View File - Development Services - City of Oxnard

2.0 Environmental SettingThis section describes the environmental setting of the Oxnard Plain and vicinity as it relatesto the GREAT Program, including physiography, climate, surface water resources, andgroundwater resources. The section utilizes information developed in previous studies,including those by the California Department of Water Resource (1958, 1965, 1967, 1971);California State Water Resources Control Board (1956); Freeman (1968); Izbicki (1996a,1996b); and Turner (1975), as summarized in the USGS report for the Simulation of Ground-Water/Surface-Water Flow in the Santa Clara-Calleguas Ground-Water Basin, VenturaCounty, California (USGS, 2003). Information was also obtained from United WaterConservation District (UWCD) in the form of direct communication (UWCD, 2003a) andreports prepared by UWCD (1998, 2001, 2003b).2.1 PhysiographyThe Oxnard Plain and Pleasant Valley are located along the coastal areas of the Santa ClaraRiver and Calleguas Creek watersheds, which together comprise the Santa Clara-CalleguasHydrologic Unit that is shown in Figure 2-1 together with the groundwater basins withinthis unit. Figure 2-1 is taken from the USGS modeling study (USGS, 2003) and shows thedetailed study area used by the USGS to simulate groundwater and surface water flow inthe Santa Clara-Calleguas Basin. The geographic features of this study area are shown inFigure 2-2, also taken from the USGS modeling study.Santa Clara-Calleguas Hydrologic Unit is located within the Transverse Mountain Ranges ofSouthern California. The Transverse Range physiographic province consists of an east-westtrending series of rugged, steep mountains and valleys in Southern California. The extent ofthis province includes the San Bernardino Mountains to the east and extends offshore fromVentura County to include the Channel Islands to the west. The east-west structure of theTransverse Ranges is oblique to the normal northwest trend of coastal California mountainranges, and is due to intense north-south compression along the San Andreas Fault. TheTransverse Ranges are one of the most rapidly rising regions on earth.Rugged mountainous terrain covers most of the northern Ventura County while broaderalluvial valleys and lower rolling topography occur in the southern portions of the County.The mountainous areas to the north rise to elevations in excess of 6,000 feet above mean sealevel. Ground surface elevations vary from about 60 to 150 feet above mean sea level on theOxnard Plain and from about 15 to 250 feet above mean sea level in Pleasant Valley. TheSanta Clara River watershed drains most of northern Ventura County and northwesternLos Angeles County, and Calleguas Creek drains most of southern Ventura County.Together, the Santa Clara-Calleguas Hydrologic Unit has a total drainage area ofapproximately 2,000 square miles. Almost 90 percent of this drainage area is characterizedby rugged topography, while the remainder consists of flatter valley floor and coastal plaintopography.W112003002SCO LW1458.DOC/ 033390002 6