Harris County Flood Control District (HCFCD) and its partners continue to add detention basin capacity along Greens Bayou to reduce the risk of flooding. I flew in a helicopter today with fellow Harris County Community Flood Resilience Task Force members Ken Willians and Bill Calligari. We flew over Greens, Halls, Hunting, and White Oak Bayous. In this post, let’s focus on what we found in Greens.
From west to east, we flew over the Cutten Basin at 249 and Beltway 8, then followed the bayou over the Antoine, Kuykendahl, Glen Forest, Aldine-Westfield, and Lauder Basins. Some have recently completed construction. Others are still under construction. Here’s a rundown of everything between US249 and US59 along Greens.
Cutten Basin
Scheduled for completion later this year, the Cutten Basin covers approximately 250 acres. It includes five compartments, four south of Greens Bayou and one north. When complete, it will hold 850 acre feet of stormwater. That’s enough to hold a foot of rain falling across approximately 1.3 square miles. It will lower the water surface elevation along Greens by a third of a foot in a hundred-year flood.
Looking S toward Beltway 8. Greens Bayou flows from right to left through the center of the frame. Looking East. Greens cuts through the upper left portion of the frame. Beltway 8 cuts through the upper right.Looking West across Hollister which cuts through the middle of the frame.
Antoine Basin
HCFCD and the Army Corps started the $80 million Antoine Basin in 2015. The Army Corps designed and built it. Satellite photos in Google Earth first show it holding water in November 2020.
Looking east along Greens toward the Antoine Basin, top right.Looking SW. West Greens Road arcs through center of frame. Greens flows from upper right to lower left. Beltway 8 near top of frame.
The completed basin holds approximately 1,650 acre-feet, or 538 million gallons of stormwater. To put that in perspective, it holds a foot of rain falling over a 2.5 square mile area, or half a foot falling across 5 square miles!
Kuykendahl Basin
Kuykendahl Stormwater Detention Basin sits on a 288-acre property near Kuykendahl Road and Ella Boulevard along an unnamed tributary of Greens Bayou. In floods, it holds water back from entering the bayou and then releases it safely and slowly after the storm has passed.
Wide shot of Kuykendahl Basin looking westKuykendahl in foreground. Note how densely populated the area is with apartments.
Contractors removed 3.61 million cubic yards of soil from the site. It holds 2,325 acre-feet, or 757.6 million gallons of stormwater. That’s a foot of rain falling across 3.6 square miles, or half a foot falling across 7.2.
Following construction, contractors planted 22.19 acres of native tree and shrubs, and 12.79 acres of stormwater quality-treatment wetlands. They also created 14.04 acres of other wetlands to replace those impacted by construction.
Ceres Environmental Services Inc. constructed the Kuykendahl basin and another to the east (see Glen Forest below). Combined, they were the largest construction contract ever managed by HCFCD up to that time. The two basins reduced or removed flooding risks and damages from more than 1,100 structures along Greens Bayou. “Avoided damages” exceed $90 million in every flood. Far more than the cost of construction.
FEMA awarded $39.2 million to the Harris County Flood Control District, under the Hurricane Ike Hazard Mitigation Grant Program (HMGP) to construct the basins and HCFCD contributed matching funds.
Google Earth satellite photos indicate construction finished for both basins in 2020.
Glen Forest
Farther east along Greens, the Glen Forest Detention Basin extends from I-45 to Imperial Valley north of Greens Road.
Looking East across I-45 at Glen Forest Basin.Looking West at Glen Forest Basin on Greens Bayou between I-45 at top of frame and Imperial Valley Drive under camera position.
The Glen Forest Basin project removed approximately 2.15 million cubic yards of soil in three connected cells. The completed basin holds approximately 894 acre-feet. That’s 1.4 square miles one foot deep or 2.8 square miles a half foot deep.
Aldine Westfield Basins: Phases 1 and 2
Farther east along Greens Bayou, directly south of Houston’s Bush Intercontinental Airport, you will find two more new basins. HCFCD completed construction on the first in April 2021. The second (to the north) then began construction and has not yet finished.
Looking East from over Aldine Westfield Road in foreground at Phase One. Beltway 8 in upper right. Note Greens Bayou turning south under Beltway in upper right.Looking ENE. Phase 2 is still under construction on Aldine-Westfield Road immediately north of Phase 1 (lower right). Note airport tower on horizon.
The two basins when complete in 2024 will hold a foot of rain falling over more than 2 square miles (1260 acre feet). That concludes your helicopter flight down Greens Bayou for today.
Greens by the Numbers
Together, these basins should hold approximately a foot of rain falling over 12 square miles.
That’s not enough to prevent flooding in another Harvey. But it will certainly reduce flooding for thousands of people. HCFCD has not yet released updated flood-risk data for the mid- and upper reaches of Greens Bayou (shown above). More news on that when it becomes available.
According to data obtained from HCFCD via a FOIA Request, Flood Control and its partners have spent more than $435 million on flood mitigation in Greens Bayou between 1/1/2000 and the end of last year. That includes money spent on all phases of all projects shown above.
Only three other watersheds have received more funding since 2000: Brays, White Oak and Sims. But more on those later.
Greens was the second most heavily damaged watershed in five major storms (Allison, Tax Day, Memorial Day, Harvey, Imelda). Those storms damaged more than 29,000 Greens structures.
58% of the population of Greens has low-to-moderate income (LMI). That ranks 6th on the LMI scale of Harris County watersheds.
This morning at 10:34 AM, the last remains of another Forest Cove townhome complex toppled to the ground. The HCFCD demolition contractor nibbled away at it last week and earlier this morning. Eventually, all but a narrow strip of the last townhome in the complex had turned into a pile of rubble.
That strip started to lean. Then, suddenly, one more touch from the excavator, and the building collapsed on itself with a billowing cloud of dust and a thunderous boom. When the dust cleared, only one last complex remained standing.
As of Saturday, 7/16/22, one of the last three buildings was completely gone along with half of the second.Early Monday, 7/18/22, demolition of the remaining portion of the second building started again.As the excavator clawed away at the building, it started to lean.Periodically, the excavator would pile more rubble under itself so it could then reach higher. Note falling doors, walls and floors, frozen in space by the camera’s fast shutter speed.What took months to build came down in seconds.Note the severe bowing of the wallon the right.
Final Collapse Caught on Camera
At this point, I sensed the building would soon collapse. So, I switched from the drone to my Nikon which can shoot many more frames per second. And then it started…
With parts of the second and third floors removed, along with most of the truss structure in the attic, the remainder of the building started to collapse in on itself.A chimney came tumbling forward.The final collapse took less than 10 seconds. Three minutes later, the dust had cleared.
Next Steps
Contractors will extract any recyclable waste from the rubble. Then, they will crush what remains so that it takes less space in a landfill. Finally, they will remove the concrete from the foundation and likely recycle that, too.
Eventually, this area will return to nature. However, what form that takes has not yet been determined. Typically, HCFCD partners with other organizations such as the Houston Parks Board to create and maintain improvements such as trails, parks or recreational space. In fact, the Houston Parks Board West Fork Trail currently ends behind the rubble in the photo above. The Parks Board plans to extend it to Edgewater Park at US59, so hikers and bikers can connect from the Kingwood Trail System to the Spring Creek Greenway.
Demo Date for Last Building
After this morning, only one Forest Cove townhome complex remains standing. That’s at 1020 Marina Drive near the community swimming pool. According to Amy Stone, a Flood Control District spokesperson, HCFCD will demolish that building starting August 1, 2022. More news to follow.
Posted by Bob Rehak on 7/18/2022
1784 Days since Hurricane Harvey
https://i0.wp.com/reduceflooding.com/wp-content/uploads/2022/07/20220718-DJI_0249.jpg?fit=1200%2C799&ssl=17991200adminadmin2022-07-18 13:22:152022-07-18 14:54:27Caught on Camera: Moment Forest Cove Townhome Toppled
The San Jacinto River Authority (SJRA) has completed its initial sand trap study, in partnership with Harris County Flood Control, and reviewed public comments. According to Matt Barrett PE, SJRA’s Manager of Water Resources and Flood Management, the SJRA is working toward a pilot study. But a successful pilot will require several things including funding partners and consultation with regulatory agencies, such as TCEQ and Texas Parks and Wildlife.
The goal of the project: intercept and remove sediment migrating downstream to reduce buildups elsewhere.
West Fork mouth bar after Harvey and before dredging. A small area at the far right had been building up before Harvey. The rest appeared when Harvey’s floodwater’s receded.
The proposed pilot sand trap could not possibly remove enough sand by itself to prevent the build up of another giant sand bar like the one above. However, a network of such traps might help.
Consultation with Regulatory Agencies
In Texas, among other things, TCEQ regulates floodplains, sand mining, and water quality. Texas Parks and Wildlife regulates rivers between the vegetation on each bank.
Possible location of trap for pilot study outside Hallett Mine on West Fork. Trap would consist of a trench through the middle of the point bar in the foreground.
But a trench at this location might run afoul of new TCEQ BMPs for sand mining that specify 100-foot buffer zones adjacent to perennial streams greater than 20-feet wide.
Schematic diagram of proposed trap at location above from initial conceptual design study finished before TCEQ adopted new BMPs.
Finding Funding Partners
SJRA must also find funding partners as it does not have a revenue source to pay for a pilot study and full construction costs of sand traps. In that regard, Barrett mentioned Harris County Flood Control and City of Houston as potential partners.
Barrett is also exploring partnerships with APOs (Aggregate Production Operations, aka sand mines). Sand mines can help defray expenses by removing sand from the traps as it accumulates. Of course, their desire to do that will depend on the location of the traps. They would prefer something close to their mines to minimize transportation costs and logistics while maximizing salability of the sand.
Hungry-Water Concern
Barrett also mentioned the need for the preliminary engineering design to avoid a “hungry water” effect which might increase erosion downstream. Hungry water results when streams have more power to transport sediment than they have available sediment. As a result, it erodes stream beds and banks to compensate.
Would Program be Extendable if Successful?
In a wide-ranging 45-minute discussion with Barrett, I raised several other potential issues. They included:
Location of the test near APOs, far upstream from the heavily damaged areas near Lake Houston where sand accumulates. There are no active sand mines between Humble and Kingwood – and few on other tributaries.
No sediment gages upstream and downstream from the test site. Not having a way to demonstrate success could limit future expansion of the program.
Potential partners that could remove sand from traps NOT located near APOs. You need a way to get sand out of a trap after it fills up. If the City of Houston or HCFCD established an ongoing maintenance dredging program, that could solve this issue.
How long an APO will remain committed to a location near a trap. After going to the expense of building a trap, SJRA would want to make sure the APO didn’t move operations to another location in a year or two. For example, some sand miners have talked about moving to the East Fork to take advantage of expected growth associated with the new Grand Parkway extension.
The SJRA must work through such issues to protect the public’s investment in the program. It has many moving parts. And the interests of all partners must align before moving forward.
Outline of Next Steps
So the next steps are:
Find partners with money whose interests align.
Obtain commitments from them.
Consult with regulatory agencies to avoid potential conflicts.
Lock down a location near an APO.
Begin preliminary engineering.
Ensure the pilot study (based on proximity to APOs) can extend to other areas (Rehak concern)
Find a way to measure success to help extend the pilot program if successful
In business, there’s an old maxim: “That which can be measured will be repeated.” Doing a pilot study that can’t be measured or replicated elsewhere helps no one.
The Army Corps has also published extensive research about the effectiveness of different sand-trap designs. Search for “Army Corps sand trap studies.” I originally became interested in the concept when I read a Corps study about a test of different trap geometries in the Mississippi River. There are many alternatives including some that could be located where water slows down at the entrance to Lake Houston (where the Harvey mouth bar appeared in 2017). Such a location would have the advantage of intercepting sediment from all upstream sources, not just the West Fork...if all the tumblers aligned.
Posted by Bob Rehak
1783 Days since Hurricane Harvey
https://i0.wp.com/reduceflooding.com/wp-content/uploads/2022/03/Screen-Shot-2022-03-27-at-6.28.40-PM.png?fit=1920%2C1206&ssl=112061920adminadmin2022-07-17 16:31:402022-07-18 11:24:51SJRA’s Next Steps After Public Comments on Sand Trap Study
Greens Bayou Detention Basin Capacity Steadily Growing
Harris County Flood Control District (HCFCD) and its partners continue to add detention basin capacity along Greens Bayou to reduce the risk of flooding. I flew in a helicopter today with fellow Harris County Community Flood Resilience Task Force members Ken Willians and Bill Calligari. We flew over Greens, Halls, Hunting, and White Oak Bayous. In this post, let’s focus on what we found in Greens.
From west to east, we flew over the Cutten Basin at 249 and Beltway 8, then followed the bayou over the Antoine, Kuykendahl, Glen Forest, Aldine-Westfield, and Lauder Basins. Some have recently completed construction. Others are still under construction. Here’s a rundown of everything between US249 and US59 along Greens.
Cutten Basin
Scheduled for completion later this year, the Cutten Basin covers approximately 250 acres. It includes five compartments, four south of Greens Bayou and one north. When complete, it will hold 850 acre feet of stormwater. That’s enough to hold a foot of rain falling across approximately 1.3 square miles. It will lower the water surface elevation along Greens by a third of a foot in a hundred-year flood.
Antoine Basin
HCFCD and the Army Corps started the $80 million Antoine Basin in 2015. The Army Corps designed and built it. Satellite photos in Google Earth first show it holding water in November 2020.
The completed basin holds approximately 1,650 acre-feet, or 538 million gallons of stormwater. To put that in perspective, it holds a foot of rain falling over a 2.5 square mile area, or half a foot falling across 5 square miles!
Kuykendahl Basin
Kuykendahl Stormwater Detention Basin sits on a 288-acre property near Kuykendahl Road and Ella Boulevard along an unnamed tributary of Greens Bayou. In floods, it holds water back from entering the bayou and then releases it safely and slowly after the storm has passed.
Contractors removed 3.61 million cubic yards of soil from the site. It holds 2,325 acre-feet, or 757.6 million gallons of stormwater. That’s a foot of rain falling across 3.6 square miles, or half a foot falling across 7.2.
Following construction, contractors planted 22.19 acres of native tree and shrubs, and 12.79 acres of stormwater quality-treatment wetlands. They also created 14.04 acres of other wetlands to replace those impacted by construction.
Ceres Environmental Services Inc. constructed the Kuykendahl basin and another to the east (see Glen Forest below). Combined, they were the largest construction contract ever managed by HCFCD up to that time. The two basins reduced or removed flooding risks and damages from more than 1,100 structures along Greens Bayou. “Avoided damages” exceed $90 million in every flood. Far more than the cost of construction.
FEMA awarded $39.2 million to the Harris County Flood Control District, under the Hurricane Ike Hazard Mitigation Grant Program (HMGP) to construct the basins and HCFCD contributed matching funds.
Google Earth satellite photos indicate construction finished for both basins in 2020.
Glen Forest
Farther east along Greens, the Glen Forest Detention Basin extends from I-45 to Imperial Valley north of Greens Road.
The Glen Forest Basin project removed approximately 2.15 million cubic yards of soil in three connected cells. The completed basin holds approximately 894 acre-feet. That’s 1.4 square miles one foot deep or 2.8 square miles a half foot deep.
Aldine Westfield Basins: Phases 1 and 2
Farther east along Greens Bayou, directly south of Houston’s Bush Intercontinental Airport, you will find two more new basins. HCFCD completed construction on the first in April 2021. The second (to the north) then began construction and has not yet finished.
Phase 1 holds approximately 667 acre-feet of stormwater and Phase II will hold another 600 acre-feet. Two 5’x4′ reinforced concrete boxes will connect the two phases and outfalls into Greens Bayou.
Together the two basins will hold a foot of rain falling over more than two square miles.
Lauder Basin
1.5 miles to south of the Aldine-Westfield Basins, you will find the Lauder Basin: Phases 1 and 2.
Phase 2 of the Lauder Basin is starting in the forested area in the upper right of the photo above.
Phase 1 completed construction late last year. In May of 2022, the Texas Water Development Board granted HCFCD more than $2.2 million to begin Phase 2.
The two basins when complete in 2024 will hold a foot of rain falling over more than 2 square miles (1260 acre feet). That concludes your helicopter flight down Greens Bayou for today.
Greens by the Numbers
Together, these basins should hold approximately a foot of rain falling over 12 square miles.
That’s not enough to prevent flooding in another Harvey. But it will certainly reduce flooding for thousands of people. HCFCD has not yet released updated flood-risk data for the mid- and upper reaches of Greens Bayou (shown above). More news on that when it becomes available.
According to data obtained from HCFCD via a FOIA Request, Flood Control and its partners have spent more than $435 million on flood mitigation in Greens Bayou between 1/1/2000 and the end of last year. That includes money spent on all phases of all projects shown above.
Only three other watersheds have received more funding since 2000: Brays, White Oak and Sims. But more on those later.
Greens was the second most heavily damaged watershed in five major storms (Allison, Tax Day, Memorial Day, Harvey, Imelda). Those storms damaged more than 29,000 Greens structures.
58% of the population of Greens has low-to-moderate income (LMI). That ranks 6th on the LMI scale of Harris County watersheds.
Posted Bob Rehak on 7/19/22
1785 Days since Hurricane Harvey
Caught on Camera: Moment Forest Cove Townhome Toppled
This morning at 10:34 AM, the last remains of another Forest Cove townhome complex toppled to the ground. The HCFCD demolition contractor nibbled away at it last week and earlier this morning. Eventually, all but a narrow strip of the last townhome in the complex had turned into a pile of rubble.
That strip started to lean. Then, suddenly, one more touch from the excavator, and the building collapsed on itself with a billowing cloud of dust and a thunderous boom. When the dust cleared, only one last complex remained standing.
We are nearing the end of a process that started in 2018.
Sequence of Photos
Final Collapse Caught on Camera
At this point, I sensed the building would soon collapse. So, I switched from the drone to my Nikon which can shoot many more frames per second. And then it started…
Next Steps
Contractors will extract any recyclable waste from the rubble. Then, they will crush what remains so that it takes less space in a landfill. Finally, they will remove the concrete from the foundation and likely recycle that, too.
Eventually, this area will return to nature. However, what form that takes has not yet been determined. Typically, HCFCD partners with other organizations such as the Houston Parks Board to create and maintain improvements such as trails, parks or recreational space. In fact, the Houston Parks Board West Fork Trail currently ends behind the rubble in the photo above. The Parks Board plans to extend it to Edgewater Park at US59, so hikers and bikers can connect from the Kingwood Trail System to the Spring Creek Greenway.
Demo Date for Last Building
After this morning, only one Forest Cove townhome complex remains standing. That’s at 1020 Marina Drive near the community swimming pool. According to Amy Stone, a Flood Control District spokesperson, HCFCD will demolish that building starting August 1, 2022. More news to follow.
Posted by Bob Rehak on 7/18/2022
1784 Days since Hurricane Harvey
SJRA’s Next Steps After Public Comments on Sand Trap Study
The San Jacinto River Authority (SJRA) has completed its initial sand trap study, in partnership with Harris County Flood Control, and reviewed public comments. According to Matt Barrett PE, SJRA’s Manager of Water Resources and Flood Management, the SJRA is working toward a pilot study. But a successful pilot will require several things including funding partners and consultation with regulatory agencies, such as TCEQ and Texas Parks and Wildlife.
The goal of the project: intercept and remove sediment migrating downstream to reduce buildups elsewhere.
The proposed pilot sand trap could not possibly remove enough sand by itself to prevent the build up of another giant sand bar like the one above. However, a network of such traps might help.
Consultation with Regulatory Agencies
In Texas, among other things, TCEQ regulates floodplains, sand mining, and water quality. Texas Parks and Wildlife regulates rivers between the vegetation on each bank.
Legislation exempts the SJRA, HCFCD and its contractors from obtaining state permits before removing sediment from the river. Regardless, the SJRA wants to work with regulatory agencies to ensure it doesn’t recommend anything that runs afoul of agency policy. Example: the newly adopted TCEQ Best Management Practices for Sand Mining. For instance, see section 2.1.1 – Vegetated Buffer Zones.
But a trench at this location might run afoul of new TCEQ BMPs for sand mining that specify 100-foot buffer zones adjacent to perennial streams greater than 20-feet wide.
Finding Funding Partners
SJRA must also find funding partners as it does not have a revenue source to pay for a pilot study and full construction costs of sand traps. In that regard, Barrett mentioned Harris County Flood Control and City of Houston as potential partners.
Barrett is also exploring partnerships with APOs (Aggregate Production Operations, aka sand mines). Sand mines can help defray expenses by removing sand from the traps as it accumulates. Of course, their desire to do that will depend on the location of the traps. They would prefer something close to their mines to minimize transportation costs and logistics while maximizing salability of the sand.
Hungry-Water Concern
Barrett also mentioned the need for the preliminary engineering design to avoid a “hungry water” effect which might increase erosion downstream. Hungry water results when streams have more power to transport sediment than they have available sediment. As a result, it erodes stream beds and banks to compensate.
Would Program be Extendable if Successful?
In a wide-ranging 45-minute discussion with Barrett, I raised several other potential issues. They included:
The SJRA must work through such issues to protect the public’s investment in the program. It has many moving parts. And the interests of all partners must align before moving forward.
Outline of Next Steps
So the next steps are:
In business, there’s an old maxim: “That which can be measured will be repeated.” Doing a pilot study that can’t be measured or replicated elsewhere helps no one.
For more information, see this post about potential sites and designs for traps. It features the most likely spot for a pilot study.
The Army Corps has also published extensive research about the effectiveness of different sand-trap designs. Search for “Army Corps sand trap studies.” I originally became interested in the concept when I read a Corps study about a test of different trap geometries in the Mississippi River. There are many alternatives including some that could be located where water slows down at the entrance to Lake Houston (where the Harvey mouth bar appeared in 2017). Such a location would have the advantage of intercepting sediment from all upstream sources, not just the West Fork...if all the tumblers aligned.
Posted by Bob Rehak
1783 Days since Hurricane Harvey