Santa Clara River


The major river in Zone 2 is the Santa Clara River with a watershed area of approximately 1,634 square miles. Other streams in Zone 2 drain primarily coastal watersheds in the City of Oxnard, City of San Buenaventura and City of Port Hueneme to the Pacific Ocean. One of the larger coastal drainages is the Arundell Barranca that drains a portion of the City of San Buenaventura foothill area outlets into the Ventura Harbor.

The Santa Clara River is the largest river system in southern California remaining in a relatively undeveloped state. Its headwaters are located in the San Gabriel Mountain near the Community of Acton in Los Angeles County, and flows westerly for approximately 84 miles through Ventura County to its outlet into the Pacific Ocean near the City of San Buenaventura. Major tributaries include Castaic Creek and San Francisquito Creek in Los Angeles County, and the Sespe, Piru and Santa Paula Creeks in Ventura County. Approximately 60 percent of the watershed is located within Ventura County. About 90 percent of the watershed is located in mountainous terrain, with the remainder consisting of the relatively flat floodplain areas of the Oxnard Plain, Santa Clarita Valley, Castaic Valley, the Santa Clara River Valley, and the floors of the larger canyons including the upper Soledad, lower Sand, Mint, Bouquet, Placerita, San Francisquito, Piru, Santa Paula, and Sespe Canyons (VCWPD, 2003).

The zone boundaries incorporate all five of the supervisorial districts for Ventura County, but most of the zone is in Supervisor District 3. The superintendent for Zone 2 is John Lagomarsino.

The climate of the Santa Clara River watershed is characterized by long, dry periods and a relatively short wet period during winter of each year. Cool moist ocean winds have a moderating effect on the climate near the coast. Frosts are rare in the coastal region and common in the inland valleys and mountains. The types of storms that may occur in the basin are general winter storms, thunderstorms, and tropical cyclones. Approximately 75 percent of the annual precipitation occurs in the months from December through March. The mean seasonal precipitation varies from about eight inches in the valley floors near the eastern boundary of the basin to over 40 inches in the highest mountains in the basin. Seasonal rainfall is approximately 14 inches near the coast at the river outlet into the Pacific Ocean.

The Santa Clara River watershed is underlain by impervious schist, quartzite, slate, limestone, and granite with extensive faulting. These rocks are exposed over large areas in the mountainous areas of the watershed. Most of the basement complex is overlain by sandstones, conglomerates, and shales that outcrop over large areas of the mountains and foothills. Alluvial deposits cover the floors of the larger valleys to a depth of more than 1,000 feet. Except on the Oxnard Plain and the major floodplains, channels are generally deeply incised with vertical walls. This configuration is generally unstable and leads to erosion, presenting a complex sediment management problem to consider in the design of flood control improvements.

The alluvial soils form a connected series of pervious deposits that serve as natural underground reservoirs for the storage of water. A forebay area at the upper end of the Oxnard Plain serves as a recharge area for the extensive confined aquifer underlying much of the Oxnard Plain. The forebay has extensive recharge areas operated by the United Water Conservation District. A bedrock intrusion near the Los Angeles/Ventura County boundary creates rising groundwater in the river channel and leads to perennial flow in the river reach downstream of the intrusion.

Major water supply reservoirs are located in the Santa Clara River watershed, including Castaic Lake, Piru Reservoir, Bouquet Reservoir, and Pyramid Lake. The District has a number of basins designed to capture debris before it enters the Santa Clara River, including Warring Canyon, Jepson, Fagan, Adams Barranca, Cavin Road, Real Wash, and Franklin Barranca debris basins. Areas of major flooding in Zone 2 include portions of the Santa Clara River near the cities of Santa Paula and San Buenaventura and local coastal drainages such as Arundell Barranca.

Santa Clara River Programs and Projects


Hydrology Studies- Partial List