Tomball staff outline drainage master plan, propose CIP projects and stricter stormwater rules

City of Tomball consultants and staff presented a drainage master plan at a workshop that maps flood-prone areas and proposes capital improvement projects, including storm sewers and subregional detention basins to reduce structure inundation in Old Town Tomball and several other basins.

The plan uses 2D hydrologic and hydraulic modeling integrated with Harris County Flood Control District stream models to refine inundation maps beyond FEMA flood data, project consultant Kurt Killian said. “HECRAS is a board of engineers program that's used worldwide specifically for stream modeling capabilities,” Killian said, adding that darker map colors indicate deeper ponding.

The city and its consultants identified near-term and ultimate improvements by basin. Examples shown to the council included phased channel deepening and culvert upgrades in the M118 basin near Lizzie Lane; enclosure and storm-sewer upgrades on the J‑13103 tributary and along Carroll, Lovett and Lubbock streets (a project tied to a separate Harris County roadway improvement); a subregional detention basin and storm-sewer lateral to serve North Cherry and Old Town; and a…