Modesto, CA Environmental Rules: Flood Elevation Requirements (2026)

201(h) defines base flood elevation, or BFE, as the water surface elevation shown on the Flood Insurance Rate Map for zones AE, AH, A1-30, VE and V1-V30 that results from a flood with a one percent or greater annual chance of occurring, commonly called the 100-year flood. 402(c). The code stops at that line: it does not add a freeboard buffer of extra feet above the BFE the way some jurisdictions do. Once construction is finished, a registered civil engineer or licensed land surveyor must certify the lowest-floor elevation, and a community building inspector must verify it before the Floodplain Administrator accepts it.

501(c)(2): they may be dry floodproofed below the BFE instead of elevated, but only with a registered engineer's or architect's certification that the structure is watertight and can resist hydrostatic and hydrodynamic loads. 201(ah)(2) prohibits all subgrade enclosed areas in residential structures, including below-grade garages and storage, because they count as basements regardless of use. 501(c)(5)(ii) lets a detached, one-story accessory structure of 600 square feet or less sit below the BFE if it is limited to parking or storage, built with flood-resistant materials, anchored against flotation, and designed to let floodwater automatically enter and exit.