Jefferson County, TX Environmental Rules: Stormwater Management (2026)

1 of the Jefferson County Subdivision and Development Regulations bars any development from releasing stormwater runoff onto neighboring property or into any county drainage ditch, swale, easement, culvert or other facility, public or private, at a rate greater than runoff would occur from the property in its undeveloped condition. 1, the drainage plan for a proposed subdivision must be provided to every entity with drainage jurisdiction in the area, including TxDOT, county drainage utilities, and cities, for their review and approval. 2 requires drainage systems to convey all channelized or concentrated flows from a 100-year storm event within a dedicated right-of-way or drainage easement at least 20 feet wide.

4 sets a 10-year storm design standard for neighborhood and local street crossings, requiring culverts to avoid headwater above the pavement edge in a 10-year event and no more than 6 inches of water over the road in a 100-year event; streets crossing the mapped 100-year floodplain cannot raise the water surface level or change floodplain limits. 5 separately caps the headwater at a 100-year event at no more than 6 inches above the roadway crown for neighborhood and local streets, though this specific limit does not apply to residential driveway culverts.

2 sets 64 contributing acres as the threshold at which a watershed must be mapped as a floodplain. 3 bars the county from accepting any street for maintenance until all drainage structures, including driveway culverts, are installed and inspected.