fractions of sediments through a conduit to downstream storage sites. None of the sediment management alternatives is free of economic and societal costs, or environmental impacts; site specific circumstances will influence the best strategy for handling sediments to minimize adverse impacts and costs, and maximize benefits within an acceptable time-frame to achieve dam removal goals and objectives.
Scope/Content: Author affiliation: U.S. Society on Dams
Scope/Content: Dam type: arch
Type: text
Identifier: ark:/86086/n2q81csg
921
Subject: Sediment and channel dynamics
Dams
Dam retirement
Place: Carmel River, CA
Matilija Creek, CA
Matilija Dam
San Clemente Dam

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