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
Mavera, a 1700-acre new development in southern Montgomery County at FM1314 and US242 has finished clearing a large section of land northwest of the intersection and started pouring concrete. Signs welcome visitors to model homes. The area, once laced with wetlands now has a massive linear detention pond and uses FM1314 for outflow control.
Looking east just north of US242 on right from over FM1314. Note wet areas in foreground. They correspond to wetlands in map below.Large green area immediately east of 1314 (diagonal) and north of US242 (bottom) correspond to wet areas in photo above. From US Fish and Wildlife Service National Wetlands Inventory Map
Areas west of FM1314 to Crystal Creek are also being cleared, but their current state of development is not quite as advanced.
Likewise, an area east of FM1314 has expanded north, almost to Gulf Coast Road. Neither is its drainage fully developed.
Looking NE at current limit of development. Gulf Coast Road runs diagonally from left to right just beyond tree line.
Long, Linear Detention
The development relies on a wide linear detention basin – more than a mile long! And that’s only the part east of FM1314!
Looking east toward upstream end of detention basin.
Two smaller basins also exist. One is currently by a small park and recreation center.
Looking WSW.Note small retention pond and rec center in upper right.
In the photo above, also note the small swales that outline lots. Will some drainage go overland? Or is underground drainage just not connected to the detention basin yet?
Same spot. Lower elevation. Looking west from eastern portion of Mavera. I’m not seeing any drainpipes from storm sewers entering pond yet.Note three new model homes near center of frame.
The development seems to have undergone a series of name changes. The land was originally known as the Denbury Tract. Later, construction plans and a drainage analysis refer to it as Madera. But now, the builders are marketing it as Mavera.
Screen capture of cover sheet from drainage planshowing first two names of development.
The drainage plans for Mavera (aka Madera/Denbury tract) rely on a hydrologic timing assessment (see last line in screen capture above).
The drainage analysis claims the development will have no downstream impact, but engineers didn’t study those areas. Nor did they study how new development upstream may have already shifted the peak of a flood.
Impact on FM1314?
Long linear detention schemes typically accelerate the flow of water. This one will rely on one culvert under FM1314 to hold back more than a mile of water collected from hundreds of acres. That will put a lot of pressure on FM1314 in a heavy storm.
Looking NW over FM1314. East is to the right. Water will flow west toward Crystal Creek out of frame to the left.
The roadway will act as a dam to detain water collected from almost all of the area shown in the photo below.
Looking east. Virtually all of the cleared area will drain through one culvert under FM1314. FM1314 runs left to right through the bottom of the frame. US242 is on right. Notice how channel is being widened, making culvert off-center. Did someone initially miscalculate or did plans change?
FEMA mapped most of this area in a ten-year flood zone. For the sake of potential home buyers, let’s also hope the engineers got the drainage calculations right.
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.
https://i0.wp.com/reduceflooding.com/wp-content/uploads/2022/07/20220716-DJI_0152.jpg?fit=1200%2C799&ssl=17991200adminadmin2022-07-16 15:56:422025-08-19 22:11:03Mavera Wetlands Bite the Dust
The Texas Water Development Board (TWDB) recently produced a fascinating short video that puts the current drought in historical perspective by comparing rainfall, temperature, and water supplies to 2011. The text and visuals below are adapted from Dr. Mark Wentzel’s presentation. Wentzel serves as a hydrologist for the TWDB.
Wentzel’s charts depict statewide averages. The Houston region has had significantly more rainfall. So look at Wentzel’s data for trends happening around us. I’ll show Houston data at the end of this post.
Comparison to 2011 Drought
Wentzel says that June was warmer and drier than normal for much of the state, the fourth consecutive month with those conditions. At the end of June, drought conditions covered 86 percent of the state, up eight percentage points from the end of May. Storage in our water supply reservoirs is at 75 percent of capacity, ten percentage points below normal for this time of year. So, Texas is in a significant drought, the worst since 2011, but not worse than 2011.
Highlights of Wentzel video
Statewide Precipitation Averages
The State average rainfall from January to June of this year: 7.8 inches, about 60 percent of normal. Bad as that may be, it’s better than in 2011 when we received less than six inches in the first half of the year, only about 40 percent of normal.
Statewide Texas precipitation averages
Comparison to 2011 Temperatures
On the next chart, Wentzel shows monthly average temperatures across the entire state for both 2022 in orange and 2011 in red. Black dots show the 20th century average for comparison. He shows maximum and minimum temperature records in gray. The gold line represents January to June of this year.
Statewide Texas temperature averages
Temperatures have been above average five out of six months. That additional heat has certainly contributed to drought, but monthly temperatures in the first half of 2011 were even hotter for four of those six months.
In 2011, the real heat came in June, July, and August when we set maximum temperature records each month.
Dr. Mark Wentzel, TWDB
Temperatures the rest of the summer and 2022 are expected to be warmer than average, but not to exceed 2011 temperatures.
Percent of State in Drought
Low rainfall and high temperatures during the first half of 2022 have brought significant drought to Texas. The U.S. Drought Monitor map for conditions as of June 28 shows 86 percent of the state impacted by drought, up eight percentage points from the end of May. More of the state is experiencing drought at the end of June this year than for any June since 2011, when 96 percent of the state was in drought.
Effect on Water Supply
Statewide, our water supply reservoirs are being impacted by the current drought, but not as significantly as in 2011. The dark line on this chart shows how storage this year compares to minimum, maximum, and median values for the day of the year from data going back to 1990. Lighter lines show how we did in 2021 and 2020. The red line shows how we did in 2011.
Texas statewide totals expressed as percent of full capacity
We began 2022 with water supply storage more than two percentage points lower than normal for the time of year. By the end of June, we’ve fallen to about ten percentage points lower than normal.
In 2011, water supply began the year closer to normal, but fell farther and faster than in 2022. By the end of June, storage was about one and a half percentage points less than this year. In the second half of 2022, Wentzel expects additional storage declines, but not as severe as in 2011 when the State reached 30-year lows by mid-October.
Bottom Line for State
We are in a significant drought, even if it’s not as bad as 2011. But the real test won’t come this summer or even this year. Our water supply systems are designed to withstand a multi-year event. Will 2022 lead to a multi-year event? It’s too early to tell, says Wentzel. “But it’s never too early to conserve water and manage demand.”
The top half of the first shows temperatures. It depicts highs in red, average ranges in green, and lows in light blue for ever day of the year. The dark blue lines show actual temperature observations year to date.
The bottom half shows actual precipitation compared to the average. You can see that for part of the year, we were actually above normal. But starting around June 1, we fell behind.
The last chart shows temperatures in July to date. The dark blue lines show actual temps compared to highs, the normal range, and lows for every date. The three stars indicate records or ties.
Posted by Bob Rehak on 7/15/22 based on information from TWDB, NWS and Dr. Mark Wentzel
1781 Days since Hurricane Harvey
https://i0.wp.com/reduceflooding.com/wp-content/uploads/2022/07/20220715-Screen-Shot-2022-07-15-at-5.03.06-PM.jpg?fit=1200%2C670&ssl=16701200adminadmin2022-07-15 18:09:582022-07-15 18:16:32How Current Drought Compares to 2011
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
Mavera Wetlands Bite the Dust
Mavera, a 1700-acre new development in southern Montgomery County at FM1314 and US242 has finished clearing a large section of land northwest of the intersection and started pouring concrete. Signs welcome visitors to model homes. The area, once laced with wetlands now has a massive linear detention pond and uses FM1314 for outflow control.
Areas west of FM1314 to Crystal Creek are also being cleared, but their current state of development is not quite as advanced.
Likewise, an area east of FM1314 has expanded north, almost to Gulf Coast Road. Neither is its drainage fully developed.
Long, Linear Detention
The development relies on a wide linear detention basin – more than a mile long! And that’s only the part east of FM1314!
Two smaller basins also exist. One is currently by a small park and recreation center.
In the photo above, also note the small swales that outline lots. Will some drainage go overland? Or is underground drainage just not connected to the detention basin yet?
The Mavera website by Centex homes says the swimming pool at the rec center will open late this summer. Pulte will also build homes in Mavera.
Name Changes and a “Beat the Peak” Drainage Analysis
I previously posted about Mavera in January. Compare the pictures taken then.
The development seems to have undergone a series of name changes. The land was originally known as the Denbury Tract. Later, construction plans and a drainage analysis refer to it as Madera. But now, the builders are marketing it as Mavera.
The drainage plans for Mavera (aka Madera/Denbury tract) rely on a hydrologic timing assessment (see last line in screen capture above).
Harris County has tried to discourage neighboring counties from using such analyses. They encourage developers to get stormwater to streams and rivers faster rather than slower. The theory is that if you can beat the peak of a flood then you aren’t adding to it. But if everybody tries to “beat the peak,” eventually you shift the peak and flood downstream neighbors. For a full discussion of drainage issues, see my previous post.
The drainage analysis claims the development will have no downstream impact, but engineers didn’t study those areas. Nor did they study how new development upstream may have already shifted the peak of a flood.
Impact on FM1314?
Long linear detention schemes typically accelerate the flow of water. This one will rely on one culvert under FM1314 to hold back more than a mile of water collected from hundreds of acres. That will put a lot of pressure on FM1314 in a heavy storm.
The roadway will act as a dam to detain water collected from almost all of the area shown in the photo below.
Let’s hope all that water doesn’t blow out the road like Colony Ridge drainage blew out FM1010 in Liberty County.
For Potential Home Buyers
FEMA mapped most of this area in a ten-year flood zone. For the sake of potential home buyers, let’s also hope the engineers got the drainage calculations right.
Potential homebuyers may also be interested in reading about the risks of building homes over wetlands.
Posted by Bob Rehak on 7/16/2022
1782 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.
How Current Drought Compares to 2011
The Texas Water Development Board (TWDB) recently produced a fascinating short video that puts the current drought in historical perspective by comparing rainfall, temperature, and water supplies to 2011. The text and visuals below are adapted from Dr. Mark Wentzel’s presentation. Wentzel serves as a hydrologist for the TWDB.
Wentzel’s charts depict statewide averages. The Houston region has had significantly more rainfall. So look at Wentzel’s data for trends happening around us. I’ll show Houston data at the end of this post.
Comparison to 2011 Drought
Wentzel says that June was warmer and drier than normal for much of the state, the fourth consecutive month with those conditions. At the end of June, drought conditions covered 86 percent of the state, up eight percentage points from the end of May. Storage in our water supply reservoirs is at 75 percent of capacity, ten percentage points below normal for this time of year. So, Texas is in a significant drought, the worst since 2011, but not worse than 2011.
Statewide Precipitation Averages
The State average rainfall from January to June of this year: 7.8 inches, about 60 percent of normal. Bad as that may be, it’s better than in 2011 when we received less than six inches in the first half of the year, only about 40 percent of normal.
Comparison to 2011 Temperatures
On the next chart, Wentzel shows monthly average temperatures across the entire state for both 2022 in orange and 2011 in red. Black dots show the 20th century average for comparison. He shows maximum and minimum temperature records in gray. The gold line represents January to June of this year.
Temperatures have been above average five out of six months. That additional heat has certainly contributed to drought, but monthly temperatures in the first half of 2011 were even hotter for four of those six months.
Temperatures the rest of the summer and 2022 are expected to be warmer than average, but not to exceed 2011 temperatures.
Percent of State in Drought
Low rainfall and high temperatures during the first half of 2022 have brought significant drought to Texas. The U.S. Drought Monitor map for conditions as of June 28 shows 86 percent of the state impacted by drought, up eight percentage points from the end of May. More of the state is experiencing drought at the end of June this year than for any June since 2011, when 96 percent of the state was in drought.
Effect on Water Supply
Statewide, our water supply reservoirs are being impacted by the current drought, but not as significantly as in 2011. The dark line on this chart shows how storage this year compares to minimum, maximum, and median values for the day of the year from data going back to 1990. Lighter lines show how we did in 2021 and 2020. The red line shows how we did in 2011.
We began 2022 with water supply storage more than two percentage points lower than normal for the time of year. By the end of June, we’ve fallen to about ten percentage points lower than normal.
In 2011, water supply began the year closer to normal, but fell farther and faster than in 2022. By the end of June, storage was about one and a half percentage points less than this year. In the second half of 2022, Wentzel expects additional storage declines, but not as severe as in 2011 when the State reached 30-year lows by mid-October.
Bottom Line for State
We are in a significant drought, even if it’s not as bad as 2011. But the real test won’t come this summer or even this year. Our water supply systems are designed to withstand a multi-year event. Will 2022 lead to a multi-year event? It’s too early to tell, says Wentzel. “But it’s never too early to conserve water and manage demand.”
Houston
The charts below comes from the National Weather Service Climate site and depicts conditions at Bush Intercontinental Airport.
The top half of the first shows temperatures. It depicts highs in red, average ranges in green, and lows in light blue for ever day of the year. The dark blue lines show actual temperature observations year to date.
The bottom half shows actual precipitation compared to the average. You can see that for part of the year, we were actually above normal. But starting around June 1, we fell behind.
The last chart shows temperatures in July to date. The dark blue lines show actual temps compared to highs, the normal range, and lows for every date. The three stars indicate records or ties.
Posted by Bob Rehak on 7/15/22 based on information from TWDB, NWS and Dr. Mark Wentzel
1781 Days since Hurricane Harvey