The countdown to D-Day (dredging day) continues. Preparation for the U.S. Army Corps of Engineers Emergency Dredging Project on the West Fork is kicking into high gear. Here are some pics from the job site and the latest schedule for when various activities will start.
Schedule for U.S. Army Corps of Engineers West Fork Emergency Dredging Project
Dozens of trucks are delivering equipment to the mobilization site.
Traffic management at the site is a major concern, prompting the Corp to request the public stay a safe distance away.
Thousands of sections of dredge pipe have been delivered to a massive “pipe farm.”
Contractor and Army Corps representatives review dredging plans at mobilization site headquarters.
Actual dredging should begin within the next two weeks. While staff and material are being organized for the dredging operation, clean up crews will remove more dead trees and other debris from the river and placement sites.
Example of debris removal from Lake Houston before dredging. This shot actually shows a city-contracted crew working on the East Fork during July. Corps crews will be conducting similar work.
Difference Between City Dredging and Corp Dredging
(NOTE: THIS POST HAS BEEN UPDATED WITH THE FOLLOWING INFO SINCE THE ORIGINAL POST) What is the difference between the city debris removal and the debris removal that the corps is doing? I went back into the contract requirements. Division 2, Section 02 41 01.01 45 stipulates, “General debris consists of trees and other vegetation within limits of dredging in the river, under the West Lake, Houston Parkway bridge, and upland areas that are to be dredged or excavated. General debris may also include, but is not limited to, metal bands, pallets, pieces of broken cable, rope, concrete rubble, construction materials, broken piles, etc. and may be encountered in the same area as above.”
So I see three main differences. The Corps subcontractor will: 1) only be working within the area to be dredged, 2) remove other types of materials that the city did not, 3) Also be responsible for cleaning up the placement areas, which the city did not.
Section 1.3.2 of the same document stipulates how they are being paid. Basically, it’s by the ton, but they are also being compensated for the cost of equipment, labor and material. The government is inspecting the scales. The complete contract requirements and plans are posted on the Reports page of this web site under Sedimentation/Dredging/Army Corps.
Additional Info About Army Corps West Fork Dredging Project
Below are some videos posted by the Corps that explain how we got to this point and how the project will progress.
The first explains how the Corps conducted the site survey.
Jim Blackburn, JD, professor of environmental law at Rice and Phil Bedient, PhD., a professor of engineering also at Rice, have just released an important new study called Houston a Year After Harvey: Where We Are and Where We Need to Be . Because of the length, detail, intricate maps and charts, and file size, this is best viewed on something larger than a smartphone.
Written for the Average Adult
Three things immediately become apparent when reviewing this 55-page report. It’s wide ranging in scope. It’s an excellent work of scholarship. And it’s well written; the average adult should be able to understand all the key concepts without difficulty.
Houston A Year After Harvey: Three Major Sections
It’s an excellent summary of what happened during Harvey, how the community is responding, and what still needs to be done – major watershed by major watershed.
The Problems of Obsolete Flood Plain Maps
This paper is organized into three main sections. First, the issues of obsolete 100-year floodplain maps and increasing rainfall are discussed because they are key to fully understanding the current dilemma and shaping alternative concepts for long-term protection. Whether or not you believe in climate change, the case for revising flood maps is pretty compelling based on the math alone. We’ve had five so-called 500-year storms in the last 25 years. Are we just spectacularly unlucky? Or do we need to revisit the assumptions and underlying math?
Any time you try to predict the frequency of rarely observed or unobserved events, such as 500-year storms, you venture way out on a limb. The data on which you base assumptions is thin. Worse, one of the fundamental precepts of extreme value analysis (EVA) is that nothing changes during the 500 years under analysis.
Good luck with that. Five hundred years ago, the U.S., Texas, Houston, developers, gasoline, F150s and sand mining didn’t even exist. As we get more data and update assumptions, flood maps are being redrawn. So are the guidelines which form the basis for different types of development. Instead of raising new homes two feet above the 100 year flood plain, officials are now talking about two feet above the 500-year flood plain.
Issues that Need to Be Addressed Watershed by Watershed
The second part of Houston A Year After Harvey is a geographic overview of the flood issues and potential responses to various watersheds across Harris County.
The discussion of the West Fork of the San Jacinto goes from pages 28-30. It starts with a discussion of sedimentation, where the sediment is coming from and why we need stronger regulation of sand mining.
In regard to sedimentation, the reports also discusses the need for dredging to restore the river’s carrying capacity.
Finally, in regard to the San Jacinto, the report discusses the need to change the operating philosophy for the dams on Lake Conroe and Lake Houston to enable pre-release as a strategy for flood mitigation. This has already happened, they note, with the approval of the TCEQ to temporarily lower the level of Lake Conroe during the peak of hurricane season.
Different Solution Sets for Different Flooding Issues
The third major portion of Houston A Year After Harvey discusses different flood management concepts for three zones of the Houston area that have different flooding issues.
The authors break the county up into three major zones, A, B and C. A stretches from Addicks/Barker to the Katy Prairie. B covers the central part of the county. And C covers coastal areas.
The discussion of Zone B (which includes the Lake Houston and San Jacinto River) includes explanations for many of the projects listed on the Harris County Flood Control District Flood Bond that we are now voting on. See pages 42 through 45.
But don’t stop there. There’s also a great description for how the Ike Dike could work in Zone C.
How All the Pieces of the Flood Bond Fit Together
All in all, Houston A Year After Harvey makes a great case for the flood bond, without ever really setting out to do that. It will help give you a better understanding for how our drainage problems affect the people around us and vice versa.
Perkins is quoted as saying, “…what [these sand mines] actually do – in contrast to what people were stating – is that they stored quite a bit of that floodwater and helped to prevent additional flooding …”
He explained how. “… For example, one 60-acre pit that’s 100 feet deep holds 6,000 acre feet of water. We’ve got some great potential capacity for off-channel storage that we could incorporate into our mining activities.” [Emphasis added twice.]
Did Mines Really Help Prevent Downstream Flooding?
Let’s suspend disbelief for a moment and examine Mr. Perkins’ theory.
The pits are already filled with water, so you only have a tiny portion of those acre feet available for storage during a flood! Not as much as he implies. Is the amount significant?
The difference between the top of the water and the top of the dikes is usually 10 to 20 feet at best. So let’s be generous to Mr. Perkins and assume 20. And let’s use the pit below as a test case. It’s 160 acres – about the size of Kingwood’s East End Park so people will have a reference.
Here’s what the same pit looks like from ground level.
Peak flow from Harvey would have filled this pit in less than 8 minutes.
How 8 Minutes was Calculated
The pit above is approximately 160 acres.
Assume 20 vertical feet are available to store water.
20 feet x 160 acres = 3200 acre feet of potential storage.
Now let’s calculate how fast Harvey would fill that up.
Approximately 150,000 cubic feet per second (cfs) flowed through this area.
There are 43,560 cubic feet in an acre foot. To find the fill rate…
150,000 cubic feet per second/43,560 = approximately 3.5 acre feet per second
To convert seconds to minutes, 3.5 x 60 = 210 acre feet per minute.
1600 acre feet of extra capacity/210 acre feet per minute = 7.6 minutes.
Thus, Harvey could have filled 20 feet in this pit in less than 8 minutes.
Contribution to Flood Reduction if You Put All Mines Together
However, if you consider all the pits on the West Fork together (20 square miles), they might have delayed flooding by 10 hours according to the same calculations. That’s starting to sound like a significant contribution. Barker and Addicks Reservoirs together store a total of 410,000 acre feet. West Fork sand mines occupy 12,800 acres. If every acre had 20 vertical feet of storage available, you would have 256,000 acre feet of storage. That might not stop Harvey but it could certainly help reduce flooding – especially in smaller floods.
Two Problems Need to Be Addressed with Perkins’ Theory
Mr. Perkins’ theory has two major flaws that would need to be addressed before it could be taken seriously by residents.
That would mean following best management practices common in other states and countries.
Ignoring Best Practices Contributes to Flooding
Regardless of storage POTENTIAL, if mines fail to follow best management practices, they are likely to do more harm than good.
Texas does not enforce best management practices common in other states, such as setbacks from rivers, sloping of dikes, and strengthening of dikes.
In Texas, we locate mines in floodways. And dikes are so thin that they often fail. Case in point: the mine we are talking about. There, dikes have been breached repeatedly. The river has cut through the pit and carried sediment downstream. That sediment then helped clog the river and create floods, not prevent them.
Rather than trying to deny what happened and change the debate, TACA should acknowledge what happened and work with citizen groups and government to create new regulations that protect the public as well as themselves.
What Really Happened in West Fork Mines During Harvey
Here’s what it looked like. This series of photos shows West Fork sand mines during Harvey on 8/30/17, one day after the peak. The river was flowing at only one-third of its peak on this day, according to the San Jacinto River Authority.
West Fork Sand Mine complex inundated by Harvey. Two of the three stockpiles in this photo were decimated by the flood. Sediment from the pits was also picked up by currents within them and carried downstream. Mine used in illustration above is in center.
Following are several close ups that show water breaching dikes, entering the mine and eroding areas within it and then carrying sediment downstream. All images taken on 8/30/17, courtesy of Google Earth and NASA.
Floodwater broke dikes, captured the sand pit and flowed straight through it.
Rapids within the mine.
Force of floodwater washed out road INSIDE mine.
Floodwater rushing out of forest into sand mine. It then flowed through and over dikes on the opposite side.
Exit Point for Floodwaters in this Mine
This next image shows the floodwaters exiting the mine on the far side after they scooped up sediment.
Floodwaters exit mine during Harvey. Photo taken on 8/30/2017.
Harvey was not the only flood when this has happened. The Memorial Day flood in 2015 and the Tax Day Flood in 2016 also saw breaches of the dikes. Those floods were much smaller and still caused problems, underscoring the need to modify permitting, regulations and best practices.
Exit point when river captured mine during Memorial Day flood in 2015.
Exit point two months later, on 7/31/2015. Breach was still unprepared and mine was leaking sediment into river.
By March of 2016, the breach had been repaired, but you can also see how sand was building up against it.
Less than a year later, when the flood waters had subsided, we can see the growth and orientation of the sand bars within the mine on the upper left in this 2017 image. This indicates that current within the mines during river capture was forcing sediment out of the mines.
I fail to see how this particular sand mine can prevent flooding. These pictures tell a different story. If the operator and TACA supported best management practices common in other states and countries, they might be able to help prevent flooding. But until that happens, I’m going to call Mr. Perkins’ claim a perfect-world generalization that has real-world limitations and exceptions.
And until TACA and the mines acknowledge the role they have played in flooding, residents will have a hard time emotionally accepting their presence in the community.
As always, these are my opinions on a matter of public interest. They are protected by the First Amendment of the United States Constitution and the Anti-SLAPP statutes of the great State of Texas.
Posted by Bob Rehak on August 11, 2018
347 Days since Hurricane Harvey
00adminadmin2018-08-11 19:47:222018-08-11 20:03:21TACA Now Claims Sand Mines Helped to Prevent Flooding Downstream
Activity at Army Corps Dredge Command Site Kicking into High Gear
The countdown to D-Day (dredging day) continues. Preparation for the U.S. Army Corps of Engineers Emergency Dredging Project on the West Fork is kicking into high gear. Here are some pics from the job site and the latest schedule for when various activities will start.
Schedule for U.S. Army Corps of Engineers West Fork Emergency Dredging Project
Thousands of sections of dredge pipe have been delivered to a massive “pipe farm.”
Contractor and Army Corps representatives review dredging plans at mobilization site headquarters.
Actual dredging should begin within the next two weeks. While staff and material are being organized for the dredging operation, clean up crews will remove more dead trees and other debris from the river and placement sites.
Example of debris removal from Lake Houston before dredging. This shot actually shows a city-contracted crew working on the East Fork during July. Corps crews will be conducting similar work.
Difference Between City Dredging and Corp Dredging
(NOTE: THIS POST HAS BEEN UPDATED WITH THE FOLLOWING INFO SINCE THE ORIGINAL POST) What is the difference between the city debris removal and the debris removal that the corps is doing? I went back into the contract requirements. Division 2, Section 02 41 01.01 45 stipulates, “General debris consists of trees and other vegetation within limits of dredging in the river, under the West Lake, Houston Parkway bridge, and upland areas that are to be dredged or excavated. General debris may also include, but is not limited to, metal bands, pallets, pieces of broken cable, rope, concrete rubble, construction materials, broken piles, etc. and may be encountered in the same area as above.”
So I see three main differences. The Corps subcontractor will: 1) only be working within the area to be dredged, 2) remove other types of materials that the city did not, 3) Also be responsible for cleaning up the placement areas, which the city did not.
Section 1.3.2 of the same document stipulates how they are being paid. Basically, it’s by the ton, but they are also being compensated for the cost of equipment, labor and material. The government is inspecting the scales. The complete contract requirements and plans are posted on the Reports page of this web site under Sedimentation/Dredging/Army Corps.
Additional Info About Army Corps West Fork Dredging Project
Below are some videos posted by the Corps that explain how we got to this point and how the project will progress.
The first explains how the Corps conducted the site survey.
https://www.youtube.com/watch?v=xvQNwKOOmeA
The next shows an aerial tour of the project.
https://www.youtube.com/watch?v=Cu4-cwsdFNc
And the final one explains their value engineering process.
https://www.youtube.com/watch?v=2se5YdNRGdA
Posted by Bob Rehak on August 14, 2018
350 Days after Hurricane Harvey
Houston A Year After Harvey: Where We Are And Where We Need To Be
Jim Blackburn, JD, professor of environmental law at Rice and Phil Bedient, PhD., a professor of engineering also at Rice, have just released an important new study called Houston a Year After Harvey: Where We Are and Where We Need to Be . Because of the length, detail, intricate maps and charts, and file size, this is best viewed on something larger than a smartphone.
Written for the Average Adult
Three things immediately become apparent when reviewing this 55-page report. It’s wide ranging in scope. It’s an excellent work of scholarship. And it’s well written; the average adult should be able to understand all the key concepts without difficulty.
Houston A Year After Harvey: Three Major Sections
It’s an excellent summary of what happened during Harvey, how the community is responding, and what still needs to be done – major watershed by major watershed.
The Problems of Obsolete Flood Plain Maps
This paper is organized into three main sections. First, the issues of obsolete 100-year floodplain maps and increasing rainfall are discussed because they are key to fully understanding the current dilemma and shaping alternative concepts for long-term protection. Whether or not you believe in climate change, the case for revising flood maps is pretty compelling based on the math alone. We’ve had five so-called 500-year storms in the last 25 years. Are we just spectacularly unlucky? Or do we need to revisit the assumptions and underlying math?
USGS did this recently and designated Harvey a 42-year flood at the West Fork and Grand Parkway.
Any time you try to predict the frequency of rarely observed or unobserved events, such as 500-year storms, you venture way out on a limb. The data on which you base assumptions is thin. Worse, one of the fundamental precepts of extreme value analysis (EVA) is that nothing changes during the 500 years under analysis.
Good luck with that. Five hundred years ago, the U.S., Texas, Houston, developers, gasoline, F150s and sand mining didn’t even exist. As we get more data and update assumptions, flood maps are being redrawn. So are the guidelines which form the basis for different types of development. Instead of raising new homes two feet above the 100 year flood plain, officials are now talking about two feet above the 500-year flood plain.
Issues that Need to Be Addressed Watershed by Watershed
The second part of Houston A Year After Harvey is a geographic overview of the flood issues and potential responses to various watersheds across Harris County.
The discussion of the West Fork of the San Jacinto goes from pages 28-30. It starts with a discussion of sedimentation, where the sediment is coming from and why we need stronger regulation of sand mining.
In regard to sedimentation, the reports also discusses the need for dredging to restore the river’s carrying capacity.
Finally, in regard to the San Jacinto, the report discusses the need to change the operating philosophy for the dams on Lake Conroe and Lake Houston to enable pre-release as a strategy for flood mitigation. This has already happened, they note, with the approval of the TCEQ to temporarily lower the level of Lake Conroe during the peak of hurricane season.
Different Solution Sets for Different Flooding Issues
The third major portion of Houston A Year After Harvey discusses different flood management concepts for three zones of the Houston area that have different flooding issues.
The authors break the county up into three major zones, A, B and C. A stretches from Addicks/Barker to the Katy Prairie. B covers the central part of the county. And C covers coastal areas.
The discussion of Zone B (which includes the Lake Houston and San Jacinto River) includes explanations for many of the projects listed on the Harris County Flood Control District Flood Bond that we are now voting on. See pages 42 through 45.
But don’t stop there. There’s also a great description for how the Ike Dike could work in Zone C.
How All the Pieces of the Flood Bond Fit Together
All in all, Houston A Year After Harvey makes a great case for the flood bond, without ever really setting out to do that. It will help give you a better understanding for how our drainage problems affect the people around us and vice versa.
The entire report is posted on this web site with permission of Rice University’s Baker Institute for Public Policy and SSPEED Center. ©2018 James A. Baker III Institute for Public Policy of Rice University. It will be permanently stored in the Reports Section under the Hurricane Harvey tab for easy future access.
Posted on August 13, 2018 by Bob Rehak
349 Days Since Hurricane Harvey
TACA Now Claims Sand Mines Helped to Prevent Flooding Downstream
David Perkins, CEO of TACA (the Texas Aggregate and Concrete Association) now claims that sand mines helped to prevent flooding downstream. The claim appeared in the current issue of Mining Technology in an article titled “Did Sand Mining Exacerbate Flooding During Hurricane Harvey?”
Perkins is quoted as saying, “…what [these sand mines] actually do – in contrast to what people were stating – is that they stored quite a bit of that floodwater and helped to prevent additional flooding …”
He explained how. “… For example, one 60-acre pit that’s 100 feet deep holds 6,000 acre feet of water. We’ve got some great potential capacity for off-channel storage that we could incorporate into our mining activities.” [Emphasis added twice.]
Did Mines Really Help Prevent Downstream Flooding?
Did they prevent flooding or could they have the potential to do so? Perhaps, but only if they followed best management practices common in other states and countries. More on that later.
Let’s suspend disbelief for a moment and examine Mr. Perkins’ theory.
The difference between the top of the water and the top of the dikes is usually 10 to 20 feet at best. So let’s be generous to Mr. Perkins and assume 20. And let’s use the pit below as a test case. It’s 160 acres – about the size of Kingwood’s East End Park so people will have a reference.
Here’s what the same pit looks like from ground level.
How 8 Minutes was Calculated
The pit above is approximately 160 acres.
Did It Delay, Reduce, or Prevent Flooding?
So this pit really wouldn’t have done much by itself to prevent flooding. It delayed flooding on the West Fork for 8 minutes in a 4-day flood. It reduced flow by 3,200 acre feet. But it did little prevent flooding as Mr. Perkins claims. To put things into perspective, the total amount of flow going into Lake Houston would have filled up NRG stadium in 3.5 minutes (see page 7).
Contribution to Flood Reduction if You Put All Mines Together
However, if you consider all the pits on the West Fork together (20 square miles), they might have delayed flooding by 10 hours according to the same calculations. That’s starting to sound like a significant contribution. Barker and Addicks Reservoirs together store a total of 410,000 acre feet. West Fork sand mines occupy 12,800 acres. If every acre had 20 vertical feet of storage available, you would have 256,000 acre feet of storage. That might not stop Harvey but it could certainly help reduce flooding – especially in smaller floods.
Two Problems Need to Be Addressed with Perkins’ Theory
Mr. Perkins’ theory has two major flaws that would need to be addressed before it could be taken seriously by residents.
That would mean following best management practices common in other states and countries.
Ignoring Best Practices Contributes to Flooding
Regardless of storage POTENTIAL, if mines fail to follow best management practices, they are likely to do more harm than good.
In Texas, we locate mines in floodways. And dikes are so thin that they often fail. Case in point: the mine we are talking about. There, dikes have been breached repeatedly. The river has cut through the pit and carried sediment downstream. That sediment then helped clog the river and create floods, not prevent them.
Rather than trying to deny what happened and change the debate, TACA should acknowledge what happened and work with citizen groups and government to create new regulations that protect the public as well as themselves.
What Really Happened in West Fork Mines During Harvey
Here’s what it looked like. This series of photos shows West Fork sand mines during Harvey on 8/30/17, one day after the peak. The river was flowing at only one-third of its peak on this day, according to the San Jacinto River Authority.
West Fork Sand Mine complex inundated by Harvey. Two of the three stockpiles in this photo were decimated by the flood. Sediment from the pits was also picked up by currents within them and carried downstream. Mine used in illustration above is in center.
Following are several close ups that show water breaching dikes, entering the mine and eroding areas within it and then carrying sediment downstream. All images taken on 8/30/17, courtesy of Google Earth and NASA.
Floodwater broke dikes, captured the sand pit and flowed straight through it.
Rapids within the mine.
Force of floodwater washed out road INSIDE mine.
Floodwater rushing out of forest into sand mine. It then flowed through and over dikes on the opposite side.
Exit Point for Floodwaters in this Mine
This next image shows the floodwaters exiting the mine on the far side after they scooped up sediment.
Floodwaters exit mine during Harvey. Photo taken on 8/30/2017.
Harvey was not the only flood when this has happened. The Memorial Day flood in 2015 and the Tax Day Flood in 2016 also saw breaches of the dikes. Those floods were much smaller and still caused problems, underscoring the need to modify permitting, regulations and best practices.
Exit point when river captured mine during Memorial Day flood in 2015.
Exit point two months later, on 7/31/2015. Breach was still unprepared and mine was leaking sediment into river.
By March of 2016, the breach had been repaired, but you can also see how sand was building up against it.
Less than a year later, when the flood waters had subsided, we can see the growth and orientation of the sand bars within the mine on the upper left in this 2017 image. This indicates that current within the mines during river capture was forcing sediment out of the mines.
I fail to see how this particular sand mine can prevent flooding. These pictures tell a different story. If the operator and TACA supported best management practices common in other states and countries, they might be able to help prevent flooding. But until that happens, I’m going to call Mr. Perkins’ claim a perfect-world generalization that has real-world limitations and exceptions.
And until TACA and the mines acknowledge the role they have played in flooding, residents will have a hard time emotionally accepting their presence in the community.
As always, these are my opinions on a matter of public interest. They are protected by the First Amendment of the United States Constitution and the Anti-SLAPP statutes of the great State of Texas.
Posted by Bob Rehak on August 11, 2018
347 Days since Hurricane Harvey