Garfield Archives - Reduce Flooding

Two Top Geologists Suggest Mouth Bar Dredging Strategy

Two world-class geologists, Tim Garfield and R.D. Kissling, both of whom live in the Lake Houston Area, agreed (at ReduceFlooding.com’s request) to offer their opinions on what would be the best strategy for dredging near the San Jacinto West Fork Mouth Bar. Garfield and Kissling helped bring mouth bar issues to the attention of the public after Harvey. Both have followed various dredging programs in that area closely ever since.

Looking west across the mouth bar on 9/11/2020 while hovering over Kings Point. Suspended sediment shows that main current of river is between remainder of the above-water portion of the mouth bar and Atascocita Point on the upper left. *Photo taken 9/11/2020.*

History

The Army Corps of Engineers dredged from River Grove Park to Kings Harbor in 2018 and 2019, removing approximately 1.8 million cubic yards. After a contentious battle with the City, the Corps then agreed to remove another 500,000 cubic yards south of the Mouth Bar in the Spring and Summer of 2019. This year, the City of Houston started removing the portion of the mouth bar that remained above water; they are still working on it (see above). Recently, FEMA agreed to remove another million cubic yards. And waiting in the wings is another $30 million that can be applied to additional dredging. State Representative Dan Huberty secured that money in the last legislature.

However, none of the various parties involved has volunteered to share their thinking about objectives and strategies behind mouth bar dredging alternatives. That’s why I asked Garfield and Kissling to offer their thoughts on what constituted the best strategy. Both worked for one of the world’s largest oil companies at the very highest levels.

Old Bathymetric Maps No Longer Valid

The first thing they realized was that they didn’t have enough data to make informed recommendations. The last published bathymetric maps were based on surveys taken before Imelda and before the Corps’ mouth-bar dredging.

Gathering Own Data

So Garfield and Kissling gathered their own data – with sonic depth finders, GPS, and a 14-foot pole with depth markings. They started upstream of the mouth bar, where the Army Corps finished its Emergency West Fork Dredging program near Kings Harbor. And they worked their way downstream beyond FM1960 to the railroad bridge.

Found Underwater Plateau 20′ High and 3 Miles Long

They found an underwater wall approximately 20′ high where the Corps stopped its first dredging program near Kings Harbor. It extended downstream more than 3 miles.

Cross section of river channel shows a rise of almost 20 feet wall on the upstream side of the mouth bar near Kings Harbor and an even greater drop near FM1960. The result: a 3-mile long underwater plateau.

That wall, they say, “…constitutes a significant and abrupt hydraulic barrier that will likely exacerbate flooding and sedimentation.”

That wall is the leading edge of a 3-mile-long underwater plateau.

*Note abrupt drop north of FM1960 Causeway.*

Recommend Following Original Channel

The cross-section graph of the river bed above represents the deepest part of the river. On either side of that centerline, the riverbed rises to two or three feet below the surface of the water. The centerline closely follows the paleo (original) channel of the river before the Lake Houston dam was built.

Garfield and Kissling recommend dredging along the deepest path (see below). They reason that would save money.

*Recommended and alternate routes identified by Garfield and Kissling* *that take advantage of deeper water.*

“This might not only be the most beneficial dredging plan, but could also be the most cost effective as it leverages the paleo-channel as much as possible,” they say. “It harnesses nature, rather than fighting it.”

The geologists also identified a second possible route farther to the east but still south of the above-water portion of the stream mouth bar (labeled SMB in diagram above).

They caution that hydraulic modeling should be used to decide the best dredging plan. Political considerations drove initial mouth bar dredging rather than data. The Corps was authorized only to dredge an amount that it believed Harvey deposited. “We should be past the politics at this point and looking to get the most bang for our bucks,” say the geologists.

Whichever strategy the City settles on, Garfield and Kissling recommend excavating a channel, not a broad area, to get the best results for the dollars invested.

Objective: Re-establish Full Channel From Kings Harbor to Lake Houston

“This new channel should be no shallower, nor narrower than the upstream dredged channel at its end dredge location (450’ wide x 26’ deep),” say the geologists.

As a minimum, the future dredging plan should re-establish a continuous and down-stream deepening channel volume from where the Corps channel dredging ended to the 1960 bridge.

Tim Garfield and RD Kissling

This will help reduce sediment build up upstream from the plateau. By accelerating water through the blockage, it will let the river carry sediment farther out into the deeper portion of the lake. It will also reduce water backup that contributes to flooding.

Read Garfield and Kissling’s full study, Evaluating West Lake Houston Bathymetry, Dredging Status and Recommendations.

Recommendations Consistent With City’s Preliminary Findings

The City has been methodically surveying Lake Houston and is in the process of developing its own maps, objectives and strategies. Stephen Costello, the City’s flood czar said they are not finished with that effort yet. However, he also said that the preliminary information they obtained suggested that a route south of the mouth bar might be the most effective.

Posted by Bob Rehak on 9/25/2020 with thanks to Tim Garfield and RD Kissling

1123 Days after Hurricane Harvey

What Happened Downstream During Harvey as Lake Conroe Released 79,000 CFS

Last night, I posted some statistics about Lake Conroe levels after the SJRA started the release during Hurricane Harvey. Tim Garfield and R.D. Kissling, two top geologists, now retired from one of the world’s largest oil companies, have looked at the release from a downstream perspective. Last year, they put everything they learned into this 69-page presentation delivered to the University of Houston Honors Program.

*From “A Brief History of Lake Houston and the Hurricane Harvey Flood,” by Tim Garfield and RD Kissling with help from Bob Rehak, 2019.*

Recap of Key Points About Lake Conroe Release

To recap several key points:

The SJRA never did let Lake Conroe rise to its allowable flowage easement. The water level in Lake Conroe peaked at 7 a.m., August 28, 2017, at 206.23 feet. The SJRA’s flowage easement is 207 feet.
Outflow exceeded inflow by 8:30 a.m. on the 28th and stayed that way for the duration of the storm. As the lake level declined, the lake had up to 3 available feet of storage capacity.
Yet the SJRA kept releasing, on average, 2X – 10X more water than it was taking in. At one point, the ratio exceeded 100:1.

Tracking the Release Down West Fork

Garfield notes that the discharge ramp up that began the evening of the 27th reached a peak discharge rate of more than 79,000 cubic feet per second (cfs) just before noon on the 28th. The discharge rate didn’t dip below 70,000 cfs until 4 a.m. on the 29th – more than 16 hours later.

Following in lockstep with the Conroe release, flow rates at downstream gauges ramped up, in lockstep. By lining up the peaks of gages downriver, you can literally see the water surging down the West Fork all the way to Lake Houston. (See left side of image above.)

Significantly, Garfield says, these gauges all showed flattening flow-rate curves before the release ramp up. Those curves then turned and steepened upward as the Conroe release pulse arrived at those gauges.

Timing and Impact of Release in Lake Houston Area

Peak flow at the Humble gauge was reached shortly after noon on the 29th, roughly 24 hours after peak discharge was reached at the dam and roughly 30 hours after the high-rate release ramp up began.

Water started creeping under the doors of Kingwood Village Estates, a senior living center in Kingwood Town Center about 1.4 miles from the West Fork, at 3 a.m., on August 29th, 2017. It kept rising all morning and finally stopped another mile further inland. Water entered the last (highest) house to flood in Kings Point (the Kingwood subdivision closest to the main body of Lake Houston) at 2 p.m. that same day, according to Elise Whitney Bishop.

Residents trying to escape as Harvey's floodwaters rose — *Kingwood Village Estates residents trying to escape as Harvey’s floodwaters rose. Twelve later died.*

The level of upper Lake Houston, as measured at US59, rose an additional 7 feet during this period.

Significant additional flooding of Kingwood homes can be tied to this same period of increased discharge.

Flow rates measured at the Grand Parkway gauge and calculated at the Humble gage indicate a flow rate increase in this period of between 70,000 to 80,000 cfs, corresponding closely to the 79,000+ peak flow rate added by the Conroe dam discharge.

“The data from the affidavits further supports several key conclusions from the Harvey Flood Fundamentals section of our University of Houston talk,” said Garfield. Those include:

The large sustained release from Lake Conroe made West Fork flooding worse. The extra 80,000 cfs increased the West Fork flow 50%.
The release occurred as the storm was abating. It significantly increased flood damage in the Lake Houston area.

*More than 4,400 structures flooded in Humble and Kingwood along the West Fork. Source: HCFCD.*

The list of damages ran well over a billion dollars.

The SJRA Argument

The SJRA maintains to this day that Lake Conroe is a water-supply reservoir, not a flood-control reservoir. See the affidavits of Hector Olmos and Chuck Gilman. Olmos is a consultant who helped design the operations manual for the gates at Lake Conroe. Gilman is the SJRA’s Director of Flood Management, hired the year after Harvey.

They are basically claiming, “We don’t have the right tool to prevent downstream flooding.”

Editorial Opinion

Editorial opinion: That excuse has always sounded hollow to me. It attempts to curtail discussion of whether the SJRA waited too long to start releasing water, released too much at the peak, and then kept on releasing too much for days.

That discussion is a matter of public concern that could save lives and property in the future. We need to have it.

Sadly, it will take the courts to figure this out. In the meantime, the SJRA has hired some of the highest priced lawyers in the country and now appears to be angling for legislative immunity by hinting at higher water prices “statewide” if liability can’t be controlled.

It all smacks of similar arguments in other industries. If you’ve lived long enough, you’ve heard them all before, such as car companies that would be driven out of business if forced to install seat belts and other safety features. Well, that prediction didn’t quite work out! Luckily, for General Motors, the addition of safety features helped fuel its resurgence.

Posted by Bob Rehak on 6/12/2020 with thanks to Tim Garfield and RD Kissling

1018 Days after 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.

Lake Houston Area Geologists Propose Dredging Objectives to Restore Conveyance, Safety

Secrecy surrounds current dredging plans for the mouth bar of the San Jacinto West Fork. We know that the Corps will finish removing 500,000 cubic yards next week. However…

Unkowns at This Time

… we don’t know exactly where they are removing sediment, how wide the area is, how deep it is, and whether they will cut a channel through the sediment dam or just shave some off the top.

*Mouth Bar of the San Jacinto West Fork immediately after Harvey*

The Corps’ refusal to divulge plans puts residents in a bind. How can we know whether they have restored conveyance and safety? We must take their word. We don’t even have a post-dredge survey showing us how they intend to leave the river.

Two Prominent Geologist Suggest Objectives

With those caveats in mind, I asked Tim Garfield and RD Kissling what objectives they would set to restore conveyance and safety. Garfield and Kissling are two prominent area geologists who first brought the mouth-bar problems to the public’s attention. Between them, they have more than 80 years of oil field experience at the highest levels, studying river basins around the world.

Here’s how they responded: “Our overriding objectives are simple:

Restore flow conveyance of the west fork into Lake Houston
Survey the entire area being dredged for depth upon completion.
Extend the upstream dredging which ended near Kings Harbor through the mouth bar area. Said another way, don’t make water flow uphill. Eliminate the ramp.
Continue the 400’ wide, approximately 20′ deep channel past the SMB until it connects into the relict channel where it is 20’ deep or deeper near the FM1960 bridge.
Develop and implement a plan for regular maintenance dredging.
Define responsibilities, budget and source of funding for future dredging.
Define a schedule of regular depth surveys in order to determine where sediments are re-accumulating and to have a better baseline for future storm events.
Build and utilize 2D- or 3D-models to help guide future dredging decisions.
Resolve disposal issues. Identify long-term placement areas and potential partnerships with industry.”

Who Will Achieve Desired Results?

These objectives make sense to me. They describe what the river used to look like before the mouth bar set up and contributed to flooding 7,000 homes and businesses. They also describe what we need to do to keep the problem from recurring. If the Corps doesn’t achieve the desired result, I hope the City, Harris County and State can. You can help by urging elected representatives to get FEMA to designate the mouth bar sediment as Category A.

Corps May Share Results When Dredging Complete

According to Congressman Dan Crenshaw’s office, the Corps has finally agreed to share with outside sources the 1D HEC-RAS model it built. Reportedly, the Corps sent a copy of the model and data to Stephen Costello, the City of Houston’s Chief Recovery Officer. Crenshaw’s office is also trying to obtain the Corps’ dredging plans and make them public.

It will be interesting to see how the Corps’ dredging results line up with Garfield’s and Kissling’s objectives.

Posted by Bob Rehak on 8/31/2019

732 Days since Hurricane Harvey

The Mouth Bar: A Dam Behind the Dam

As tonight’s town hall meeting with Houston Mayor Sylvester Turner, Council Member Dave Martin, Chief Resiliency Officer Steve Costello and Chief Recovery Officer Marvin Odum approaches, it’s important to understand that the U.S. Army Corps of Engineers is NOT currently scheduled to dredge the mouth bar at the confluence of the West Fork and Lake Houston.

The scope of the current West Fork Emergency Dredging Project includes 2.1 miles between River Grove Park and Chimichurri’s. The Corp will remove 1.8 million cubic yards of sand clogging the river in that area. However, they will leave two to three times that much sediment at the mouth of the West Fork – between King’s Point and Atascocita Point…unless something changes soon.

The “Mouth Bar,” a giant sand bar that blocks the West Fork of the San Jacinto, backing the river up into Kingwood and Humble. Water depth is generally 1-3 feet around this bar. Max channel depth in places is just 5-8 feet.

The “mouth bar” which we have talked about extensively in previous posts forms a dam of sorts behind the Lake Houston dam. It backs water up into the heavily populated Humble/Kingwood/Atascocita corridor.

Tim Garfield and RD Kissling, two local retired geologists, first sounded the alarm about this blockage. Since then, many people have been working to bring the mouth bar within the scope of the current project. Garfield and Kissling have also continued to review Corps survey data and developed additional insights.

Tonight Garfield and Kissling shared these thoughts.

You could walk along the red line from Scenic Shores to Kings River Estates, and except for crossing the paleo channel at five to eight feet, you would not even get your shirt wet. It should be approximately 25 feet deep in this area.
Shallowest path follows red line.

The Corps survey data is in the background. The red line represents the shallowest points of the lake/river.
Without removing the mouth bar, water will have to flow uphill approximately 40 feet between the West Lake Houston Parkway Bridge and Lake Houston.
Water will have to rise approximately 40 feet between West Lake Houston Parkway and the Mouth Bar to reach Lake Houston. Subtract five or six feet for the deepest parts of the channel on either side of the bar.
If the city dropped the lake level 12 feet overnight – but the mouth bar remained – you would see an earthen dam 6 feet higher than the lake, behind which West Fork floodwater would still back up and flood our neighborhoods.
Adding flood gates without removing the mouth bar will not protect us from flooding.

With those happy thoughts, let’s hope that the City has some good news to share tonight re: removal of the mouth bar. Council Member Martin and others have been working diligently with the County, State, and Federal Governments to include the mouth bar in the current dredging project or fund it as a second project that follows the first closely.

Doing so could save taxpayers $17 million in mobilization costs.

The meeting will be held Tuesday, October 9 at 6:30 p.m., at the Kingwood Community Center, 4102 Rustic Woods, Kingwood, TX 77345.

Posted by Bob Rehak on October 9, 2018

406 Days since Hurricane Harvey

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