Tag Archive for: Tree Lane Bridge

City Begins Tree Lane Bridge Repairs

This morning, City of Houston contractors began clearing access points for the Tree Lane Bridge repairs in Kingwood next to Bear Branch Elementary where more than 600 students attend classes.

The City announced the kickoff of the project on February 21, 2024, but work actually started today.

Photo on 4/9/2024. Step one: lumberjacks clearing access for Tree Lane bridge repair work.

Extent of Damage

This is actually the second round of repairs. The City made some rudimentary efforts in 2020 that ultimately proved ineffective. Four years later, erosion under the bridge is more extensive now than then.

I took all the pictures below on 4/7/24.

Tree Lane Bridge before start of Round 2 repairs. Collapse of East retaining wall.

The forensic report blames the damage on “failure of riprap.” Riprap is boulders placed in the stream designed to reduce erosion by slowing the flow of water, breaking it up, and providing a protective barrier.

However, the forensic analysis indicates that water flow in Bens Branch undermined the rip rap.

Soil beneath riprap can be eroded if the rock was just placed on top without any buffer between the layers such as a geotextile fabric or smaller riprap (crushed stone).

In this case, erosion removed more than a foot of soil behind the concrete walls, under the base, and under the existing riprap.

Tree Lane Bridge Before Start of Round 2 Repairs
Tree Lane Bridge before start of Round 2 repairs. Downcutting under bridge.

You can see from the exposed utilities that the creek has downcut. This downcutting extends several hundred feet upstream of the bridge. And that’s part of the problem. It allowed water to get behind and under the existing channel linings.

Headward erosion downstream on west side and exposed utilities.

Construction plans call for:

  • Removing all the existing material under the bridge and on the sides of the banks
  • Installing a new concrete channel (bottom and sides) that will maintain the flow line of the stream.
  • Repairing outfalls.

The engineer’s report claims the proposed U-shaped channel will hold the current side slopes of the bridge and allow for the drop in the flow line.

For More Information

See the Report of Findings, construction plans, and the City’s official Engage Houston web page.

For pictures of how the bridge looked after the last round of repairs, see this post from 3/31/2020.

For pictures of a flood responsible for much of the damage, see this post from 1/29/23.

A Silver Lining

The damage to the Tree Lane bridge has been so rapid, that it occurred twice within the time many Bear Branch students attended the adjacent elementary school. Perhaps it will inspire curiosity about flooding among some of these students, spur them to pursue engineering careers, and perhaps prevent such dangers in the future.

Safety Precaution

The City hopes to complete the Tree Lane bridge project sometime this summer, weather permitting. Please observe traffic warning signs, cones and flags for the duration. And keep curious children away from heavy equipment which will be maneuvering in tight spaces with limited visibility.

Posted by Bob Rehak on 4/9/2024 with help from Chris Bloch of the Bear Branch Trail Association

2415 Days since Hurricane Harvey

CoH Public Works Kicks Off Tree Lane Bridge Rehab Project

City of Houston (COH) Public Works Department held a kick-off meeting with contractors and the Bear Branch Trail Association (BBTA) this morning for the Tree Lane Bridge Rehabilitation Project. Public Works and the contractors outlined plans for the project. They also discussed access through BBTA property and safety protocols.

Chris Bloch (left) and Lee Danner (center) of BBTA met with contractor and Houston Public Works representatives at bridge on 2/21/24.

Construction should begin by mid-March and take approximately 150 days.

Project Scope

The $909,000 project will involve:

  • Creating access areas for equipment
  • Removing all existing concrete under the bridge and along the sidewalls
  • Establishing a 2-foot deep by 32-foot-wide low-flow channel from 20 feet upstream to 20 feet downstream of the bridge
  • Rebuilding wing walls
  • Restoring outfalls for local drainage
  • Restoring the work site and replanting trees.

See the construction plans here.

Safety Warning

Contractors will meet with the Bear Branch Elementary School principal to understand normal drop-off and pick-up times. They will then work around those times to try to minimize traffic interference.

Regardless, the City urged parents to warn children to stay away from the construction zone, which will be on both sides of the bridge. Lots of heavy equipment will be maneuvering in tight spaces with limited visibility near Bear Branch Elementary. Observe all traffic warnings and flag men.

Reason for Project

Embankments under the bridge have degraded significantly in the last 10 years. This is largely because of jetting.

Jetting is caused when water backs up behind a bridge that is too small for the volume of water coming down a stream. Pressure upstream of the bridge forces turbulent water to shoot out the downstream side destroying anything in its way. See six images below taken 2/21/24.

Looking upstream at eastern side of bridge. Jetting has blown out concrete under the bridge.
Damaged storm sewer outfall.
Exposed abutment
Downcutting as floodwater tries to make more room for itself.
Jetting continues to erode a large basin south of the bridge.
Note how narrow creek is upstream (Left). Right = effect of jetting downstream.

It Wasn’t Always This Way

The erosion has started in the last ten years and accelerated with upstream development.

In general, developments increase the time of accumulation of runoff. Compared to a densely developed area, when rain falls on a forest, it trickles its way to the creek. But if it falls on concrete and rooftops, it rushes to the creeks through storm sewers.

For illustration purposes, the graph below shows the actual change along Brays Bayou.

time of accumulation
Change in time of accumulation in Brays Bayou as watershed developed over 85 years.

If development were sufficiently mitigated, post-development runoff would be no higher than pre-development. But given the amount of recent erosion, some development upstream from Tree Lane is likely insufficiently mitigated.

I’ve lived near the Tree Lane Bridge for 40 years. For the first 30, erosion was no problem. Now look at it. Compare the two satellite images below.

In 2014, you could barely see creek.
Same area in 2023.

Chris Bloch, an engineer, says that at the time of Imelda in 2019, the open space under the bridge was 500 square feet. The design approved by COH and Harris County Flood Control District will add approximately 64 square feet in the form of a low-flow channel. Contractors will add that where the stream has already downcut.

If the 500 SF estimate is accurate, another 64 SF would represent a 12.8% increase in the carrying capacity of the channel under the bridge.

Will It Be Enough Conveyance?

This will be the second time in three years that the city has repaired the bridge and its embankments.

The state of the bridge now is worse than it was after Imelda, BEFORE the last repair job. And no storms since Imelda have even came close to Imelda’s magnitude. That means insufficiently mitigated development may have played a role in building flood peaks faster and higher; and undermining the bridge.

So, will 12.8% be enough to eliminate more jetting? Only time will tell. Keep your fingers and toes crossed.

Sign Up for Project Updates

You can sign up for project updates by visiting Houston Public Works’ “Engage Houston” page for this project.

Posted by Bob Rehak on 2/21/24

2367 Days since Hurricane Harvey

Tree Lane Bridge over Bens Branch Still Standing

The recent drought has reduced the rate of erosion under the Tree Lane/Bens Branch Bridge for now. But with wetter weather expected, we need to accelerate the repair effort. Recent pictures show the desperate need for repairs to the bridge. It’s next to Bear Branch Elementary School where more than 600 students attend grades K-5.

Power of Moving Water

The current state of this bridge and the area around it is a testament to the power of moving water … more than engineers designed the bridge to handle.

Water jetting under the bridge during storms has ripped away great slabs of concrete, eroded side walls, and partially blocked a storm drain outfall.

Condition of Tree Lane Bridge over Bens Branch on 11/24/23

It has also eroded the channel. Rip rap has done little to halt the erosion.

11/24/23. Condition of Tree Lane Bridge over Bens Branch.

Downcutting has exposed utility lines. And stormwater has carried chunks of concrete downstream like toothpicks.

11/24/23. Bens Branch downstream of Tree Lane Bridge.

Before Hurricane Harvey, the tree canopy in this area was so dense, one could barely see Bens Branch from the air. Now, there’s a gaping hole in the landscape caused by the “jetting.”

11/24/23. Downstream erosion of greenbelt caused by jetting water from under bridge.

As more and more water builds up behind the bridge during storms, it causes water to shoot under the bridge with greater pressure and accelerate erosion.

One can’t help but wonder whether the random and cumulative impact of several large storms caused this damage. Whether insufficiently mitigated upstream development helped nature along. Or whether the bridge simply reached the end of its normal life.

The City of Houston attempted to repair this bridge in March 2020. By January of 2023, it was worse than ever. And in June of 2023, I wrote about damage accelerating.

But a prolonged, intense drought last summer put an end to the acceleration. A close comparison of recent photos with those taken six months ago shows that the bridge now looks much like it did last June.

When Will Bridge Be Fixed?

I have learned that both the City of Houston and Harris County Flood Control District (HCFCD) are studying the bridge. In August, the City even allocated money to fix it. However, HCFCD worried about the impact to its Bens Branch channel. The two entities are now trying to reach a mutually agreeable solution.

Having lived near here for 40 years, one thing is clear to me. We can’t count on drought to prevent more erosion forever.

During El Niño years (like now), much of Texas is cooler and wetter than average. Northern storms generally track farther south, producing more clouds, rain and severe weather, according to the NWS.  

Perhaps we’ll get some good news on Tree Lane bridge repairs or replacement by Christmas. I’ll let you know when we get the engineering report.

Posted by Bob Rehak on 11/28/24

2282 Days since Hurricane Harvey

Flood Damage To Tree Lane Bridge Over Ben’s Branch Accelerates

Since I last reported on damage to the Tree Lane Bridge over Ben’s Branch in January, the situation has worsened considerably.

  • Concrete reinforcements under and on both sides of the bridge have collapsed from undercutting, erosion and jetting.
  • The stream has downcut, exposing pipelines.
  • Jetting has carved out a cavernous area south of the bridge.
  • Erosion has reached within a few feet of a utility corridor.
  • Storm sewer outfalls have been exposed, undercut and punctured by massive slabs of displaced concrete.
  • Bridge supports, once protected by sidewalls, have been exposed to more erosion.

Pictures Taken on 6/12/23 Show Extent of Damage

The bridge will probably not collapse in the next big rain. However, the cumulative damage to all these components underscores the need for urgent repair. It also underscores the need for mitigation to reduce the jetting that caused the damage.

Looking at downstream eastern side of Tree Lane bridge
Looking NE at downstream, eastern side of Tree Lane bridge
Wider shot from same position reveals two exposed pipelines.
Looking upstream under Tree Lane Bridge. Downcutting under bridge threatens western wall also.
Looking upstream under Tree Lane Bridge. Note how downcutting threatens western (left) wall also.
Giant slabs of concrete have destroyed outfall.
Giant slabs of concrete have destroyed outfall.
AS
Erosion downstream of the Tree Lane bridge now is within approximately ten feet of a utility corridor.

Damage Accelerating, Repaired Just Three Years Ago

The city repaired the Tree Lane Bridge in March of 2020. Compare this post to see how it looked then. It’s amazing how much damage could be done in three years to a bridge that weathered multiple hurricanes and tropical storms for more than 50 years.

That’s a testament to insufficiently mitigated development upstream that sends ever greater volumes of water downstream – more than the opening under the bridge was designed for.

For a description of how jetting works, check this post. Basically, water backs up behind the bridge, putting greater pressure on the water flowing under the bridge.

Let’s hope the City can repair the Tree Lane Bridge again before school starts in the fall. The bridge borders Bear Branch Elementary School where 638 students attend classes.

Please check bridges near you and report any damage.

Posted by Bob Rehak on 6/12/2023

2113 Days since Hurricane Harvey

Tree Lane Bridge over Ben’s Branch Damaged…Again

Recent heavy rains and high-density upstream development on Ben’s Branch in Montgomery County have increasingly placed pressure on the aging Ben’s Branch Bridge over Tree Lane. The bridge is immediately adjacent to Bear Branch Elementary School in Kingwood and its 638 students.

The City of Houston repaired the bridge less than three years ago in March 2020. But…

5-Year Rain Leaves Bridge Worse Than Before Repairs

I took the photo below on 1/24/23 when Kingwood experienced a five year rain according to the gage at US59.

Photo taken on 1/24/2023 after 3.6 inches of rain in 2 hours.

I went back today to see what it looked like after the water went down.

After another 1.5 inch rain on 1/29/23. Note how the concrete fragment is pinching off street drainage for Bear Branch Village.

The issue, in my opinion, has to do with more and more water jetting through the narrow opening of the bridge. The turbulence has undermined concrete armoring on the banks that protects bridge supports. It has also carved out a huge area in the stream just south of the bridge.

Photo taken on Tuesday 1/24/23 as jetting erodes area south of bridge.

Exacerbated by Upstream Issues

The Preserve At Woodridge, upstream on Ben’s Branch offers 13 homes to the acre. It’s one of several high-density developments recently built along Ben’s Branch and its tributaries.
Detention pond south of St. Martha Catholic Church owned by MUD. Looking S. Water flows R to L. Note how outlet is bigger than inlet.

The detention pond above on Ben’s Branch had its outlet wall blown out during Harvey 5.5 years ago and has not been fixed since.

An aging bridge. More water coming downstream. Insufficient mitigation. Eroding banks. 638 children. A perfect storm, so to speak. Let’s hope the City can expedite the repairs.

You encourage what you tolerate.

It’s time for people to speak up.

Posted by Bob Rehak on 1/29/23

1979 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.

City Completes Repairs on Tree Lane Bridge, But Concerns Remain

The City of Houston has completed repairs on the Tree Lane Bridge over Ben’s Branch…at least for now. The City partially concreted a wing wall and placed riprap in the stream bed to help reduce erosion and scour. However, the root cause of the damage remains. Upstream development without adequate detention is funneling more and more water into Ben’s Branch. The higher volume will continue to contribute to scouring and erosion in major storms unless detention ponds upstream are built and fixed.

Water Under the Bridge

As I struggled to understand what I was looking at, an online search revealed this excellent 196-page, well-illustrated document. It’s titled “AN ILLUSTRATED GUIDE FOR MONITORING AND PROTECTING BRIDGE WATERWAYS AGAINST SCOUR.” Robert Ettema, Tatsuaki Nakato, and Marian Muste from the College of Engineering at the University of Iowa produced it for the Iowa Department of Transportation.

It begins with a maxim: “Person who overlooks water under bridge will find bridge under water.”

The document points out that bridge engineers often assume that a stream channel will maintain its course and dimensions. But most channels adjust their alignment and shape in response to floods and land-use changes in their watersheds. That has happened on Ben’s Branch in recent years.

“Channel changes sometimes have severe consequences for bridge waterways,” say the authors.

Scour and Progressive Degradation

A review of the entire paper reveals two types of destructive forces at work on the Tree Lane Bridge.

Long-term scour is one. It occurs over a time scale of several years, and usually includes progressive degradation and lateral bank erosion due to channel widening or meander migration.

Progressive degradation is another. It features the almost permanent lowering of the river bed at a bridge site owing to changes in the watershed [e.g., head-cut progression (head-cutting), or human activities (e.g., channel straightening or urbanization)]. 

The area around the Tree Lane bridge supports has been badly eroding for years. A 12-inch water line that was once buried 5 feet below the stream bed is now at the water surface. See below.

How the area downstream from the bridge looked in December before repairs started.

Scour and erosion under and around bridges are constant problems for engineers. This bridge is a great example. Any time a structure interrupts the flow of floodwater, it creates turbulence (vortices in the flow) that can lead to erosion.

From “AN ILLUSTRATED GUIDE FOR MONITORING AND PROTECTING BRIDGE WATERWAYS AGAINST SCOUR.”

During Harvey, scour destabilized the Union Pacific and US59 bridges across the West Fork. Both had to be replaced for safety.

The Tree Lane Bridge doesn’t appear to be to that point yet. But the heavier load placed on Ben’s Branch by new upstream developments, such as Woodridge Village, Woodridge Forest, and Brooklyn Trails, may be pushing this bridge beyond its design capacity.

Source: FEMA. Bridge constricts water flow (from top to bottom). The pressure of water stacking up behind the bridge forces the water to accelerate under the bridge, causing erosion and scour. See below.
Major storms in the last four years have eroded a large area immediately downstream from the bridge.

Concrete and Rip Rap Should Help in Short Term

To address these problems, the City repaired part of a concrete wing wall. They also placed riprap (boulders) downstream from the bridge and below a stormwater drain.

Riprap breaks up the flow of water and slows it down. This reduces erosion and scour.

Partially concreted wall (left) and riprap at Tree Lane Bridge over Ben’s Branch, Kingwood, TX. Photo courtesy of COH Public Works.
Tree Lane Bridge repairs, Kingwood, TX.
Tree Lane Bridge repairs, Kingwood, TX. Photo courtesy of COH Public Works.

…But Root Causes for Damage Remain

However, problems remain, both here and upstream.

  • That 12-inch water line could be taken out in the next flood by a tree flowing downstream. If the flood lasts for several days as it did during Harvey, the loss of water would be a major inconvenience to the residents of Bear Branch.
  • Inadequate detention upstream will continue to erode both the stream banks and bed at accelerating rates.

Until we can address the root causes of such damage, I fear that maintenance on this bridge will be a constant, long-term issue…despite the City’s best intentions.

Slabs of concrete still lean against water main.
In extreme event, water could still get behind concrete repair and peel it away from bank.

Posted by Bob Rehak on 3/31/2020

945 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.

Tree Lane Bridge over Ben’s Branch: Before and After Repairs

Yesterday, I posted about the hidden costs of flooding. Here’s another one: infrastructure repairs. And another one: re-doing infrastructure repairs. Like those to the Tree Lane Bridge over Ben’s Branch.

History of Issue

Upstream development in Montgomery County with insufficient and un-repaired detention pond capacity started dumping excess water into Ben’s Branch. It didn’t take long for the area under the Tree Lane bridge next to Bear Branch Elementary to start eroding badly.

Tree Lane was already a pinch point in the Ben’s Branch floodway. That and the combination of even more water during the Tax Day, Memorial Day, Harvey, May 2019, and Imelda floods all took a toll. The picture below shows what the bridge looked like on December 1, 2019. Hundreds of kids cross this bridge on their way to Bear Branch Elementary every day.

The Before Shot: Taken November 31, 2019

After taking the shot above, I emailed it to the City. To their credit, they sent crews out right away to repair it. Heavy equipment sat at the site for 2.5 months.

After the Repairs

About two weeks ago, the last piece left the job site. So today, I drove by to get an “after” shot. See the improvements below.

The After Shot: Taken 2/29/2020, three months later.

The City put rip rap across the creek to reduce erosion from water shooting out from the storm sewer in the upper right. They also broke up some of the large slabs of concrete to form additional rip rap.

However, it appears that they:

  • Have done little to stabilize the bridge supports.
  • Left slabs of concrete leaning against an exposed pipeline.
  • Threw a traffic sign and traffic cone into the creek.
  • Left about 50 bags of sand on the large slab at the left.

Someone else could have dumped the construction materials and sign. Crappy looking areas always encourage illegal dumping.

Enlargement of detail from previous shot showing sand that has been left behind or dumped.

I’m guessing that the rip rap may help reduce erosion from the storm sewer. But…

I see little here to stop erosion from upstream of Tree Lane or reduce danger to the pipeline. More important, the City did nothing to increase conveyance under the bridge.

The Tree Lane Bridge still forms a pinch point that restricts conveyance of Ben’s Branch.

Of course, the City may handle the conveyance issue in a second job. That could help build a case for doubling those drainage fees.

Posted by Bob Rehak on 2/29/2019

914 Days after Hurricane Harvey