Diversion Ditch Study Did Not Consider Obvious Opportunities that Might Have Reduced Costs, Flood Risk
7/30/25 – The Preliminary Engineering Report (PER) of Kingwood Diversion Ditch Conveyance Improvements makes no reference to three obvious detention opportunities that could potentially reduce project costs and help protect people in Kingwood from flooding. Harris County Flood Control District (HCFCD) commissioned the PER in 2021 after the Kingwood Area Drainage Analysis identified fixing Diversion Ditch issues as one of the top priorities in Kingwood.
Chris Bloch, a local engineer and flood activist says he showed the detention opportunities to HCFCD. However, Neel-Schaffer did not consider them in its report for unknown reasons.
Detention South of River Will Not Help Flooding Along Diversion Ditch
The Neel-Schaffer PER recommended building 405 acre-feet of detention south of the San Jacinto West Fork.
The location south of the river may help people downstream, but it will do nothing to reduce the volume of water flowing down the Diversion Ditch during a major storm.
Detention south of the river will help people farther down the West Fork. But Bloch points out that locating detention along the Diversion Ditch would help both Kingwood residents and others downstream.
Overview: Three Stormwater Detention Opportunities Inside Kingwood
Bloch consulted with Stan Sarman before Sarman’s untimely death several years ago. Sarman was one of the consulting engineers who designed Kingwood’s original drainage for Friendswood. Bloch says that he and Sarman identified several recommendations to improve Kingwood drainage. From north to south, they include:
- Adding detention between Northpark Drive and St. Martha Catholic Church
- Removing a berm between Kings Manor and Kings Mill detention ditches, then increasing the width and depth of the combined ditches
- Creating extra capacity near the proposed new San Jacinto River outfall of the Diversion Ditch.
According to Bloch, these alternatives could provide far more capacity than the 405-acre feet that Neel-Schaffer says it needs – especially if combined with some channel-widening opportunities. I will discuss channel widening in a future post. But first, let’s look closer at these three.
Opportunity #1
Neel-Schaffer evidently didn’t look at anything north of the Harris/Montgomery County line. Since Neel-Schaffer released its PER, the Lake Houston Redevelopment Authority announced plans to build 100 acre-feet of detention in the area where the Diversion Ditch splits off from Bens Branch just north of Northpark. That’s a quarter of the needed 405 acre-feet right there.
Opportunity #2
Removing the berm between the Kings Mill and Kings Manor ditches and increasing the width and depth of the combined ditches would provide another 100 acre-feet of detention capacity. Both ditches are owned by Montgomery County Municipal Utility Districts.
Kings Mill is under fire to reduce runoff due to the new high-density Northpark Enclave development. Construction plans show runoff entering the Northpark evacuation route during extreme high-water events.
Plus, additional Enclave runoff will further reduce Diversion-Ditch capacity. Parts of the Diversion Ditch have a 50% chance of flooding every year.
Opportunity #2 could help mitigate both Enclave and Diversion-Ditch capacity issues.
Opportunity #3
Neel-Schaffer recommends extending the Diversion Ditch from below Deer Ridge Park to the West Fork – without forcing it to make an S-turn through River Grove Park.
That coincides with one of the recommendations originally made by Sarman and Bloch. But Sarman and Bloch also called for construction of a large pond at the outfall location. This pond would slow water velocities exiting the Diversion Ditch and provide a sediment-settling area before the water enters the River.
Depending on the configuration, such a pond could provide another 80 to 100 acre-feet of inline detention.
High Cost of Detention South of River
Those three alternatives alone could provide approximately three quarters of the needed detention and reduce flood risk for more than 500 residents who flooded near the Diversion Ditch during Harvey.
Bloch and Sarman identified other opportunities within the ditch to expand capacity. They could easily bring the total to far more than the 405 acre-feet needed.
Neel-Schaffer makes a frank confession about its detention recommendation south of the West Fork on page 38 of its Preliminary Engineering Review. It says that…
“Although an offsite stormwater detention basin is feasible, the prospective benefits are negligible.”
Neel-Schaffer Kingwood Diversion Ditch Preliminary Engineering Review, Page 38
Yet the projected cost of the basin they proposed is between a quarter and a third of total project costs – almost $15 million out of $55 million. In fairness, Neel-Schaffer says on the same page, “Due to limited effectiveness and significant cost, the recommended detention basin should be further examined during final design.”
Final Design Getting Underway
On May 8, 2025, Harris County Commissioners Court approved a motion to advertise final design and construction of the diversion ditch project for bids. However, an engineering design firm has not yet been selected.
When they are, I hope they evaluate some of these recommendations.
A transmittal from HCFCD Executive Director Dr. Tina Petersen shows that the EPA and Texas Water Development Board have apparently pledged $7 million to the project. That won’t cover much construction. So, Petersen says HCFCD will continue to look for more grants. Her timeline shows construction starting in mid-2028…if she can find the money.
These recommendations may help make the project more affordable.
Posted by Bob Rehak 7/30/25
2892 Days since Hurricane Harvey
