Sand Mining Best Management Practices: Vegetation

Sand mining best practices throughout the country and the world urge operators to leave vegetation in place until they are ready to mine an area. The reason: to reduce erosion. However, approximately 60 acres of the sand mine below on the East Fork of the San Jacinto where it meets Caney Creek and White Oak Creek was cleared but not mined – just in time for two 500-year floods.

Approximately 65 acres of this mine were cleared before two five-hundred year floods, contributing to downstream sedimentation in the East Fork, even though only about three acres of the area was mined.

Removing Vegetation Risks Sedimentation Downstream

The cleared area lies totally in the 100-year flood plain and was inundated. Satellite images of the area downstream from the cleared land show a sudden buildup of sand. While the sand did not all come from the cleared area, one wonders how much sedimentation could have been prevented by following best practices.

The following sequence of images shows the rapid removal of vegetation.

The white outlined area will be totally cleared before Harvey. On April 8, 2014, it was all dense forest. 

By March 3, 2016, most of the area was cleared.

By January 23, 2017, just before Harvey, the area was entirely cleared.

Risk from Flooding

This FEMA flood hazard map shows that the entire area lies within with 100-year flood plain (aqua) and adjacent to the floodway (cross-hatched area).

Before and After: Results

This image from 2014 shows the area in question when it was still forested. Note how little sand is in the river downstream from the mine.

Here’s the same view after vegetationwas cleared and the area was inundated by Harvey in 2017. Note all the sediment in the river downstream.

Much of the sand and sediment washed downstream is invisible to satellite photos because it’s under dense forest canopy. This area (downstream the sand mine being discussed) was once wetlands. A boardwalk through those wetlands had to be excavated from several feet of sand after Harvey.

Here’s what part of the same trail looked like before it was excavated. Approximately 30 acres of the park were blanketed with dunes up to 10 feet tall after Harvey. Every trail in the park required repairs. Total cost: approximately $200,000 to Kingwood residents.

A bird’s nest that was ten feet up in a tree is now knee high. Many of the trees along the Eagle Point trail in East End Park are buried under so much sand that they are dying. 

An Ounce of Prevention

It’s impossible to tell how much of the sand above resulted from the removal of vegetation?  Previous posts showed how the mines stockpile also eroded. The river itself contributed sediment. However, if the mine were not in the flood plain and if the miners had not removed so much vegetation so far in advance of mining, we wouldn’t be having this discussion.

So why do miners favor the floodplains and floodways? Why to they remove vegetation years before it will be mined? Is it all about the relentless pursuit of efficiency at the expense of safety?

Tomorrow, we will look at economics, taxation and how some well-intentioned laws passed in the late seventies to protect family farms helped fuel a boom in sand mining.

Posted September 24, 2018

391 Days since Hurricane Harvey

Opportunities to Speed Recovery

The things government does now to protect us from future flooding – and the speed with which it does them – will make the difference between long-term recovery and decay.

In many ways, we’ve made incredible progress since Harvey – the initial frenzy of volunteerism, the massive trash pickup, repairing homes, re-establishing businesses, rebuilding infrastructure, re-opening schools, organizing an emergency (albeit partial) dredging project, passing a $2.5 billion flood bond, and more. The amount of activity  speaks volumes about the character of the community. But recovery is far from complete.

The old HEB store still has not been leased to a new tenant.

Confidence determines whether people will rebuild. Without confidence, people are reluctant to invest. You can see lack of confidence in empty shops up and down West Lake Houston Parkway and in “for sale” signs in front of homes. People are saying, “I’m not going to risk this again.”

So what will give people confidence and speed recovery?

Expand Dredging

The Army Corps has started dredging a small portion of the West Fork – about 1.2 miles between Kings Lake Estates and River Grove Park. This will take until April or May of next year to complete. However, the biggest blockage in the river is NOT part of this project. The “mouth bar” where the river meets the lake will remain. Unless a second project to address that can be funded, bid and mobilized before the first is done, taxpayers will be forced to pay another $18 million in mobilization/demobilization fees – all over again.

First dredge on the San Jacinto is now working an area west of the West Lake Houston Parkway Bridge. Photo courtesy of Keith Jordan.

Even if the mouth bar is addressed, the rest of the West Fork, the East Fork and parts of Lake Houston will need to be dredged in order to clear channels through the upper Lake Houston area.

To prevent the current blockages from recurring and flooding us again, we should also develop a maintenance dredging program in perpetuity.

Reduce Sedimentation

Sedimentation comes from several sources: a) natural stream erosion, B) urbanization, and C) sand mining. With the exception of creating more upstream detention, we can’t do much to control A or B. We can, however, do something about the 20 square miles of sand mines in the floodways upstream from us.

FEMA defines floodways as the main channel of the river during a flood – where the water moves the fastest. With the exception of one sand mine between Lake Houston and I-45, part of every single sand mine lies in the floodway.

West Fork sand mines on 8/30/17, one day after the peak from from Harvey

Moving mines out of the floodway will require legislation that puts more distance between mines and rivers. As far as I can tell, Texas is the only state that does not require a minimum setback. We need greater setbacks because rivers migrate over time and capture pits during floods. This process is well understood and predictable.

We’ve seen several instances of ruptured mine dikes on the West Fork – some that have gone unprepared for years and increased the rate of sedimentation. This contributes to the sand and sediment clogging our rivers, the destruction of downstream properties, and dredging costs which are substantial.

Improve Ditch Maintenance

Harris County has agreed to take over ditch maintenance for the City of Houston. However, the City of Houston is still looking for deeds and easements that should have been transferred and recorded during annexation 22 years ago. This does NOT inspire confidence. Once the County receives permission to clean and clear the ditches, it can proceed. County flood control crews have been surveying in anticipation of receiving the documents. Money has also been freed up in the Flood Control budget with the passage of the flood bond.

Create More Upstream Detention

Holding water upstream during a flood lowers water levels downstream. The County has identified potential land to build another reservoir on far western Cypress Creek. That should help. But it’s a long term project and one of hundreds in the flood bond package.

We should also remember that more water came down the East Fork during the peak of Harvey than the West Fork. Additional upstream detention on both forks will help reduce the input during floods and raise confidence.

Add More Flood Gates to Lake Houston

In March, the Mayor promised 10 additional flood gates for Lake Houston so that we could shed water faster during a flood. This pr0ject has progressed somewhat since then, but slowly. The City has filed an application with FEMA which has received a high score from the Texas Division of Emergency Management (TDEM). TDEM ranks applications for FEMA funding coming from Texas.

Nonetheless, some officials have said that additional gates could take 10 years to actually build. Given the fact that we’ve had five so-called “500-year storms” in the last 25 years (1994, 2001, 2015, 2016, 2017), 10 years is too long. Many older residents won’t live long enough to see those gates. We can and must do better. We won World War II in less than half that time.

Plead for Speed

Delays in these mitigation projects will undermine confidence and recovery. Conversely, fast-tracking these projects will restore confidence and speed recovery.

We also need to streamline government disaster recovery. Let’s face it. It has taken more than a year since Hurricane Harvey to get one dredge on the San Jacinto River. We can do better. We need to do better.

As always, these are my opinions on matters of public policy 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 September 22, 2018

389 Days Since Hurricane Harvey

Dredging Starts, But Not Where Planned

The Army Corps of Engineers Emergency West Fork Dredging Project started yesterday, but not where planned. The Corps originally said it would start slightly east of West Lake Houston Parkway bridge and work its way back west to River Grove Park. Contract documents indicated the eastward limit of dredging would include the area south of Kings Harbor. However, today dredging started west of the bridge, between the Kingwood Country Club Forest Course and Kings Lake Estates. That puts the start of dredging approximately in the middle of the contracted area.

From US Army Corps’ contract plans for West Fork Dredging project. Note arrow pointing to power lines in C-102.

Photo courtesy of Keith Jordan, a Kings Lake Estates resident, shows first dredge set up behind row of trees on West Fork. Note high tension power lines seen in the right of photo as a reference to the map above.

Jordan said, “Literally watching constant dredging occurring about 200 yards in front of my boat house in the river. Motors seem to be running 24/7 with lights on boats at night.”  He later sent me this image.

Photo Courtesy of Keith Jordan. 

Approximate starting point of dredging. Satellite image courtesy of Google Earth.

When asked about noise from the operation, Jordan replied, “Just hear a steady hum from inside the house. Nothing bad.”

I asked about the change in plans because Kings Harbor was one of the worst flooded areas in Kingwood. One hundred percent of the businesses were destroyed along with three apartment complexes. This is also the area were Ben’s Branch empties into the river.

The Corps has not yet explained the reason for the change in plans. They did, however, send these additional shots of the dredge in operation.

First dredge in operation on location in the middle of the contracted area.

First dredge at work near Kings Lake Estates. There appears to be a mechanical dredge working in front of the hydraulic dredge.

The dredge weighs approximately 27 tons and will be in the river 24 hours per day until early May of 2019 according to the Corps.

Over 4.5 miles of high density polyethylene pipeline measuring 24 inches in diameter is in position and will help move over 1.8 million cubic years of sediment and debris.

Corps officials are asking recreational boaters to stay clear of the dredge and be aware of debris removal pipelines and booster pumps within the river.

Posted by Bob Rehak on 9/20/18

388 Days since Hurricane Harvey

 

 

 

 

 

First Dredge Moves Down River

Ever since Hurricane Harvey departed the Houston region more than a year ago, anxious residents have waited for this day. Today dredges begin removing massive amounts of sediment blocking the West Fork of the San Jacinto River. The Army Corps conducted a survey that confirmed the sediment contributed to flooding. But it has taken virtually six months to bid the project, award the job, and mobilize.

The first dredge has left it’s dock at the command site for the Emergency West Fork Dredging Project. Photo courtesy of Lake Houston Area Chamber of Commerce.

This morning, the first dredge left its dock.

As late as yesterday afternoon, workers were busy preparing it.

Final prep on first dredge happened on Tuesday, September 18.

Cranes loaded final supplies onto dredges at the US Army Corps of Engineers Command Site on September 18, 2018 for the Emergency West Fork Dredging Project.

Overcoming Delays

In the last few weeks, the Corps experienced several delays. First a key part for the first dredge had to be remanufactured and shipped to the job site. Then heavy storms swarmed the Houston area last week. Because the cranes above act like lightening rods, every time thunder was heard, work had to stop until the threat passed.

Finally, as other equipment such as dredge pipe and booster pumps were moved down the river into position, it became apparent that additional sedimentation had clogged the river since the Corps did its initial survey. That meant that sediment had to be removed before the dredges could get into position to start dredging.

Here are two pictures that show the depth of the pontoons on the barge and one of the areas it must move through.

Note the depth of the pontoons on the barge; image taken several weeks ago when dredge was being assembled..

It must move through water as little as 18 inches deep to get to its starting position.

A giant sandbar almost completely blocks the west fork of the San Jacinto River just downstream from River Grove Park.

Clearing the Way

The Corps stated Monday that mechanical dredges were scooping out a channel for the hydraulic dredges and on Tuesday, this scoop was seen between River Grove and the blockage above.

Clearing the way for the hydraulic dredges

Starting at West Lake Houston Parkway and Moving Back Upstream to River Grove

According to the Corps, dredging will start in the Kings Harbor area, slightly east of the West Lake Houston Parkway Bridge. Work will then progress upriver toward River Grove Park in Kingwood, the end of this particular project.

Plans for Subsequent Phases Still Uncertain

No one has yet announced plans to dredge the mouth bar, the East Fork or to perform maintenance dredging after all of the major blockages have been removed.

For those who wonder how this dredging will work, the dredges stir up sediment then suction it into pipelines that are miles long. Booster pumps stationed at regular intervals keep the slurry moving through the pipes back upstream to old sand pits where it will be stored.

How Dredging Works

This picture shows the business end of the second dredge.

This object will be lowered into the water and rotate to stir up sediment which will then be suctioned into pipelines that carry the slurry back to placement areas.

Dredge pipeline is already in place.

Periodic booster pumps will keep slurry moving upriver to disposal areas.

Safety Warning

The U.S. Army Corps of Engineers requests recreational boaters to stay a safe distance from dredging operations. This equipment weighs hundreds of tons and cannot maneuver as quickly as recreational boaters. Don’t expect them to get out of your way. The safest thing to do is to stay out of this reach of the river until dredging has completed.

Posted by Bob Rehak on 9/19/18

386 Days since Hurricane Harvey

 

Report on September Meeting of Lake Houston Area Grassroots Flood Prevention Initiative

Matt Zeve, Bill Fowler and I each made presentations at the Lake Houston Area Grassroots Flood Prevention initiative this evening.

Zeve Addresses Flood Bond and Flood Map Updates

Zeve, Director of Operations for Harris County Flood Control District spoke about the recently approved $2.5 billion Harris County Flood Bond and updates to flood maps. He indicated that timetables for projects should be completed within the next several weeks. He also indicated that the county has already approved drainage work in Huffman and fielded numerous questions from the audience about Taylor Gully, Ben’s Branch, upstream detention and more. Zeve expects flood maps to be updated in 2021 and stated that mitigation efforts could affect those, but that homeowners will have a chance to appeal them.

Rehak Presents Updates on Dredging, The Mouth Bar and Sand Mining

Bob Rehak updated residents on .Dredging, The Mouth Bar and Sand Mining. Dredging, he says, officially started today though not in the way that some expected. The first of two dredges launched today, a 270-ton diesel powered dredge. The launch had been delayed by a key part that had to be remanufactured and reshipped, then inclement weather. The tall construction cranes had to shut down every time lightning was heard in the area because they act like lightning rods. When the dredge finally started making it’s way downriver today, a mechanical dredge had to clear the way. The river was 18 inches deep in places but the dredge draws 3.5 feet of water. That’s how bad the sedimentation was; we needed a dredge for the dredge.

Dredging will take place to the left of the white line, but not to the right. Chimichurri’s in Kings Harbor is the dividing line. Those thousands of numbers on the image represent survey points by the Army Corps Average depth around the mouth bar is 1-3 feet. Max depth is 5 feet in some cross sections. Water will actually have to flow uphill about 40 feet to get past the mouth bar.

Dredging will start near Chimichurri’s just east of West Lake Houston Parkway. The Corps and Great Lakes will then work their way back toward River Grove Park. They expect to finish dredging by April 1, next year. Demobilization could take until early May.

Rehak also addressed the issue of the mouth bar and updated residents on political efforts by City, County, State and Federal officials to jumpstart the next phase of dredging before this one ends so that $18 million in mobilization and demobilization fees do not have to be duplicated for a second job. No plans have gelled yet, but Houston City Council Member Dave Martin may have an announcement to make at his Town Hall Meeting on October 9.

The final part of Rehak’s presentation addressed efforts to reduce sedimentation at its source to reduce the cost of dredging over the long run. Potential solutions include upstream detention, sand traps, and legislation or regulation that changes the way sand mines operate. Rehak specifically mentioned that moving sand mines out of the floodway would solve a host of problems.

Grassroots Co-Chair Clarifies Lake-Lowering Policies, Floodgate Possibilities, and Need for Flood Insurance

Bill Fowler, co-chair of the Lake Houston Area Grassroots Flood Prevention Initiative, opened the meeting by updating the community on policies to coordinate the lowering of Lake Conroe and Lake Houston to provide residents with extra protection from flooding when severe weather is expected. Fowler also gave an update on additional flood gates for Lake Houston. Then he discussed flood insurance and the related issue of redrawing flood plain maps which Harvey made obsolete. Copies of Fowler’s presentations can be found here.

Zeve did not work from a presentation. His remarks were supported by material from the Harris County Flood Control District website. He did, however, specifically urge residents to review the ever expanding Kingwood section of the site.

Diverse Audience of Approximately 200

Approximately 200 residents attended the meeting. Surprisingly, about a third of those did not flood during Harvey. The large turnout by non-flooded residents may have had to do with the flood insurance theme. Fowler emphasized that everyone needs flood insurance;

45 percent of the people who flooded in Harvey were outside of the 500-year flood plain and 64% of those did not have flood insurance.

Thanks to Volunteers

Many thanks to Dianne Lansden, also a co-chair for the Lake Houston Area Grassroots Flood Prevention Initiative for coordinating the meeting; Fran Barrack for refreshments and Bill McCabe for sign ins.

Posted by Bob Rehak on September 18, 2018

385 Days since Hurricane Harvey

Reminder: Monday Night Meeting of Grassroots Flood Prevention Initiative

The next meeting of the Lake Houston Area Grassroots Flood Prevention initiative will be Monday night, 6:30pm, at the Kingwood Community Center.

Matt Zeve, Deputy Executive Director for the Harris County Flood Control District, will discuss Lake Houston area projects approved in the recent County Flood Bond. Zeve will also address planned updates to Flood Plain Maps. The new maps could lead to increases in flood insurance rates and affect your home’s market value.

Meeting Specifics

  • Date: September 17, 2018
  • Time: 6:30 – 8:30
  • Place: Kingwood Community Center
  • Address: 4102 Rustic Woods, Kingwood

Matt Zeve. Director of Operations for Harris County Flood Control District

About Matt Zeve

Zeve is the Deputy Executive Director for the Harris County Flood Control District. He will be one of the people primarily responsible for planning and implementing the projects covered by the recently approved $2.5 billion Flood Bond program..

His work will affect 4.5 million people in Harris County, including the City of Houston.  The District has jurisdiction over the primary stormwater facilities in the county, which consist of about 1,500 channels, totaling 2,500 miles in length, as well as more than 60 regional stormwater detention basins and a 2.5-square mile wetlands mitigation bank.

After graduating from Texas A&M University with Bachelor’s and Master’s Degree in Civil Engineering, Zeve successfully practiced engineering as a consultant in the private sector before joining the Harris County Flood Control District in November, 2015. He has spent his entire professional career working on drainage projects primarily in the Houston Metropolitan area.

Updates on Other Flood Issues

Additionally, Grass Roots leaders will update the community on other issues affecting the potential for flooding in the Lake Houston Area, such as additional flood gates for Lake Houston, dredging, sand mines, lowering of Lakes Conroe and Houston, and more.

If you have specific questions or concerns, please email them ahead of time so the group can prepare to address them. Send suggestions to: Bill Fowler, co-chair of the Grass Roots Initiative at txwil43@yahoo.com.

Spread the Word

Please forward this page t0 everyone you know in our area.  Flood prevention impacts the peace of mind and economic well-being of everyone.

 

Posted September 16, 2018 by Bob Rehak

383 Days since Hurricane Harvey

 

 

First Dredge Moving Into Starting Position Sunday

All of the equipment for dredging the West Fork is now reportedly in the river and the first dredge should move to it’s starting position on Sunday.

Keith Jordan, a Kingwood geologist, flood-mitigation activist, and avid boater, sent me pictures today taken from the West Fork. They show dredging prep work by the U.S. Army Corps of Engineers and Great Lakes Dredge and Dock. It appears, according to Keith, that they have now loaded all of their dredging equipment into the San Jacinto River and are ready to start actual dredging Sunday or Monday.

I know this must be a sweet moment for Keith. He was one of the first in Kingwood to raise the alarm about sediment in the river. He authored one of the early Post-Harvey presentations on sedimentation issues called “Dig It.” And he testified before the Texas House of Representatives committee looking into the causes of flooding during Harvey.

Keith generously agreed to share his images with the Lake Houston community. I’m not sure what each of these shows, but together they show a lot of hustle and heavy equipment.

Tender boat pushing pontoon with mechanical debris removal equipment

One of two dredges being made ready.

One of two dredges making ready

Dredge pipe on West Fork, part of USACE Emergency Dredging Project. The Corps and its vendor, Great Lakes Dredge and Dock, have welded hundreds of 40-foot sections into 1000 foot strings that will convey dredged material back to the placement sites.

Stay tuned. More news to follow. The first dredge will be moved into position Sunday, weather permitting, with actual dredging operations beginning on Monday. The starting point: West Lake Houston Parkway, near Chimichurri’s,

They will then move west, upstream, to River Grove Park, which is the westerly limit of dredging.

The Corps’ objective is to restore the West Fork’s carrying capacity to pre-Harvey conditions by opening up the channel. The project should last through next April.

They intend to remove 1.8 million cubic yards of sand and sediment, more than enough to fill up the Astrodome.

Posted by Bob Rehak (and Keith Jordan) on September 15, 2018

282 Days Since Hurricane Harvey

 

 

 

 

 

 

Another Storm Brewing: The Groundwater Debate and How It Relates to Flood Risk

Groundwater relates to flooding? Yes. Here’s how. And here’s why you should care, especially now.

In November, Montgomery County voters will elect board members to the Lone Star Groundwater Conservation District who may advocate using more groundwater, a move that some believe could give residents cheaper water in the short run, but which could also cause subsidence, contribute to flooding, create shortages, raise costs and limit growth in the long run.

Unequal Groundwater Withdrawals, Unequal Subsidence

Subsidence is scientifically well documented and understood. Removing groundwater from clay causes the clay to compress. When that happens, you sink. And once clay is compressed, it stays compressed forever – even when rehydrated.

Yet some Montgomery County voters are advocating removing more groundwater because, at this moment, it’s cheaper than surface water. They are betting their future and their neighbors’ futures on it.

Subsidence can contribute to flooding because not everybody subsides equally. While Kingwood only subsided two feet in the last century, one part of Baytown subsided so much that it became uninhabitable in about half that time.

In 1944, the area that would become Brownwood in Baytown was starting to show signs of development.

By 1978, Brownwood was well developed…and sinking fast.

Today, the area floods so much that it is uninhabitable. All the homes are gone. Brownwood has been turned into a park.

The “Pump-Now, Let-Somebody-Else-Pay-Later” Mentality

Subsidence generally happens so slowly that some people claim it’s not a problem. Especially those on higher ground. They want to continue to pump water from their wells because they perceive it to be cheaper than surface water. It can be…at least in the short run..until wells run low or dry. Then pumping costs increase…often along with salinity…and the people who depend on the well are out of water and out of luck.

Gulf Coast Aquifers: Source Harris-Galveston Subsidence District. Much of the water in Montgomery County used for human consumption is pumped from the Jasper aquifer.

Depleting at More Than 500X the Recharge Rate

Still, some people say, “I’ll worry about that when it happens.” Problem is:

The rate of depletion will exceed the rate of recharge by more than 500X.

More Expensive in Long Run

Now consider this. As pressure in an aquifer decreases, the cost of bringing water to the surface increases dramatically, sometimes to the point where recovery is no longer economical, i.e., competitive with surface water. It’s much like the oil industry. As a rule of thumb, half the oil in reservoirs is left in the ground because it’s too expensive to recover.

For all these reasons, most counties in the region are trying to switch people to surface water. Their groundwater withdrawals have either declined or stayed the same.

Counties surrounding Montgomery have either decreased groundwater pumping or kept it constant.

Meanwhile, Montgomery County’s groundwater withdrawals have soared.

Montgomery County groundwater pumping, however, has generally increased in the last three decades.

A report by LBG Guyton Associates to the Lone Star Groundwater Conservation District showed that the largest increase in pumping since 2000 has occurred in Montgomery County. Pumping in surrounding counties has generally decreased since 2000.

Montgomery County Growth

The surge in Montgomery County groundwater usage is largely because Montgomery County has grown so quickly. With the exception of Fort Bend County, Montgomery County is growing faster than any county in the region on a percentage basis.

Houston Region growth last year by county. In percentage terms, Montgomery County trailed only Fort Bend County. 

So Why Worry NOW?

Water resources take so long to develop that they need to be planned 50 years into the future. The Houston region’s population tripled in the last 50 years.

If Montgomery County expects to grow that fast in the next 50, where will the water come from to support that growth? Especially if voters undermine the financial viability of the half-billion dollar surface-water treatment plant – that they just built – by shifting to groundwater!

Proponents of unlimited groundwater pumping in Montgomery County will ELECT directors of the Lone Star Groundwater Conservation District for the first time in November.

If people vote for candidates who advocate use of “cheaper” groundwater in the short term, they will also be voting for subsidence and policies that limit long-term growth. Without question, they will be betting their future on a rapidly depleting water source.

If that’s the will of the people, so be it. I just hope they don’t set a precedent that residents in neighboring counties follow. If so, we could all be sunk.

Red contours show subsidence in the last century. Blue contours show how much subsidence has increased in the first sixteen years of this century. Note the widening gap between red and blue at the top of the frame. It shows that subsidence in Montgomery and northern Harris Counties is increasing at an increasing rate. Parts of Harris County have subsided 10 feet! Source: Harris-Galveston Subsidence District.

Posted 9/14/2018 by Bob Rehak

382 Days since Hurricane Harvey

Note: Because this is such an important issue, I have created a new tab titled Subsidence on the Reports page. 

Dredging, Tropic, Lake, Ditch, and Retail Updates: Sometimes Progress is Measured in Inches

Updates on several subjects.

This afternoon, the U.S. Army Corps of Engineers issued a two-sentence press release about the start of their emergency West Fork dredging project.

Two-Sentence Dredging Update

It simply said, “USACE contractors are prepared to begin moving the first dredge on Sunday afternoon with operations possibly beginning Monday. If weather conditions pose threats to operational safety, dredging along West Lake Houston Parkway will begin when conditions improve.”

Tropical Development Complicates Dredging

Safety issues related to a potential tropical rain event now have the Corps concerned about safety. Note that orange X in the oval below that’s aimed toward the Texas coast..

Low Pressure System in Gulf has 50% Chance of Formation for up to 5 days.

Latest Tropical Updates for Gulf

As of 3PM Thursday, the National Hurricane Center (NHC) said about it, “A weak low pressure center has formed a couple of hundred miles east-southeast of Brownsville, Texas. In addition, showers and thunderstorms in association with this system have become more numerous today. While upper-level winds are generally conducive for development of a tropical depression, the system only has about a day before it reaches the western Gulf coast. An Air Force Reserve Hurricane Hunter aircraft is currently en route to investigate the low.”

Regardless of development, heavy rainfall and gusty winds are expected across portions of northeastern Mexico and Texas on Friday and Saturday.

Monitor the progress of this system, and refer to local weather forecasts.

Lakes Already Lowered in Advance of Rainmaker

In preparation for the storm, Lake Conroe has already been lowered to its seasonally adjusted target of 199 mean feet above sea level.

Level of Lake Houston has also been lowered. 

Lowering the two lakes gives us an additional buffer against flooding, but still, a rain-swollen river is no place for a 270 ton dredge tethered to hundreds of thousands of pounds of dredging pipe.

Updates on Ben’s Branch

Let’s just pray we don’t get so much rain that the ditches back up. When last we talked about ditches, the City had mistakenly sent the wrong easements to the county, so  that the county could  maintain Kingwood ditches. The City finally regrouped on the 11th. On the 12th, the City contacted Kingwood Association Management’s Ethel McCormick. McCormick is working to put the City together with the Bear Branch Trail Association and the Kings Crossing Association re: easements. More news on that when there’s news to share.

County Begins Surveying Ben’s Branch

In the meantime, Harris County is wasting no time. In expectation of the easements, they were already out surveying the ditches to determine how much silt and debris needed to be removed.

Harris County Surveying Truck near Ben’s Branch

Just east of West Lake Houston Parkway, a Harris County Flood Control Surveying Crew was seen this week trying to calculate the debris that needs to be removed from Ben’s Branch.=

Harris County Surveying Crew in Ben’s Branch just west of West Lake Houston Parkway. Crews are trying to estimate how much silt needs to be removed to restore the carrying capacity of the ditch. Note the surveyor in the far background on the island. 

Blockages like those above created during Harvey contributed to flooding in Town Center and Kings Crossing. Note the proximity of Ben’s Branch to the back of the old HEB shopping center on the northwest corner of Kingwood Drive and West Lake Houston Parkway.

I asked Matt Zeve, Director of Operations for Harris County Flood Control whether they planned to use the silt from Ben’s Branch to increase the height of the levies or whether they planned to remove it. The answer: remove it.

Work on Ben’s Branch cannot begin too soon. Uncertainty concerning this important waterway restrains the retail recovery throughout the central part of Kingwood.

The old HEB store still has not been leased to a new tenant. 

Without a lead tenant in the old HEB space, leasing the smaller stores in this center is a long shot, especially when the flood risk has not yet been reduced.

Many prospective tenants are waiting on signs from the City and County that flood remediation is about to begin. The 20,000 sf Kelsey Seybold Clinic has also been vacant since Harvey and has a For Lease sign in the window.

Other high visibility retail and rental spaces also remain vacant, i.e., the Chase Bank on Kingwood Drive and West Lake Houston Parkway, the new Memorial Hermann Health Care Facility, several apartment communities, and much of King’s Harbor.

Plea for Progress to Government

It will take more than deals to lure retailers and residents back to these locations; it will also take genuine progress in flood remediation – much faster progress than we have seen in the year since Harvey. People need confidence that their investments in buildout, inventory, and equipment will not be taken in the next flood. We spent a year talking about remediation; let’s get started.

Posted 9/13/2018 by Bob Rehak

380 Days since Hurricane Harvey

Flooding and Floodplains in the Houston Area: Past, Present, and Future

On August 24th, Dr. William R. Dupré , Professor Emeritus of Earth & Atmospheric Sciences from the University of Houston, gave a presentation at the Kingwood Community Center sponsored by the Houston Geological Society. The presentation is titled Flooding and Floodplains in the Houston Area: Past, Present, and Future. Professor Dupre’ has given ReduceFlooding.com permission to post his presentation. It consists of two parts. Together, they will help you understand how and why floodplains change over time.

Urbanization is just one of many factors cited by Dr. Dupré that increase flooding.

The Basics of Flooding, Floodplains and Measurement

In Part 1, Dupré focuses on the basics of flooding, flood plains and measurement.  He begins by explaining:

  • The difference between drainage basins, networks and watersheds
  • How stream gages work
  • How and where to find flood data (USGS, SJRA, Harris County Flood Warning System)
  • How to compare hydrographs from different locations and assess your risk of flooding
  • The difference between annual recurrence intervals and annual exceedance probabilities
  • How to understand flood maps
  • Assumptions behind flood plain calculations
  • Different types of flooding (overbook, ponding, sheet flow, etc.)

At the end of Part 1, Dupré shows how some of these concepts apply to different watersheds within Harris County and discusses how flooding dangers differ in various parts of the County.

How and Why Floodplains Change Over Time

In Part 2, Dupré goes into greater detail about how floodplains change over time.  The four main reasons include:

  • More data and a longer record
  • Changing land use, (i.e., urbanization, prairie restoration, etc.)
  • Structural changes (dams, levees, channelization and detention/retention basins)
  • Changing climate

Part 2 concludes with a discussion of changing approaches to flood control and a brief discussion of the recently approved Harris County flood bond.

Do Sand Mines Play a Role?

Part 2 includes a discussion of sand mining under “Causes of Changes in Sediment and Sedimentation. Dupré talks about different types of sand mines and their impacts. While the professor and I disagree about the interpretation of several satellite images, we agree wholeheartedly about the need to locate pits outside of a ‘channel migration’ zone, as regulations  in Washington state and Arizona require.

The danger, he says, is that rivers can migrate to and through sand mine dikes. If this happens after abandonment of the mine, no one will me there to repair the dikes and the river will reroute itself through the pit, carrying stored sediment downstream.

Who Will Benefit from This Presentation

If you enjoy earth sciences, as I do, these presentations will feel like going back to college. If you’re simply a homeowner trying to figure out why you flooded, you’ll find lots of food for thought in these two presentations. If you’re debating whether to buy flood insurance, these presentations will make you a believer.

Key Messages

One of the key takeaways from Part 1 is that you should not think of the 100-year (1%) floodplain as a bright line where you’re safe on one of it and not safe on the other. Dupré calls that choice a “false binary.” He urges people to think of flood plains as ever shifting and flood plain boundaries as very fuzzy lines, much like the cone of uncertainty used for hurricane path prediction. The width of the line represents the margin of error behind the calculation of probabilities.

After reviewing Part 2, you should come away with a better appreciation for how gradual, almost unnoticeable changes in your environment can increase your flood risk.

Related Reading

The points Dr. Dupré  makes support the conclusions drawn in a report by the Bayou City Initiative titled “Houston A Year after Harvey: Where We Are and Where We Need to Be,” especially the section on the need to revise outdated flood maps.

Remember Flood Control Presentation At Community Center on 9/17

Matt Zeve, Director of Operations for Harris County Flood Control, will also discuss flood map revisions in his upcoming talk at the Kingwood Community Center on September 17 at 6:30. Don’t forget to mark your calendar.

Posted by Bob Rehak on September 11, 2018

378 Days since Hurricane Harvey and 17 years since 9/11