Brownsville | Flood, Drainage and Windstorm

Brownsville Flood, Drainage and Windstorm Rules: Elevation, Fill, Detention and Inspections

Brownsville lies in Cameron County, which the state windstorm law lists as a first tier coastal county, and its flood maps come from the Cameron County flood study. Three sets of rules shape a building site there: the City's flood damage prevention rules in Section 5.5 of the Unified Development Code (UDC), its stormwater rules in Section 5.6, and the state's windstorm inspection program for coastal counties. The City Commission tightened the first two on January 6, 2026. This page explains each rule in plain terms and gives the section for it. The Brownsville overview has the short version.

The Maps and Who Applies Them

A special flood hazard area is land the federal flood maps show with a one percent or greater chance of flooding in any year. The base flood is that one percent flood; Article 6 calls it "Also known as the 100-year flood." The base flood elevation is the height its water is expected to reach. Section 5.5.5 adopts "The Flood Insurance Study (FIS) for Cameron County Texas and Incorporated Areas Volume 1 of 3," dated February 16, 2018, with its Flood Insurance Rate Maps (FIRMs) of the same date "and any revisions thereto."

Section 5.5.11 names the City Engineer as the Floodplain Administrator. That official reviews every floodplain development permit, the permit Section 5.5.6 requires "to ensure conformance with the provisions for flood damage prevention," and decides where a mapped line falls when the map and the ground disagree. The application shows the lowest floor height of each new or improved building, measured from mean sea level, and how any watercourse would change. Section 5.5.10 warns that the rules do "not imply that land outside the areas of special flood hazards or uses permitted within such areas will be free from flooding or flood damages." The FY 2027 fee schedule lists a "Flood zone verification" at $10.

How High to Build

Source: Brownsville UDC Section 5.5.15 (Supplement 26) as amended by Ordinance No. 2025-235.119, passed January 6, 2026.

The core rule is in Section 5.5.15.B.1: "New construction and substantial improvement of any residential structure shall have the lowest floor (including basement), elevated to two (2) feet above the base flood elevation." The extra two feet above the expected flood level is called freeboard. Article 6 of the UDC gives no definition of "substantial improvement," so ask the Floodplain Administrator how the City measures it before you plan a large repair. The same paragraph reaches beyond the mapped zones: "All residential structures that are constructed outside of a designated Special Flood Hazard Area shall be elevated two (2) feet above the highest adjacent grade," which is the highest ground touching the building. A registered professional engineer, architect or land surveyor certifies the height to the Floodplain Administrator.

Space below the lowest floor used only for parking, access or storage must let floodwater in and out. Section 5.5.15.B requires "A minimum of two (2) openings on separate walls having a total net area of not less than 1 square inch for every square foot of enclosed area," with the bottom of each opening "no higher than one (1) foot above grade," unless an engineer or architect certifies another design.

What Changed on January 6, 2026

Ordinance No. 2025-235.119 rewrote Sections 5.5.12, 5.5.15, 5.6.8 and 5.6.9. Its preamble ties the changes to the National Flood Insurance Program and to FEMA's Community Rating System, a program that can lower flood insurance premiums for owners in towns with stronger rules. The municode text has not been updated, and the copy in the ordinance bank is a scan that drops some words, so read the signed ordinance with the City before relying on a single line. The changes that matter for a small housing project are these:

• Equipment. Heating, ventilation, plumbing, air conditioning and electrical equipment must be "at least two (2) feet above the base" flood elevation. The older text asked only that it be designed to keep water out.
• Fill. Fill is earth brought in to raise ground. The new text allows it in the special flood hazard area only when it is "mitigated by a compensatory storage requirement at a 1:1 ratio," which means digging out the same volume of flood storage elsewhere.
• Rise in flood level. Where no floodway is mapped, new building or fill in the mapped A zones may not raise the base flood by more than "0.1-ft at any point within the community," where the older text allowed one foot. An engineer certifies any excavation or fill against the same 0.1-foot limit.
• Manufactured homes. In existing parks and subdivisions, the older choice of a floor at the base flood or 36-inch piers gives way to a floor "at least two (2) feet above the base" flood elevation.
• Roads. New roads in a special flood hazard area must be at or above the base flood elevation, with "a minimum freeboard of 1.0 foot above BFE" where feasible.
• Critical facilities. Hospitals, shelters, schools and similar buildings go outside the 500-year flood area where possible, or 3 feet above the base flood.

Fill used under a building in any A zone must still meet Section 5.5.15.B.7: compacted "to at least ninety five percent (95%) of Standard Laboratory Maximum Density (Standard Proctor)," and made of "fine grained soils of low permeability." The January 2026 text adds that lumber, sheetrock, trees, tires, refuse and other matter that rots may not be used as fill.

Floodways, Variances and Flood Land

A floodway is the channel and nearby land that must stay open to carry the base flood. Section 5.5.15.E says "Encroachments are prohibited, including fill, new construction, substantial improvements and other development within the adopted regulatory floodway" unless hydrologic and hydraulic studies show no rise in flood levels.

The Board of Adjustment hears flood variances under Section 5.5.14. A variance needs "a good and enough cause," a finding of "exceptional hardship," and proof that it will not raise flood heights or threaten public safety; it must be "the minimum necessary." One listed case is new construction "on a lot of one-half (0.5) acre or less in size contiguous to and surrounded by lots with existing structures constructed below the base flood level." The owner receives written notice that a lower floor brings higher flood insurance costs. No variance is issued in a floodway if it would raise flood levels.

The subdivision rules add two limits. Section 3.4.1.G says land subject to a 100-year flood "shall not be subdivided, re-subdivided or developed" until the developer shows a usable building site through a flood study and a FEMA Conditional Letter of Map Revision, and building waits for the final Letter of Map Revision. Section 5.5.15.C requires base flood elevation data for a subdivision of "greater than fifty (50) lots or five (5) acres, whichever is lesser."

Stormwater and Drainage

Section 5.6 applies to "all subdivision and site plan applications for property within the City limits and City's extraterritorial jurisdiction." It exempts "Additions or modifications to existing single family structures" and "Any site development that does not disturb more than one (1) acre land, provided that it is not a part of a larger common development plan." Plans follow the City's "Minimum Requirements for Drainage Reports and Plans," and the City has adopted a coastal guide for low impact development, which means site design that soaks up, filters and slows rain where it falls.

The January 2026 text of Section 5.6.8.A.1 sets the main number: site designs control peak runoff from the "2, 25, and 50-year" storms "to match the peak flow of pre-development conditions for all sites greater than 0.5-ac." A detention basin or similar feature usually does that work. The final plan is signed by a Texas engineer, the owner dedicates a maintenance easement and records a maintenance covenant, and every facility gets "an annual inspection." If a facility becomes a danger, the owner has "sixty (60) days" after written notice to repair it. The City may also require a performance bond equal to the cost of the stormwater work "plus twenty-five (25) percent."

Easements carry the water. Under Section 3.3.3, storm drainage easements are at least "twenty (20) feet" wide over enclosed systems, and "Drainage easements cannot be fenced." Brownsville also has resacas, bodies of water the code names in its easement rules. The same section lets the utility provider or the City Engineer ask for an access easement on a lot that fronts a resaca, for "Resaca maintenance, water transportation, dredging," dedicated "for the benefit and use of the Brownsville public utilities board." Section 5.2.4 says land "within a Resaca or subject to inundation by a 100 year flood will not be accepted as parkland."

A drainage fee is in progress. The FY 2027 Master Fee Schedule adds a "Stormwater Utility Fee" row, "Special Revenue to address Flooding, Erosion, and Water Quality," with "4.99 - 6.25" in the new amount column and no unit printed. Ordinance No. 2026-1825, which would add drainage utility fees to Chapter 102 of the Code of Ordinances, had its first reading on October 6, 2026 and was on the October 7 agenda for second reading. VanPlex has not seen the vote or the adopted rates.

Windstorm Inspections

Windstorm and hail insurance on the Texas coast often comes from the Texas Windstorm Insurance Association (TWIA). Insurance Code 2210.003 lists Cameron County among the fourteen "first tier coastal" counties. The Texas Department of Insurance (TDI) says "Properties in 14 coastal counties and in parts of Harris County east of Highway 146 are in a designated catastrophe area," and that "To buy a TWIA policy, most homes and properties must have a certificate of compliance." That certificate is the WPI-8.

• TDI says "Most new construction, roof replacements, major repairs, and other alterations require an inspection and certificate of compliance."
• A TDI inspector or an appointed Texas licensed professional engineer inspects the work while it is in progress; TDI says its inspectors "must perform inspections during" the construction or repair.
• The builder files Form WPI-1 with TDI "before beginning construction."
• "TDI inspectors do not charge an inspection fee." Appointed engineers set their own rates.
• TDI's Corpus Christi field office serves Cameron County, and TDI lists "TDI Adopts 2024 Building Codes - Effective April 1, 2026" for its windstorm standards.

A finished building with no inspection needs a post-construction inspection by an appointed engineer, which TDI says "may cost more." Plan the WPI-1 filing and the inspection dates with the City building permit. The insurance and flood page covers flood insurance.

Where to Go Next

Related on VanPlex: the Brownsville overview, insurance and flood in Texas and building codes from duplex to fourplex.

Frequently Asked Questions

Official sources (checked October 2026)