San Antonio, TX Environmental Rules: Flood Zones (2026)

Section 34-912 classifies floodplains within the Edwards Aquifer Recharge Zone by drainage area: a minor floodplain drains 100 to 320 acres, an intermediate floodplain 320 to 640 acres, and a major floodplain more than 640 acres, per the Sec. 34-908 definitions. Delineation is based on a 100-year frequency flood and a channel in its unaltered state, consistent with the citywide floodplain regulations in Chapter 35 (the Unified Development Code). Inside a floodplain preservation area, Sec. 34-912(b) prohibits essentially all construction activity, development, and alteration, carving out only specific exceptions: arterial, collector, or residential street crossings built to the standards in Sec.

34-965; utility crossings; fences that don't obstruct flood flows; public and private parks and open space limited to trails for hiking, jogging, non-motorized biking, and nature walks; and water quality or flood-control systems built with minimum disruption. 5% slopes up to 100 feet on slopes over 10%, where impervious cover is barred outright. Before any project inside these boundaries can proceed, Sec. 34-910 requires a letter of certification from SAWS's resource protection and compliance department, which expires if the project hasn't shown progress within three years.

Section 34-914 extends the floodplain preservation area and buffer requirement into the city's extraterritorial jurisdiction for watersheds over 300 acres. Violations are enforced by SAWS under Sec. 34-909: a conviction is a Class C misdemeanor punishable by $200 to $2,000 per violation, and the city may also seek a civil penalty of up to $1,000 per violation, rising to $5,000 for violations that pollute waters draining into the city's storm sewer system. Recipients of a notice of violation have 15 working days to respond in writing or are deemed to have admitted the violation.