Historical Background

The Los Angeles River has always been subject to flooding outside of its banks. Only as Los Angeles began to urbanize did flooding become an issue. Major floods in the 19th and early 20th century lead the LA County Board of Supervisors  in 1914 to build dams in the mountains to slow runoff and catch debris, but local taxpayers were unwilling to provide enough money to complete more extensive flood control plans. After two disastrous floods in the 1930’s the US Government took over the flood control program and the Army Corps of Engineers built five flood control dams in the San Fernando and San Gabriel valleys to control storm runoff.

On New Year’s Day 1934, major flooding focused national attention on the LA River and by July 1935, President Franklin D. Roosevelt approved funding that began the channelizing of the LA River Congress expanded the flood control duties of the US Army Corps of Engineers with passage of the Flood Control Act of 1936 giving the agency sole responsibility for providing flood control on the nation’s rivers and streams.

Following significant rainfall in February 1938 the Big Tujunga Dam was near capacity by early march, with parts of the San Fernando Valley starting to flood. In order to save the dam structure the floodgates on the Big Tujunga Dam were opened, but the water released in combination with the full creeks and washes created a catastrophic, overflowing river that destroyed homes in Universal City along with the Lankershim Bridge, where 5 people fell to their death. By the time the rain subsided on the night of March 3, 1938 at least 96 people had died across Southern California.

Work began in 1938 on both the Hansen and Sepulveda Dams, as well as the continued channelization of the LA River. Work continued over the next 20 years and the work along the full length of the river was complete by 1960. The capacity of the flood control channel for the Lower LA River was increased in the 1990’s with the construction of additional levees.

1800’s Before Settlement


1930  7th st. Bridge


1938 Flood waters from LA River at Griffith Park


1938 Colfax Avenue Bridge Studio City


US Army Corp Flood Control Testing Model – Tujunga Wash


1949 Laurel Canyon Channel Construction

  1.   Seaver Central For Western History Research / Natural History Museum Los Angeles County
  2.   Department of Special Collections, University of Southern California Library / California Historical Society Collection
  3.   US Army Corps of Engineers / Los Angeles District
  4.   Regional History Center / USC
  5.   Los Angeles Public Library / Herald Examiner Collection