sediment being swept downstream from Colony Ridge

Search For Sediment Solutions Should Lead Straight to Colony Ridge

Harris County Flood Control, SJRA, and the Cities of Humble and Houston using funding provided in part by the Texas Water Development Board are searching for sediment solutions in the Upper San Jacinto River Basin. Their major scientific study includes all or parts of seven counties: Harris, Montgomery, Waller, Grimes, Walker, San Jacinto and Liberty – all land draining into Lake Houston.

From Technical Memorandum 1 of the Upper San Jacinto River Basin Regional Sedimentation Study.

The high-level goal: to better manage sediment in the river basin. Sediment reduces both floodway conveyance and the storage capacity of Lake Houston. Both contribute to the frequency and severity of flooding.

Among other things, the study partners hope to prioritize sediment hot spots so they can develop sediment solutions and recommendations.

I hope they look at Colony Ridge. It exemplifies a major hot spot and points the way to an obvious sediment solution – better enforcement of existing regulations.

Scope and Status of Sediment Study

The study is now about half complete. With much of the fieldwork complete, the partners will next focus on modeling, hotspot identification, area prioritization and sediment solutions, according to Matt Barrett, Water Resources and Flood Management Division Manager atSJRA.

To date, the study has examined a variety of factors:

  • Topographical characteristics (watershed size, length, slope, relief, etc.)
  • Land Cover (degree of development, forested percentage, agricultural, wetlands)
  • Soil Types and Erodibility
  • Meteorological (annual rainfall amounts and intensity).

The Colony Ridge area receives some of the highest rainfall totals and highest intensity rains in the river basin.

From Technical Memorandum #2 of the USJRB Sedimentation Study, Page 16. Colony Ridge location circled in red.

Colony Ridge also ranks among the most erodible areas in the entire river basin.

Soil erodibility in the basin. From Technical Memorandum #2, Page 13. Colony Ridge circled in blue.

So, you would hope that a development 50% larger than Manhattan, which is decimating forests and filling in wetlands would receive some scrutiny.

Colony Ridge erosion
Colony Ridge ditch has widened approximately 80 feet in 6 years due to lack of erosion control measures such as backslope interceptor swales and grass.
Colony Ridge is now 50 percent bigger than Manhattan
Rivers of mud in Colony Ridge. Even the erosion is eroding.
Guess which way to colony ridge
Sediment coming down the East Fork (right) from Colony Ridge
East Fork Mouth Bar cost $18 million to dredge.
San Jacinto East Fork Mouth Bar between Kingwood and Huffman cost $18 million to dredge.

Sediment Solutions Must Address Development Practices

Erosion occurs naturally. But poor development practices can accelerate the rate of erosion unnaturally.

Regulations in Liberty County call for backslope interceptor swales to prevent sheet flow over the sides of ditches. I have yet to see one such system anywhere in the 30+ square miles of Colony Ridge. What you typically see is this.

All that sediment washes downstream where it reduces the carrying capacity of rivers and the storage capacity of Lake Houston.

Liberty County regulations also call for planting grass on the side slopes of ditches and detention basins. The grass reduces erosion, too. But you don’t see much grass on those side slopes either.

Compare the ditch above with the ditch below in Harris County to see how grass and backslope interceptor swales can reduce erosion.

Small swales behind main slopes capture sheet flow heading toward the ditch. Pipes then take runoff to the bottom of ditch, thus reducing erosion on side slopes.

Here’s Colony Ridge again.

Three-mile-long Colony Ridge drainage ditch has no grass or backslope interceptor swales.

Address the Elephant in the Room Before the Next Disaster

Ironically, both Liberty and Harris County have almost identical regulations for erosion control. Harris County enforces them; Liberty County doesn’t.

Enforcement of development regulations is the elephant in the room.

So, as the SJRA and its partners search for sediment solutions, here’s one simple recommendation. Enforce regulations already on the books.

Colony Ridge and other developments that skirt regulations represent a disaster waiting to happen. Unfortunately, it will probably take a disaster, such as Harvey, to cause leaders to take action. But by then, it will be too late.

Posted by Bob Rehak on 10/20/23

2242 Days since Hurricane Harvey

The thoughts expressed in this post represent opinions on matters of public concern and safety. They are protected by the First Amendment of the US Constitution and the Anti-SLAPP Statute of the Great State of Texas.