Santa Monica Bay Watershed

The Santa Monica Bay watershed, with its 55 miles of coastline and beaches, covers 385 square miles. Its northern boundary extends along the crest of the Santa Monica Mountains from the Ventura-Los Angeles County line on the west to the Ballona Creek watershed on the east. South of Ballona Creek, the natural drainage area is a narrow strip that extends south from Ballona Creek to the tip of the Palos Verdes Peninsula, bordered by the Pacific Ocean to the west and the Dominguez Channel watershed to the east. The entire watershed has approximately 200 separate storm drain outlets that convey over 30 billion gallons of runoff to Santa Monica Bay each year.

The Santa Monica Bay watershed contains 27 sub-watersheds that are separated into seven jurisdictions. Much of the terrain in the watershed’s northern portion is rugged open space and contains many canyons that carry runoff directly to the Bay. Topanga and Malibu Creeks are the two largest waterways in this area. The creeks are fed both by tributary creeks and by channelized storm drains in and near developed areas. Portions of Malibu, Agoura Hills, Westlake Village, and Los Angeles are located in this part of the watershed. The mid- and southern portions of the watershed are more urban and contain portions of Los Angeles, Santa Monica, El Segundo, Manhattan Beach, Redondo Beach, the Palos Verdes Estates, and Rancho Palos Verdes. This area is highly developed with a network of storm drains carrying flows to Santa Monica Bay.

Water Quality in the Santa Monica Bay Watershed

As of March 2012, the USEPA has approved 22 TMDLs throughout the region that list the City of Los Angeles as a responsible jurisdiction. These include waterbodies within the Los Angeles River, Ballona Creek, Santa Monica Bay, and Dominguez Channel Watersheds.

Santa Monica Bay’s beaches and other waterbodies within the watershed are impaired by pollutants (e.g. trash, bacteria, and toxics) mainly because portions of the watershed have large, dense population centers and significant amounts of impervious ground surface that prevent urban runoff from infiltrating into underground aquifers. There are several Total Maximum Daily Loads (or TMDLs) for water bodies in the watershed, which target nearshore debris, DDTs and PCBs, and wet and dry weather bacteria. Marina del Rey has TMDLs targeting toxics and bacteria.

Santa Monica Bay’s Enhanced Watershed Management Program (or EWMP) identifies compliance measures to address Santa Monica Bay TMDLs and other water quality mandates, while maximizing potential benefits of storm water for local water supply. 

Related PDF documents available:

SMB JG 7 Draft CIMP (3.1mb)
SMB JG 2 and 3 EWMP Work Plan (2.9mb)
SMB JG 7 Draft WMP (2.1mb)
MdR Toxics TMDL Implementation Plan (2.4mb)
MdR Bacteria TMDL Implementation Plan (9.0mb)
SMB Bacteria TMDL Implementation Plan (1.3mb)
SMB Trash Monitoring and Reporting Plan (3.7mb)
SMB JG 2 and 3 Draft CIMP (3.5mb)
MdR Draft CIMP (3.8mb)
MdR EWMP Work Plan (4.6mb)