Cuyama River

Zone 4 has a total of about 225,000 acres divided between several unconnected areas. The southeast area includes 61,000 acres of the coastal drainages of the Malibu area, including Malibu Canyon, Lake Sherwood, Potrero Creek, and Westlake. The northwest area is primarily the watershed of the Cuyama River with about 150,000 acres in Ventura County. The remaining 14,000 acres in the relatively undeveloped northeast corner of the District drain outside of the County to the northeast. The northeast and northwest portions of Zone 4 generally only require maintenance activities to protect the existing agricultural fields from bank erosion (VCFCD, 1967).

The zone boundaries incorporate four of the five of the supervisorial districts for Ventura County. Most of the northeast and northwest portions of the zone are in District 3 with a small portion of the northwest area in District 1. Most of the southwest portion of the zone is in District 2, while a small portion is in District 4. The superintendent for Zone 4 is Ernie Bravo.

The climates of the Zone 4 watersheds are 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 in the watersheds near the coast. Frosts are rare in the coastal region and common in the inland valleys and mountains.

The southeast portion of the zone receives less rainfall than the northern sections. Coastal creeks located in this portion of the zone include Little Sycamore Canyon, Big Sycamore Canyon, and La Jolla Canyon. Precipitation occurring during winter season extending from November through March is approximately 85 percent of the rainfall total. Mean annual precipitation varies from about 13 inches at the coast to a maximum of 20 inches in the higher elevations. Lake Sherwood, Lake Eleanor, and Westlake provide recreational opportunities and flood control for this portion of the zone.

Southeastern Zone 4 topography is typified by rugged, mountainous terrain with some flatter valleys where residential development has occurred. The watershed is part of the Transverse Range geomorphic province of California. The geologic structures in the watershed are a results of different sequences of sandstones, shales, conglomerates, and siltstones lain down during the different geologic periods, with basaltic flows and intrusives also occurring.