Yorba Linda, CA Environmental Rules: Flood Elevation Requirements (2026)

Yorba Linda Municipal Code Section 15.12.140(C) requires that new construction and substantial improvement of any structure in a special flood hazard area have the lowest floor, including basement, elevated to or above the base flood elevation, with nonresidential structures given the option to instead meet floodproofing standards. Upon completion, the elevation of the lowest floor must be certified by a registered professional engineer or surveyor, or verified by the Community Building Inspector, and that certification or verification must be provided to the Floodplain Administrator. In Zones AH or AO, the lowest floor must instead be elevated above the highest adjacent grade at least as high as the depth number shown on the Flood Insurance Rate Map, or at least two feet if no depth number is specified.

Nonresidential structures may alternatively be floodproofed so the structure is watertight below the base flood level, with structural components able to resist hydrostatic and hydrodynamic loads, certified by a registered engineer or architect. Fully enclosed areas below the lowest floor that are subject to flooding must be designed to automatically equalize hydrostatic flood forces, meeting a minimum of two openings totaling at least one square inch of net area per square foot of enclosed area, with the bottom of openings no higher than one foot above grade, unless certified to meet an equivalent local floodproofing standard approved by the Federal Insurance Administrator.

Manufactured homes must independently meet the anchoring and elevation standards of Section 15.12.170, including that the lowest floor be at or above the base flood elevation.