San Luis Rey

San Diego County Department of Parks and Recreation http://ceres.ca.gov/wetlands/geo_info/so_cal/san_luis_index.html

The San Luis Rey River Estuary is located in the City of Oceanside. The watershed extends into unincorporated San Diego County. The vast majority of the 164-acre floodplain is privately owned. The Oceanside Harbor and the lower river channel are owned by the City of Oceanside.

San Luis Rey River is an ephemeral river which stays dry most of the time. In 1977, the peak discharge at the mouth was estimated for a 100-year flood to be 51,000 cubic feet per second. The river is confined by a 400-foot wide earthen channel bounded by two levees along the lower seven miles. Mineral and aggregate mining has occurred at several sites in the river channel. The Henshaw Dam, built in 1922, controls 36% of the watershed.

Wetlands in the floodplain were once used for agriculture. The City of Oceanside discharged treated wastewater into the river from 1958 to 1974. The estuary at the mouth of the river was dredged in 1964 to create the Oceanside Harbor.

Today, the Oceanside General Plan Land Use Element designates the majority of the San Luis Rey River floodway as General Open Space or Agricultural. The lower part of the river is within a designated Resource Conservation Area overlay in the County General Plan.

The wetland is used by eight “sensitive” bird species. Other special status species include black-shouldered kite, white-faced ibis, western snowy plover, Belding’s savannah sparrow, and least Bell’s vireo.

The estuary, which once sprawled more than 2,200 acres, has been altered by agriculture and urban development within the floodplain and watershed; and mineral and aggregate extraction in the channel. A Habitat Conservation Plan has been developed for the river’s least Bell’s vireo population and is currently being implemented. The plan designates 12 acres of riparian habitat west of I-5 as Conserved Habitat.