Located in Los Angeles, California, the Sepulveda Dam is a project of the U.S. Army Corps of Engineers, built in 1941, at a cost of $6,650,561, to withhold winter flood waters along the Los Angeles River. It is located south of center in the San Fernando Valley, about eight miles east of the river's official source in the western end of the Valley.
Sepulveda Dam, along with Hansen Dam in the north San Fernando Valley, was constructed after the historic 1938 floods on the Los Angeles River, which killed 144 people. Sepulveda Dam was placed at the then current edge of the city (1940). East of the dam the river was crowded into a narrow bottom by the city's growth. One legacy of Sepulveda Dam is the huge undeveloped area in the center of the Valley — used for wildlife and urban park. But another legacy of the 1938 Los Angeles River flood was the post-WWII channelization of all the Valley's dry washes, which along with the post-WWII rapid suburbanization left the Valley with hot, dry, concrete-lined river bottoms instead of greenbelts and connecting bikepaths.
Behind the dam, the Sepulveda Basin is home to several large recreation areas including Woodley Park, a model aircraft field, The Japanese Garden, a wildlife refuge, a water reclamation plant, and an armory. The Basin is kept free of urban over-building so that water can build up there during a prospective hundred-year flood.