Tag Archive for: dredging

Seasonal Lowering of Lake Conroe Begins August 1

On August 1, the City of Houston Public Works Department, the San Jacinto River Authority (SJRA) and the Coastal Water Authority (CWA) plan to begin lowering the level of Lake Conroe as part of a joint operations plan to mitigate flooding threats during the peak of hurricane season. The plan calls for lowering Lake Conroe gradually through small releases – about an inch a day – until the lake level reaches 199 msl (mean feet above sea level).

Intent of gradual lowering of Lake Conroe is to avoid another 79,000 cubic-feet-per-second release rate as we experienced during Harvey. Until normal flow is restored to the West Fork, Lake Conroe will be lowered temporarily and seasonally to mitigate flood risk.

Lake Conroe to Be Lowered 2 Feet Through September

This initial lowering will last through the end of September to create additional storage in Lake Conroe which could delay releases and minimize release rates during a storm, thereby providing a buffer against flooding for residents who live downstream of the dam.

The next lowering would occur during the peak of the spring rainy season – from April 1 – May 31, 2019. However, that lowering would only be by a foot – to 200 msl, because the rain threat is usually lower in spring.

Only Until Dredging Restores River’s Flow

The joint operations plan calls for continuing to lower Lake Conroe seasonally in this manner while the U.S. Army Corps of Engineers dredges the West Fork of the San Jacinto to restore flow.

Hurricane Harvey deposited tremendous amounts of silt in the West Fork which  physically changed the river’s ability to safely pass water during storms. Hence, the dredging.

Phase-One Dredging Has Already Started

Phase one will go from River Grove Park to the West Lake Houston Parkway bridge. Great Lakes, the contractor hired by the Corps, has 269 more days to complete the initial phase.

Phase-Two Still Needs Funding

The total project could take longer. Community leaders are now working furiously to arrange funding to dredge the remainder of the west fork, including the mouth bar.

Mobilization and demobilization comprise 25 percent of the total phase one project costs (approximately $18 million out of almost $70 million). Having phase two ready to start before phase one ends could save that money, creating extra value for taxpayers and enabling even more dredging, say for instance, on the East Fork.

Temporary Lake Conroe Lowering Could Last Up to 3 Years

The City, SJRA, and CWA will continue the seasonal lowerings for up to three three years. They will monitor progress of the dredging and annually re-evaluate the need to lower Lake Conroe. If the river’s flow is restored before three years, the temporary lowering would cease.

Lakes will Operate under Two Different Strategies

LAKE CONROE
Lake Conroe is located upstream from Lake Houston. Large pre-releases immediately before a storm run the risk of pushing water into Lake Houston at a rate that could flood residents. Therefore, the SJRA will release at a much more gradual, controlled rate and maintain the lower level until the largest flood threat passes.

LAKE HOUSTON
Lake Houston, as the lowest lake on the river system, can pre-release more safely. Therefore CWA will pre-release from Lake Houston if the National Weather Service predicts more than 3 inches of rain within the San Jacinto River basin in a 48-hour period. Coastal Water Authority will lower Lake Houston to 41.5 feet from its normal elevation of 42.5 feet.

To track lake levels visit:

  • Lake Conroe – www.sjra.net
  • Lake Houston – www.coastalwaterauthority.org

4 Million People Depend on City for Water

Lake Conroe and Lake Houston comprise two of the largest parts of the City’s drinking water system. More than 4 million Houstonians and residents of the greater Houston region rely on water provided by the City.

Posted by Bob Rehak on July 30, 2018

335 Days since Hurricane Harvey

Clock Starts Ticking on Army Corps Dredging Project

Officials from the U.S. Army Corps of Engineers (USACE) announced yesterday afternoon that representatives from Great Lakes Dredge & Dock Company, LLC of Oak Brook, IL, met with Corps’ contracting and project managers for a pre-construction conference. The meeting finalized project requirements for the $69,814,060 dredging and debris removal emergency operation and the clock has started ticking on the project.

The easterly limit of the U.S. Army Corps’ emergency dredging project on the West Fork of the San Jacinto.

The FEMA-funded project covers about two miles of the West Fork of the San Jacinto River near the West Lake Houston Parkway and Lake Houston. FEMA guidelines limit the operation to restoring pre-Harvey conditions.

Beginning of First Phase

“This is the beginning of the first phase of a very challenging project,” said Al Meyer, a USACE Galveston District administrative contracting officer.  “This project involves dredging and debris removal of 1.8 million cubic yards of sediment that has contributed to recent flooding in that area.”

The Focus for Next Week

He said the community should start to see activity within the next two-weeks. According to Corps Colonel Mark Williford, next week  teams will be engaged in:

  • Pre-dredge hazard surveys
  • Before-cut surveys
  • Disposal-area surveys
  • Staging-area set up

Meyer, a professional engineer with more than 35 years’ experience with the Corps, says the conference allowed project team members to interact with Great Lakes representatives to ensure a complete understanding of contract requirements.

“The clock starts today; our contractors have 270 days to complete the project that will work to reduce, but not eliminate flooding, and return the area to pre-Harvey conditions.” said Meyers.

Less than 4 Months from Survey to Dredging

This will be one of the first projects initiated as a direct consequence of Hurricane Harvey.

Corps surveying began in April to determine sediment levels within the West Fork of the San Jacinto River after FEMA responded to a State of Texas request under the Stafford Disaster Relief and Emergency Act of 1988. Since then, the Corps has developed models based on their survey findings, evaluated several different dredging plans, finalized specifications, bid the project, vetted the bids, awarded the job and started mobilizing for it.

The USACE Galveston District was established in 1880 as the first engineer district in Texas to oversee river and harbor improvements. The district is directly responsible for maintaining more than 1,000 miles of channel, including 250 miles of deep draft and 750 miles of shallow draft as well as the Colorado River Locks and Brazos River Floodgates.

Posted 7/19/2018 by Bob Rehak

324 Days since Hurricane Harvey

County Position on More Detention, Dredging and Gates for Flood Bond

Today, I received feedback from Harris County on adding “more detention, dredging and gates” (Plea for DDG) to the upcoming flood bond referendum. The good news: Additional dredging, detention and gates will be achievable within the bond. The bad news: based on the feedback, there is still one hurdle to clear: finding partners to share dredging costs.

The mouth bar where the West Fork meets Lake Houston. Fosters Mill and King’s Point are in the background.

Background on Plea for DDG: Detention, Dredging and Gates

You may recall that RecoverLakeHouston, the Lake Houston Area Chamber, and the Lake Houston Area Grass Roots Flood Prevention Initiative (as well as I) all lined up to support the Plea for DDG. The idea: during floods, more detention, dredging and gates would reduce input, increase throughput and speed up output.

Giant Turnout

The community turned out in force to support the initiative. The response literally overwhelmed county officials at the meeting. Seven to eight hundred people attended, making it the most attended of all the watershed meetings to date. Typically, meetings have been drawing one to two hundred people according to those who have attended multiple meetings.

Because of the large number of attendees in Kingwood and the open house format, many people felt the meeting was somewhat chaotic. Worse, some attendees received feedback from a small number of the county employees who mistakenly told them that dredging was NOT possible under the bond.

Clearing up the Confusion

I received this email from the county today. It clarifies their position on all three requests:

Thank you for your input in support of #PleaForDDG for the San Jacinto River watershed.  Your submission has been recorded and considered by the Harris County Flood Control District staff.

With regard to drainage improvements for the the San Jacinto River watershed, the Flood Control District is partnering with Montgomery County, the City of Houston and the San Jacinto River Authority to determine short-term and long-term improvements, such as:

  • Expanding the Flood Warning System (http://www.harriscountyfws.org) into Montgomery County to include new rainfall and stream level gages
  • Improved coordination between the two county Offices of Emergency Management during disasters
  • A vegetation and sediment management plan with the goal to reduce the amount of silt and sand eroding into the river
  • Regional mitigation projects such as river dredging, buyouts and detention basins

Dredging to restore the San Jacinto River and Lake Houston

On July 6, 2018, the US Army Corps of Engineers awarded a contract to Great Lakes Dredge and Dock, in the amount of $69,814,060 to remove sediment and debris resulting from Hurricane Harvey from the West Fork of the San Jacinto River. The Bond Program does include funding that could provide a portion of the cost share for any future dredging work on the East Fork/West Fork/Lake Houston area. Any future dredging project would have to be a collaborative effort between the City of Houston, the Coastal Water Authority, and possibly the State of Texas. At this time, no details have been worked out on future dredging. The Flood Control District will update the Bond Program maps to indicate another Partnership Project (green cross symbol) within the San Jacinto River watershed exhibit noting East Fork/West Fork/Lake Houston Dredging. The description will be “Potential Partnership Project with the City of Houston, Coastal Water Authority, and the State of Texas to permit, design, and complete dredging of the East Fork/West Fork/Lake Houston area waterways to reduce flooding risks.” The dollar amount will be shown as $50M from Harris County Flood Control District and TBD (to be determined) for the City of Houston, the Coastal Water Authority, and the State of Texas. The Flood Control District cannot commit nor obligate other agencies to allocate funding due to the fact that there is no agreement in place for the dredging project.

Detention/Sediment Basins West and North of Highway 59

These improvements are included in the list of potential projects within the bond program (see local projects F-88, F-14, and F-15 which will be used for Planning, Right-Of-Way Acquisition, Design and Construction of General Drainage Improvement along the San Jacinto River and Cypress Creek west of Highway 59). For drainage improvements north of Highway 59, the Flood Control District is coordinating with Montgomery County on a watershed study to investigate flooding problems and identify where detention basins could best serve to reduce flooding risks along the San Jacinto River.

Tainter Gates on Lake Houston Dam

On July 10, 2018, as a result of the community input process, the Flood Control District has added a Partnership Project (green cross symbol) to the list of potential projects within the bond program for the design and construction of additional gates. The partners would be the City of Houston and the Coastal Water Authority since they are the entities that have jurisdiction over the lake and the dam structure; our agency does not. The Bond Program could, however, provide partial funding of up to $20M for this effort.

When considering project ideas suggested by the community, the Flood Control District will prioritize projects that meet its mission to provide flood damage reduction projects that work, with appropriate regard for community and natural values. You can learn more about the project ranking criteria on our website: https://www.hcfcd.org/bond-program/community-input/

Thank you again for sharing your input. The bond election will be held on August 25 with early voting on August 8.

After reading this, I emailed Harris County Flood Control for one more clarification. Was spending $50 million on dredging contingent upon finding partners to share the cost? The answer: Yes. Fifty million, they say, is not sufficient by itself to do the dredging necessary.

So Where Does that Leave Us?

Additional gates for Lake Houston seem to be within scope and well supported.

More upstream detention seems to be within scope and also well supported. However, before any action can take place, the San Jacinto Watershed study must be completed. It is rumored to cost around $2 million and has been awaiting funding since late March. Presumably, the County’s share of the funding would come from this bond if it passes. The study would take a year or more to complete.

No one can say at this time what the study’s recommendations would be. So there is some uncertainty surrounding the request for more upstream detention. Please note, however, that other groups further upstream, for instance on Cypress Creek, are also requesting more upstream detention. My feeling? If the bond passes, more upstream detention is very likely. However, of all the projects, detention would take the longest to complete because it involves identifying and acquiring land.

Finally, additional dredging is also within scope and well supported. However, dredging has the highest degree of uncertainty associated with it because it will require partners who have not been approached and who have not committed any dollars.

To reduce uncertainty surrounding dredging before the bond, we would likely have to obtain commitments from one or more other stakeholders who are mentioned in the email above.

Recommended Next Steps

Before the bond referendum, area leaders need to actively seek support from those other stakeholders and communicate the outcome so that voters can make informed decisions about their votes. Of all three measures, dredging could be implemented the quickest.

In the meantime, residents should continue to submit their requests for more detention, dredging and gates. A groundswell of support will help send a message to the county’s potential partners.

Posted July 17, 2018 by Bob Rehak

322 Days since Hurricane Harvey

Lake Houston Chamber Launches Plea for DDG

The Lake Houston Chamber has launched its latest campaign in a series of flood mitigation efforts. Called the “Plea for DDG,” it is designed to:

  • Help educate residents and business owners about three key proposals that could address the root causes of flooding in the Lake Houston Area
  • Help turn out a crowd at Harris County’s flood bond meeting on July 10, 6 p.m., at Kingwood Park High School.

Purpose of Flood Bond Meeting

The purpose of the flood bond meeting is to solicit input from residents on the things that they believe will best help the largest numbers of people.

DDG: More Detention, Dredging and Gates

DDG stands for more Detention, Dredging and Gates, three proposals that will reduce flooding here.

The U.S. Army Corps of Engineers is NOT addressing this giant sand bar in its dredging project – a big reason why we need to get the County to address additional dredging in its flood bond package. 

Harvey taught us that we had vulnerabilities. We had more water coming downstream than the San Jacinto’s current channel and the Lake Houston Dam could handle in a timely way. We need to fix those problems so residents know that a 1% storm will leave a home above the 100-year flood plain high and dry. Likewise for a 500-year flood. To do that:

Less input. More throughput. Faster output.

It’s simple. Logical. Achievable. And should restore drainage to original design assumptions.

Now we just need to get enough people to show up and request these things at the bond meeting for the county to include them in the bond package.

Drag your friends, relatives and neighbors to this meeting…especially the ones that didn’t flood.

Remind them that the flood affected this entire community. Tell them why more detention, dredging and gates are so important.

Get them to request more dredging, detention and gates from the County. These three measures could help virtually everyone who lives in the area.

DDG: A two step process

We have to make sure we get the right measures into the bond package. Then we have to get people to vote for it.

Right now, nothing is more important to the future of this area.

This bond package will be used to:

  • Pay for capital projects outright
  • Qualify us for federal matching grants that could triple the amount of dollars available to us (beyond the amount voters approve).
  • Free up money in the Flood Control District’s current capital budget so that the Distict can step up maintenance on ditches (which we also desperately need).

So tell everyone you know to “Plea for DDG” – more detention, dredging and gates – at the bond meeting on July 10, 2018, 6-8 p.m., at Kingwood Park High School.

For more information about the Chamber’s campaign, see recoverLakeHouston.com.

Posted 7/2/2018 by Bob Rehak

308 days since Hurricane Harvey

A Model for the Future of the San Jacinto

The rapid growth of sand mining along the San Jacinto has contributed to an increasing rate of sedimentation of the river and Lake Houston.

Consequences of Increased Sedimentation

Sediment has contributed to:

  • Flooding that cost residents and businesses billions of dollars in damages during Harvey.
  • Forcing taxpayers to spend tens, if not hundreds of millions of dollars in dredging costs to restore the river’s carrying capacity and reduce flood risk.
  • Decreasing the capacity of Lake Houston at a time when the City is about to add 1.5 million users to it’s main water system.
  • Increasing the City’s water purification costs, which are passed along to customers.
  • Impairing fish populations and recreational opportunities

Ignoring Best Management Practices for Buffer Zones

Following best management practices that are common in other states – especially those that mandate buffer zones between mines and rivers – might have prevented or reduced many of these problems. But those practices were not followed here; miners mine so close to the San Jacinto that dikes are broken repeatedly. When caught, miners pay fines averaging $800.

The Lone Exception In Texas

With one exception, Texas has shown little desire to force miners to follow best management practice for setbacks in flood prone areas. That exception is the John Graves Scenic Riverway, a pilot project on a small portion of the Brazos River near Mineral Wells, about 40 miles west of Fort Worth.

Legislation Addressed Water-Quality Impacts from Sand Mining

The legislation that created the Riverway forms a precedent for imposing stricter regulations on sand mining in the Houston region. The name “Scenic” belies the major purpose of the legislation, which was to address water-quality impacts from rock, and sand and gravel mining operations.

Perhaps there’s an opportunity to create a protected area much like that one here.

Statewide Survey Found Widespread Noncompliance

The TCEQ conducted a statewide survey of 316 quarries in 62 counties, beginning in April, 2004. It revealed that noncompliance with permits was a statewide problem. It also revealed that noncompliance sometimes resulted in significant detrimental effects to water quality. One such area was the one that eventually became the John Graves Scenic Riverway area, where best management practices were not being followed.

Key Elements of Legislation Protecting Water

Legislation that formed the area focused on stormwater discharges and their effect on water quality. Key provisions included:

  • Stricter erosion controls and effluent limits
  • Reclamation of quarries and financial provisions to ensure reclamation
  • Restoration of receiving waters in the event of an unauthorized discharge
  • Prohibition of mining within two hundred feet of the river and the hundred-year flood plain
  • Prohibitions against locating quarries in areas subject to frequent flooding.

Brazos River Authority photo shows setback of mines from the Brazos River in the John Graves Scenic Area, one of the main requirements of legislation.

Contrast the previous photo with this one. On the San Jacinto, mines operate within the floodway with as little as 40 feet of separation from the river. One mine (lower right) operated with a broken dike for more than 3 years. Dikes in this area have been broken and breached at least six times since 2015. 

Model For San Jacinto

The Brazos River protection plan could benefit not only the Lake Houston Area, but Houston itself and other upstream communities, such as Porter as well.

The San Jacinto River, one of the main sources of the area’s drinking water, flows through, not around, sand mines on a regular basis. The mines are not only located within the 100-year flood plain, many are located within the FLOODWAY! This means they are in the main flow of the river during floods and experience higher velocities. Approximately 150,000 cubic feet of water per second flowed through these mines during the peak of Harvey, washing out roads and dikes.

USGS Maps Show Mining in Floodway

Twenty-square miles of exposed sand and sediment exist within these mines between I-69 and I-45. This screen capture below is just upstream from I-69.

Some West Fork mining operations are not only in the floodplain, they are in the FLOODWAY! The Red/Aqua cross-hatched areas above show the floodway, while the Aqua shows the 100-year flood plain.

Other sand mines farther upstream are in the 100-year flood plain as well. Some are also in the floodway. See for yourself.

Photos Contradict TACA Claims

TACA, the Texas Aggregate and Concrete Association, claims that water “backs into mines during floods,” but quite the opposite is true; it roars through them, ruptures roads and dikes, and carries exposed sand downstream.

Other tributaries contribute sediment to Lake Houston and the West Fork. However, other tributaries do not have 20 square miles of exposed, unprotected surface on their banks in the form of sand mines. And other tributaries are not flushed with an additional 80,000 cubic feet of water per second when Lake Conroe opens its flood gates as it did during Harvey.

Mines Contribute to Loss of River and Lake Capacity

Lake Houston is losing capacity at a rate of increase that parallels the rate of growth in sand mining.

Houston City Council Member Dave Martin says that the San Jacinto River and Lake Houston will soon supply drinking water to more than two million people, including residents of Houston, Humble, Bellaire, Jersey Village and other cities.

However, Lake Houston is rapidly losing capacity because of sedimentation at a time when demand for its water is increasing exponentially.

The capacity of Lake Houston is decreasing at an increasing rate. By 2011, the Lake had already lost 25% of its capacity. Results of the sedimentation survey done this year have not yet been released.

Mines Contribute to Turbidity, Increasing Water Treatment Costs

When the State protected the Brazos in the early 2000’s, sand mining was not nearly the problem on the San Jacinto that it is today.

Every time it rains, turbidity in the water increases the City’s water treatment costs, by 20% to 100%, according to Houston City Council Member Dave Martin. “We also see significantly more challenges in capturing and removing the solids through the plants dewatering facilities.”

USGS shows how the clarity of Lake Houston changes before and after every major storm.

Add Dredging Costs to the Damage Assessment

Dredging a tiny 2.1 mile stretch of the West Fork of the San Jacinto is likely to cost taxpayers up to $70 million – and that does not even include the giant bar at the mouth of the West Fork that is backing water up,  contributing to flooding, rerouting the river through neighborhoods and threatening infrastructure.

That estimated $70 million is just the tip of the iceberg. Maintenance dredging that returns the river and lake to their original design capacities could cost far more.

$70 million covers dredging only from River Grove Park to a few hundred yards past the West Lake Houston Parkway Bridge. It does not include the East Fork, the West Fork between Fosters Mill and the Lake, the giant mouth bar at the junction of the West Fork and the Lake, Lake Houston above the FM1960 Bridge, or West Fork upstream from River Grove.

That’s an additional 13+ miles. And keep in mind that the U.S. Army Corps is only dredging to pre-Harvey depths. Returning the lake and river channel to their original 100-year flood design capacity would require deeper dredging. That would cost more per mile than the current project between River Grove and Kings Harbor.

Make Mines Part of the Solution, Not the Problem

Prohibiting mining within the 100-year flood plain will create a natural buffer between mines and the river that can trap sand before it becomes a problem.

As mines play out in the area between I-69 and I-45, they can help solve our sedimentation and flooding problems by being:

  • Restored as wetlands
  • Refilled to their natural grades with the spoils from dredging
  • Turned into detention ponds.

Previously, some miners have remediated sand pits after they played out, but many others have not. This pit, for instance, one block north of Townsen next to North Houston Ave. in Humble has been left unfenced, ungraded and unplanted for years. It currently poses a danger to children who play in it and businesses building around it.

Defunct Humble sand pit on North Houston Road just north of Townsend Blvd. Note steep, unvegetated slopes, lack of berms, lack of fencing, and proximity to back of new bank building on adjacent property – all violations of best practices in most states. 

Fortunately, the U.S. Army Corps of Engineers plans to use this pit and one other as a placement site for the spoils from its current emergency dredging project.

Let’s create a protected waterway on the San Jacinto, much like the John Graves area on the Brazos.

Posted July 1, 2018 by Bob Rehak

306 Days since Hurricane Harvey

Lake Houston Area’s Most Pressing Needs for Flood Bond Referendum

On August 25, Harris County residents will vote on a historic flood bond proposal. Everyone asks, “Will the bond include projects that help this area?”

That of course, raises the question, “What does the Lake Houston Area need?”

We Must Address Root Causes of Flooding HERE

Several factors make flooding here different from other parts of the region. Since Harvey, I’ve corresponded almost daily with experts in geology, hydrology, sedimentation, meteorology, city planning, engineering, mining, and disaster relief. The goal: to identify root causes of flooding in THIS area. They fall into three main “buckets”:

  • Sedimentation. Sand and silt clog the San Jacinto everywhere. The Army Corps’ emergency dredging project will remove only part of the sand from a 2.1 mile stretch of the West Fork, and not even touch the East Fork. One of the largest blockages at the mouth of the West Fork will remain. And the Corps will only restore the areas it dredges to pre-Harvey conditions, not pre-1994 conditions.
  • Releases from the dam at Lake Conroe can increase the volume of water flowing between Humble and Kingwood by ONE-THIRD. Of the roughly 240,000 cubic feet per second flowing down the west fork, 80,000 cubic feet of water per second came from the Lake Conroe dam. Many Lake Houston area residents say the onset of flooding coincided with release from Lake Conroe.
  • We have a bottleneck at Lake Houston. In a flood, much more water converges on Lake Houston than Lake Conroe. At the peak of Harvey, Lake Houston took in 492,000 cubic feet per second whileLake Conroe took in only 130,000 CFS. Seven different watersheds converge on Lake Houston. Yet until water reaches the spillway of the dam, our floodgates have one-tenth the discharge capacity of Lake Conroe’s. This effectively eliminates pre-release as a mitigation strategy.

We Need Specific Solutions, Not Generic

True solutions to flooding in the Lake Houston area must address these unique challenges. Generic solutions, such as buyouts with bond money  will help, but won’t affect many people. Pushing new development further away from rivers will help, but will not restore the carrying capacity of the San Jacinto, increase the discharge rate of the Lake Houston dam, or offset discharges from Lake Conroe.

We Need: Dredging, Detention, More Gates

The objective of the Lake Houston Area’s flood mitigation efforts should be, in my opinion and the opinion of many engineers, to restore our drainage systems to their original design capacity. Homes located outside of the 1% (100-year) risk area should not flood until we get a 1% flood. The same goes for the .02% level (500-year flood).

Experts generally focus on three categories of solutions that will help achieve those objectives: dredging, detention and greater discharge capacity for the dam, i.e., adding more gates. We need all three. No one solution will do the job by itself.

Additional DREDGING can remove sediment, restore carrying capacity, eliminate water backing up, and get us back to level of the original design assumptions.

Additional  DETENTION on the West Fork will help offset discharges from the Lake Conroe dam, which affected the heavily populated area between Humble and Kingwood, where the worst and most damage took place.

Additional GATES on Lake Houston will help relieve the bottleneck created by the different discharge rates between Lake Conroe and Lake Houston.

Here’s a diagram that shows what we need in the flood bond, where we need it, and why.

Reduce flooding in the Lake Houston Area with additional dredging, detention and drainage.

Of the three types of projects, dredging is the easiest and fastest to implement. It can buy us time while we build additional dams and gates. That could take years.

More Explanation to Follow

I will elaborate on each of these in coming days.

Harris County Commissioners and executives from the Flood Control District will hold a meeting in Kingwood on July 10 to solicit input from the community on the flood bond.

Hopefully, this series of posts will help focus discussion on the things that will do the most good for the largest number of people at the lowest cost.

Mark Your Calendars for July 10

In the meantime, mark your calendars for July 10. The County wants your input. Get your friends and neighbors to do the same. If you want peace of mind, we need to restore our ditches, rivers, and drainage systems to their original design capacity.

The location of the bond meeting may change because of the expected turnout and need for parking. So check back often.

Posted June 26, 2018, by Bob Rehak, 14 days before the flood bond meeting and…

301 days since Hurricane Harvey.

The Case for Dredging the “Mouth Bar”

A “mouth bar” is a sandbar that builds up at the mouth of a river where it meets a standing body of water, such as Lake Houston. The West Fork of the San Jacinto has a world-class whopper of a mouth bar.

How and Why Mouth Bars Form

A mouth bar forms when water in the river slows down as it spreads out in a standing body of water. The lower velocity of the river can no longer suspend particles of sediment. According to academic and petroleum geologists I talked to, this phenomenon exists in rivers everywhere. In fact, mouth bars are an essential element of delta formation.

Sequence of Events in Formation

As a mouth bar grows in height and emerges from the river, it backs water up and slows it down. This causes the river upstream of the mouth bar to gradually fill with sediment, ultimately choking the river and forcing it to seek a new path. At this point, the higher pressure created by the backwater forces the river to seek new channels. At this point, typically the river splits into two (bifurcates). This accounts for the branching structures found in most deltas.

That is exactly what’s happening where the West Fork of the San Jacinto meets Lake Houston as this series of time-lapse images shows. Note the growth of the mouth bar in areas highlighted in white below.

2011 image of the mouth bar where the West Fork of the San Jacinto meets Lake Houston. Note how bar has formed at tip of main channel.

 

By 2013, the mouth bar had taken on a triangular shape where it was starting to split the main flow of the river.

 

Image taken on the last day of 2016. The mouth bar grew considerably in the Tax Day and Memorial Day floods in 2015 and 2016, primarily by extending its length. 

 

October 2017. During Hurricane Harvey, the mouth bar doubled in size. It definitely splits the flow of the river now. 

On 9/14/17, the bar looked like this from a helicopter.

Approximately two-thirds of the homes damaged by flooding in the upper Lake Houston area were between this bar and where the U.S. Army Corps of Engineers will stop dredging.

Historical Context: A Lesson in Geomorphology

The growth of this mouth bar was predictable. Brown & Root said in 2000 that it would emerge exactly where it did. What will happen in the future if we don’t dredge it? That, too, is predictable. See this presentation by William Dupré, professor of geosciences at the University of Houston. Professor Dupré’s presentation, given at  the Houston Geological Society April conference on flooding, contains excellent illustrations of how rivers migrate laterally over time.

Consequences of Not Dredging

A retired chief geologist for a leading oil company (who specialized in sedimentation) tells me that if this bar is not dredged, we could expect the following consequences. It will, he says:

  • Continue to grow in height, width and length.
  • Slow down and back up water behind it.
  • Force increased sedimentation upstream (including areas soon to be dredged)
  • Likely also increase the frequency and magnitude of overbank flooding upstream of the mouth bar
  • Jeopardize homes, bridges, pipelines and other infrastructure on both sides of the river as it branches.

Two Options for Dredging

The contract that the Army Corps of Engineers expects to sign with a dredging vendor does NOT currently include this bar in its scope. I wish it did for all the reasons listed above.

The proposed contract includes a clause that allows expansion of scope if both the Corps and Contractor agree on it. That would be the most cost efficient way to address this problem. Dredges will already be on the river. Millions of dollars of mobilization costs for second dredging project could be avoided and the issue could be addressed sooner.

However, if expanding the scope of the Corps project is not possible, I believe residents of the Lake Houston area should insist that the County covers it in the upcoming flood bond referendum.

Posted by Bob Rehak on 6/23/2018

298 Days since Hurricane Harvey

 

 

 

 

 

 

 

Top Priorities for Lake Houston Area Flood Mitigation

The fast-approaching Harris County Flood Bond referendum on August 25 is forcing people to focus on their top mitigation priorities.

Harris County Flood Control Bond Page at https://www.hcfcd.org/bond-program/.

Here is the current list of projects included in the Bond Proposal. Scroll down to page 7 to see those associated with the San Jacinto Watershed as of 6/1/18. Only one item from MY top four is currently on the County’s priority list.

Here are four things that I think would make the biggest impact for this area. Do you agree?

Top Priorities

  1. More river dredging. We must restore the velocity and carrying capacity of the entire river, not just a small portion of the West Fork and not just to pre-Harvey conditions.  The Army Corps of Engineers is restoring a 2-mile stretch to pre-Harvey conditions. But we need to dredge deeper and further. And we need to do it on a regular basis. In 2000, Brown & Root recommended dredging and periodic maintenance as the best option they examined to mitigate flooding. Neither was ever done. That’s a huge part of the reason why we face increased flood risk today. Personally, I’d like to see the East and West Forks restored to their 2000 condition.
  2. More floodgates on Lake Houston. Freese and Nichols found that 14 additional gates could have lowered the flood level during Harvey by up to 1.9 feet. That could help reduce flooding both upstream and downstream from the dam. It could also help reduce flooding downstream. By releasing water before a storm hits in a gradual, controlled fashion, you can create more capacity within the lake so you can discharge water at a lower rate as the reservoir fills back up.
  3. More upstream detention. Offset Lake Conroe releases by capturing and holding water elsewhere. Everybody from here to Waller County seems to be lobbying for this. Small dams along the streams and bayous could temporarily hold back flood waters before they reach highly populated areas. Spring and Cypress Creeks are popular candidates. Lake Creek has also been mentioned. Finally, TACA pointed out that sand mines could make excellent detention ponds – my favorite alternative.
  4. Better ditch maintenance. Before Harvey, many of our drainage ditches became silted and clogged with fallen trees. Some, like Ben’s Branch, near the public library, still have islands and standing water in them. Keeping these ditches clear and free flowing should be a high priority at all times to eliminate internal flooding.

Consensus Starting to Emerge

Monday, at separate meetings of the Lake Houston Area Grass Roots Flood Prevention Initiative and the Recover Lake Houston Task Fork, I saw consensus emerging around these flood mitigation measures. Together, these top priorities seem to have the best chance of actually reducing flooding in the Lake Houston area.

What are your top priorities? Whether you agree or disagree with these, please communicate your thoughts to Harris County Flood Control ASAP. The County is actively soliciting ideas for the bond proposal right now.

According to Community Impact, Judge Ed Emmett said the county hopes to have a final list of projects to share with the public by Aug. 1. Early voting will begin on Aug. 8. Thus, we have only six weeks to influence the project list.

Leveraging Local Dollars

County bond money can be used to leverage Federal matching funds from FEMA and HUD grants. These grants usually operate on a 75/25 or 90/10 basis, returning $3 to $9 for every dollar put up. If voters approve the$2.5 billion referendum, it could potentially bring in tens of billions of additional dollars. This flow chart explains how the Flood Control District’s funding works.

Federal dollars for Harvey flood mitigation efforts are available now, but may go elsewhere if we don’t act. So it’s important that we:

  • Make sure the language in the proposed bond accommodates our needs
  • Pass the bond
  • Focus the money where it will do the most good

Here is where the proposed bond language stands as of this date. See BondLanguageAsOf6.13.18.  It will most likely be modified before voting begins, based on what officials hear from citizens at a series of meetings being held in all 22 watersheds throughout Harris County.

Give the County Your Thoughts

Remember, according the Greater Houston Flood Mitigation Consortium, the Lake Houston area historically has received 0% of the region’s flood mitigation dollars, but sustained 14% of the region’s damage during Harvey. Let’s make sure we get our fair share of flood control dollars this time around.

Call 713-684-4107 or mail comments to 9900 Northwest Freeway, Houston, Texas 77092, ATTN: Bond Program Communications.

Come to the meeting with Judge Ed Emmett at the Kingwood Community Center on July 10 from 6 to 8 pm. Learn more about bond proposal and give the Judge your feedback directly.

Posted by Bob Rehak 6/13/2018

288 days since Hurricane Harvey