Hidalgo County, TX Environmental Rules: Flood Zones (2026)

Hidalgo County's flood risk is driven by the Rio Grande along its southern border, the Arroyo Colorado, and a flat Lower Rio Grande Valley topography that drains slowly. The Hidalgo County Drainage District No. 1 (HCDD No. 1) maintains the Hidalgo County Master Drainage System (HCMDS), and operates a permitting program requiring developer approval before any land-development project can outfall into the HCMDS. Per the District, 'one-third of the flood loss claims are from properties located outside of the mapped 1% (100-year) floodplain,' and HCDD No. 1 advises that 'everyone lives in a flood zone.' FEMA initiated a Flood Insurance Study update for Hidalgo County in 1996 to determine regulatory floodplain limits along approximately 20 miles of HCDD No. 1 channels. Hidalgo County and incorporated cities (McAllen, Edinburg, Mission, Pharr, etc.) are NFIP-participating communities, meaning property owners can purchase federally-backed flood insurance. The Floodplain Administrator for unincorporated areas is HCDD No. 1's General Manager, Raul E. Sesin, P.E., C.F.M. (956-292-7080); each incorporated city designates its own administrator. New construction in Special Flood Hazard Areas must obtain a floodplain development permit and meet base-flood-elevation requirements set by the relevant administrator. Specific freeboard requirements vary by jurisdiction and should be confirmed with the local floodplain administrator.