Lewisville, TX Environmental Rules: Flood Zones (2026)

Chapter 5.5, Flood Damage Prevention, applies to all areas of special flood hazard within Lewisville's jurisdiction (§ 5.5-5), which the city defines using the FEMA Flood Insurance Study and Flood Insurance Rate Map for Denton County dated April 18, 2011, and for Dallas County dated July 7, 2014 (§ 5.5-6). Before altering land or building in a mapped special flood hazard area, an owner must obtain a floodplain development permit (§ 5.5-7); the city manager or a designee serves as floodplain administrator and reviews, approves, or denies every application (§§ 5.5-12, 5.5-13).

Applications go on forms from the administrator and must show the elevation of the lowest floor of new or substantially improved structures, floodproofing elevations for nonresidential buildings, and any planned alteration of a watercourse (§ 5.5-14). The administrator weighs danger to life and property, susceptibility to flood damage, access for emergency vehicles, and the availability of non-flood-prone alternative sites before ruling (§ 5.5-14(2)). No structure or land may be located, altered, or have its use changed without full compliance with the chapter (§ 5.5-8). A property owner who disputes the administrator's decision can appeal to the city's appeal board, which hears variance requests and can attach conditions to any variance it grants; a board decision can be further appealed to a court of competent jurisdiction (§ 5.5-15).

Variances are barred inside a designated floodway if they would raise flood levels during a base flood discharge, and the administrator keeps a public record of every permit action, reporting variances to FEMA on request.