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| 1999-2000 Hydrologic Report |
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EROSION
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Each year eroded material in various forms (debris consisting of rock, sand, trees, etc.) flows out of the mountain watersheds of Los Angeles County. In an effort to control this potentially disruptive force, the Department maintains a series of debris basins in canyon mouths and upstream stabilization structures in selected watersheds.
The purpose of a debris basin is to entrap the sediment flows emanating from the canyon and let the relatively desilted water pass into the downstream flood control channels.
The Department maintained 115 debris basins during the reporting period. The combined total maximum capacity of the basins is approximately 7,780,900 cubic yards. Design data on these facilities are in a table and their locations are shown in a PDF map (1.67MB).
Data for sediment inflow at individual debris basins and
Unpublished information may be obtained by contacting:
Los Angeles County Department of Public Works
Water Resources Division
P.O. Box 1460
Alhambra, CA 91802-1460
...or telephone: (626) 458-6120
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STABILIZATION STRUCTURES:
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The Department has constructed stabilization structures to control erosion in natural canyons. These structures serve to prevent down cutting by stabilizing alluvium deposits. In addition, they store debris generated by the watershed and serve to stabilize side banks, reducing side slope sloughing and bank erosion.
The Department maintained 217 stabilization structures in 47 major watersheds during the reporting period. The Department has not constructed any stabilization structures since the 1973-74 water year.
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The Department has constructed emergency structures (rail and timber) to entrap the debris from burned watersheds. The structures serve to protect improvements (road, channel, residence, etc.) located downstream of the watersheds.
During the reporting period, 32 emergency structures existed with a total maximum capacity of 253,000 cubic yards. Maps of areas burned during the reporting period can be obtained by contacting the custodian of hydrologic records.
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