Santa Clara River County Floodway Map Revisions

On June 28, 2022, the Los Angeles County Board of Supervisors adopted an ordinance for the new County Floodway Map Nos. 43-ML26.2, 43-ML 27.2 and 43-ML 28.1 which map the Capital Flood floodplain, floodway and water surface levels in the main stem of the Santa Clara River between the River’s confluence with Castaic Creek and the I-5 Freeway. The new maps reflect better hydrologic data, today’s topography (“lay of the land”), and modern hydraulic engineering modeling, and thus map more accurately the areas of flood hazard associated with the County Capital Flood along the Santa Clara River in the Castaic vicinity.

There are no governmental flood insurance mandates associated with the County Floodway Maps. The County Floodway Maps are used to inform property owners and residents of flood hazards in the vicinity and to regulate development in the floodplain and floodway to ensure flood hazards are not increased.

In May 2022, the owners of the properties affected by the floodplain and floodway boundary changes resulting from the proposed County Floodway Maps were notified of the proposed changes and of the upcoming Board of Supervisors meeting to consider approval of the ordinance for introduction.

California Environmental Quality Act (CEQA) Notices of Exemption for the ordinance introduction are posted below, and at the County of Los Angeles Registrar-Recorder/County Clerk office at 12400 Imperial Hwy, Norwalk, CA 90650 and its web page: California Environmental Quality Act - CEQA (

For questions regarding the proposed map revisions, please contact Ms. Patricia Wood at


CEQA Notices of Exemption for Ordinance Introduction - Posted at County Clerk on June 23, 2022

CEQA Notices of Exemption for Ordinance Adoption - Posted at County Clerk on June 28, 2022