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

Tustin's floodplain chapter (City Code §§ 9801-9806) implements the National Flood Insurance Program locally. The Building Official serves as the City's Floodplain Administrator and must approve a development permit under Section 9803a before construction begins in a mapped Special Flood Hazard Area. Section 9804a(3) sets the elevation standard: residential and nonresidential structures in Zones A1-30, AE and AH must have their lowest floor, including a basement, at or above the base flood elevation, defined in Section 9802 as the flood with a one percent annual chance of occurring, called the 100-year flood.

Nonresidential buildings may substitute floodproofing under Section 9804a(3)(c)-(d) if a registered engineer or architect certifies the structure watertight below the base flood level. Fully enclosed areas below the lowest floor need at least two openings totaling one square inch of net area per square foot of enclosed space, with opening bottoms no higher than one foot above grade, per Section 9804a(3)(e). Manufactured homes must meet the same elevation floor and be anchored with over-the-top and frame ties capable of carrying 4,800 pounds, per Section 9804d.

Within a designated floodway, Section 9804e bars any encroachment, including fill, unless an engineer certifies no rise in flood levels during the base flood. Owners seeking relief apply to the City Council sitting as the Variance Board under Section 9805a, which weighs factors including danger to life, availability of alternative sites and expected flood velocity; variances are barred inside a floodway if they would raise flood levels. Appeals from the Floodplain Administrator's determinations go to the Planning Commission under Section 9806a.