As part of its 2019 bond program, League City hired LJA Engineering to do 2D analysis of the city’s watersheds so the city could create a comprehensive drainage plan. According to the city’s website, the budget for developing the plan, along with a flood gauge warning system, is $800,000.
LJA representative John Grounds said the goal of the study was to define the city’s existing drainage infrastructure and identify future problems and how to solve them. LJA used previous studies and Atlas 14 rainfall data to do their modeling, Grounds said.
Most, if not all, of the proposed solutions included creating detention ponds along ditches.
For instance, Corum Ditch had channel improvements completed in 2011, but they are not enough to convey water during large storms. Grounds said dozens of acres of detention ponds need to be created, the channel needs to be modified, and the storm sewer needs to be upgraded to prevent flooding in the ditch.
Robinson Bayou needs four detention ponds, and two nearby bridges need to be replaced because the existing ones further exasperate flooding. These improvements will result in water flowing more directly into Clear Creek, Grounds said.
Jarbo Bayou is highly affected by tides, but the 2D modeling did not include a study of storm surge flooding. Still, analysis shows the area needs a couple detention ponds and an increase to the storm sewer’s capacity, Grounds said.
Magnolia Bayou contains mostly undeveloped land to the west. As such, it is hard to predict what future development might do, Grounds said.
“The drainage in that area—it’s not very well defined,” he said. “The channel doesn’t really know where it wants to be yet.”
That said, detention ponds would help, and any upstream development should not release water to the downstream channel; by doing that, the need for ponds might be mitigated, Grounds said.
Mayor Pro Tem Hank Dugie said this study should be forwarded to the Houston-Galveston Area Council, which is the entity by which League City could apply for grants to fix these problems.
“H-GAC definitely needs to have this,” Dugie said, implying City Council should consider passing a resolution making H-GAC aware of the study.
Additionally, the Texas Department of Transportation would benefit from knowing which bridges are working against the city’s drainage efforts, Dugie said.