Flood Zones in Jefferson County, Texas: DD6 and DD7

Why Jefferson County has two drainage districts instead of one county office

Most Texas counties handle floodplain administration through a single county engineering or development office. Jefferson County doesn't, because the Texas Legislature created two separate, independent political subdivisions decades apart to handle drainage in different halves of the county: Jefferson County Drainage District No. 6, established by a Commissioners Court order in January 1920 following a January 1919 voter election under the state's 1905 Drainage District Act (CORRECTED 2026-09, superseding an earlier framing that treated 1905 -- the year of the enabling statute, not DD6's own creation -- as DD6's founding date), covering the northern county including Beaumont, and Jefferson County Drainage District No. 7 in 1946, covering the southern county including Port Arthur, Groves, Nederland, and Port Neches. Neither district reports to the county government -- each has its own board, budget, engineering staff, and rules, funded through its own tax base. A buyer or builder needs to identify which district's boundary a specific parcel falls in before assuming which rulebook, contact, and review process applies.

DD6's net-zero runoff policy: a real, enforced design standard

Jefferson County Drainage District No. 6 covers roughly 487 square miles and maintains more than 1,247 miles of channels and 38 detention basins. Its current Drainage Criteria Manual, updated in July 2025, sets a district-wide policy requiring net-zero increase in runoff between existing and proposed site conditions for new development, redevelopment, or site modifications that add impervious surface -- meaning a builder can't simply pave or roof over more of a lot and let the extra runoff become someone else's problem downstream. Where DD6's review determines a proposed development would have an adverse impact on surrounding areas, on-site detention becomes a required part of the project design, with the district's manual specifying engineering details down to detention-basin side-slope construction (a 4:1 slope standard). This is a real, technical design requirement that a builder's civil engineer needs to account for from the earliest site planning, not a formality to satisfy after the fact.

DD7's low-elevation service area and Taylor's Bayou drainage

Jefferson County Drainage District No. 7 covers a smaller area -- roughly 107 square miles -- but a genuinely different topography: about two-thirds of DD7's service area, covering Port Arthur, Groves, Nederland, and Port Neches, sits below 5 feet of elevation above sea level, with 60 to 70 percent of the district's runoff ultimately draining to Taylor's Bayou. Average rainfall in the area runs around 53 inches a year. That combination -- low elevation, high rainfall, and a single dominant drainage bayou -- means flood risk and drainage capacity in DD7's territory deserve a different level of scrutiny than land in DD6's higher-lying northern service area, even within the same county. A parcel's specific elevation and its relationship to Taylor's Bayou's capacity are worth confirming directly with DD7 rather than assumed from a FEMA flood map alone.

What to check before building or subdividing in Jefferson County

1. Confirm which drainage district -- DD6 (roughly northern county, Beaumont) or DD7 (roughly southern county, Port Arthur area) -- covers the specific parcel before contacting either office, since their rules, staff, and review processes are separate.
2. For land in DD6's jurisdiction, ask directly whether a proposed project triggers the net-zero-runoff detention requirement and get the district's current Drainage Criteria Manual rather than relying on a general statement of the policy.
3. For land in DD7's jurisdiction, ask specifically about the parcel's elevation relative to the district's below-5-foot low-lying areas and its drainage relationship to Taylor's Bayou.
4. Remember that a FEMA Flood Insurance Rate Map is an estimate based on assumed rainfall parameters, not a guarantee -- both districts note that actual storms can produce flooding deeper and more widespread than the mapped floodplain shows, which matters for insurance and construction-elevation decisions alike.