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Imelda Floods Ben’s Branch Schools, Homes at Three Choke Points

Disclaimer: I spent the better part of a day driving down every street that borders Ben’s Branch. I saw damage clustered in three areas. It’s possible other areas were affected but the City had removed trash before I got there.

At least two schools, 7 homes, and one business flooded along Ben’s Branch in Kingwood during Imelda. All were located near choke points along the creek. And massive recent upstream development likely played a role in each case. That new development also played a role in eroding the margin of safety between floodwaters and foundations all along the creek – even for homes and businesses that did not flood. Total damages will likely exceed $3 million along Ben’s Branch in Kingwood.

Three circles represent choke points where virtually all structural flooding happened on Ben’s Branch during Imelda. See discussion below.

Ben’s Branch Now and 10 Years Ago: Influence of Upstream Development

Area in white box is roughly 800 acres. Three quarters of it was not developed ten years ago (see below). Red line marks the course of Ben’s Branch through a series of retention ponds and new ditches that now contribute more water faster during heavy rains.
Same area in 2009, only ten years ago.. Neither Woodridge Forest, Woodridge Village, nor the Kroger Center at 59 had started development yet, though some areas had been cleared.

Imelda Tested Design Limits of Drainage Systems

Most drainage systems are designed to protect homes and businesses from a hundred-year flood. Imelda was a hundred year flood. The storm tested the design limits of flood infrastructure everywhere along Ben’s Branch in Kingwood.

Based on its peak intensity of 4.56 inches in one hour (as measured at the US59/West Fork gage), Imelda qualified as a 100-year storm. Streets, storm drains and ditches are designed to handle that much as an upper limit. And for the most part they did. Especially because builders usually elevate most structures at least two feet above the hundred-year flood plain.

Those extra two feet act as a margin of safety and as a hedge against future upstream development.

Limits Exceeded in Several Places During Imelda

In each case where homes, businesses or schools flooded along Ben’s Branch, unique circumstances eliminated that margin of error and resulted in flooded structures.

With the exception of one low-lying home I found in Hunter’s Ridge very close to the creek, all of the structural damage took place at three choke points along the creek.

Choke Point #1: Northpark and Ben’s Branch

Where Ben’s Branch crosses under Northpark Drive, two things happen. A ditch from the new Woodridge Forest subdivision joins it. And then all that water is forced into a culvert that crosses under Northpark Drive.

These two culverts constrained water flowing under Northpark Drive and backed it up past Hidden Pines at the stoplight in the background. When water started flowing over the road for approximately two blocks, this part of Kingwood was cut off.

To my knowledge, no one has ever upgraded that culvert despite significant upstream development. It backs water up for several blocks during heavy rains and forces water OVER Northpark Drive. This caused at least six homes near Aspen Glade west of Hidden Pines to flood.

When water backed up and flowed over Northpark, it cut off both inbound and outbound traffic. It also broke through the fences of homes that back up to Northpark.

East-West fences were pushed in from the north by water overflowing across Northpark Drive. This location is a block west of the culverts.
Looking north toward Northpark Drive at Hidden Pines. North-South Fences were pushed out to the East by water trying to return to Ben’s Branch across Hidden Pines to the right. Note the new fence. It had just been replaced after the May 7th flood.
The scene on Aspen Glade Drive in North Woodland Hills. These homes are west of Hidden Pines and back up to Northpark Drive.
A resident of Aspen Glade shows how high the water got in front of his house during Imelda.
A worried Lela Yorba wonders how her family will ever recover from the second flood in four months, and whether she should even try. Despite living on Aspen Glade for decades, her home had never flooded before May of this year.
The interior of Yorba’s flooded home during Imelda. Image courtesy of Lela Yorba.
Yorba’s garage during the peak of Imelda. Image courtesy of Lela Yorba.
Floodwaters crept up to the foundations on the far side of the street but did not enter homes according to Yorba. Image courtesy of Lela Yorba.
One week after Imelda, Yorba tries to turn wet walls back into dry walls.

Impact of New Development

Net: the flooding of homes on Aspen Glade was likely caused by an undersized culvert at North Park that could not convey all the water coming from hundreds of acres of new development. When the water backed up, it rushed over North Park for approximately two blocks. Eyewitness reports and FaceBook videos peg the height at a foot above the roadway.

In the last 10 years, more than 600 acres have been developed north of North Park between 59 and Woodland Hills. More new homes are being built every day.

Much of the drainage from the new development joined Ben’s Branch just before it reached the culverts.

This drainage ditch from many of those new homes in Woodridge Forest joins Ben’s Branch east of Hidden Pines in the background where multiple homes flooded. This is additional drainage coming into the creek at a point where part of it can not be siphoned off into the diversion ditch that runs down the west side of the villages of North and South Woodland Hills.

Choke Point #2: Woodland Hills Drive and Ben’s Branch

About two or three blocks east of the culverts under Northpark, between St. Martha Catholic School and Kids in Action, Ben’s Branch narrows down again. It quickly funnels from a wide, excavated ditch to a narrow stream cutting through dense forest. See photo below.

Hovering over Woodland Hills Drive in a helicopter looking east. Ben’s Branch narrows between Kids in Action on the left and St. Martha’s school (out of frame on the right). Both flooded. Note how the fence was pushed in by the force of the water.

At this choke point, both the school and Kids in Action, flooded. Repairing the school after the May flood cost St. Martha $900,000. Repairing Kids in Action cost $500,000. This time it will cost each even more.

Behind St. Martha’s, Ben’s Branch becomes a narrow creek filled with trees. This further slows water down and backs it up. It remains like this most of the way to Kingwood Drive. Image courtesy of Father TJ Dolce.
The natural creek also makes many tight turns. Here, it makes a 150 degree turn followed by a 90 degree turn. Image courtesy of Father TJ Dolce.

The results were costly. St. Martha’s lost two classroom buildings plus its playground.

One of the two St. Martha School buildings flooded by Imelda.
Flooded corridor.
Flooded classroom.

Until the school buildings can be dried, disinfected and rebuilt, classes are being held on upper floors and in other parish buildings. No children were ever endangered by the flood. Parish personnel started evacuations to higher buildings as soon was water started coming into the parking lot, the lowest point on the campus.

Across the creek, Kids in Action, one of Kingwood’s most popular day care and after school facilities, had its own problems.

A distraught Diane Havens, owner of Kids in Action, tries to keep a brave face after she loses the use of her beautiful facilities for the second time in four months.
Hand sanitizer is the second thing you see in the reception area now.
Havens is bringing in four of these mobile units to hold classes until the first floor of Kids in Action can be restored again.

Haven’s spent $500,000 repairing her facilities after the May 7th flood. That’s a lot for a small business. She’s determined to weather this storm, too. But she worries that some of her clients may grow impatient in the inconvenience during repairs.

Choke Point #3: Kingwood Drive and Ben’s Branch

As Ben’s Branch approaches Kingwood Drive from the northwest, it spreads out into a 100+ acre forested area that includes the Creekwood Nature Center. But just before it crosses under Kingwood Drive, Ben’s Branch’s flood plain funnels down between Kingwood High School and the old H-E-B shopping center. At that point, a second branch of the stream joins it from the north. After crossing under Kingwood Drive, it is further constricted on the east side by commercial development. This represents another choke point.

The Kingwood High School Gym and Natatorium (bottom left) took on floodwater during Imelda.

The Kingwood High School gym and natatorium took on several inches of water during Imelda when drains and/or Ben’s Branch backed up. Merchants in the old H-E-B shopping center also report being stranded in their stores for two hours at the peak of Imelda as water from Ben’s Branch raced through the parking lot. Merchants said the water was inches from coming in their stores.

While many of the businesses south of Kingwood Drive in Town Center and Kings Harbor reported having water lapping at their foundations, I found none that reported flood damage.

No Simple Fix

I can’t think of a simple fix to all of three of these problems. Fixing one could compound the others. For instance, it would be simple to replace the culverts under Northpark with a bridge when the street is widened. However, that would just increase the volume of water backing up where the creek narrows between St. Martha’s School and Kids in Action. That would likely flood them even worse.

Channelizing the creek all the way to Kingwood Drive would likely be unpalatable from a political point of view. Four reasons: Few people in that area were affected. They all love their greenbelts. And the costs would be high. That would make the Benefit/Cost ratio of the project a non-starter.

One Possible Solution

One possible solution: convert the unused land around St. Martha’s new church north of Northpark Drive to additional detention. That’s valuable land and detention is expensive, but it may be a better alternative than losing the school which was just expanded in 2008. Father TJ Dolce is pitching that idea and hopes the Archdiocese would approve the use of their vacant land for detention. The big question: Would it be enough to make a difference.

Drainage Study Already Under Way

Thankfully, Harris County Flood Control is conducting a Kingwood-wide drainage study right now. They are studying Ben’s Branch. Hopefully, their talented engineers will be able to find the optimum solution that protects everyone. I sure hope they find it soon because these people are every bit as desperate as the people who flooded twice in Elm Grove and North Kingwood Forest.

Ben’s Branch may affect fewer structures. But it probably affects more people when you add up enrolled students and their families.

Posted by Bob Rehak on 10/1/2019 with help from Father TJ Dolce, Diane Havens, Lela Yorba, Daryl Palmer and National Helicopter Service.

763 Days since Hurricane Harvey and 12 since Imelda