Sepulveda Dam , along with Hansen Dam located in the north San Fernando Valley , was constructed in response to the historic 1938 floods which killed 144 people . Sepulveda Dam was placed at what was at the time , the current edge of the city . East of the dam the river was crowded into a narrow bottom by the city 's growth . One legacy of Sepulveda Dam is its flood control basin , a large and undeveloped area in the center of the Valley , used mostly for wildlife refuge and recreation . But another legacy of the 1938 Los Angeles River flood was the post-World War II channelization of all the Valley 's dry washes , which along with the post-World War II rapid suburbanization left the Valley with hot , dry , concrete-lined river bottoms instead of greenbelts . Although now , in part , these are being devolved as interconnecting bike paths . 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
1938 floods
Los Angeles flood of 1938
Sepulveda Dam