Tex. Water Code § 16.321

The Commissioner of the General Land Office shall adopt and enforce reasonable rules and regulations necessary for protection from flooding on barrier islands, peninsulas, and mainland areas fronting on the Gulf of Mexico. Rules and regulations adopted pursuant to this section shall be limited to those matters that political subdivisions are authorized to address under Section 16.315 of this code. Except as otherwise provided by this section, all actions taken by political subdivisions under Section 16.315 of this code with respect to flooding on barrier islands, peninsulas, and mainland areas fronting on the Gulf of Mexico must comply with rules and regulations adopted by the commissioner under this section. A political subdivision may adopt rules that are more stringent than those adopted by the commissioner under this section, provided the stricter provisions are intended to ensure compliance with the National Flood Insurance Program's rules, regulations, and policies.