Tag Archive for: Diversion Ditch

HCFCD Recommends Expanding Diversion Ditch as First Priority in Kingwood

At the Harris County Flood Control District’s (HCFCD) Kingwood Area Drainage Analysis meeting tonight, HCFCD recommended that expansion of the Kingwood Diversion Ditch should be the community’s highest priority.

The Diversion Ditch project would help address several potential problems. Expanding it would remove 62 structures from inundation areas and another 586 structures would benefit from improved local drainage. In addition, the project:

  • Can divert floodwater from Ben’s Branch, which will be a much more complicated project, taking more time.
  • Has a 300-foot right-of-way, of which only half is being used
  • Has bridges that already span the entire 300 feet.
  • Will help carry floodwaters from rapidly growing south Montgomery County.

History of Diversion Ditch

In the early days of Kingwood, Friendswood Development Company built the Diversion Ditch to reduce water flowing into Ben’s Branch. But since then, upstream development and larger rains have stressed the capacity of both Ben’s Branch AND the Diversion Ditch. Engineers estimate that peak flows have doubled since 1985.

Most of Ben’s Branch is Natural Channel

Ben’s Branch cuts diagonally through the heart of Kingwood. See red lines below. More than half its length – between Woodland Hills and Rocky Woods Drive is natural channel. Widening it will be complicated and take much time.

Red Line indicates approximate path of Ben’s Branch through Kingwood.

Ben’s Branch Now at 2-Year Level of Service

However, areas on both sides of Ben’s Branch are threatened by flooding as you can see in the image below from FEMA’s Flood Hazard Viewer.

Ben’s Branch once had a 100-year level of service, meaning it had enough carrying capacity to prevent homes from flooding in everything but a 100-year rain. Models based on new Atlas-14 rainfall probability frequencies indicate that the channel’s capacity is now down to a 2-year level of service. That means it will flood in minor rains, exactly as St. Martha School did last year.

Worse yet, Ben’s Branch has decreased to a 2-year level of service throughout its length.

HCFCD Kingwood Area Drainage Analysis
Source: Fema’s Flood Hazard Layer Viewer. Cross-hatched equals floodway, aqua = 100 year floodplain, brown = 500-year floodplain. Floodplains shown above are based on pre-Atlas-14 rainfall probability statistics. An Atlas-14 hundred-year rain is about 30-40% higher than the old hundred-year rain.

When flood maps are updated based on Atlas-14 statistics, those floodplains will likely expand…unless we do something to handle more floodwater before then.

However, Ben’s Branch will not move to preliminary engineering right away.

How to Protect Against Bigger Rains and More Upstream Development

The Kingwood Area Drainage Analysis sought to understand what we need to do to restore a 100-year level of service to all ditches and streams based on Atlas 14. Of the 19 ditches and streams studied, nine need improvement. The level of service for some, including Ben’s Branch, has been reduced to 2 years.

Expanding the Diversion Ditch is the fastest way to take pressure off of Ben’s Branch.

The Diversion Ditch intersects Ben’s Branch at the new St. Martha Church. It then flows south to Deer Ridge Park and then winds through River Grove Park. See the white line below.

Kingwood Diversion ditch (white line) intersects Ben’s Branch near the new St. Martha Church.

Expansion Capacity Already Built into Diversion Ditch

Engineers foresaw the day when Kingwood would need more drainage capacity due to upstream development in Montgomery County. They built the Kingwood Diversion Ditch to handle the extra stormwater. They also made the bridges over the diversion ditch wider than they needed at the time. Finally, they dedicated a flood easement on both sides of the ditch that was wider than they needed, so they could expand the ditch later without encroaching on neighboring properties. Here’s how it looks from the air.

Looking north across Northpark Drive toward Bens Branch, which cuts diagonally from left to right through the middle of the frame. Note the ample clearance under the bridge and the wide shoulders of the ditch. St. Martha Church is in the upper left.
Looking south toward Kingwood Drive at the Diversion Ditch. King’s Mill is on right in foreground.

Both Kings Mill and Kings Manor now drain into the Diversion Ditch. But they came long AFTER Diversion Ditch construction. Other new upstream developments that drain into the Diversion Ditch and Ben’s Branch include Brooklyn Trails and Woodridge Forest, both in Montgomery County.

As a result, the Diversion Ditch itself has decreased to a 2- to a 25-year level of service in places. However, it still offers a 100-year level of service in others.

Looking NE toward Deer Ridge Park from over Hamblen Road. A corner of Deer Ridge Estates is on the left. The diversion ditch cuts in front of the park (upper left to lower right) and goes into an area largely undeveloped on its way to the river (out of frame to the right).

Impact on River Grove Park

Once the Diversion Ditch passes through the area shown in the photo above, it enters wetlands and winds through River Grove Park. Two questions arise. How do we protect, from additional flow:

  • The park?
  • People downstream on the West Fork?

The first question is simple: split the flow in two. Take part through the undeveloped area west of the park. See the green below.

Green Line represents one possible route for diversion of the diversion ditch.

The second question is more complicated. We need a retention basin to hold the extra stormwater until the peak of any flood passes on the West Fork. But where? The closer you get to the river, the lower the elevation. Because of that, the basin could fill with floodwater from the river before it fills with floodwater from upstream. Fortunately, some large tracts of land exist on higher ground that could be purchased. HCFCD estimates the need at 1248 acre-feet. Preliminary engineering should start soon to address these issues.

Upstream Development Not Addressed by Analysis

Unfortunately the Kingwood Area Drainage Analysis did not address upstream development issues in Montgomery County. That was beyond the scope of work. Regardless, such issues must be addressed somehow, someday soon. Otherwise, even the improvements we invest in today could soon be overwhelmed by additional floodwaters.

In that sense, these channel improvements represent a stopgap measure. The real solution lies in making everyone in the region realize that we are all in this together.

Additional Resources

If you missed the presentation, you can view it on YouTube.

Here is a PDF that contains the District’s summary of the Kingwood Study. It includes a spreadsheet comparing the improvements plus data sheets on the nine recommended projects.

The ten remaining channels/streams already offer a 100-year level of service. Therefore, no improvements are needed. HCFCD felt Taylor Gully should be the next priority after the Diversion Ditch. But the possible purchase of Woodridge Village may require re-thinking project requirements. Specifically, if Woodridge turns into a giant detention basin, the channel may not need as much deepening or widening.

Posted by Bob Rehak on 10/20/2020

1148 Days since Hurricane Harvey

HCFCD Begins Kingwood Diversion Ditch Repairs

Last week, while driving through Forest Cove, I noticed construction activity and Harris County Flood Control District signs at the Kingwood Diversion Ditch near Walnut Lane. The area downstream from the bridge has some of the worst erosion of any ditch in Kingwood.

Area Now Under Repair As It Looked in 2009

Kingwood Diversion Ditch in 2009. Looking south from Walnut Lane. Forest Cove on right.

Erosion was bad for years and only got worse during major storms in 2015, 2016, and 2017. Massive slabs of the banks broke off in chunks, threatening trails and adjacent homes.

Since the picture above in 2009, the ditch has eroded both down and outward to increase its conveyance as new subdivisions upstream scabbed off of Kingwood’s infrastructure.

Pictures of Work in Progress Today

Oh, what a difference a decade makes! Note the exposed storm drains in the pictures below that you cannot see in the picture above.

Looking south from Walnut Lane Bridge. Exposed, elevated and crushed storm drains due to erosion.

The erosion left storm drains elevated and exposed to the ravages of floodwaters. Some were crushed, causing water to back up into streets and drainage ditches during heavy rains.

The area that collapsed circa 2009 above is the same area shown under construction today.

The velocity of water through this ditch during floods has earned it the nickname “Kingwood Rapids” from white-water enthusiasts.

Storm drains left exposed and elevated as the ditch widened and deepened itself to accommodate upstream development such as Woodridge Forest.
HCFCD works to restore and stabilize banks, and repair damaged storm drains.
Crumpled drains being removed by excavator.

How the Diversion Ditch Got Its Name

The Kingwood Diversion Ditch got its name when Friendswood realized that Ben’s Branch could not hold all the water being brought to it by adjacent subdivisions.

So Friendswood literally built a ditch that diverts a portion of the water coming down Ben’s Branch from Montgomery County just above Northpark Drive.

The point of diversion. Believe it or not, that’s Ben’s Branch flowing from bottom to top. As Ben’s Branch squeezes down, it forces water into the diversion ditch, which splits off to the right, just south of the new St. Martha’s Catholic Church.
From there, the ditch goes under Northpark Drive, past Woodland Hills, and south to the river.

Luckily, Friendswood designed the bridges over the Diversion Ditch to accommodate expansion of the ditch. HCFCD is studying that possibility now as part of the Kingwood Area Drainage Analysis. Results of the study should be published this fall.

Posted by Bob Rehak on 6/5/2020

1011 Days after Harvey

HCFCD Begins New Kingwood Drainage Ditch Repairs

Harris County Flood Control District has quietly started repairs to two more Kingwood Drainage Ditches. The first is G103-33-01, the ditch between Fosters Mill and Kings Point that enters the river near the mouth bar at Scenic Shores. The second is the Kingwood Diversion Ditch, G-103-38-00. It runs down the west side of Woodland Hills, crosses Kingwood Drive by the fire station, then descends to the lake between Trailwood Village and Forest Cove.

Work In Progress as of Monday 5/11/2020

Erosion on the ditch between Fosters Mill and Kings Point that enters Lake Houston near the mouth bar (background) undergoes repair.
Turbulence downstream of weirs, bottom left, commonly results in erosion.
Here’s what the erosion looked like before repairs started. Picture taken in 2018 courtesy of HCFCD.
Close up of eroded drain pipe near weir.

Work on Diversion Ditch Expected to Start This Week

According to Beth Walters of Harris County Flood Control, work on the Diversion Ditch should start this week. Below are several pictures taken of severe erosion that threatens homes and trails.

Looking west at Property in Deer Ridge Estates threatened by erosion of Kingwood Diversion Ditch. Looking west. Picture taken Jan. 2019.
Looking south at the Kingwood Diversion Ditch erosion just south of Walnut Lane. This area is a perennial problem. Photo taken in 2009. Kayakers have dubbed this area the Kingwood rapids. During floods, it offers the only white water experience in Kingwood.

Ditch maintenance includes erosion repairs, silt buildup removal, mowing, de-snagging (removing downed trees), and removing collapsed drainpipes.

Erosion in Kingwood Diversion Ditch near fire station on Kingwood Drive.

Additional details are not yet available on the length of time repairs will take.

Left unrepaired, such erosion can destroy property and trails. These repairs are part of HCFCD’s ongoing maintenance efforts.

Here’s a list of planned maintenance projects on other ditches around the Kingwood area.

Posted by Bob Rehak on 5/17/2020

992 Days after Hurricane Harvey

HCFCD Crews Work on Thanksgiving Day to Clear Ben’s Branch

Earlier this week, I reported an improbable meeting in Huffman on the eve of Thanksgiving that showed promise to increase conveyance on Luce Bayou. This story is even more amazing holiday miracle. Harris County Flood Control District (HCFCD) crews worked on Thanksgiving Day to clear trees blocking Ben’s Branch.

HCFCD has a right to cut trees 50 feet on either side of the centerline of the Ben’s Branch and clearing started Thanksgiving week. Photo courtesy of Thomas Blailock.

I did not personally see them but received an email with images from Thomas Blailock Thursday. Blailock says, “The contractor is UFLGC from Ackerman, MS. They had 7 trucks and around 20 employees clearing on Thanksgiving Day. They have been here for 4-5 days.”

I saw evidence of their work at Tree Lane. The areas on either side of Bens Branch look like they got a haircut.

Such clearing reduces the chances that trees will fall into the creek during storms, get hung up on other trees and form “beaver dams” that back water up into neighborhoods.

Result of One Year of Negotiation

The clearing follows a year of negotiation between HCFCD, Friendswood and Bear Branch Trail Association. The Association owns the greenbelt, but Friendswood still exercises deed restrictions.

The Community had mixed reaction to news of the agreement. Many were thankful for progress. Others felt the agreement didn’t go far enough. Many, like Blailock, hoped the creek could be widened or straightened.

Judging by how difficult it was to work out terms of this compromise, widening or straightening won’t happen any time soon – even as upstream development continues to dump more water faster into the creek.

An Alternative That Could Help

I have heard, however, that HCFCD has examined the possibility of widening the Kingwood Diversion ditch that runs down the western side of Woodland Hills and crosses under Kingwood Drive near the fire station. Preliminary reports from HCFCD indicate that a) their easement includes enough room to widen the ditch, b) no bridges would have to be widened (they were built with enough room under them to widen the ditch), and c) that could divert water from Ben’s Branch that would help reduce flooding along the creek.

Looking south down the diversion ditch from over Northpark Drive. That’s Woodland Hills on the left and Kings Mill on the right.
Looking north along the diversion ditch toward where it intersects with Ben’s Branch in front of the new St. Martha Church. That’s Ben’s Branch crossing left to right, parallel with the power lines.
HCFCD’s easement and the bridges are wide enough to widen the ditch without rebuilding the bridges. Note the extra room under the bridges on the right of the water.

Nothing is final yet. The Kingwood Area Drainage Assessment is not yet complete. So things could change. But don’t be surprised if you see this as a future recommendation.

For a full review of issues along Ben’s Branch from Kingwood Drive north past Northpark Drive and St. Martha’s new church, check out this thorough, thought-provoking presentation by Chris Bloch. It underscores the need to use all means possible to improve conveyance.

For more information about HCFCD work in the Kingwood Area, see this page on their new, updated website.

Posted by Bob Rehak on 11/30/2019 with help from Thomas Blailock and Chris Bloch

824 Days after Hurricane Harvey and 72 after Imelda