Montgomery County Commissioners Court will take up proposed changes to the county’s Drainage Criteria Manual and its Development Regulations on September 18, listed as Item 12A on the agenda. The proposal would revise the manual the county adopted in 2025, its first substantial rewrite in decades, adding a section on tailwater, the downstream water level that governs how easily upstream runoff can drain away, along with an expanded list of approved modeling software, a new base level engineering section, and clarified detention design and drainage submittal requirements.
A separate amendment on the same agenda would give commissioners’ offices a fourteen calendar day window to acknowledge development plans in writing before those plans move to the county engineering department for final approval.
Montgomery County sits upstream of the Lake Houston area. Water leaving the county runs down the West Fork of the San Jacinto River into Lake Houston, so the detention and drainage standards Montgomery County sets for new subdivisions help determine how much runoff reaches Kingwood, Humble and Atascocita. The county’s current rules differ from Harris County’s on two points the proposal does not change: Montgomery County allows fill in the 500 year floodplain and requires homes to be built to the 100 year flood elevation, while Harris County prohibits the fill and requires the 500 year elevation.
