Tag Archive for: FOIA

Latest Flood-Mitigation Funding Trends

New data obtained from Harris County Flood Control District via a FOIA Request breaks down flood-mitigation funding by watershed through the end of 2021. It shows where your flood-bond money is going. It also debunks some popular myths. Those include the oft repeated:

  • Rich watersheds get all the funding; poor watersheds get none.
  • Partner funding favors rich watersheds because home values are higher.
  • HCFCD has historically discriminated against low-to-moderate income (LMI) watersheds.

Eight out of 23 watersheds in Harris County have a majority of residents that fall into the LMI category. That means a majority make less than the average annual income for the region. As the data below shows, those eight LMI watersheds get the vast majority of county, partner, and total funding. In fact, four have received 54% of total flood-mitigation funding since 2000.

Funding now correlates more highly with LMI population than damage!

Data also calls into question why some feel compelled to tweak the equity prioritization framework endlessly.

Improved Basis for Reporting

Before I dive into the data, though, let me point out that between the 3Q21 and the end of last year, the county changed the way it compiles historical data. Instead of using the start/stop dates in project management software and reporting only completed projects, the county is now using invoice dates. This produces much higher accuracy. Dollars do not spill over from one period into another. The new data also reflects spending on projects that are ongoing, but still open.

In response to my FOIA Request, the county provided spending using both the old and new methods. They differ by roughly $615 million. Of that, approximately $215 million reflects actual fourth-quarter spending and $400 million reflects the change in when expenses are recognized.

Spending by Watershed

The rank order of spending by watershed has not changed much since last year. Several watersheds moved up or down by a place or two.

The top four are still the top four in the same order. But some of the amounts changed radically, mostly due to the change accounting. For instance, White Oak increased from $387 million to $521 million. But out of the $134 million difference, $102 million comes from when expenses are recognized.

Because this gets so confusing, and because the rank order did not change much, I will use only the new totals compiled by invoice date from now on. I will not compare old and new totals based on the different accounting methods.

Spending by watershed between 1/1/2000 and 12/31/2121 broken down by county and partner contributions, and LMI/Other watersheds.

Graphs of Spending

Here’s a graph of total funding by watershed since 2000, arranged from highest to lowest.

Watersheds rank ordered by amount of flood-mitigation funding received between 1/1/2000 and 12/31/2121.

Funding correlates with population. But you can see notable exceptions below. Some watersheds get far more funding than their proportion of the population, i.e., White Oak, Sims and Greens. Others get far less.

Spending is not allocated proportionately to population in all cases. Six out of eight LMI watersheds received more funding than their population alone would justify.

But population alone does not tell the whole story. Some watersheds are huge and some small. So I also looked at population density per square mile. The curves correlated even less.

Graphing population density vs. total spending shows more variance. Of the eight LMI watersheds, four (Brays, White Oak, Sims, and Greens) get far more than their population density alone would dictate.

As we saw last year, funding flows primarily to damage. The chart below plots funding versus the total number of structures in each watershed damaged in five major storms (Allison, Tax Day, Memorial Day, Harvey, and Imelda). The slope of the curves closely match. But several major exceptions exist.

Historical Discrimination?

Many community groups from LMI neighborhoods have alleged historical discrimination in the distribution of flood-mitigation funding. I just don’t see it. All of the pie charts below take into account all funding between 1/1/2000 and 12/31/2021 based on invoice dates.

The county itself sent almost 60% of its flood-mitigation funding to one third of the watersheds with majority LMI populations.
An even larger percentage came from partner funding.
Whether you look only at county funding, partner-funding, or the total, the picture is still roughly the same. One third of the watersheds get almost two thirds of the funding.
Top 4 include Brays, White Oak, Sims and Greens. All have an LMI percentage higher than 50%.

LMI Population Now Correlates Higher with Funding than Damage

A coefficient of correlation of 1.0 is considered perfect. A good example: between gallons of gas in your car and the distance they will take you.

As a result of the constant tweaking of the equity funding formula, “Population” and “LMI Population” now correlate more highly with “Funding” than “Damage.” The correlation between “Funding since 2000” and:

  • Population Density = .54
  • Damage = .85
  • Population = .87
  • LMI Population = .89

Statisticians consider all of the last three very high.

With all the rhetoric flying around these days, it’s more important than ever to have facts to base your decisions on. To see all the original data from my FOIA Request, click here.

Posted by Bob Rehak on 2/26/2022

1642 Days since Hurricane Harvey

How to Find and Verify Flood-Related Information: Part II

This is Part II in a series about how to find and verify flood-related information. Yesterday’s post focused on finding good information about flood vulnerabilities. This second part will focus on reviewing developers’ plans. The second can compound the first.

The very first sentence of the Texas Water Code § 11.086 begins with a warning not to flood your neighbors. It says, “No person may divert or impound the natural flow of surface waters in this state, or permit a diversion or impounding by him to continue, in a manner that damages the property of another by the overflow of the water diverted or impounded.”

The second sentence declares that a person injured by diverted water may sue to recover damages. Of course, at that point the damage has already been done. Lawsuits are expensive and take years. And the defendant, usually a developer, will always point to plans prepared by a professional engineer and approved by a government body. Suing them will require expert witnesses. And the defendant will likely claim that you wouldn’t have flooded except for an Act of God.

Lawsuits are tall, expensive mountains to climb. So concerned residents near new developments are better off closely scrutinizing plans before they’re built and closely monitoring construction to ensure developers follow the plans.

You can’t stop development. But you can ensure developers play by the rules.

But how do you find and verify their plans?

Need to Find and Verify Info

If you notice a large piece of property for sale near you, monitor it closely. Check with the listing agent. Also check Houston’s Plat Tracker website. It’s updated before every meeting of the Planning Commission and shows items on their agenda. Houston also maintains a map-based website that shows projects in various stages of approval throughout the City and its extra-territorial jurisdiction.

Leap into action if you find a potential cause for concern near you. The next step is to obtain the development’s plans, the drainage impact analysis and soil tests. The developer must prove “no adverse impact” to people and properties downstream.

How you obtain those plans and studies depends on the development’s location. If inside a municipality, check with your city council representative. If you live outside a municipality, your best starting point will probably be your county engineer or precinct commissioner.

The plans are public information and must be provided in response to Freedom of Information Act (FOIA) Requests.

Signed, Stamped, Approved and So Obviously Wrong

In every case I reviewed during the last four years where someone flooded because of a new development, something jumped out of the plans that should have raised concerns for reviewers, but didn’t.

For instance, after Colony Ridge engineers apparently mischaracterized soil types, Plum Grove flooded repeatedly. The engineer said soils would let more water soak in than actually could. That meant the developer didn’t have to build as many detention ponds and could sell more lots. But it also contributed to flooding homes downstream.

Another example, the engineers for Woodridge Village claimed there were no floodplains on the property when there were. The property just hadn’t been surveyed yet.

In those cases, multiple other issues surfaced after close review. Wetlands that had been ignored. Substandard construction of detention ditches that led to severe erosion. Failure to implement stormwater quality controls. Failure to follow plans. Ignoring Atlas-14 requirements that led to undersizing detention ponds by 40%. And more.

In another development, I spotted safety issues related to river migration that had been ignored. Underground parking next to the floodway of the San Jacinto River. Failure to consider flood evacuation.

Concerned citizens must learn how to obtain and review such plans for potential problems or hire a consulting engineer.

Here are some things I’ve learned to look for.

Soil Tests

Are they accurate? Were the samples taken at representative points? Or did they conveniently ignore wetlands? Permeability of the soils will affect the amount of detention needed. The level of the water table could affect the amount of detention provided.

  • Highly permeable soils like sand have a high rate of infiltration and will let developers get away with less detention. Clay-based soils will require more. One engineer told me, “Soils like Colony Ridge reported don’t exist in the State of Texas.”
  • If plans call for a ten-foot deep detention pond, but the soil test encounters a shallower water table, that will compromise the pond’s capacity. Capacity should be calculated from the top of standing water, not the bottom of the pond. If the pond is already half full, that half shouldn’t count.

You can check the soils that a developer reports against the USDA national soil database.

Floodplain Issues

Floodplain maps in Harris County are currently being revised. That may not be the case in surrounding counties. The lack of updated flood maps endangers current residents, by letting developers build to old and ineffective standards.

Developers often try to beat the implementation of new requirements. This happened in the case of Woodridge Village. It’s also happening in the case of the Laurel Springs RV Park and Northpark South along Sorters-McClellan Road. The entrance to the Northpark development sits in a bowl. A quick check of the elevation profile on the USGS National Map confirmed that. During Harvey, local residents tell me that not even high-water rescue vehicles could get through that intersection. Put the Cajun Navy on standby now.

Wetland Issues

Filling wetlands requires an Army Corps permit for some, but not all wetlands. Whether they fall under the Corps’ jurisdiction depends on how far up in the branching structure of a watershed they are. Those near the main stem are jurisdictional. Three levels up may not be.

The US Fish and Wildlife service has thoroughly documented wetlands in this area. Check their National Wetlands Database and appeal to the Corps if you find a problem. At a minimum, the developer may be forced to buy mitigation credits somewhere nearby, which could help reduce flooding.

Drainage Issues

Is a new development’s detention pond capacity adequate? Is it based on the right percentage of impermeable cover? If the pond(s) fill up, where will the water go?

Calculating detention capacity requires math skills most people don’t have. But you can check the basis for the calculations. Are plans based on new Atlas-14 requirements? Are plans meeting current Houston and Harris County requirements?

Current City of Houston and Harris County Requirements for Detention Pond Capacity

In the case of the RV park, the developer will provide roughly half the current capacity requirement thanks to a grandfather clause in the regs. You can find construction guidelines for Houston, Harris County, MoCo and Liberty County on the Reports Page under the Construction tab.

Also see where they’re routing excess water in case of an overflow.

In the case of the Laurel Springs RV Park, the developer said they would route the water to a detention pond near Hamblen and Laurel Springs in anything greater than a two year rain. See below.

Screen Capture from Laurel Springs RV Resort Drainage Impact Report shows that in anything greater than a 2-year rain, overflow water will could threaten homes in Lakewood Cove.
RV Park Site Outlined in White. Overflow described above would presumably follow red path.
Laurel Springs RV Park as of 11/29/21. Detention pond will go in foreground, but overflow will go into pond at top of frame according to text above.

Missing Details from Drainage Impact Analysis

I have requested additional details three times from the City but still have not received them. I suspect they may not exist. All other plan requests have been filled.

So what happens when the Lakewood Cove detention pond fills up? Or gets covered up in a flood? Overflow from the RV park will contribute to flooding someone downstream.

The developer also said excess capacity would get to the Lakewood Cove pond by overland sheet flow. That could threaten homes on the southwest corner of Lakewood Cove – visible in the middle of shot above.

But a City engineer reviewing the plans said overflow would follow the railroad tracks on the western side of the RV park. Hmmmm. Two engineers – one who developed the plans and another who approved them – 180 degrees apart. What’s a concerned citizen to do?

If the engineers who develop and review such plans were always right, no one would ever flood. But we do. So always find and verify those plans.

To see the first part of this series, click here.

Posted by Bob Rehak on 11/29/2021

1553 Days since Hurricane Harvey

The thoughts expressed in this post represent opinions on matters of public concern and safety. They are protected by the First Amendment of the US Constitution and the Anti-SLAPP Statute of the Great State of Texas.

Perry Contractors Now Focusing on Finish Work for Detention Ponds

Perry Homes’ current contractors have excavated 3X more detention pond volume in ten weeks than the previous contractors did in virtually two years. During this past week, they finished excavating three ponds on the northern section of Woodridge Village. Together, they comprise 77% of the total detention volume for the whole site.

Excavation Done, but Finish Work Remains

That doesn’t mean they’re totally done with the ponds. Recent aerial photos show that they still have much finish work to do. That includes:

  • Shaping the sides
  • Creating backslope swales
  • Installing pipes to funnel water from the swales into the ponds and channels
  • Ensuring water can flow out of Adams Oaks in Porter on the west side of the subdivision into Taylor Gully as it previously did
  • Creating concrete “pilot channels” in the center of the ponds and larger channels
  • Planting grass along the sides of the slopes to reduce erosion
  • Installing outflow control in several places to hold back floodwaters
  • Building maintenance roads around the ponds

Elm Grove resident Jeff Miller, who monitors the progress of construction daily, says crews are already hard at work on many of those tasks.

Ponds NOT Expanded Beyond Initial Plans

Miller has compared the width and depth of ponds to the initial plans and verified that the ponds are being built to original specifications. Since the ponds were designed to meet pre-Atlas 14 rainfall requirements, that means the site will still hold 30-40% less runoff than needed to meet current regulations.

Still, surrounding residents in Porter, North Kingwood Forest and Elm Grove who flooded twice last year will find three large ponds on the northern section a welcome addition. They provide some measure of extra protection. Residents will have four times more upstream detention volume than they had during Imelda.

Racing Against Risk

With the peak of hurricane season now less than two months away, Perry Homes is in a race against risk. The company may regret the six months of virtual inactivity between the completion of pond S2 and the start of work on ponds N1, N2, and N3 in early April.

The faster pace of current construction puts pressure on Harris County and the City of Houston to complete an offer if an offer will be made. Elm Grove residents lobbied the City and County to purchase the property and build a regional flood detention facility. They center would also help protect downstream residents on the East Fork and Lake Houston.

However, at a Kingwood Town Hall Meeting in February, Mayor Pro Tem Dave Martin announced that the City would not participate in a deal. He said it was the County’s responsibility.

In April, the County announced that it would consider purchasing the land if the City contributed land in lieu of cash to cover half the purchase price.

Then in May, the County increased its demands. The County now wants the City to contribute land in lieu of cash to cover half the purchase AND construction costs for creating additional detention.

County and City Clamp Down on Communications

Since then, the County has clamped down on communications regarding this subject. Rumors suggest that all parties are still trying to make a deal happen. But the County has denied all FOIA requests and referred them to the Texas Attorney General for a ruling on their denials. That often happens when negotiations are in progress, according to a knowledgeable source.

What Happens Next?

At the contractor’s current rate of progress, it’s entirely possible that contractors will complete all work on detention ponds in July.

The City and County blew through a May 15 deadline that Perry put on the deal. But a “For Sale” sign at the Woodland Hills entrance remains on the property.

With approximately $14 million dollars invested in the property, with hurricane season here, with lawsuits pending, and knowing that the amount of detention is insufficient to hold a 100-year rain, Kathy Perry must be sweating bombshells.

Ms. Perry may be hoping for a City/County offer, but she can’t be counting on one. If she were, she could have sold the dirt coming out of those detention ponds. Instead, however, she’s building up land elsewhere on the site to keep her options open and develop the site if a deal falls through.

That dirt will have to be moved again at taxpayer expense if the county builds additional detention ponds.

Pictures of Site as of 6/19/2020

Here’s what the site looked like as of 6/19/2020.

Looking NW from over Taylor Gully toward Pond N2, the largest on the property.
The connecting channel between N1 at the top of the frame and N2 along the western edge of the property has been excavated. Note the pilot channel that contractors have started in the distance.
At Mace Street in Porter, contractors created a concrete face for the twin culverts on the upstream side, but not yet on the downstream side. Note the earthen dam holding water back while contractors complete the pilot channel running off the bottom of the frame.
Above Mace Street, contractors are still putting in pipes between the channel and backslope swales.
The Webb street entrance to the site has been removed to connect N1 (out of frame on the top) with N2 (out of frame on the lower left).
Looking SE at N1.
Looking South at N3, which runs down the eastern edge of the property.
More pipes are being put in to channel water from backslope swales to the pond so water won’t erode the face of the pond. Not the rills already cut in the dirt.
Looking SE. The southern half of N3 where it connects with Taylor Gully in the upper right.
N3’s connection to Taylor Gully is now wide open. It’s not clear how this connection will be completed to release the water at a slow controlled rate.
The two culverts under the bridge over Taylor Gully should slow the water from N2 (upper right) and N1 (out of frame) down.

Need for Grass if Deal Not Reached Quickly

Note how the grass on the southern side of the gully has all died. That raises a question. If Perry, the City and County do not complete a purchase agreement soon, will Perry plant grass on the northern section to slow runoff. Right now, it’s all hard-packed dirt.

Most of northern section is hard packed dirt which increases runoff rate.

Planting grass over an area this large would be a big investment and might get in the way of construction if Perry decides to develop the land. But it will reduce flood and legal risks.

Posted by Bob Rehak on 6/20/2020

726 Days after Hurricane Harvey and 275 after Imelda

Recently Obtained Documents Raise Questions about Amount of Sediment in Mouth Bar Due to Harvey

ReduceFlooding.com has obtained a copy of the study withheld by the Army Corps that the Corps used to justify dredging only 500,000 cubic yards from the mouth bar of the San Jacinto West Fork. The Corps refused to supply it in response to my Freedom of Information Act (FOIA) request in June. However, the City of Houston did supply the Corps document in response to a similar FOIA request. Now, thanks to Council Member Dave Martin, the public has an opportunity to compare the two studies side by side for the first time.

Kings River resident near mouth bar wading in knee deep water almost to West Fork channel marker. Caution: do not let children attempt this. Pockets of deeper water may exist that could cause drowning. Picture taken eight days ago. The island being excavated in the distance has since been removed; see last image in post.

After reviewing the Corps document, I can see why the Corps refused to supply it. It has more holes in it than a West Texas stop sign.

History of Controversy

For almost a year, the City and the Army Corps have argued over how much sediment was deposited in the mouth bar of the San Jacinto river by Hurricane Harvey. That determines how much dredging FEMA will fund. Initially, the City recommended working with two Texas Water Development Board sedimentation surveys conducted in 2011 and 2018. But no measurements exist from the period immediately BEFORE Harvey – only AFTER. So the Corps rejected that idea.

Corps Demands then Rejects Stockton Protocol

To determine Harvey volume, the Corps then required the City to provide direct measurement of the sediment through something called the Stockton Protocol. (See this memo from Stephen Costello, Houston’s Chief Recovery Officer, outlining this request and the reasons for it.)

The Stockton Protocol combines ultra-high-resolution CHIRP seismic data with core sampling. The seismic identifies layer thickness and the core sampling identifies layer composition. (Note: the process is somewhat like the oil field practice of confirming seismic with core samples from exploratory wells.) The hope: that by analyzing changes in sediment composition (such as color, grain size, roundness, hardness, etc.), researchers can differentiate Harvey sediment from other floods and then measure it accurately.

Core sample from Tetra Tech Study. Different colors and consistencies indicate sediment came from different floods.

The Army Corps recommended a Texas A&M Galveston professor, Dr. Timothy Dellapenna, to do the research. However, the City of Houston and A&M could not agree on contract terms. Therefore, the City hired Tetra Tech, to perform the research that Dr. Dellapena outlined.

Corps Produces Own Analysis

Tetra Tech concluded Harvey deposited 1.4 million cubic yards in the mouth bar (although they didn’t state it that clearly). The Corps rejected Tetra Tech’s results and produced its own study. That study concluded Harvey deposited only 283,000 cubic yards in the mouth barone fifth as much. However, the Corps authorized 500,000 cubic yards to compensate for the margin of error and additional sediment they would have to dredge just to reach the mouth bar.

At the end of the day, even with 500,000 cubic yards, those two estimates still vary by almost 3X. According to Houston City Council Member Dave Martin, the Corps never explained why they rejected the Tetra Tech analysis.

The Corps simply accepted its own results and started dredging without public explanation or input. The Corps document raises many questions that may or may not have valid answers.

The USGS gauge used by the Corps for its analysis stopped working during the peak of Harvey when most sediment would have been moving. The Corps report did not acknowledge this.

Corps Analysis Requires Explanations Never Supplied

Why did the Corps:

  • Base its analysis on a gage at US59 that stopped functioning during the peak of Harvey, when most sediment was moving?
  • Assume Harvey distributed sediment in the same patterns over the same distances as lesser storms?
  • Ignore build up of sediment from Tax Day and Memorial Day storms at the mouth bar as a factor that could have increased the percentage of sediment falling out of suspension during Harvey?
  • Not consider bank erosion downstream from the gage, relying instead on standard charts for “bed-load transport” for sandy rivers?
  • Ignore approximately 20 square miles of sand mines in the West Fork floodway where loose sand and silt were inundated by 131,000 cubic feet of water per second, unlike previous storms?
  • Use a 1-D instead of a 2- or 3-D model for this complex environment?
  • Not publicly disclose model inputs/outputs and data for peer review and validation?
  • Initially reject the use of two TWDB surveys, then reverse course and base all of their findings on them – without explaining why?
  • Exclude extreme data from their study, even though Harvey was one of the most extreme rainfall events in U.S. history?
  • Mislabel all charts, graphs and photos in its report?
  • Refuse to disclose their report in response to a FOIA request, contrary to official Army policy?
  • Omit the organization’s name and the author’s name from the report?
  • Treat the volume that Tetra Tech found related to Harvey in the mouth bar area alone as if it represented the total volume deposited in the entire West Fork by Harvey?

Corps Rejects Use of TWDB Surveys, Then Bases Own Analysis On Them

To estimate Harvey-related volume, the City initially proposed analyzing two Texas Water Development Board sedimentation surveys from 2011 and 2018.

The Corps rejected that idea, suggested the Stockton Protocol, rejected those findings, then based its own analysis on the two TWDB surveys it rejected earlier. This is like following a Three-Card Monte game!

Here is the full text of the Corps’ 4-page unsigned study. We now know that…

Basically, the Corps tried to estimate the amount of sediment that Harvey’s flow could theoretically carry. That would depend on velocity and sediment size/weight. But the gage at US 59 stopped recording at the peak of Harvey. So they also had to estimate the discharge (volume of flow in cubic feet per second [cfs]). Then they used industry-standard curves to estimate sediment transport based on estimated discharge. But they discarded rates over 45,000 CFS because they produced unexpectedly high values.

They also ignored the presence of mile-wide sand mines upstream. The river ruptured the dikes of those mines and captured the pits during Harvey.

West Fork Sand Mine Complex inundated by Harvey. This reach of the river is normally about 150 feet wide. On this day, the day AFTER Harvey’s peak, the flow was more than a mile wide.

Corps Rules Out Extremes for Extreme Event

The Corps says in its report, “there are no measurements above 45,000 cubic feet per second.” Yet the combined peak flows coming from the West Fork, Spring and Cypress Creeks reached approximately 240,000 cubic feet per second during Harveyfive times more. The faster and higher the flow, the more sediment that can be transported downstream and over greater distances.

When the industry-standard sediment transport curves yielded unacceptably high results, the Corps resorted to a simple 1-D model (developed earlier for another purpose) to calculate the sediment load, because flows beyond 45,000 cubic feet per second “produced sediment loads far beyond a reasonable range.”

Corps Assumes Harvey Transported Same Percentage To Mouth Bar as Other Storms

One potentially fatal assumption: The Corps assumes that Harvey transported the same percentage of its sediment load to the mouth bar as all other storms between 2011 and 2018. Said another way, they assume that Harvey behaved LIKE all other storms. Yet not all those floods inundated sand mines.

Moreover, had the Corps measured river bank erosion at intervals between 2011 and 2018, they would have found that virtually all of it occurred during Harvey and very little occurred during Tax Day, Memorial Day and other storms.

Quantum Leap in Erosion Not Factored In

Harvey’s erosive power was NOT proportional to other storms, as the photos below show. River banks eroded more than a hundred feet during Harvey in many places. Yet the Corps report never even mentions erosion.

In 2011, the distance from the ridgeline of this home on Riverbend Drive to the West Fork was 326 feet.
On 1/23/2017, after the Tax and Memorial Day Floods, the distance had decreased only 2 feet.
This shows how much shoreline Harvey ALONE eroded. The yellow line is exactly the same length as after the 2016 floods.
After Harvey, the new distance to the river bank was 216 feet – 108 feet less.

The Tax and Memorial Day Floods combined eroded this river bank by 2 feet. Harvey alone eroded it another 108 feet – 50 times more!

Photographic analysis shows similar quantum leaps in erosion related to Harvey elsewhere along the West Fork.

  • Another home west of River Grove Park lost 27 feet between 2011 and early 2017, but 111 feet in Harvey.
  • River Grove Park lost 0 feet from 2011 to early 2017, but 74-feet in Harvey.
  • Romerica lost 62 feet between 2011 and early 2017, but 144 feet in Harvey.

Net: In four days, Harvey eroded from 2X to 75X more sediment than all other storms during the previous six years. It did NOT act proportionally.

The shearing force of 240,000 cubic feet per second coming down the West Fork literally pulled thousands of trees out by their roots and dislodged sediment disproportionately compared to previous floods (see below). The Gallery page of this web site clearly shows the extent of this devastation. It contains 450 images taken from a helicopter on 9/14/2017, two weeks after Harvey.

Hurricane Harvey ripped trees out by their roots to a degree that previous storms did not. This increased erosion exponentially compared to other storms.

Corps Assumes Mouth Bar Growth Did Not Affect Percentage Deposited by Harvey

The Army Corps also assumes that Harvey transported the same fraction of the total sediment load (20%) to the mouth bar that all storms did between 2011 and 2018. That’s a dubious assumption for several reasons:

  • Previous storms progressively built a wall across the mouth of the West Fork that grew higher and higher during the study period.
  • As it grew, that wall increasingly slowed water down and likely accelerated the rate of deposition behind it (which helps explain why the Corps had to dredge its way to the mouth bar).

Yet the Corps based its estimate on a constant 20%. Page 3 of their report spells out the assumption. Harvey, they say, deposited approximately the same fraction of sediment at the mouth bar as all other storms did during the period between surveys.

This constant 20% contradicts numerous anecdotal reports from lakeside residents and boaters claiming that Harvey carried vastly more sediment to the mouth bar (and their yards/docks) than previous storms. The wife of the resident wading across the river in the image above told me that, on a scale of 1 to 5, the Tax and Memorial Days floods deposited sediment in her yard equal to a 1. But Harvey, she said, was a 6. In other words, off the scale.

No wonder the Corps didn’t want the public looking at this!

Taxpayers Deserve Independent Scientific Review

Professionals rarely like to have their conclusions questioned. However, those who have confidence in their conclusions welcome peer and public review. They encourage second opinions and provide all of their data for review. They also welcome the opportunity to explain and defend their results. None of those things happened in this case.

Instead, the Corps concealed its results as if this involved national security, not public safety. Why? That may be the biggest question of all associated with this project.

The Corps has an excellent, hard-earned reputation. This study undermines it.

As mentioned above, the Tetra Tech study may also have flaws, but the Corps never revealed what its concerns were.

Only one thing is certain. Public safety rests on wildly differing studies. Taxpayers deserve an independent scientific review to resolve the differences between these two studies. The City concurs with the findings in this post and also calls for an independent scientific review. The Corps could not be reached for comment; their new public affairs officer does not list her phone number.

Dredging will likely end next week, with the Corps proclaiming it has restored the conveyance of the river to pre-Harvey conditions (when they have no pre-Harvey measurements).

So we need an independent scientific review to happen quickly. Email you Congressmen and Senators immediately.

Corps Plans Still Being Kept from Public

The Corps still has not released its dredging plans, despite a FOIA request made in June when mouth bar dredging started.

Visual observations of the operation suggest that they are dredging a wide area by three feet, to a total depth of about five feet, instead of trying to cut a channel through the mouth bar. That would leave something like an underwater mesa, still blocking the flow and still trapping sediment. Water coming downriver would have to climb a steep hill to get over it.

If that is an accurate assessment, the Corps would leave a sediment wall under the water approximately 30-35 feet high and 1-2 miles long in the mouth of the West Fork.

Congressman Dan Crenshaw reviews progress of dredging operation on Friday, August 16. Looking southwest towards Atascocita. Notice how the small island in the first image above has now been removed. The mouth bar itself will remain in place, most of it underwater now where it is invisible to the public.

Others Scrambling to Pick Up the Pieces

It may look like the Corps has dredged. But it also looks like the Corps will leave 80-90% of the mouth bar in place. Remember, sand bars are like ice bergs in the sense that what you see above water is small compared to the amount you can’t see below water.

At this point, City, County, State and Federal leaders are scrambling to put together a plan to address the rest of the sediment. Some of that sediment is clearly pre-Harvey. I will discuss options for removal of that portion and maintenance dredging in a future post.

Posted by Bob Rehak on 8/20/2019

721 Days after Hurricane Harvey

As in previous posts on this subject, I promise the Corps that I will print their rebuttal verbatim if they disagree with any of the points in this post.