Each year eroded material in various forms (debris consisting of rock, sand, trees, etc.) flows out of the mountain watersheds of the County of Los Angeles. In an effort to control this potentially disruptive force, Public Works maintains a series of debris basins in canyon mouths and upstream stabilization structures in selected watersheds.
DEBRIS BASINS:
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.
Public Works maintained over 100 debris basins during the reporting period. 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Data for sediment inflow at individual debris basins and unpublished information may be obtained by contacting:
County of Los Angeles
Department of Public Works
Water Resources Division
Hydrology Section
P.O. Box 1460
Alhambra, CA 91802-1460
...or telephone: (626) 458-6120
STABILIZATION STRUCTURES:
Public Works 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.
Public Works 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.
EMERGENCY STRUCTURES:
Public Works 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.
Watersheds within the County of Los Angeles periodically burn. Maps of areas burned during the reporting period can be obtained by contacting the Water Resources Division/Hydrology Section.
