Saticoy & Wells Community Plan & Development ... - City Of Ventura

Saticoy & Wells Community Plan and Code EIRSection 4.8 Hydrology and Water Quality4.8 HYDROLOGY AND WATER QUALITYThis section addresses impacts to local and regional hydrology, as well as temporary and longtermimpacts to surface water and groundwater quality. Water supply impacts are discussed inSection 4.14, Utilities and Service Systems.4.8.1 Settinga. Hydrology. The City of Ventura is located within the western portion of the SantaClara River Basin. The City’s general drainage pattern begins in the hills above of the City andterminates at the Ventura River, the Santa Clara River or the Pacific Ocean. Within the ProjectArea, water is transported through overland flows or by Ventura County Watershed ProtectionDistrict (VCWPD) natural and concrete-lined barrancas. Long Canyon, located in the hills northof the Project Area, drains to Brown Barranca, a drainage that is under the jurisdiction of theVCWPD. Brown Barranca is the primary drainage in the Project Area and transitions between aconcrete lined channel to a heavily vegetated earthen ditch that crosses the Parklands site in asoutheasterly direction from Telegraph Road on the north to the Santa Clara River to the south.Franklin-Wason Barranca transports water from Peppertree Canyon located northeast of theProject Area and partially forms the eastern border of the Project Area near Darling Road. Thisdrainage, like Brown Barranca, also continues south to the Santa Clara River.The Project Area is a predominantly built environment with approximately 300 acres ofundeveloped land previously or currently used for agriculture. Impermeable surfaces in thedeveloped portions of the Project Area prevent water from infiltrating, increasing the amount ofrunoff reaching the storm drainage infrastructure.b. Drainage. The Project Area consists of approximately 1,000 acres that extends fromTelegraph Road to the north down to the Santa Clara River to the south. The Project Areagently slopes to the south toward the Santa Clara River. Project Area elevations range fromabout 240 feet above mean sea level at the northern boundary to approximately 130 feet abovemean sea level in the southern portion of the Project Area. The Project Area is predominantlydeveloped, but also contains approximately 300 acres of agricultural and undeveloped landsand drains overland toward the Santa Clara River via the Brown and Franklin-Wasonbarrancas.c. Flood Hazards. The Federal Emergency Management Agency (FEMA) has definedthe 100- and 500-year flood hazard areas within the Project Area through the publication ofFlood Insurance Rate Maps (FIRMs), which establish base flood heights and flood zones for 100-year and 500-year storm events. The 100-year storm event is defined as a storm that has a 1%probability of occurring in any given year, while a 500-year storm event has a 0.2% chance ofoccurring in any given year. A “floodplain”, also called a flood zone, is the lowland adjacent toa river, lake or ocean and is designated by the frequency of the flood that is large enough tocover it. For example, a 100-year floodplain will be covered by a 100-year flood, while a 500-year floodplain will be covered by a 500-year flood. The “floodway” is the channel of a river orstream plus any adjacent floodplain areas that must be kept free of encroachment so that the100-year flood can be conveyed without substantial (greater than one foot) increases in floodheights. Planning policies typically prohibit urban development, activities, and structures4.8-1City of Ventura