Ballona Creek - Watershed and Course

Watershed and Course

The Ballona Creek watershed totals about 130 square miles (340 km2). Its land use consists of 64% residential, 8% commercial, 4% industrial, and 17% open space. The major tributaries to the Ballona Creek and Estuary include Centinela Creek, Sepulveda Canyon Channel and Benedict Canyon Channel; most of the creek's minor tributaries have been obliterated by development or paved over and flow into Ballona Creek as a network of underground storm drains.

At the time of Spanish settlement, the Los Angeles River turned to the west just south of present-day Bunker Hill, joining Ballona Creek just to the west of its current channel. However, during a major flood in 1825, the Los Angeles River's course changed to its present channel, and Ballona Creek became a completely distinct waterway. Much of the above-ground section of the creek was lined with concrete as part of the flood-control project undertaken by the United States Army Corps of Engineers following the Los Angeles Flood of 1938.

Ballona Creek Watershed climate can be characterized as Mediterranean with average annual rainfall of approximately 15 inches per year over most of the developed portions of the watershed. The flow rate in the Creek varies considerably from a trickle flow of about 14 cubic feet (0.40 m3) per second during dry weather to 71,400 cubic feet (2,020 m3) per second during a 50-year storm event.. Ballona Wetlands and Del Rey Lagoon are connected to the Ballona Estuary through tide gates.