On August 25, Harris County residents will vote on a historic flood bond proposal. Everyone asks, “Will the bond include projects that help this area?”
That of course, raises the question, “What does the Lake Houston Area need?”
We Must Address Root Causes of Flooding HERE
Several factors make flooding here different from other parts of the region. Since Harvey, I’ve corresponded almost daily with experts in geology, hydrology, sedimentation, meteorology, city planning, engineering, mining, and disaster relief. The goal: to identify root causes of flooding in THIS area. They fall into three main “buckets”:
Sedimentation. Sand and silt clog the San Jacinto everywhere. The Army Corps’ emergency dredging project will remove only part of the sand from a 2.1 mile stretch of the West Fork, and not even touch the East Fork. One of the largest blockages at the mouth of the West Fork will remain. And the Corps will only restore the areas it dredges to pre-Harvey conditions, not pre-1994 conditions.
Releases from the dam at Lake Conroe can increase the volume of water flowing between Humble and Kingwood by ONE-THIRD. Of the roughly 240,000 cubic feet per second flowing down the west fork, 80,000 cubic feet of water per second came from the Lake Conroe dam. Many Lake Houston area residents say the onset of flooding coincided with release from Lake Conroe.
We have a bottleneck at Lake Houston. In a flood, much more water converges on Lake Houston than Lake Conroe. At the peak of Harvey, Lake Houston took in 492,000 cubic feet per second whileLake Conroe took in only 130,000 CFS. Seven different watersheds converge on Lake Houston. Yet until water reaches the spillway of the dam, our floodgates have one-tenth the discharge capacity of Lake Conroe’s. This effectively eliminates pre-release as a mitigation strategy.
We Need Specific Solutions, Not Generic
True solutions to flooding in the Lake Houston area must address these unique challenges. Generic solutions, such as buyouts with bond money will help, but won’t affect many people. Pushing new development further away from rivers will help, but will not restore the carrying capacity of the San Jacinto, increase the discharge rate of the Lake Houston dam, or offset discharges from Lake Conroe.
We Need: Dredging, Detention, More Gates
The objective of the Lake Houston Area’s flood mitigation efforts should be, in my opinion and the opinion of many engineers, to restore our drainage systems to their original design capacity. Homes located outside of the 1% (100-year) risk area should not flood until we get a 1% flood. The same goes for the .02% level (500-year flood).
Experts generally focus on three categories of solutions that will help achieve those objectives: dredging, detention and greater discharge capacity for the dam, i.e., adding more gates. We need all three. No one solution will do the job by itself.
Additional DREDGING can remove sediment, restore carrying capacity, eliminate water backing up, and get us back to level of the original design assumptions.
Additional DETENTION on the West Fork will help offset discharges from the Lake Conroe dam, which affected the heavily populated area between Humble and Kingwood, where the worst and most damage took place.
Additional GATES on Lake Houston will help relieve the bottleneck created by the different discharge rates between Lake Conroe and Lake Houston.
Here’s a diagram that shows what we need in the flood bond, where we need it, and why.
Reduce flooding in the Lake Houston Area with additional dredging, detention and drainage.
Of the three types of projects, dredging is the easiest and fastest to implement. It can buy us time while we build additional dams and gates. That could take years.
More Explanation to Follow
I will elaborate on each of these in coming days.
Harris County Commissioners and executives from the Flood Control District will hold a meeting in Kingwood on July 10 to solicit input from the community on the flood bond.
Hopefully, this series of posts will help focus discussion on the things that will do the most good for the largest number of people at the lowest cost.
Mark Your Calendars for July 10
In the meantime, mark your calendars for July 10. The County wants your input. Get your friends and neighbors to do the same. If you want peace of mind, we need to restore our ditches, rivers, and drainage systems to their original design capacity.
The location of the bond meeting may change because of the expected turnout and need for parking. So check back often.
Posted June 26, 2018, by Bob Rehak, 14 days before the flood bond meeting and…
301 days since Hurricane Harvey.
00adminadmin2018-06-26 12:41:302018-06-26 20:28:59Lake Houston Area’s Most Pressing Needs for Flood Bond Referendum
Note: This is the first article in a series on sand mine best management practices. It focuses on insufficient natural buffers between the mines and the San Jacinto river. Subsequent posts will focus on land clearing, site reclamation practices, and more.
A comparison of sand mining actual and best management practices found that performance shortfalls in local mines exacerbate sedimentation in the San Jacinto River, contrary to assertions by the Texas Aggregate and Concrete Association (TACA) that sand mining has environmental benefits.
Proximity of mines to San Jacinto River in non-flood conditions.
TACA claims that when a river floods, the current is so weak that sand and sediment are deposited inside of mines. An analysis of satellite and aerial photos shows, though, that the current is strong enough to break dikes, destroy roads, re-route the river through mines, and carry sediment downstream.
TACA sounds eerily reminiscent of Richard Pryor when his wife caught him in bed with another woman. “Who you going to believe? Me or your lyin’ eyes?”
In at least one case, a broken dike has gone unrepaired for years while pollution continues to escape into the San Jacinto, the main source of water for Lake Houston and millions of people.
Dangers of Sand Mining
Numerous states and countries acknowledge the following risks of sand mining. Most impose regulations on the industry because sand and silt washed downstream from mines can:
“Sand and gravel mining operations can potentially cause off-site impacts to water quality if site planning and BMPs are not factored into every aspect of the mining operation.”
“…BMPs … should be utilized … to prevent pollutants from leaving the mining operation.”
“Siltation is considered the highest nonpoint source priority of concern in wetland areas and the second highest priority affecting lakes (1992 Report to Congress).”
“Mining related activities have been estimated to cause 7 percent of the nation’s nonpoint source impacts to lakes and 17 percent to coastal waters.”
Comparing Texas Practices to Other Areas’
Texas does not make it clear what the state’s best management practices (BMPs) for sand mines are. So how do sand mines along the San Jacinto measure up to other states’ and countries’ guidelines? Not well.
One focus of their BMPs is the use of buffer zones, setbacks and strips of vegetation to reduce erosion and control sedimentation. The minimum distance between mine and river in most cases is 100 feet. Some specify more.
Alaska, for instance, discourages mines from locating within 1000 feet of a public water source, i.e., the San Jacinto which feeds Lake Houston, the main drinking water source for millions of people. The minimum near other bodies of water in Alaska is 200 feet.
Malaysia specifies a 50 meter setback (164 feet) from all river channels.
Australia prohibits sand mining in sensitive areas altogether.
In Texas along the San Jacinto, miners often excavate to within 40-50 feet of rivers, and remove vegetation to build dirt roads on the remaining narrow strip between the mine and the river. These thin, sandy barriers provide little defense against floods. They have been repeatedly breached, as you will see below. The river often runs right through mines, carrying sand and sediment downstream.
Types of Barriers against Sedimentation
Louisiana mandates a minimum 100-foot buffer adjacent to perennial streams. The state recommends a dual defense against sedimentation: vegetation and structural measures. Their best practices guide states, “Vegetation is an inexpensive and effective way to protect soil from erosion. It also decreases erosion from flowing water by reducing its velocity. Roots hold soil and increase infiltration. Topsoil should be added where existing soils are not suitable for adequate vegetative growth.”
Vegetative controls include:
Maintaining buffer zones between mine and river
Sod stabilization techniques. Sodding can be more than 99 percent effective in reducing erosion.
Protection of trees involves preserving and protecting selected trees that exist on the site prior to development.
Temporary and permanent seeding
Structural controls include:
Diversion ridges, berms or channels of stabilized soil
Silt fences
Sediment basins with banks sloped at 2:1 or less
Dikes – Must be well compacted and vegetated, with an outlet pipe or coarse aggregate spillway
Riprap protection – at the outlet end of culverts or channels to reduce the depth, velocity and energy of water so that the flow will not erode the receiving stream.
Check dams – Small dams less than 2 feet high constructed across swales or drainage ditches to reduce flow velocity and erosion.
Aggregate stabilized site entrances – at least 50 feet long to reduce sediment tracked onto public roads. Tire washing may also be needed.
Good housekeeping practices for fuel, debris, sediment from unstabilized areas, etc.
Post-construction stormwater management measures
Retention ponds
Vegetated swales and natural depressions that filter sediments from runoff with side slopes of 4:1 or less.
A Visual Comparison
Note the images below. The first represents the ideal; it is taken from the Louisiana BMP guide. The rest are from the West Fork of the San Jacinto in the last three years.
Image of ideal stream bank from Louisiana Sand Mining Best Practices Guide. Note vegetation, grass, gradual slope and aquatic plants.
West Fork Sand Mine, 9/14/2018. During Harvey, 150,000 cubic feet per second came rushing down this narrow channel and flooded 20 square miles of exposed sand in more than a dozen different mines.
Consequences of NOT Following BMPs
The image above and the following images all come from a small area of investigation shown below.
2.1 miles from Northpark Drive and US59, and 3.1 miles upstream from the US59 bridge.
The following images demonstrate what happens when miners work too close to the river. Numbers on the first image correspond to close-ups that follow.
Inundation of sand mines during Harvey on 8/30/17. Numbers correspond to close-ups below. All photos courtesy of Google Earth.
1 – Rapids within sand mine.
2 – Water rushing into mine, creating turbulence.
3 – Water takes a shortcut across meander through mine.
4 – Washed out road INSIDE sand mine during Harvey.
5 -Sand bars within sand mine in conjunction with ruptured dikes prove sand was carried downstream. Photo taken on 10/28/2017 (after Harvey).
In a white paper circulated among Texas state legislators called The Societal and Environmental Benefits of Sand Mining. TACA insists, “When [water invades a sand mine during a flood], the velocity of the water slows significantly, losing its ability to keep sediments in suspension and the stream or river begins to deposit its sediment load. When flood waters back into an area where a sand and gravel pit is located, the pit becomes a sediment trap for the flood waters and their sediments.” This series of photos directly refute TACA’s claims.
Why do we allow sand mines to operate in areas that flood repeatedly and violently, so near the drinking water source for millions of people?
Un-repaired Dike Still Leaks Sediment after 3 Years
Are the mines following Best Management Practices? The dike on the right in the images below ruptured in 2015 and still has not been repaired. Note sediment streaming into the West Fork.
Dike ruptured during flood in 2015 (see image below). It continues to spew sediment into the river.
Geologists say that once a river “captures” a sand mine, it repeatedly tries to take that same route in subsequent floods. This is a direct consequence of mining too close to the river.
Cautionary Advice from India
Sustainable Sand Mining Management Guidelines from India state, “Floodplain Extraction should be set back from the Main Channel. In a dynamic alluvial system, it is not uncommon for meanders to migrate across a floodplain. In areas where sand and gravel occurs on floodplains or terraces, there is a potential for the river channel to migrate toward the pit. If the river erodes through the area left between the excavated pit and the river, there is a potential for “river capture,” a situation where the low-flow channel is diverted though the pit. In order to avoid river capture, excavation pits should be set back from the river to provide a buffer, and should be designed to withstand the 100-year flood… Adequate buffer widths and reduced pit slope gradients are preferred over engineered structures which require maintenance in perpetuity.”
Sand Miners Externalize Costs
Because these West Fork sand mines did not consider violent floods in their design and construction criteria, taxpayers downstream bear the cost of remediation. Dredging of the West Fork will cost tens of millions of dollars – for the initial 2.1 mile phase alone! That doesn’t even include recurring and unnecessarily high costs of water treatment because of turbidity.
Posted 6/24/18 by Bob Rehak
299 days since Hurricane Harvey
00adminadmin2018-06-23 20:01:152018-06-24 10:00:04Do Local Sand Mines Follow Best Management Practices?
A “mouth bar” is a sandbar that builds up at the mouth of a river where it meets a standing body of water, such as Lake Houston. The West Fork of the San Jacinto has a world-class whopper of a mouth bar.
How and Why Mouth Bars Form
A mouth bar forms when water in the river slows down as it spreads out in a standing body of water. The lower velocity of the river can no longer suspend particles of sediment. According to academic and petroleum geologists I talked to, this phenomenon exists in rivers everywhere. In fact, mouth bars are an essential element of delta formation.
Sequence of Events in Formation
As a mouth bar grows in height and emerges from the river, it backs water up and slows it down. This causes the river upstream of the mouth bar to gradually fill with sediment, ultimately choking the river and forcing it to seek a new path. At this point, the higher pressure created by the backwater forces the river to seek new channels. At this point, typically the river splits into two (bifurcates). This accounts for the branching structures found in most deltas.
That is exactly what’s happening where the West Fork of the San Jacinto meets Lake Houston as this series of time-lapse images shows. Note the growth of the mouth bar in areas highlighted in white below.
2011 image of the mouth bar where the West Fork of the San Jacinto meets Lake Houston. Note how bar has formed at tip of main channel.
By 2013, the mouth bar had taken on a triangular shape where it was starting to split the main flow of the river.
Image taken on the last day of 2016. The mouth bar grew considerably in the Tax Day and Memorial Day floods in 2015 and 2016, primarily by extending its length.
October 2017. During Hurricane Harvey, the mouth bar doubled in size. It definitely splits the flow of the river now.
On 9/14/17, the bar looked like this from a helicopter.
Approximately two-thirds of the homes damaged by flooding in the upper Lake Houston area were between this bar and where the U.S. Army Corps of Engineers will stop dredging.
Historical Context: A Lesson in Geomorphology
The growth of this mouth bar was predictable. Brown & Root said in 2000 that it would emerge exactly where it did. What will happen in the future if we don’t dredge it? That, too, is predictable. See this presentation by William Dupré, professor of geosciences at the University of Houston. Professor Dupré’s presentation, given at the Houston Geological Society April conference on flooding, contains excellent illustrations of how rivers migrate laterally over time.
Consequences of Not Dredging
A retired chief geologist for a leading oil company (who specialized in sedimentation) tells me that if this bar is not dredged, we could expect the following consequences. It will, he says:
Continue to grow in height, width and length.
Slow down and back up water behind it.
Force increased sedimentation upstream (including areas soon to be dredged)
Likely also increase the frequency and magnitude of overbank flooding upstream of the mouth bar
Jeopardize homes, bridges, pipelines and other infrastructure on both sides of the river as it branches.
Two Options for Dredging
The contract that the Army Corps of Engineers expects to sign with a dredging vendor does NOT currently include this bar in its scope. I wish it did for all the reasons listed above.
The proposed contract includes a clause that allows expansion of scope if both the Corps and Contractor agree on it. That would be the most cost efficient way to address this problem. Dredges will already be on the river. Millions of dollars of mobilization costs for second dredging project could be avoided and the issue could be addressed sooner.
However, if expanding the scope of the Corps project is not possible, I believe residents of the Lake Houston area should insist that the County covers it in the upcoming flood bond referendum.
Posted by Bob Rehak on 6/23/2018
298 Days since Hurricane Harvey
00adminadmin2018-06-23 09:33:092018-06-23 10:57:33The Case for Dredging the “Mouth Bar”
Lake Houston Area’s Most Pressing Needs for Flood Bond Referendum
On August 25, Harris County residents will vote on a historic flood bond proposal. Everyone asks, “Will the bond include projects that help this area?”
That of course, raises the question, “What does the Lake Houston Area need?”
We Must Address Root Causes of Flooding HERE
Several factors make flooding here different from other parts of the region. Since Harvey, I’ve corresponded almost daily with experts in geology, hydrology, sedimentation, meteorology, city planning, engineering, mining, and disaster relief. The goal: to identify root causes of flooding in THIS area. They fall into three main “buckets”:
We Need Specific Solutions, Not Generic
True solutions to flooding in the Lake Houston area must address these unique challenges. Generic solutions, such as buyouts with bond money will help, but won’t affect many people. Pushing new development further away from rivers will help, but will not restore the carrying capacity of the San Jacinto, increase the discharge rate of the Lake Houston dam, or offset discharges from Lake Conroe.
We Need: Dredging, Detention, More Gates
The objective of the Lake Houston Area’s flood mitigation efforts should be, in my opinion and the opinion of many engineers, to restore our drainage systems to their original design capacity. Homes located outside of the 1% (100-year) risk area should not flood until we get a 1% flood. The same goes for the .02% level (500-year flood).
Experts generally focus on three categories of solutions that will help achieve those objectives: dredging, detention and greater discharge capacity for the dam, i.e., adding more gates. We need all three. No one solution will do the job by itself.
Additional DREDGING can remove sediment, restore carrying capacity, eliminate water backing up, and get us back to level of the original design assumptions.
Additional DETENTION on the West Fork will help offset discharges from the Lake Conroe dam, which affected the heavily populated area between Humble and Kingwood, where the worst and most damage took place.
Additional GATES on Lake Houston will help relieve the bottleneck created by the different discharge rates between Lake Conroe and Lake Houston.
Here’s a diagram that shows what we need in the flood bond, where we need it, and why.
Reduce flooding in the Lake Houston Area with additional dredging, detention and drainage.
Of the three types of projects, dredging is the easiest and fastest to implement. It can buy us time while we build additional dams and gates. That could take years.
More Explanation to Follow
I will elaborate on each of these in coming days.
Hopefully, this series of posts will help focus discussion on the things that will do the most good for the largest number of people at the lowest cost.
Mark Your Calendars for July 10
In the meantime, mark your calendars for July 10. The County wants your input. Get your friends and neighbors to do the same. If you want peace of mind, we need to restore our ditches, rivers, and drainage systems to their original design capacity.
The location of the bond meeting may change because of the expected turnout and need for parking. So check back often.
Posted June 26, 2018, by Bob Rehak, 14 days before the flood bond meeting and…
301 days since Hurricane Harvey.
Do Local Sand Mines Follow Best Management Practices?
Note: This is the first article in a series on sand mine best management practices. It focuses on insufficient natural buffers between the mines and the San Jacinto river. Subsequent posts will focus on land clearing, site reclamation practices, and more.
A comparison of sand mining actual and best management practices found that performance shortfalls in local mines exacerbate sedimentation in the San Jacinto River, contrary to assertions by the Texas Aggregate and Concrete Association (TACA) that sand mining has environmental benefits.
Proximity of mines to San Jacinto River in non-flood conditions.
TACA claims that when a river floods, the current is so weak that sand and sediment are deposited inside of mines. An analysis of satellite and aerial photos shows, though, that the current is strong enough to break dikes, destroy roads, re-route the river through mines, and carry sediment downstream.
TACA sounds eerily reminiscent of Richard Pryor when his wife caught him in bed with another woman. “Who you going to believe? Me or your lyin’ eyes?”
In at least one case, a broken dike has gone unrepaired for years while pollution continues to escape into the San Jacinto, the main source of water for Lake Houston and millions of people.
Dangers of Sand Mining
Numerous states and countries acknowledge the following risks of sand mining. Most impose regulations on the industry because sand and silt washed downstream from mines can:
Louisiana: Leader in Communicating Best Practices
The Louisiana Best Management Practices Guide to sand mining is one of the most concise, candid and clearly written guides in the world. Government and industry developed it together. The refreshingly honest introduction states:
Comparing Texas Practices to Other Areas’
Texas does not make it clear what the state’s best management practices (BMPs) for sand mines are. So how do sand mines along the San Jacinto measure up to other states’ and countries’ guidelines? Not well.
One focus of their BMPs is the use of buffer zones, setbacks and strips of vegetation to reduce erosion and control sedimentation. The minimum distance between mine and river in most cases is 100 feet. Some specify more.
Types of Barriers against Sedimentation
Louisiana mandates a minimum 100-foot buffer adjacent to perennial streams. The state recommends a dual defense against sedimentation: vegetation and structural measures. Their best practices guide states, “Vegetation is an inexpensive and effective way to protect soil from erosion. It also decreases erosion from flowing water by reducing its velocity. Roots hold soil and increase infiltration. Topsoil should be added where existing soils are not suitable for adequate vegetative growth.”
Vegetative controls include:
Structural controls include:
A Visual Comparison
Note the images below. The first represents the ideal; it is taken from the Louisiana BMP guide. The rest are from the West Fork of the San Jacinto in the last three years.
Image of ideal stream bank from Louisiana Sand Mining Best Practices Guide. Note vegetation, grass, gradual slope and aquatic plants.
West Fork Sand Mine, 9/14/2018. During Harvey, 150,000 cubic feet per second came rushing down this narrow channel and flooded 20 square miles of exposed sand in more than a dozen different mines.
Consequences of NOT Following BMPs
The image above and the following images all come from a small area of investigation shown below.
2.1 miles from Northpark Drive and US59, and 3.1 miles upstream from the US59 bridge.
The following images demonstrate what happens when miners work too close to the river. Numbers on the first image correspond to close-ups that follow.
Inundation of sand mines during Harvey on 8/30/17. Numbers correspond to close-ups below. All photos courtesy of Google Earth.
1 – Rapids within sand mine.
2 – Water rushing into mine, creating turbulence.
3 – Water takes a shortcut across meander through mine.
4 – Washed out road INSIDE sand mine during Harvey.
5 -Sand bars within sand mine in conjunction with ruptured dikes prove sand was carried downstream. Photo taken on 10/28/2017 (after Harvey).
In a white paper circulated among Texas state legislators called The Societal and Environmental Benefits of Sand Mining. TACA insists, “When [water invades a sand mine during a flood], the velocity of the water slows significantly, losing its ability to keep sediments in suspension and the stream or river begins to deposit its sediment load. When flood waters back into an area where a sand and gravel pit is located, the pit becomes a sediment trap for the flood waters and their sediments.” This series of photos directly refute TACA’s claims.
Un-repaired Dike Still Leaks Sediment after 3 Years
Are the mines following Best Management Practices? The dike on the right in the images below ruptured in 2015 and still has not been repaired. Note sediment streaming into the West Fork.
Dike ruptured during flood in 2015 (see image below). It continues to spew sediment into the river.
Geologists say that once a river “captures” a sand mine, it repeatedly tries to take that same route in subsequent floods. This is a direct consequence of mining too close to the river.
Cautionary Advice from India
Sustainable Sand Mining Management Guidelines from India state, “Floodplain Extraction should be set back from the Main Channel. In a dynamic alluvial system, it is not uncommon for meanders to migrate across a floodplain. In areas where sand and gravel occurs on floodplains or terraces, there is a potential for the river channel to migrate toward the pit. If the river erodes through the area left between the excavated pit and the river, there is a potential for “river capture,” a situation where the low-flow channel is diverted though the pit. In order to avoid river capture, excavation pits should be set back from the river to provide a buffer, and should be designed to withstand the 100-year flood… Adequate buffer widths and reduced pit slope gradients are preferred over engineered structures which require maintenance in perpetuity.”
Sand Miners Externalize Costs
Because these West Fork sand mines did not consider violent floods in their design and construction criteria, taxpayers downstream bear the cost of remediation. Dredging of the West Fork will cost tens of millions of dollars – for the initial 2.1 mile phase alone! That doesn’t even include recurring and unnecessarily high costs of water treatment because of turbidity.
Posted 6/24/18 by Bob Rehak
299 days since Hurricane Harvey
The Case for Dredging the “Mouth Bar”
A “mouth bar” is a sandbar that builds up at the mouth of a river where it meets a standing body of water, such as Lake Houston. The West Fork of the San Jacinto has a world-class whopper of a mouth bar.
How and Why Mouth Bars Form
A mouth bar forms when water in the river slows down as it spreads out in a standing body of water. The lower velocity of the river can no longer suspend particles of sediment. According to academic and petroleum geologists I talked to, this phenomenon exists in rivers everywhere. In fact, mouth bars are an essential element of delta formation.
Sequence of Events in Formation
As a mouth bar grows in height and emerges from the river, it backs water up and slows it down. This causes the river upstream of the mouth bar to gradually fill with sediment, ultimately choking the river and forcing it to seek a new path. At this point, the higher pressure created by the backwater forces the river to seek new channels. At this point, typically the river splits into two (bifurcates). This accounts for the branching structures found in most deltas.
That is exactly what’s happening where the West Fork of the San Jacinto meets Lake Houston as this series of time-lapse images shows. Note the growth of the mouth bar in areas highlighted in white below.
2011 image of the mouth bar where the West Fork of the San Jacinto meets Lake Houston. Note how bar has formed at tip of main channel.
By 2013, the mouth bar had taken on a triangular shape where it was starting to split the main flow of the river.
Image taken on the last day of 2016. The mouth bar grew considerably in the Tax Day and Memorial Day floods in 2015 and 2016, primarily by extending its length.
October 2017. During Hurricane Harvey, the mouth bar doubled in size. It definitely splits the flow of the river now.
On 9/14/17, the bar looked like this from a helicopter.
Approximately two-thirds of the homes damaged by flooding in the upper Lake Houston area were between this bar and where the U.S. Army Corps of Engineers will stop dredging.
Historical Context: A Lesson in Geomorphology
The growth of this mouth bar was predictable. Brown & Root said in 2000 that it would emerge exactly where it did. What will happen in the future if we don’t dredge it? That, too, is predictable. See this presentation by William Dupré, professor of geosciences at the University of Houston. Professor Dupré’s presentation, given at the Houston Geological Society April conference on flooding, contains excellent illustrations of how rivers migrate laterally over time.
Consequences of Not Dredging
A retired chief geologist for a leading oil company (who specialized in sedimentation) tells me that if this bar is not dredged, we could expect the following consequences. It will, he says:
Two Options for Dredging
The contract that the Army Corps of Engineers expects to sign with a dredging vendor does NOT currently include this bar in its scope. I wish it did for all the reasons listed above.
The proposed contract includes a clause that allows expansion of scope if both the Corps and Contractor agree on it. That would be the most cost efficient way to address this problem. Dredges will already be on the river. Millions of dollars of mobilization costs for second dredging project could be avoided and the issue could be addressed sooner.
However, if expanding the scope of the Corps project is not possible, I believe residents of the Lake Houston area should insist that the County covers it in the upcoming flood bond referendum.
Posted by Bob Rehak on 6/23/2018
298 Days since Hurricane Harvey