Kingwood Diversion Ditch Preliminary Engineering Review Released

2/8/2025 – Harris County Flood Control District (HCFCD) has finally released the full text of the Kingwood Diversion Ditch Preliminary Engineering Review and its supporting files. The report, which was originally due in 300 days took more than 1400 days. When asked why it took so long, a HCFCD representative replied, “Personnel turnover.”

The files transmitted to Commissioners Court on 2/6/25 include:

• The study itself
• Appendices
• Exhibits

See links to all of them at the bottom of this post.

Altogether, the 175 megabytes of materials include hundreds of pages. I could not even post some files because they exceeded the size limit of my website or because they were engineering files that required specialized software to open.

I have uploaded what I can. However, I have not studied them all thoroughly yet. Based on a preliminary scan, here are some of the highlights.

Three Alternatives Evaluated

Neel-Schaffer, the engineering company that produced the report, considered three alternatives. Each improves stormwater carrying capacity of the ditch and relieves some of the pressure on Bens Branch. The two are connected near the Northpark Drive Fireworks Stand. The three alternatives include the following features:

• Alternative 1 – A widened Kingwood Diversion Ditch including grass-lined trapezoidal channel, one drop structure and a new outfall of the Kingwood Diversion Ditch to West Fork San Jacinto River.
• Alternative 2 – A widened Kingwood Diversion Ditch including a benched channel section above Ordinary High-Water Mark, two drop structures and a new outfall of the Kingwood Diversion Ditch to West Fork San Jacinto River.
• Alternative 3 – A widened Kingwood Diversion Ditch including a Natural Stable Channel Design Sections with riffle and pools and a new outfall of the Kingwood Diversion Ditch to West Fork San Jacinto River.

Alternative #3 Recommended

For each alternative, Neel-Schaffer examined:

• Hydraulic performance
• Increased channel conveyance capacity
• Costs and benefits in relation to the reduction in the area of inundation
• Environmental impacts
• Construction feasibility.

The engineers recommended Alternative 3 after comparing:

• Capital cost estimates
• Stormwater detention cost estimates
• Maintenance costs per 10 years
• Number of parcels, acres and structures removed from the 1% annual chance floodplain

The table below summarizes their benefits.

Even though alternative #3 was the most expensive to construct, lower maintenance costs would offset the increase within 28 years.

Features Included in Recommendation

The recommended project alternative includes:

• A diversion structure at the intersection of the Diversion Ditch and Bens Branch to reduce the volume flowing into Bens Branch
• Channel conveyance improvements to the Diversion Ditch
• Bridge replacements at Kingwood Drive, Walnut Lane, Deer Ridge Estates Boulevard and the pedestrian bridge at Lake Village Drive
• A new outfall to the West Fork San Jacinto River, just west of Woodland Hills Drive/River Grove Park
• A stormwater detention basin on the south side of the San Jacinto West Fork.

The bridges at Northpark Drive will also be rebuilt, but as part of the Northpark Expansion Project.

Impacts on Bens Branch

In each alternative, stormwater flow to Bens Branch was restricted by pipes. That forces more stormwater into the expanded Diversion Ditch.

The Flood Control District’s guidelines allow for the use of a minimum pipe diameter of 24-inches. That would take enough stormwater flow out of Bens Branch to improve it from a 2-year level of service to a 100-year level.

Remember, the function of the Diversion Ditch is to take stormwater out of Bens Branch. Friendswood hoped to minimize flooding through the western half of Kingwood by using two channels instead of one to convey stormwater.

Detention Basin Also Recommended South of West Fork

Neel-Schaffer also evaluated the need for stormwater detention storage volume to mitigate adverse impacts of the proposed alternatives. They recommend one across the West Fork on high ground.

Funding Not Identified Yet

Funding does not currently exist for any construction. HCFCD would have to apply for grants. The Preliminary Engineering Report outlines several possible sources of funding. However, Stephanie Zertuche, Flood Control’s Project Manager, says that pursuit will likely happen as part of the next phase – construction engineering – when costs are locked down.

However, that assumes that the project even gets that far. $55 million to remove 34 structures from the 100-year flood plain will be a difficult sell based on the Benefit/Cost Analysis alone.

But there are other factors to consider. We shouldn’t forget that:

• 12 people died along Bens Branch during Harvey.
• The entire Kingwood Town Center area was under water
• Thousands of people got cut off from evacuation routes.
• Kingwood High School flooded to the second floor and thousands of students had to be bussed to other schools for a year.

Social benefits go far beyond cost and are hard to quantify.

To Review the Original Docs…

Below are links to all the Kingwood Diversion Ditch Preliminary Engineering Report documents.

• Kingwood Diversion Ditch Preliminary Engineering Review
• Kingwood Diversion Ditch Typical Cross Section for Alternative #1
• Kingwood Diversion Ditch Typical Cross Section for Alternative #2
• Kingwood Diversion Ditch Typical Cross Section for Alternative #3
• Kingwood Diversion Ditch Bridge Assessment
• Kingwood Diversion Ditch Stream Condition Assessment
• Kingwood Diversion Ditch Stormwater Detention Basin Alternatives
• Kingwood Diversion Ditch Threatened/Endangered Species Habitat Assessment
• Kingwood Diversion Ditch Exhibit 1 Project Area
• Kingwood Diversion Ditch Exhibit 2 FEMA Map
• Kingwood Diversion Ditch Exhibit 3 Historical Flooding
• Kingwood Diversion Ditch Exhibit 4 Topographical Map
• Kingwood Diversion Ditch Exhibit 5 Land Use Cover
• Kingwood Diversion Ditch Exhibit 6 Existing Parcel and Right of Way
• Kingwood Diversion Ditch Exhibit 7 Waterlines
• Kingwood Diversion Ditch Exhibit 8 Wastewater Lines
• Kingwood Diversion Ditch Exhibit 9 Pipelines
• Kingwood Diversion Ditch Exhibit 10 Utilities
• Kingwood Diversion Ditch Exhibit 11 Stormwater Lines
• Kingwood Diversion Ditch Exhibit 12 Inundation Map 50%
• Kingwood Diversion Ditch Exhibit 13 Inundation Map 10%
• Kingwood Diversion Ditch Exhibit 14 Inundation Map 0.2%
• Kingwood Diversion Ditch Exhibit 15 Inundation Map 1%

For ease of future reference, I’ve also linked them on the Reports Page under the Harris County Flood Control District tab.

If you are an engineer in the Humble/Kingwood Area, please help. Send me your opinions through the contact page of this website.

Even if you don’t read the entire study, you may be interested in seeing where your home stands in relation to the new expanded floodplains under Atlas 14. Those inundation maps at the bottom of the list are very interesting.

Posted by Bob Rehak on 2/8/25

2720 Days since Hurricane Harvey