On May 18, Josh Alberson and I gave Tony Buzbee a tour of sediment and sand mining issues on the San Jacinto River. Buzbee is a candidate for Mayor of Houston and got to witness first hand some of the problems I have been talking about for almost two years now. On Caney Creek, we stumbled across a giant breach in the dike of the Triple-PG mine in Porter. We reported it immediately to the TCEQ.
Massive breach in dike between Triple PG Mine and Caney Creek, May, 2019
Two-Week Discharge
Investigators actually observed the unauthorized discharge of process water from the mine into the City’s drinking water supply. It continued for approximately two weeks.
Not One, But Two Massive Breaches
The TCEQ found not one, but two breaches. The first was on the southwest side of the mine. Water entered the mine from a breach of the dike near White Oak Creek. The water then swept through the mine and exited through a second breach on Caney Creek. That meant the two creeks were actually flushing process water out of the mine into the drinking water supply for two million people.
The TCEQ finished its investigation in July and cited the operation for failing to prevent the unauthorized discharge of process water. The TCEQ told them to repair and widen their dikes. They did. Case closed.
This same mine has been investigated five times in five years by the TCEQ for various problems detailed in this report. The mine is owned by a cardiologist from Nacogdoches named Guniganti. His family operates it.
The basic problem with this mine is its location. It sits at the confluence of two floodways. That’s why the dikes were blown out. That’s why Harvey’s floodwaters swept through it. Continuing to operate this mine is like flying a plane into conditions that you know are unsafe.
No Disincentive for Dangerous Business Practices
Yet there’s no disincentive for dangerous business practices. Investigators told the operators to fix the breaches. They did. Business will go on as usual. Until the next disaster.
As a society, why do we tolerate this?
We even seem to venerate it. How strange that one family’s profit outweighs the health and safety of millions! The legislature had an opportunity to fix this problem this year. However, one bill that would have established best practices for sand mining and another that would have established minimum setbacks from rivers for sand mines never made it out of committee. Likewise HB-908 proposed by State Representative Dan Huberty that would have provided meaningful financial penalties for such bad practices never made it out of committee.
The thoughts expressed in this post represent my opinions on matters of public interest 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/2019/05/Mine-Breech.jpg?fit=1500%2C1000&ssl=110001500adminadmin2019-08-23 00:01:462019-08-23 00:19:45TCEQ Observes Triple-PG Sand Mine Discharging Wastewater Directly into Tributary of Lake Houston
Next week will mark the second anniversary of Hurricane Harvey. As we look back and build forward, we should also remember previous storms and how flooding shaped the a city called Houston and the people who inhabit it.
Houston History Magazine
In this regard, a reader forwarded me several links to a fascinating magazine. Debbie Z. Harwell, PhD., is managing editor of Houston History Magazine and a history teacher at the University of Houston.
Dr. Harwell was helping birth a new edition of Houston History focused on industrial accidents when Harvey hit. It was too late in her publication schedule to refocus the issue; she had been working on it for almost a year. So she wrote an introduction that helped put the storm in historical perspective. She wrote it sitting on a couch while Harvey’s rains beat against her windows.
Short-Term Memory Loss of Long-Term Needs
Prophetically, she titled the intro “Short-term Memory Loss of Long-term Needs.” In it, she says, “As a city and as a country we seem to suffer from short-term memory loss. Our memory of the flood is wiped out not by old age but by the next big news story, or even the next tweet. Past floods have similarly faded from the collective memory (until it happens again), with few willing to spend money on the necessary infrastructure to produce real change.”
Houston History also published a photo essay of Houston Floods called “Lest We Forget.” Former Houston Post photographer Joel Draut collected the photos and wrote the accompanying text. Interestingly, one of the most significant floods happened in 1837, one year before Louis Daguerre invented the first commercially viable photographic process, now known as the daguerreotype.
In an August 1836 advertisement, the Allen brothers proclaimed that Houston would become “ …beyond all doubt, the great interior commercial emporium of Texas.” Thirteen months later rains from a hurricane in September 1837 flooded the city’s Main Street to a depth of four feet. This inundation did not deter developers.
As I looked through page after page of forgotten photos from 1929, 1935, 1960, and 1973, I was struck by how similar they were to Harvey images. They were grainier. They were black and white. But aside from that, the images could have been from any one of a hundred more contemporary calamities, such as Katrina, Ike, Rita, or Harvey. Sometimes, even the dates were the same, like the Memorial Day flood of 1929 shown below. The location: Franklin and Milam. The bayou: Buffalo.
Photo courtesy of Houston History Magazine and Houston Metropolitan Research Center, Houston Public Library.
“Lest We Forget” is a short but great and sobering read. I highly recommend it.
Survivors, Volunteers, Responders Tell Their Harvey Stories
Dr. Harwell is also one of the driving forces behind a project called Resilient Houston: Documenting Hurricane Harvey. “We did an oral history harvest at the Kingwood Community Center last October,” said Dr. Harwell, “and excerpts from those interviews appear on the site. Almost half of those are from Kingwood – survivors, volunteers, responders. We will be adding more at the end of the fall semester.”
Posted by Bob Rehak on 8/22/2019with thanks to Dr. Debbie Harwell and Joel Draut
723 Days since Hurricane Harvey
https://i0.wp.com/reduceflooding.com/wp-content/uploads/2019/08/Memorial-Day-1929.jpg?fit=1500%2C993&ssl=19931500adminadmin2019-08-21 23:43:102019-08-22 09:12:56Lest We Forget: Houston’s History of Flooding
ReduceFlooding.com has obtained a copy of the study withheld by the Army Corps that the Corps used to justify dredging only 500,000 cubic yards from the mouth bar of the San Jacinto West Fork. The Corps refused to supply it in response to my Freedom of Information Act (FOIA) request in June. However, the City of Houston did supply the Corps document in response to a similar FOIA request. Now, thanks to Council Member Dave Martin, the public has an opportunity to compare the two studies side by side for the first time.
Kings River resident near mouth bar wading in knee deep water almost to West Fork channel marker. Caution: do not let children attempt this. Pockets of deeper water may exist that could cause drowning. Picture taken eight days ago. The island being excavated in the distance has since been removed; see last image in post.
After reviewing the Corps document, I can see why the Corps refused to supply it. It has more holes in it than a West Texas stop sign.
History of Controversy
For almost a year, the City and the Army Corps have argued over how much sediment was deposited in the mouth bar of the San Jacinto river by Hurricane Harvey. That determines how much dredging FEMA will fund. Initially, the City recommended working with two Texas Water Development Board sedimentation surveys conducted in 2011 and 2018. But no measurements exist from the period immediately BEFORE Harvey – only AFTER. So the Corps rejected that idea.
The Stockton Protocol combines ultra-high-resolution CHIRP seismic data with core sampling. The seismic identifies layer thickness and the core sampling identifies layer composition. (Note: the process is somewhat like the oil field practice of confirming seismic with core samples from exploratory wells.) The hope: that by analyzing changes in sediment composition (such as color, grain size, roundness, hardness, etc.), researchers can differentiate Harvey sediment from other floods and then measure it accurately.
Core sample from Tetra Tech Study. Different colors and consistencies indicate sediment came from different floods.
The Army Corps recommended a Texas A&M Galveston professor, Dr. Timothy Dellapenna, to do the research. However, the City of Houston and A&M could not agree on contract terms. Therefore, the City hired Tetra Tech, to perform the research that Dr. Dellapena outlined.
At the end of the day, even with 500,000 cubic yards, those two estimates still vary by almost 3X. According to Houston City Council Member Dave Martin, the Corps never explained why they rejected the Tetra Tech analysis.
The Corps simply accepted its own results and started dredging without public explanation or input. The Corps document raises many questions that may or may not have valid answers.
The USGS gauge used by the Corps for its analysis stopped working during the peak of Harveywhen most sediment would have been moving. The Corps report did not acknowledge this.
Corps Analysis Requires Explanations Never Supplied
Why did the Corps:
Base its analysis on a gage at US59 that stopped functioning during the peak of Harvey, when most sediment was moving?
Assume Harvey distributed sediment in the same patterns over the same distances as lesser storms?
Ignore build up of sediment from Tax Day and Memorial Day storms at the mouth bar as a factor that could have increased the percentage of sediment falling out of suspension during Harvey?
Not consider bank erosion downstream from the gage, relying instead on standard charts for “bed-load transport” for sandy rivers?
Ignore approximately 20 square miles of sand mines in the West Fork floodway where loose sand and silt were inundated by 131,000 cubic feet of water per second, unlike previous storms?
Use a 1-D instead of a 2- or 3-D model for this complex environment?
Not publicly disclose model inputs/outputs and data for peer review and validation?
Initially reject the use of two TWDB surveys, then reverse course and base all of their findings on them – without explaining why?
Exclude extreme data from their study, even though Harvey was one of the most extreme rainfall events in U.S. history?
Mislabel all charts, graphs and photos in its report?
Refuse to disclose their report in response to a FOIA request, contrary to official Army policy?
Omit the organization’s name and the author’s name from the report?
Treat the volume that Tetra Tech found related to Harvey in the mouth bar area alone as if it represented the total volume deposited in the entire West Fork by Harvey?
Corps Rejects Use of TWDB Surveys, Then Bases Own Analysis On Them
To estimate Harvey-related volume, the City initially proposed analyzing two Texas Water Development Board sedimentation surveys from 2011 and 2018.
The Corps rejected that idea, suggested the Stockton Protocol, rejected those findings, then based its own analysis on the two TWDB surveys it rejected earlier. This is like following a Three-Card Monte game!
Basically, the Corps tried to estimate the amount of sediment that Harvey’s flow could theoretically carry. That would depend on velocity and sediment size/weight. But the gage at US 59 stopped recording at the peak of Harvey. So they also had to estimate the discharge (volume of flow in cubic feet per second [cfs]). Then they used industry-standard curves to estimate sediment transport based on estimated discharge. But they discarded rates over 45,000 CFS because they produced unexpectedly high values.
They also ignored the presence of mile-wide sand mines upstream. The river ruptured the dikes of those mines and captured the pits during Harvey.
West Fork Sand Mine Complex inundated by Harvey. This reach of the river is normally about 150 feet wide.On this day, the day AFTER Harvey’s peak, the flow was more than a mile wide.
When the industry-standard sediment transport curves yielded unacceptably high results, the Corps resorted to a simple 1-D model (developed earlier for another purpose) to calculate the sediment load, because flows beyond 45,000 cubic feet per second “produced sediment loads far beyond a reasonable range.”
Corps Assumes Harvey Transported Same Percentage To Mouth Bar as Other Storms
One potentially fatal assumption: The Corps assumes that Harvey transported the same percentage of its sediment load to the mouth bar as all other storms between 2011 and 2018. Said another way, they assume that Harvey behaved LIKE all other storms. Yet not all those floods inundated sand mines.
Moreover, had the Corps measured river bank erosion at intervals between 2011 and 2018, they would have found that virtually all of it occurred during Harvey and very little occurred during Tax Day, Memorial Day and other storms.
Quantum Leap in Erosion Not Factored In
Harvey’s erosive power was NOT proportional to other storms, as the photos below show. River banks eroded more than a hundred feet during Harvey in many places. Yet the Corps report never even mentions erosion.
In 2011, the distance from the ridgeline of this home on Riverbend Drive to the West Fork was 326 feet.
On 1/23/2017, after the Tax and Memorial Day Floods, the distance had decreased only 2 feet.
This shows how much shoreline Harvey ALONE eroded. The yellow line is exactly the same length as after the 2016 floods.
After Harvey, the new distance to the river bank was 216 feet – 108 feet less.
The Tax and Memorial Day Floods combined eroded this river bank by 2 feet. Harvey alone eroded it another 108 feet – 50 times more!
Photographic analysis shows similar quantum leaps in erosion related to Harvey elsewhere along the West Fork.
Another home west of River Grove Park lost 27 feet between 2011 and early 2017, but 111 feet in Harvey.
River Grove Park lost 0 feet from 2011 to early 2017, but 74-feet in Harvey.
Romerica lost 62 feet between 2011 and early 2017, but 144 feet in Harvey.
Net: In four days, Harvey eroded from 2X to 75X more sediment than all other storms during the previous six years. It did NOT act proportionally.
The shearing force of 240,000 cubic feet per second coming down the West Fork literally pulled thousands of trees out by their roots and dislodged sediment disproportionately compared to previous floods (see below). The Gallery page of this web site clearly shows the extent of this devastation. It contains 450 images taken from a helicopter on 9/14/2017, two weeks after Harvey.
Hurricane Harvey ripped trees out by their roots to a degree that previous storms did not. This increased erosion exponentially compared to other storms.
Corps Assumes Mouth Bar Growth Did Not Affect Percentage Deposited by Harvey
The Army Corps also assumes that Harvey transported the same fraction of the total sediment load (20%) to the mouth bar that all storms did between 2011 and 2018. That’s a dubious assumption for several reasons:
Previous storms progressively built a wall across the mouth of the West Fork that grew higher and higher during the study period.
As it grew, that wall increasingly slowed water down and likely accelerated the rate of deposition behind it (which helps explain why the Corps had to dredge its way to the mouth bar).
This constant 20% contradicts numerous anecdotal reports from lakeside residents and boaters claiming that Harvey carried vastlymore sediment to the mouth bar (and their yards/docks) than previous storms. The wife of the resident wading across the river in the image above told me that, on a scale of 1 to 5, the Tax and Memorial Days floods deposited sediment in her yard equal to a 1. But Harvey, she said, was a 6. In other words, off the scale.
No wonder the Corps didn’t want the public looking at this!
Taxpayers Deserve Independent Scientific Review
Professionals rarely like to have their conclusions questioned. However, those who have confidence in their conclusions welcome peer and public review. They encourage second opinions and provide all of their data for review. They also welcome the opportunity to explain and defend their results. None of those things happened in this case.
Instead, the Corps concealed its results as if this involved national security, not public safety. Why? That may be the biggest question of all associated with this project.
The Corps has an excellent, hard-earned reputation. This study undermines it.
As mentioned above, the Tetra Tech study may also have flaws, but the Corps never revealed what its concerns were.
Only one thing is certain. Public safety rests on wildly differing studies. Taxpayers deserve an independent scientific review to resolve the differences between these two studies. The City concurs with the findings in this post and also calls for an independent scientific review. The Corps could not be reached for comment; their new public affairs officer does not list her phone number.
Dredging will likely end next week, with the Corps proclaiming it has restored the conveyance of the river to pre-Harvey conditions (when they have no pre-Harvey measurements).
So we need an independent scientific review to happen quickly. Email you Congressmen and Senators immediately.
Corps Plans Still Being Kept from Public
The Corps still has not released its dredging plans, despite a FOIA request made in June when mouth bar dredging started.
If that is an accurate assessment, the Corps would leave a sediment wall under the water approximately 30-35 feet high and 1-2 miles long in the mouth of the West Fork.
Congressman Dan Crenshaw reviews progress of dredging operation on Friday, August 16. Looking southwest towards Atascocita. Notice how the small island in the first image above has now been removed. The mouth bar itself will remain in place, most of it underwater nowwhere it is invisible to the public.
Others Scrambling to Pick Up the Pieces
It may look like the Corps has dredged. But it also looks like the Corps will leave 80-90% of the mouth bar in place. Remember, sand bars are like ice bergs in the sense that what you see above water is small compared to the amount you can’t see below water.
At this point, City, County, State and Federal leaders are scrambling to put together a plan to address the rest of the sediment. Some of that sediment is clearly pre-Harvey. I will discuss options for removal of that portion and maintenance dredging in a future post.
Posted by Bob Rehak on 8/20/2019
721 Days after Hurricane Harvey
As in previous posts on this subject, I promise the Corps that I will print their rebuttal verbatim if they disagree with any of the points in this post.
https://i0.wp.com/reduceflooding.com/wp-content/uploads/2019/08/USGS.08069500.140334.00065..20170829.20170830..0..pres_.gif.png?fit=580%2C430&ssl=1430580adminadmin2019-08-20 16:14:592019-08-21 11:07:08Recently Obtained Documents Raise Questions about Amount of Sediment in Mouth Bar Due to Harvey
TCEQ Observes Triple-PG Sand Mine Discharging Wastewater Directly into Tributary of Lake Houston
On May 18, Josh Alberson and I gave Tony Buzbee a tour of sediment and sand mining issues on the San Jacinto River. Buzbee is a candidate for Mayor of Houston and got to witness first hand some of the problems I have been talking about for almost two years now. On Caney Creek, we stumbled across a giant breach in the dike of the Triple-PG mine in Porter. We reported it immediately to the TCEQ.
Two-Week Discharge
Investigators actually observed the unauthorized discharge of process water from the mine into the City’s drinking water supply. It continued for approximately two weeks.
Not One, But Two Massive Breaches
The TCEQ found not one, but two breaches. The first was on the southwest side of the mine. Water entered the mine from a breach of the dike near White Oak Creek. The water then swept through the mine and exited through a second breach on Caney Creek. That meant the two creeks were actually flushing process water out of the mine into the drinking water supply for two million people.
The TCEQ finished its investigation in July and cited the operation for failing to prevent the unauthorized discharge of process water. The TCEQ told them to repair and widen their dikes. They did. Case closed.
Classic Example of Pit Capture
The breeches appear to be the result of heavy rains in early May. This is a prime example of pit capture. High pressure in the floodway causes dike failure. The river or stream then flows through the mine and breaks out the opposite side. The same thing happened during Harvey when floodwaters carried away a large part of the mine’s stockpile.
Repeated Violations
This same mine has been investigated five times in five years by the TCEQ for various problems detailed in this report. The mine is owned by a cardiologist from Nacogdoches named Guniganti. His family operates it.
The basic problem with this mine is its location. It sits at the confluence of two floodways. That’s why the dikes were blown out. That’s why Harvey’s floodwaters swept through it. Continuing to operate this mine is like flying a plane into conditions that you know are unsafe.
No Disincentive for Dangerous Business Practices
Yet there’s no disincentive for dangerous business practices. Investigators told the operators to fix the breaches. They did. Business will go on as usual. Until the next disaster.
We even seem to venerate it. How strange that one family’s profit outweighs the health and safety of millions! The legislature had an opportunity to fix this problem this year. However, one bill that would have established best practices for sand mining and another that would have established minimum setbacks from rivers for sand mines never made it out of committee. Likewise HB-908 proposed by State Representative Dan Huberty that would have provided meaningful financial penalties for such bad practices never made it out of committee.
Tax Breaks Instead of Penalties
This Guniganti family even gets tax breaks from Montgomery County. The appraisal district gives timber and agricultural exemptions to areas actively being mined. Go figure!
Posted by Bob Rehak on 8/23/2019
724 Days after Hurricane Harvey
The thoughts expressed in this post represent my opinions on matters of public interest and safety. They are protected by the First Amendment of the US Constitution and the Anti-SLAPP statute of the great State of Texas.
Lest We Forget: Houston’s History of Flooding
Next week will mark the second anniversary of Hurricane Harvey. As we look back and build forward, we should also remember previous storms and how flooding shaped the a city called Houston and the people who inhabit it.
Houston History Magazine
In this regard, a reader forwarded me several links to a fascinating magazine. Debbie Z. Harwell, PhD., is managing editor of Houston History Magazine and a history teacher at the University of Houston.
Dr. Harwell was helping birth a new edition of Houston History focused on industrial accidents when Harvey hit. It was too late in her publication schedule to refocus the issue; she had been working on it for almost a year. So she wrote an introduction that helped put the storm in historical perspective. She wrote it sitting on a couch while Harvey’s rains beat against her windows.
Short-Term Memory Loss of Long-Term Needs
Prophetically, she titled the intro “Short-term Memory Loss of Long-term Needs.” In it, she says, “As a city and as a country we seem to suffer from short-term memory loss. Our memory of the flood is wiped out not by old age but by the next big news story, or even the next tweet. Past floods have similarly faded from the collective memory (until it happens again), with few willing to spend money on the necessary infrastructure to produce real change.”
Two years after Harvey and Dr. Harwell’s essay, we struggle with that same issue. The floodplain homes that she referenced in her Fall 2017 issue are back on the agenda only in Montgomery County this time. So are loopholes in regulations that allow developers to build with detention ponds.
Historical Photo Essay of Houston Flooding
Houston History also published a photo essay of Houston Floods called “Lest We Forget.” Former Houston Post photographer Joel Draut collected the photos and wrote the accompanying text. Interestingly, one of the most significant floods happened in 1837, one year before Louis Daguerre invented the first commercially viable photographic process, now known as the daguerreotype.
In an August 1836 advertisement, the Allen brothers proclaimed that Houston would become “ …beyond all doubt, the great interior commercial emporium of Texas.” Thirteen months later rains from a hurricane in September 1837 flooded the city’s Main Street to a depth of four feet. This inundation did not deter developers.
As I looked through page after page of forgotten photos from 1929, 1935, 1960, and 1973, I was struck by how similar they were to Harvey images. They were grainier. They were black and white. But aside from that, the images could have been from any one of a hundred more contemporary calamities, such as Katrina, Ike, Rita, or Harvey. Sometimes, even the dates were the same, like the Memorial Day flood of 1929 shown below. The location: Franklin and Milam. The bayou: Buffalo.
“Lest We Forget” is a short but great and sobering read. I highly recommend it.
Survivors, Volunteers, Responders Tell Their Harvey Stories
Dr. Harwell is also one of the driving forces behind a project called Resilient Houston: Documenting Hurricane Harvey. “We did an oral history harvest at the Kingwood Community Center last October,” said Dr. Harwell, “and excerpts from those interviews appear on the site. Almost half of those are from Kingwood – survivors, volunteers, responders. We will be adding more at the end of the fall semester.”
Posted by Bob Rehak on 8/22/2019 with thanks to Dr. Debbie Harwell and Joel Draut
723 Days since Hurricane Harvey
Recently Obtained Documents Raise Questions about Amount of Sediment in Mouth Bar Due to Harvey
ReduceFlooding.com has obtained a copy of the study withheld by the Army Corps that the Corps used to justify dredging only 500,000 cubic yards from the mouth bar of the San Jacinto West Fork. The Corps refused to supply it in response to my Freedom of Information Act (FOIA) request in June. However, the City of Houston did supply the Corps document in response to a similar FOIA request. Now, thanks to Council Member Dave Martin, the public has an opportunity to compare the two studies side by side for the first time.
History of Controversy
For almost a year, the City and the Army Corps have argued over how much sediment was deposited in the mouth bar of the San Jacinto river by Hurricane Harvey. That determines how much dredging FEMA will fund. Initially, the City recommended working with two Texas Water Development Board sedimentation surveys conducted in 2011 and 2018. But no measurements exist from the period immediately BEFORE Harvey – only AFTER. So the Corps rejected that idea.
Corps Demands then Rejects Stockton Protocol
To determine Harvey volume, the Corps then required the City to provide direct measurement of the sediment through something called the Stockton Protocol. (See this memo from Stephen Costello, Houston’s Chief Recovery Officer, outlining this request and the reasons for it.)
The Stockton Protocol combines ultra-high-resolution CHIRP seismic data with core sampling. The seismic identifies layer thickness and the core sampling identifies layer composition. (Note: the process is somewhat like the oil field practice of confirming seismic with core samples from exploratory wells.) The hope: that by analyzing changes in sediment composition (such as color, grain size, roundness, hardness, etc.), researchers can differentiate Harvey sediment from other floods and then measure it accurately.
The Army Corps recommended a Texas A&M Galveston professor, Dr. Timothy Dellapenna, to do the research. However, the City of Houston and A&M could not agree on contract terms. Therefore, the City hired Tetra Tech, to perform the research that Dr. Dellapena outlined.
Corps Produces Own Analysis
At the end of the day, even with 500,000 cubic yards, those two estimates still vary by almost 3X. According to Houston City Council Member Dave Martin, the Corps never explained why they rejected the Tetra Tech analysis.
The Corps simply accepted its own results and started dredging without public explanation or input. The Corps document raises many questions that may or may not have valid answers.
Corps Analysis Requires Explanations Never Supplied
Why did the Corps:
Corps Rejects Use of TWDB Surveys, Then Bases Own Analysis On Them
To estimate Harvey-related volume, the City initially proposed analyzing two Texas Water Development Board sedimentation surveys from 2011 and 2018.
Here is the full text of the Corps’ 4-page unsigned study. We now know that…
Basically, the Corps tried to estimate the amount of sediment that Harvey’s flow could theoretically carry. That would depend on velocity and sediment size/weight. But the gage at US 59 stopped recording at the peak of Harvey. So they also had to estimate the discharge (volume of flow in cubic feet per second [cfs]). Then they used industry-standard curves to estimate sediment transport based on estimated discharge. But they discarded rates over 45,000 CFS because they produced unexpectedly high values.
They also ignored the presence of mile-wide sand mines upstream. The river ruptured the dikes of those mines and captured the pits during Harvey.
Corps Rules Out Extremes for Extreme Event
The Corps says in its report, “there are no measurements above 45,000 cubic feet per second.” Yet the combined peak flows coming from the West Fork, Spring and Cypress Creeks reached approximately 240,000 cubic feet per second during Harvey – five times more. The faster and higher the flow, the more sediment that can be transported downstream and over greater distances.
When the industry-standard sediment transport curves yielded unacceptably high results, the Corps resorted to a simple 1-D model (developed earlier for another purpose) to calculate the sediment load, because flows beyond 45,000 cubic feet per second “produced sediment loads far beyond a reasonable range.”
Corps Assumes Harvey Transported Same Percentage To Mouth Bar as Other Storms
One potentially fatal assumption: The Corps assumes that Harvey transported the same percentage of its sediment load to the mouth bar as all other storms between 2011 and 2018. Said another way, they assume that Harvey behaved LIKE all other storms. Yet not all those floods inundated sand mines.
Quantum Leap in Erosion Not Factored In
Harvey’s erosive power was NOT proportional to other storms, as the photos below show. River banks eroded more than a hundred feet during Harvey in many places. Yet the Corps report never even mentions erosion.
Photographic analysis shows similar quantum leaps in erosion related to Harvey elsewhere along the West Fork.
The shearing force of 240,000 cubic feet per second coming down the West Fork literally pulled thousands of trees out by their roots and dislodged sediment disproportionately compared to previous floods (see below). The Gallery page of this web site clearly shows the extent of this devastation. It contains 450 images taken from a helicopter on 9/14/2017, two weeks after Harvey.
Corps Assumes Mouth Bar Growth Did Not Affect Percentage Deposited by Harvey
The Army Corps also assumes that Harvey transported the same fraction of the total sediment load (20%) to the mouth bar that all storms did between 2011 and 2018. That’s a dubious assumption for several reasons:
Yet the Corps based its estimate on a constant 20%. Page 3 of their report spells out the assumption. Harvey, they say, deposited approximately the same fraction of sediment at the mouth bar as all other storms did during the period between surveys.
This constant 20% contradicts numerous anecdotal reports from lakeside residents and boaters claiming that Harvey carried vastly more sediment to the mouth bar (and their yards/docks) than previous storms. The wife of the resident wading across the river in the image above told me that, on a scale of 1 to 5, the Tax and Memorial Days floods deposited sediment in her yard equal to a 1. But Harvey, she said, was a 6. In other words, off the scale.
Taxpayers Deserve Independent Scientific Review
Professionals rarely like to have their conclusions questioned. However, those who have confidence in their conclusions welcome peer and public review. They encourage second opinions and provide all of their data for review. They also welcome the opportunity to explain and defend their results. None of those things happened in this case.
Instead, the Corps concealed its results as if this involved national security, not public safety. Why? That may be the biggest question of all associated with this project.
As mentioned above, the Tetra Tech study may also have flaws, but the Corps never revealed what its concerns were.
Only one thing is certain. Public safety rests on wildly differing studies. Taxpayers deserve an independent scientific review to resolve the differences between these two studies. The City concurs with the findings in this post and also calls for an independent scientific review. The Corps could not be reached for comment; their new public affairs officer does not list her phone number.
Dredging will likely end next week, with the Corps proclaiming it has restored the conveyance of the river to pre-Harvey conditions (when they have no pre-Harvey measurements).
Corps Plans Still Being Kept from Public
The Corps still has not released its dredging plans, despite a FOIA request made in June when mouth bar dredging started.
Visual observations of the operation suggest that they are dredging a wide area by three feet, to a total depth of about five feet, instead of trying to cut a channel through the mouth bar. That would leave something like an underwater mesa, still blocking the flow and still trapping sediment. Water coming downriver would have to climb a steep hill to get over it.
If that is an accurate assessment, the Corps would leave a sediment wall under the water approximately 30-35 feet high and 1-2 miles long in the mouth of the West Fork.
Others Scrambling to Pick Up the Pieces
It may look like the Corps has dredged. But it also looks like the Corps will leave 80-90% of the mouth bar in place. Remember, sand bars are like ice bergs in the sense that what you see above water is small compared to the amount you can’t see below water.
At this point, City, County, State and Federal leaders are scrambling to put together a plan to address the rest of the sediment. Some of that sediment is clearly pre-Harvey. I will discuss options for removal of that portion and maintenance dredging in a future post.
Posted by Bob Rehak on 8/20/2019
721 Days after Hurricane Harvey
As in previous posts on this subject, I promise the Corps that I will print their rebuttal verbatim if they disagree with any of the points in this post.