Yesterday, I posted about how major storms transport the vast majority of the sediment that flushes down rivers. That’s a major reason to have wide buffers between mines and rivers, and to get the mines out of the floodway. One major event, as we have seen, can alter a river and people’s lives forever. However, in Texas we allow sand mining right up to the edge of the river, increasing the potential for erosion.
Scalping 20 Square Miles of Forest Increased Erosion Potential
We all know from science classes that when you remove ground cover, you increase the potential for erosion. That’s exactly what the sand mines upstream from the Humble/Kingwood area have done. They have removed about 20 square miles of ground cover to expose sand. And because virtually all of the mines are in the floodway, they effectively increase the riverbed width during floods by an average of 33X. Here’s the basis for the calculation.
Exposed Sand in Floodwater is 33X Wider than Natural Riverbed
Between I-45 and I-69 on the West Fork, a distance of 20 miles, we have approximately 20 square miles of sand mines. So we have one square mile of mines per mile.
If you lined all mines up, end to end, you would have a swath exactly one mile wide.
But the river is, on average, only .03 miles wide. Thus, mines widen the effective riverbed width by average of 33X.
By removing all the surface vegetation, miners also increased the potential for erosion during extreme storms, such as Harvey, by 33X.
To put a mile-wide riverbed in perspective, that’s twice as wide as the muddy Mississippi …in the Delta region.
Sediment Dams Increase Flood Levels
That helps explain how so much sand piled up virtually overnight during Harvey. The flood was wide enough to inundate the mines. Afterwards, a nearly continuous trail of sand along both shores of the West Fork led directly to the Humble/Kingwood area as the pictures in my gallery show. In many places, this trail was more than 5 feet deep. Here’s what it looked like onshore in River Grove Park.
Note height of sand in River Grove Park relative to parking sign in background.
Plus there was far more sand in the river after the flood than before.
If the river AND both shores were ALL higher after the storm than before, then it stands to reason that most of that sand had to come from somewhere other the river itself.
Looking at a satellite image, the barren sand mines dominate the landscape like no other feature in the watershed. The obvious conclusion is that much of the sand came from mines like this …
West Fork Mine Complex day after peak of Harvey when floodwaters were already receding. Exposed sand surface increased potential for erosion relative to river which snakes diagonally through photo. Image courtesy of Google Earth.
… and wound up in places like this.
Sand left behind by Hurricane Harvey on both flanks of the west fork of the San Jacinto River. Looking northeast toward Forest Cove where apartment buildings or townhomes were destroyed. Note sand in treetops in foreground.
A drainage ditch (center left) that empties the entire western third of Kingwood at River Grove Park was virtually closed off by a sandbar approximately 10 feet high and 1500 feet long. It was deposited during Harvey. An estimated 500+ homes above this point flooded.A six foot high dune not present before Harvey virtually blocks the West Fork just south of Kingwood Country Club.A giant sand dune has formed at the mouth of the west fork of the San Jacinto. It is not being addressed by the Army Corps dredging project but should be. Thousands of homes upstream from the blockage flooded during Harvey.
Huge Pre/Post Increases in Deposition Rates Since Sand Mining
In its final report on Hurricane Harvey, Harris County Flood Control District confirms the enormity of the deposition. It says, “Large amounts of debris and heavy sedimentation upwards of 4.0-8.0 ft in some locations have been noted especially along the West Fork of the San Jacinto River.” (See Page 7.) But how does this compare to the deposition rate before Harvey?
Sedimentation Rate Much Higher than Before Sand Mining
Large-scale sand mining on the West Fork began shortly after that and has grown ever since. On the East Fork, sand mining began in the early 2000s.
The Texas Water Development Board created the difference map below by comparing data collected in 2011 with data collected from March through June of 2018. Remember, three or four of those years were drought years when very little sediment came down river. Virtually all of what you see below happened during the last three years. We can also see from satellite photos that most of that happened during Harvey.
West Fork Difference Map. Red/orange/yellow/green areas represent decreases in sediment since last survey. Blue, violet and white represent increases.
Assuming we gained on average about 3 feet per acre, that means the City lost approximately 10,000 acre-feet of storage in this ONE SECTION of the lake in only three years.
Current Rate Estimated 22X Higher
That’s about an 11X increase per year compared to the Turner Collie & Braden study which measured the ENTIRE lake. However, we can also roughly adjust for the difference in lake and sample sizes shown above. Page 9 of the Brown & Root report in 2000 says that the area shown above collects a little less than half (42%) of the sediment flowing into the lake. So we can assume that 11X at least doubles to 22X. (Because there’s more in the bottom portion of the lake than the top.)
22X is less than 33X, but consistent with earlier observations when you consider that much of the sand was deposited on shores, as you saw in the River Grove photo.
Caused by Mining or Nature?
Some of this sand also came from urban runoff. And some undoubtedly came from other tributaries, such as Spring and Cypress Creeks, which have fewer mines. Some also came from the East Fork watershed, where there is a huge active sand mine on Caney Creek. Regardless, 131,000 cfs cut across that statistical mile-wide swath of sand on the West Fork during Harvey.
Analysis of satellite and aerial photos leads me to believe that the river carried millions of cubic yards of sand and sediment downstream from the mines, including their stockpiles. That sand, I believe, helped to create the blockages shown above, which contributed to flooding throughout the heavily populated Humble and Kingwood areas.
Let’s Get Sand Mines Out of the Floodway
Miners claim that the currents in Harvey were not strong enough to carry sand out of their mines. Several world-leading hydrologists that I have talked to claim the opposite. As one said, “Of course it could.”
That’s why we need to pass legislation moving mines back from the river. We can’t reduce natural sedimentation, but we can reduce man-made sedimentation by putting sand mines out of the reach of rushing floodwaters.
As always, these are my opinions on matters of public policy. They are protected by the First Amendment of the United States Constitution and the Anti-SLAPP statute of the Great State of Texas.
Posted by Bob Rehak on December 17, 2018
475 Days since Hurricane Harvey
https://i0.wp.com/reduceflooding.com/wp-content/uploads/2018/03/Harvey-SanJac_41.jpg?fit=2000%2C1333&ssl=113332000adminadmin2018-12-17 19:38:252018-12-17 19:38:33How Sand Mines Increased Erosion Potential by 33X During Harvey
“SESSION A: SEDIMENT SOURCES AND TRANSPORT PROCESSES” made months worth of arguments, complaints and frustrating meetings suddenly fall into sharp focus. I quickly realized our problem.
I can’t post the paper here for copyright reasons. So I will link to it and quote brief passages in a review. The author was Ronald J.Gibbs, Center for Colloidal Science, College of Marine Studies, University of Delaware.
His paper begins by looking at the largest rivers in the world and rank ordering them by their discharge (flow) rates. He then talks about factors that influence sedimentation, such as soil types, river gradient, and weather events.
Rare Weather Plays Mammoth Role in Sedimentation
In case after case, extreme weather played a hugely dominant role in sediment transport. For instance…
…in one storm on the Delaware River, a two day discharge represented three full years of average discharge.
An even more spectacular example: a storm struck the Eel River in California. “In a three day period, the Eel River carried more sediment past Scotia, California than it had during the previous seven years.”
“In ten days, the transport was equivalent to the previous ten average years.”
“To put this into perspective, the total suspended discharge for the Eel River was 168 million tons that year, which compares with the 184 million tons carried by the Mississippi River past St. Louis during the same year.” I had never even heard of the Eel River, so this caught my attention.
Difficulty of Measuring
The authors’ point: This tremendous variability, occurring over a period of many years, is exceedingly difficult to sample and to understand because it is normally very expensive to prepare for sampling these types of rare events. However, sudden events are extremely significant in terms of quantity of sediments discharged…”
A Storm Like Harvey
Another example: the Susquehanna, which flows south through eastern Pennsylvania before entering Maryland and Chesapeake Bay. Gibbs referenced another study that estimated sediment discharged in one week (June 22–28, 1972) during a major storm. “The Susquehanna River probably discharged greater than 50 x 10(6) metric tons of suspended sediment than had been discharged during the past three decades, and probably even during the past half century.”
50 million more tons of sediment in one week than during the previous fifty years!
Annual Patterns Follow Extremes, Too
Gibbs looked at both extremely rare events like this and typical annual patterns. He found that,
“During 1 percent of a year (3.6 days), most rivers discharge better than one-half to two-thirds of their sediments for that year.”
These observations illustrate how important rare events are in transporting sediment. Gibbs says, “They dominate deposition over many years and greatly affect dredging and shoaling activities.”
I knew that most sediment transport happened during floods. But I until I read this study, I did not understand how extreme the disparities between normal and flood transport were.
Implications for Regulators and Legislators
Suddenly, the tumblers clicked into place. I understood why the Brown & Root study quoted sediment transport figures for the West Fork, Spring Creek and Cypress Creek, and then told people to ignore them; they measured suspended solids when the streams were moving only at about 60 cfs, not 131,000 cfs as during Harvey.
Suddenly, I also understood how TACA, the TCEQ and state legislators could conclude that mining in floodways was OK. They look at the 99%, not the 1%. But the 1% is when all the damage occurs.
As a business person, I might have made the same mistake. Conventional wisdom dictates that you design systems for the 99%, and that you’ll go broke chasing that last 1%. Or more to the point, the last .2%.
Design for Disaster: The 1% Solution
Very few industries design for extreme events. In the airline business, the cost of a crash is unthinkable. Nuclear power plants simply cannot go out of control. Every pacemaker has to work. For almost everything else, 99% success gets you a nice Christmas bonus and a promotion. But when the cost of failure is a major portion of the nation’s fourth largest city…
As a legislator, you listen to the carefully crafted arguments of TACA and say to yourself, “This was a force majeure event, an act of God. We can’t ask them to design their mines for that. They’ll go broke!” And you never stop to think, “Yes, I can. No, they won’t. It’s simple. I ask them to move out of the floodway. It doesn’t cost them a dime out of pocket. They just don’t mine so close to the river.”
At least you don’t realize it’s that easy until the sediment sent downstream by Hurricane Harvey dams the river and contributes to wiping out 16,000 homes, 3,300 businesses, a college, a high school, a hospital, a fire station, entire subdivisions, and entire shopping centers. Repairs for all of the above also wiped out billions in equity, college funds and retirement savings.
We Need to Fix A Business Model that Destroys Growth
If that doesn’t move you, consider that it also slowed the growth of an area from 6% to 1%. That’s what happened in the Humble ISD right after voters approved a $575 million bond referendum.
Attention: governor, developers, aggregate producers, concrete manufacturers, legislators, mayors, city council members, county commissioners, chambers of commerce, do you really want to bet on a business model that destroys growth?
Sometimes, it makes more sense to think of the 1% solution than the 99%. This is one of those times. In fact, the 1% is the ONLY thing we should be focusing on as we consider legislation to fix the broken sand mining model. What good is building cheap roads if you drive residents to move out of state?
These are my opinions on matters of public policy and protected under First Amendment of the U.S. Constitution and the Anti-SLAPP statute of the Great State of Texas.
Posted by Bob Rehak on 12/16/2018
474 Days since Hurricane Harvey
https://i0.wp.com/reduceflooding.com/wp-content/uploads/2018/10/KWDriveAndForestGarden1.jpeg?fit=1200%2C1597&ssl=115971200adminadmin2018-12-16 21:49:302018-12-17 10:20:3399% Solutions to a 1% Problem Are No Solutions at All
When Great Lakes (Dredge #2) punched through the side bar at River Grove Park last week, I got a rare chance to take some close up pictures of men at work. Here’s what the “cutter basket” of a dredge looks like when it’s clean. Just looking at it, the teeth inspire fear. It looks like a nightmare out of a John Carpenter movie.
The rows of teeth stir up sand, and saw through roots and submerged deadwood. Pumps then suction the sand through the holes between the blades. Photo courtesy of Don Harbour.
Why Dredging Can Be So Slow
However, submerged plant material sometimes gets caught in the teeth and clogs the inlet. This slows the intake of sand. To restore the flow, the dredge operator calls for a service crew, lifts the cutter basket out of the water, and men remove the debris by hand. It was a real productivity show-stopper.
Before cleaning, roots and weeds clog the cutter basket. During cleaning, men manually remove debris, such as the weeds you see in the background, that get caught on teeth.Half hour later, after cleaning, the dredge finally lowers the cutter basket back into the water and resumes dredging. Note the pile of debris now in the boat.
For those who care to dig a little deeper into dredging, this web site explains how companies vary the shapes of cutter baskets to reduce the number of these time out situations.
There’s a real science to the way they design these things. The objective is to reduce the number of unwanted objects that make it into the pipe. If the pipe clogs, it could take much longer to fix.
Posted by Bob Rehak on December 15, 2018
473 Days after Hurricane Harvey
https://i0.wp.com/reduceflooding.com/wp-content/uploads/2018/12/Cutterhead.jpg?fit=856%2C914&ssl=1914856adminadmin2018-12-15 00:30:202018-12-15 11:17:17Picking the Teeth of a Dredge
How Sand Mines Increased Erosion Potential by 33X During Harvey
Yesterday, I posted about how major storms transport the vast majority of the sediment that flushes down rivers. That’s a major reason to have wide buffers between mines and rivers, and to get the mines out of the floodway. One major event, as we have seen, can alter a river and people’s lives forever. However, in Texas we allow sand mining right up to the edge of the river, increasing the potential for erosion.
Scalping 20 Square Miles of Forest Increased Erosion Potential
We all know from science classes that when you remove ground cover, you increase the potential for erosion. That’s exactly what the sand mines upstream from the Humble/Kingwood area have done. They have removed about 20 square miles of ground cover to expose sand. And because virtually all of the mines are in the floodway, they effectively increase the riverbed width during floods by an average of 33X. Here’s the basis for the calculation.
Exposed Sand in Floodwater is 33X Wider than Natural Riverbed
To put a mile-wide riverbed in perspective, that’s twice as wide as the muddy Mississippi … in the Delta region.
Sediment Dams Increase Flood Levels
That helps explain how so much sand piled up virtually overnight during Harvey. The flood was wide enough to inundate the mines. Afterwards, a nearly continuous trail of sand along both shores of the West Fork led directly to the Humble/Kingwood area as the pictures in my gallery show. In many places, this trail was more than 5 feet deep. Here’s what it looked like onshore in River Grove Park.
Plus there was far more sand in the river after the flood than before.
Looking at a satellite image, the barren sand mines dominate the landscape like no other feature in the watershed. The obvious conclusion is that much of the sand came from mines like this …
… and wound up in places like this.
Or places like those below, where it formed sediment dams, which the Army Corps says contributed to flooding.
Huge Pre/Post Increases in Deposition Rates Since Sand Mining
In its final report on Hurricane Harvey, Harris County Flood Control District confirms the enormity of the deposition. It says, “Large amounts of debris and heavy sedimentation upwards of 4.0-8.0 ft in some locations have been noted especially along the West Fork of the San Jacinto River.” (See Page 7.) But how does this compare to the deposition rate before Harvey?
Sedimentation Rate Much Higher than Before Sand Mining
In 1983, Turner Collie & Braden, an engineering consulting firm, estimated the loss of lake capacity due to sedimentation at 311 acre-feet per year. (See page 9.)
Large-scale sand mining on the West Fork began shortly after that and has grown ever since. On the East Fork, sand mining began in the early 2000s.
The Texas Water Development Board created the difference map below by comparing data collected in 2011 with data collected from March through June of 2018. Remember, three or four of those years were drought years when very little sediment came down river. Virtually all of what you see below happened during the last three years. We can also see from satellite photos that most of that happened during Harvey.
The map above shows we gained 1.0 to 5.5+ feet of sediment in most of the 3400 acre area between the mouth bar and FM1960.
Current Rate Estimated 22X Higher
That’s about an 11X increase per year compared to the Turner Collie & Braden study which measured the ENTIRE lake. However, we can also roughly adjust for the difference in lake and sample sizes shown above. Page 9 of the Brown & Root report in 2000 says that the area shown above collects a little less than half (42%) of the sediment flowing into the lake. So we can assume that 11X at least doubles to 22X. (Because there’s more in the bottom portion of the lake than the top.)
22X is less than 33X, but consistent with earlier observations when you consider that much of the sand was deposited on shores, as you saw in the River Grove photo.
Caused by Mining or Nature?
Some of this sand also came from urban runoff. And some undoubtedly came from other tributaries, such as Spring and Cypress Creeks, which have fewer mines. Some also came from the East Fork watershed, where there is a huge active sand mine on Caney Creek. Regardless, 131,000 cfs cut across that statistical mile-wide swath of sand on the West Fork during Harvey.
Analysis of satellite and aerial photos leads me to believe that the river carried millions of cubic yards of sand and sediment downstream from the mines, including their stockpiles. That sand, I believe, helped to create the blockages shown above, which contributed to flooding throughout the heavily populated Humble and Kingwood areas.
Let’s Get Sand Mines Out of the Floodway
Miners claim that the currents in Harvey were not strong enough to carry sand out of their mines. Several world-leading hydrologists that I have talked to claim the opposite. As one said, “Of course it could.”
That’s why we need to pass legislation moving mines back from the river. We can’t reduce natural sedimentation, but we can reduce man-made sedimentation by putting sand mines out of the reach of rushing floodwaters.
As always, these are my opinions on matters of public policy. They are protected by the First Amendment of the United States Constitution and the Anti-SLAPP statute of the Great State of Texas.
Posted by Bob Rehak on December 17, 2018
475 Days since Hurricane Harvey
99% Solutions to a 1% Problem Are No Solutions at All
Today, I read a scientific article that talked about 99% solutions to 1% problems. It hit me between the eyes with the force of a freight train. It was written 30 years before Hurricane Harvey for a 1987 symposium sponsored by the U.S. Navy called Sedimentation Control to Reduce Maintenance Dredging of Navigational Facilities in Estuaries.
“SESSION A: SEDIMENT SOURCES AND TRANSPORT PROCESSES” made months worth of arguments, complaints and frustrating meetings suddenly fall into sharp focus. I quickly realized our problem.
I can’t post the paper here for copyright reasons. So I will link to it and quote brief passages in a review. The author was Ronald J.Gibbs, Center for Colloidal Science, College of Marine Studies, University of Delaware.
His paper begins by looking at the largest rivers in the world and rank ordering them by their discharge (flow) rates. He then talks about factors that influence sedimentation, such as soil types, river gradient, and weather events.
Rare Weather Plays Mammoth Role in Sedimentation
In case after case, extreme weather played a hugely dominant role in sediment transport. For instance…
An even more spectacular example: a storm struck the Eel River in California. “In a three day period, the Eel River carried more sediment past Scotia, California than it had during the previous seven years.”
“To put this into perspective, the total suspended discharge for the Eel River was 168 million tons that year, which compares with the 184 million tons carried by the Mississippi River past St. Louis during the same year.” I had never even heard of the Eel River, so this caught my attention.
Difficulty of Measuring
The authors’ point: This tremendous variability, occurring over a period of many years, is exceedingly difficult to sample and to understand because it is normally very expensive to prepare for sampling these types of rare events. However, sudden events are extremely significant in terms of quantity of sediments discharged…”
A Storm Like Harvey
Another example: the Susquehanna, which flows south through eastern Pennsylvania before entering Maryland and Chesapeake Bay. Gibbs referenced another study that estimated sediment discharged in one week (June 22–28, 1972) during a major storm. “The Susquehanna River probably discharged greater than 50 x 10(6) metric tons of suspended sediment than had been discharged during the past three decades, and probably even during the past half century.”
Annual Patterns Follow Extremes, Too
Gibbs looked at both extremely rare events like this and typical annual patterns. He found that,
These observations illustrate how important rare events are in transporting sediment. Gibbs says, “They dominate deposition over many years and greatly affect dredging and shoaling activities.”
I knew that most sediment transport happened during floods. But I until I read this study, I did not understand how extreme the disparities between normal and flood transport were.
Implications for Regulators and Legislators
Suddenly, the tumblers clicked into place. I understood why the Brown & Root study quoted sediment transport figures for the West Fork, Spring Creek and Cypress Creek, and then told people to ignore them; they measured suspended solids when the streams were moving only at about 60 cfs, not 131,000 cfs as during Harvey.
As a business person, I might have made the same mistake. Conventional wisdom dictates that you design systems for the 99%, and that you’ll go broke chasing that last 1%. Or more to the point, the last .2%.
Design for Disaster: The 1% Solution
Very few industries design for extreme events. In the airline business, the cost of a crash is unthinkable. Nuclear power plants simply cannot go out of control. Every pacemaker has to work. For almost everything else, 99% success gets you a nice Christmas bonus and a promotion. But when the cost of failure is a major portion of the nation’s fourth largest city…
As a legislator, you listen to the carefully crafted arguments of TACA and say to yourself, “This was a force majeure event, an act of God. We can’t ask them to design their mines for that. They’ll go broke!” And you never stop to think, “Yes, I can. No, they won’t. It’s simple. I ask them to move out of the floodway. It doesn’t cost them a dime out of pocket. They just don’t mine so close to the river.”
At least you don’t realize it’s that easy until the sediment sent downstream by Hurricane Harvey dams the river and contributes to wiping out 16,000 homes, 3,300 businesses, a college, a high school, a hospital, a fire station, entire subdivisions, and entire shopping centers. Repairs for all of the above also wiped out billions in equity, college funds and retirement savings.
We Need to Fix A Business Model that Destroys Growth
If that doesn’t move you, consider that it also slowed the growth of an area from 6% to 1%. That’s what happened in the Humble ISD right after voters approved a $575 million bond referendum.
Sometimes, it makes more sense to think of the 1% solution than the 99%. This is one of those times. In fact, the 1% is the ONLY thing we should be focusing on as we consider legislation to fix the broken sand mining model. What good is building cheap roads if you drive residents to move out of state?
These are my opinions on matters of public policy and protected under First Amendment of the U.S. Constitution and the Anti-SLAPP statute of the Great State of Texas.
Posted by Bob Rehak on 12/16/2018
474 Days since Hurricane Harvey
Picking the Teeth of a Dredge
When Great Lakes (Dredge #2) punched through the side bar at River Grove Park last week, I got a rare chance to take some close up pictures of men at work. Here’s what the “cutter basket” of a dredge looks like when it’s clean. Just looking at it, the teeth inspire fear. It looks like a nightmare out of a John Carpenter movie.
The rows of teeth stir up sand, and saw through roots and submerged deadwood. Pumps then suction the sand through the holes between the blades. Photo courtesy of Don Harbour.
Why Dredging Can Be So Slow
However, submerged plant material sometimes gets caught in the teeth and clogs the inlet. This slows the intake of sand. To restore the flow, the dredge operator calls for a service crew, lifts the cutter basket out of the water, and men remove the debris by hand. It was a real productivity show-stopper.
For those who care to dig a little deeper into dredging, this web site explains how companies vary the shapes of cutter baskets to reduce the number of these time out situations.
There’s a real science to the way they design these things. The objective is to reduce the number of unwanted objects that make it into the pipe. If the pipe clogs, it could take much longer to fix.
Posted by Bob Rehak on December 15, 2018
473 Days after Hurricane Harvey