Tag Archive for: coastal water authority

Reservoir Coordination Still Elusive After 53 Years

4/6/26 – One of the biggest “lessons learned” from Harvey is that coordinated Joint Reservoir Operations are crucial. The San Jacinto River Basin has two reservoirs controlled by dams. But coordinating their operation to reduce flooding remains elusive after 53 years.

The San Jacinto River Authority (SJRA) finished the Lake Conroe dam in 1973, but is still seeking public input on its Joint Reservoir Operations Study. They hope to have a first draft of the study by the end of 2026.

Benefits of Reservoir Coordination

Other authorities around the world have long recognized the benefits of coordinating the operations of multiple dams on their rivers. Benefits include:

  • Enhanced flood control and mitigation – By acting in tandem, dams can reduce flood peaks more efficiently than isolated dams.
  • Improved water security and drought resilience – Coordinated dam systems can manage water storage across a basin to alleviate water stress during dry seasons.
  • Reduced sediment transport –  Tandem operation can reduce peak flows that cause heavy erosion, clogging rivers and downstream lakes.
  • Increased hydropower generation – Although not a factor in the San Jacinto Basin, coordinated operations allow water to be used multiple times as it passes through a series of dams, exponentially increasing total energy output from the same water resource.
  • Environmental sustainability – Strategic releases of water can sustain downstream ecosystems, habitats, and species, as seen in the U.S. Sustainable Rivers Program.
  • Improved navigation and trade – A system of coordinated locks and dams can regulate river flow consistently, facilitating the transport of goods via barges and promoting regional economic development.
  • Water security – Upstream dams can supplement the water supply in downstream dams that may support major metropolitan areas. Lake Conroe, for instance, provides backup to the smaller Lake Houston, which is the primary water supply for more than 2 million people.

River Authorities that Manage Multiple Dams for Flood Control

Examples of coordinated management abound. Take for instance:

  • In Texas, the Lower Colorado River Authority (LCRA) provides a textbook example of coordinated dam management for flood control through the Highland Lakes system. The LCRA manages a “staircase” of six dams northwest of Austin. All six assist with flood mitigation. They operate as an integrated unit to protect downstream communities.
  • Tennessee Valley Authority manages a network of 9 main-river dams and 22 tributary dams. The system is designed to catch heavy runoff in tributary reservoirs before it reaches the main river, significantly reducing flood risks for downstream cities like Chattanooga. The TVA operates these dams as a single unit. That way, they also ensure a consistent water depth of at least 11 feet along the entire 652-mile main channel. That lets 28,000 barges transport goods annually.
  • The Columbia River System (CRS) consists of 14 federal dam projects managed as a coordinated system for power, flood control, and fish protection.
  • California Department of Water Resources found that “weather-informed reservoir operations” at Lake Oroville and New Bullards Bar Reservoir can further reduce flood risk for communities along the Yuba and Feather rivers during extreme atmospheric river storm events and potentially benefit water supply during drier periods.
  • In the Delaware River Basin, a “flexible flow management program” mitigates flooding impacts immediately downstream of reservoirs.

Two Key Houston-Area Reservoirs Have Different Missions, Management

So, why can’t the SJRA manage two dams?

For one thing, SJRA only controls Lake Conroe. The Coastal Water Authority controls Lake Houston.

For another, the two dams have slightly different goals and radically different construction.

  • Lake Conroe was conceived as a water supply and flood control reservoir (even though SJRA now claims Lake Conroe is strictly for water supply). Lake Conroe’s tainter gates can release 150,000 CFS.
  • Lake Houston, on the other hand, is primarily for water supply. It has limited flood control capability because of its fixed height spillway. Lake Houston has only four small gates with a combined release capacity of 10,000 cubic feet per second (CFS).

Engineers are currently studying ways to add more and bigger tainter gates to Lake Houston. The current plan under study would boost the release rate to 78,000 CFS, thus matching the highest release rate ever from Lake Conroe (during Harvey). That would enable better coordination between the dams.

Why It Matters

Timing of releases can materially affect downstream flooding in a densely developed floodplain. During Harvey, a wall of water 11 feet high was going over the Lake Houston spillway. 16,000 homes and 3300 businesses behind the dam flooded. It backed water up for miles. Lake Houston’s Dam had 5X more water going over it than Niagra Falls usually does – enough to fill NRG Stadium in 3.5 minutes – 425,000 CFS.

Lake Houston Dam During Harvey. Can you even see the gates at the right end of the spillway?

Twenty percent of all homes and forty percent of all businesses in the area were affected.

Lake Houston Area Flood Task Force

Getting the water out faster is crucial. But it must be done safely. In a way that doesn’t hurt downstream interests.

While Coastal Water Authority figures out how to add more gates, SJRA is building a forecasting tool for the entire watershed that has the potential to:

  • Improve coordination between the dams
  • Inform decisions about pre-releases and gate operations
  • Enhance emergency management

For More Information

See SJRA’s presentation at the Humble Civic Center on 3/5/26 for more on Joint Reservoir Operations.

See ReduceFlooding’s new Lessons page for more “lessons learned” about flooding. It’s my attempt to distill my most important findings from more than 3000 posts since Harvey.

Posted by Bob Rehak on 4/6/26

3142 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.

SJRA Joint-Reservoir Operations Study Meeting: A Wake-up Call

3/7/26 – On 3/5/26 at the Humble Civic Center, the San Jacinto River Authority (SJRA) held the first of three meetings to discuss its Joint Reservoir Operations Study. In several respects, the meeting was a wake-up call:

  • During Q&A, SJRA learned how impatient the downstream public is for flood-mitigation solutions – 8.5 years after Hurricane Harvey.
  • Public comments showed that PTSD from flooding still lingers.
  • The average age of attendees appeared to be in their sixties. Younger homeowners and newcomers to the region who have no memory of flooding were largely absent.
  • Several comments by speakers suggested upstream residents around Lake Conroe are still resistant to the idea of any “pre-release.”
  • SJRA has no formal pre-release program anymore. As one speaker said, “There are no designated dates or amounts or anything like that. But we work very closely with City of Houston. They make decisions on what we’d like to do.”

Theory of Pre-Release

The idea behind “pre-release” is to release water ahead of a storm, so a reservoir, such as Lake Conroe or Lake Houston, has additional capacity to absorb incoming floodwater. That can shave flood peaks by spreading out releases over longer periods.

SJRA’s Water Resources and Flood Management Division Manager Matt Barrett, PE, said…

“One of the main objectives of the study is to determine if there are any benefits to pre-releases from Lake Conroe and Lake Houston.”

Matt Barrett

Findings in Other River Basins

Studies around the world have proven that pre-releases do have benefits … in certain conditions.

California Department of Water Resources found that “weather-informed reservoir operations” at Lake Oroville and New Bullards Bar Reservoir can further reduce flood risk for communities along the Yuba and Feather rivers during extreme atmospheric river storm events and potentially benefit water supply during drier periods.

Also in California, the Army Corps of Engineers found that “forecast-informed reservoir operations” could increase water supply without increasing flood risk.

In the Delaware River Basin, a “flexible flow management program” mitigates flooding impacts immediately downstream of reservoirs.

A peer-reviewed Journal of Hydrology case study on the Bavarian Danube concluded that coordinated operation of reservoirs in river basins has great potential to improve flood mitigation.

City of Houston Experience

And experience in the San Jacinto River Basin since Harvey has also proven pre-releases have benefits. The City of Houston Public Works Department has documented numerous instances when pre-releases helped prevent downstream flooding, according to Dave Martin, former Houston Mayor Pro Tem.

Pushback from Lake Conroe Association

But pre-release is politically unpopular with Lake Conroe residents. The Lake Conroe Association (LCA) constantly speaks out against it in SJRA board meetings, lawsuits, community meetings, and complaints to the TCEQ. While LCA articulates its concerns as a loss of valuable water, the concerns stem from perceived impacts on recreation and property values.

Iterations of Lake Conroe Pre-Release Strategies

As a result, SJRA has modified its pre-release protocol several times since Harvey.

  • At first, SJRA lowered Lake Conroe during the two wettest seasons of the year: Spring and Hurricane Season.
  • SJRA then restricted the amounts and durations of the lowering.
  • Currently, SJRA lowers Lake Conroe on an as-needed basis – days or hours before major storms. They call the strategy “Active Storm Management.”

The City of Houston owns two-thirds of the water in Lake Conroe and can call for as much as it wants, any time it wants. SJRA reportedly would prefer the City continues calling for the water, so that it doesn’t have to take the heat from the Lake Conroe Association.

Clearly, Active Storm Management is a compromise between upstream and downstream interests. But how does SJRA know when and how much to release before a storm. That depends on weather and the certainty of forecasts. How much rain will fall where? How fast? And how much will run off?

Another Study Objective: Forecasting Tool

That’s where another objective of the Joint Reservoir Operations Study comes in: development of a forecasting tool.

Joint Reservoir Operations Study
Objectives of Joint Reservoir Operations Study

See more details about the forecasting tool below.

The question in my mind is not IF pre-lease is feasible, but WHEN. Clearly, there are some cases where pre-release from Lake Conroe alone does not make sense, i.e., when a storm approaches from the south, as Harvey did and Lake Houston (without its new flood gates) could not release water fast enough to keep up with any release from Conroe. That would just make flooding worse.

But in other situations, i.e., when a storm approaches from the north or northwest, it might make sense – especially after Lake Houston receives its new floodgates. Then you would not be stacking floodwaters from different directions on top of each other.

Scope of Work Associated with Study

The Joint Reservoir Operations Study will also look at past releases from both Lake Houston and Lake Conroe, and use lessons learned to help inform the Lake Houston Gate Operations Policy.

With the data collected, SJRA will develop models that reflect the addition of new gates for the Lake Houston Dam. Then they will evaluate 20 different pre-release scenarios, such as the possibilities mentioned above.

As of this meeting, SJRA had not yet determined which scenarios they would evaluate. However, they will evaluate the consequences on water supply in both lakes.

The worry: if the forecast is wrong and a storm veers away, pre-releases could negatively impact water supply.

Finally, the study will determine the best ways to communicate pre-releases to stakeholders.

The Flow-Forecasting Tool mentioned above will incorporate data from multiple sources, including rainfall, a network of more than 70 stream gages, outflow from Lake Conroe and a model of the watershed. It will inform both gate operations and local officials.

To see the entire presentation, click here. It will help you understand some of the constraints on dam operations including:

  • Governance of the reservoirs.
  • Components of Lake Houston Water Supply Operations
  • Historical floods
  • Proposed improvements to the Lake Houston Dam
  • Runoff from sub-watersheds
  • Differences between water-supply and flood-control reservoirs; Lakes Conroe and Houston are both water-supply reservoirs
  • Construction differences between the two dams

Next Meetings and More Information

As the study progresses throughout the year, SJRA will hold two more public meetings. A mid-year meeting will be held at Lake Conroe to review progress. And SJRA hopes to reveal the results of the study in The Woodlands before the end of the year.

For more information, see LCLHJointOps.com.

Even if you can’t make the meetings, SJRA welcomes public comments on the study, flood-risk locations and flood impacts.

Posted by Bob Rehak on 3/7/26

3112 Days since Harvey

Wastelands to Wetlands, Part III: Turning Ideas into Action

3/31/25 – In the first two parts of this “Wastelands to Wetlands” series, I presented a vision for restoration of the San Jacinto West Fork and listed all the various parties who have an interest in the effort and could help. But how do you coordinate them? Who would take responsibility/authority for ensuring restoration? And how would you measure their success? That is the focus of this post.

My purpose is to start a dialogue that gets people moving in the direction of a solution. I don’t claim to have all the answers. Nor do I believe that this is the only way to get to a solution.

Need for Leader to Guide Restoration

Right now, no group or leader exists for such an effort. But restoration will never happen unless someone takes the initiative (or has the responsibility) to turn ideas into action.

In business, I learned that if you put two people in charge of a project, no one is in charge. Right now, we have more than a dozen groups theoretically in charge of permitting various aspects of restoration. But none is in charge of oversight and coordination. That’s a problem.

Do We Use Existing Group or Start New One?

Several contenders for the job already exist. But do they have the knowledge, skills, funding and desire to take on the additional work?

The San Jacinto River Authority (SJRA) theoretically has the authority. And they have established a flood management division. But do they have the desire to take on the environmental restoration job? They architected a massive Master Drainage Plan for the entire river basin. But after more than four years, they have yet to implement one recommendation from it. SJRA seems focused on capturing water in Lake Conroe and selling it.

Further downstream, the Coastal Water Authority has the responsibility for managing Lake Houston. But no one has given them responsibility for fixing upstream issues between the two lakes that pollute their water.

Unless one of these two groups accepts restoration as a mission and dedicates the resources to achieving it, we need to create another authority responsible for the area between Lake Conroe and Lake Houston – a West Fork Restoration Authority.

Mission Defined

Their mission: turn wastelands into wetlands. How? 1) Restore abandoned mines using a combination of grants and matching funds dedicated to the effort by the state legislature. 2) Monitor active mines to ensure they comply with their abandonment plans when the time comes. 3) Coordinate the efforts of all affected parties to ensure they are additive and contribute to the long-range plan over time.

Creating such an authority would require action by the state legislature in 2027. It’s too late for this session.

Board Structure

A board appointed by the governor and affected parties, such as the City of Houston, Montgomery County, the mining industry, and residents, could manage the West Fork Restoration Authority.

Suggested Success Metrics

How would they measure success? Here’s a list of major needs, metrics, and milestones.

  • A) Completion of business plan
  • B) Acquisition of staff
  • C) Completion of engineering study
  • D) Design of solution and component parts
  • E) Costs estimates
  • F) Publication of long-term plan with stages/tasks outlined
  • G) Successful grant applications, funds raised
  • H) Permits obtained
  • I) Acres revegetated
  • J) Linear feet of trails installed
  • K) Reduction of erosion
  • L) Water-quality improvements
  • M) Publication of quarterly and annual progress reports
  • N) Creation of case study that communicates knowledge gained to guide similar efforts elsewhere

Time Limited

The State’s Sunset Commission would review the Restoration Authority at regular intervals (currently 12 years) and dissolve it after completion of its job or for lack of progress.

Need

Do we need such an Authority? In my opinion, YES! The economic future of the region depends on eliminating the blight that contributes to flooding. The West Fork has:

  • Approximately 20 square miles of sand mines, many abandoned, between Lake Houston and I-45
  • Become completely blocked in some areas
  • Broken through the dikes of at least five sand mines.

The American Rivers organization named the West Fork one of the most endangered rivers in America.

And we still have not completed a $200 million dredging program that began in 2018.

Back in 2019, I posted 72 pictures that showed the extent of sand mining on the West Fork. Sadly, not much has changed since then. In fact, things have gotten worse.

West Fork Sand-Mining Problems
Hallett Mine on West Fork. Picture taken March 19, 2025. Pit in foreground has been captured by river, cutting off normal channel to right.

We need the area’s elected leaders to work together to restore the West Fork as mines like the one above play out and the miners move on to other areas.

We need their help in turning Wastelands into Wetlands. Otherwise, the next generation will be stuck with the situation below.

New Sand Mining BMPs needed to offset sediment pollution.
Confluence of Spring Creek (left) and West Fork (right) with its 20 square miles of sand mines. Photo taken in January 2025

Posted by Bob Rehak on 3/31/25

2771 Days since Hurricane Harvey

Flood-Control, Water-Supply Dam Differences Help Explain Delay on Lake Houston Gates

9/29/24 – When talking about using the Lake Houston Dam to help control flooding, one often hears experts say, “That’s not a flood-control dam. That’s a water-supply dam.” So, what’s the difference? And why does it make a difference?

The purpose of the dam influences its design, operation and management. An insider familiar with the effort to add more gates to the Lake Houston Dam said last week that engineers at both Houston Public Works and the Coastal Water Authority have resisted trying to modify a water-supply dam for flood control.

This is not the only reason this project has taken so long to get off the ground. But it helps explain why new, higher capacity Lake Houston gates are just now going into final design – 2588 days after the storm that made the need abundantly clear.

To put that in perspective, 2588 days is almost twice the number of days that it took to win World War II.

Conflicting Purposes, Designs

The primary purpose of a flood-control dam is to reduce flood risk by controlling the flow of water downstream during heavy rains. They accomplish this by temporarily holding back the flow of water. They then release it later in a controlled fashion to smooth out peaks and reduce flood damage.

To mitigate flooding, flood-control dams:

  • Often have lower water levels under normal conditions to accommodate sudden influxes of water.
  • Have large spillways and gates to rapidly release water when needed.
  • Are designed with a large storage capacity relative to the expected flood volumes.
  • Are sometimes kept partially empty to ensure sufficient space for incoming floodwaters.
  • Have more robust construction to withstand sudden large inflows and outflows.

On the other hand, the primary purpose of water-supply dams is to store water for human consumption (drinking, bathing, irrigation, industry, etc.).

To ensure consistent supply, a water-supply dam:

  • Prioritizes a consistent water level to ensure a reliable supply of water throughout the year, even during droughts.
  • Is usually kept at higher levels.
  • Stores water over longer periods.
  • Is managed to ensure sufficient supply throughout the year, with a focus on maximizing storage before dry seasons.

In summary, a flood-control dam is designed and managed to mitigate floods by managing excess water. However, a water-supply dam aims to store water for human use.

In practice, these extremes aren’t quite as mutually exclusive as the terms might imply.

Seasonal Management and Its Alternatives

Seasonal management strategies can help bridge the gap between the two. For instance, operators often manage both types of dams seasonally so they have more storage space during rainy seasons when flood risk spikes.

The SJRA adopted a seasonal lake-lowering strategy for several years after Harvey. But because of political pushback from Lake Conroe residents, the strategy was abandoned after several years.

“Stop the Drop” protesters pack an SJRA board meeting in December 2019.

SJRA now uses another hybrid strategy called “active storm management.” “Active Storm Management” seeks to manage lake levels by releasing water based on real-time weather forecasts to manage reservoir levels more effectively.

Other operators use a similar strategy known as FIRO (Forecast-Informed Reservoir Operations). Advanced forecasting models predict inflows and adjust dam releases preemptively.

Lake Houston, Lake Conroe Both Water-Supply Dams

Both Lake Conroe and Lake Houston are water-supply dams. But Lake Houston, built in the early 1950s, has a 3160-foot, fixed-height spillway with four small gates capable of releasing only 10,000 cubic feet per second (CFS) combined. Clearly, engineers prioritized consistent water level over flood mitigation when designing this dam. The small gates make it difficult and time consuming to release water before it reaches the level of the spillway.

According to the Houston Public Works Drinking Water Operations Group, Lake Houston supplies water to 2.2 million people.

Lake Conroe, built in 1973, has five large gates capable of releasing 150,000 CFS. It was designed as an alternate water supply for the City of Houston. The City financed its construction and owns two thirds of the water in the lake.

Lake Conroe has nothing comparable to the fixed-height spillway on Lake Houston.

3160-foot concrete and steel spillway on Lake Houston

Compared to spillway above, gates on Lake Houston can release only a small amount. But the spillway can release more than Lake Conroe. See below. It just can’t release that much before a storm.
Lake Houston Dam during Harvey. The wall of water flowing out of the lake was 11 feet higher than the spillway.

During the peak of Harvey, an estimated 425,000 CFS went over the Lake Houston Spillway – 5 times the average flow of Niagara Falls.

In contrast, Lake Conroe released about 80,000 CFS from its gates during Harvey. So why the push to add more gates to Lake Houston?

Gates Key to Hybrid Strategy

Simple. Bigger gates are key to both water conservation and Active Storm Management. Right now, Lake Houston’s gates are so small that lowering the lake significantly can take days. During that time, storms can veer away.

That long lead time creates uncertainty that jeopardizes what Houston Public Works and the Coastal Water Authority see as their primary mission – providing water for 2.2 million people.

We just can’t create extra storage capacity in Lake Houston fast enough with the existing gates.

Why is Design Taking So Long?

But with more, larger gates, Lake Houston could release enough water in hours to create extra storage capacity. And operators would have confidence that water would not be wasted. So why are the gates taking so long?

Design of more gates for Lake Houston has just now started. Using Harvey as a starting point, we are now almost at twice the amount of time that it took to win World War II.

It’s hard to believe that if everyone agreed with the need for more flood gates, it would have taken this long to start design.

In that regard, I have heard of pushback from both Houston Public Works and Coastal Water Authority. The pushback had to do with the mission of the organizations: to supply water. They just didn’t want to risk wasting it in case we encountered drought.

But our two backup water sources (Lake Conroe and Lake Livingston) combined have 15 times the volume of Lake Houston. So the City probably won’t run short anytime soon.

Flood Mitigation Not In CWA Mission

The Coastal Water Authority, which is the City’s contract operator for Lake Houston, does not even mention “flooding” on its website. That’s right. CWA doesn’t mention the word in its mission statement, guiding principles, strategies, or tactics. They do, however, mention “pumps” 15 times on their Strategic-Plan page. That should give you some idea of their priorities: water supply.

Hopefully, Mayor John Whitmire’s recent appointment of former State Representative Dan Huberty to the Coastal Water Authority Board will help the CWA see Lake Houston from more than one perspective. Huberty has advocated for the gates since Harvey.

Posted by Bob Rehak on 9/29/24

2588 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.

Harvey’s Seventh Anniversary Update on Lake Houston Floodgates Project

8/28/24 – In its July 10 board meeting, the Coastal Water Authority (CWA) unanimously approved a motion to move forward with final design for 11 new Lake Houston floodgates. Houston will now consider the same motion at its September 11th City Council Meeting. If approved, final engineering design of the gates will commence.

Separately, Houston Mayor John Whitmire appointed former State Representative Dan Huberty to the CWA board. Huberty, an early proponent of the gates project, may be able to help accelerate it moving forward.

The Most Talked About Flood-Mitigation Project

Since Hurricane Harvey seven years ago, I’ve authored 278 posts discussing additional Lake Houston floodgates. From the public’s standpoint, beyond a doubt, the gates are the most eagerly anticipated flood-mitigation measure considered after Harvey.

The most recent post appeared on 5/25 of this year after meeting with members of the Coastal Water Authority, Houston City Council and Houston Public Works at the dam. Not much has changed since then with the exception of some legal formalities.

The Coastal Water Authority Board met on July 10 to vote on an amendment to an Interlocal Agreement (ILA). FEMA and the Texas Division of Emergency Management previously approved the ILA amendment in April. It covers additional engineering services, the cost of final design, and changes from the initial scope of work.

The CWA board approved the ILA amendment unanimously. Final engineering of the new Lake Houston floodgates can now move forward with Black & Veatch as soon as the City approves it.

Minutes of the CWA meeting indicate that, before voting, members discussed potential downstream impacts. The minutes also noted that no significant impacts were found after extensive hydraulic modeling.

Next Up: City Council Vote on 9/11

The amended interlocal agreement will now go before Houston City Council on September 11th for consideration. If approved, final design of the gates could begin soon thereafter.

Need for Lake Houston Floodgates

The Lake Houston Floodgates Project will add 11 new gates to the dam in the earthen embankment to the east of the concrete spillway.

Proposed location for new tainter gates
Approximate location for 11 new Lake Houston floodgates.

The new floodgates will increase the current discharge capacity by an additional 80,000 cubic feet per second (CFS). That roughly equals the discharge rate from Lake Conroe during Hurricane Havey – 79,000 CFS.

Currently, Lake Houston floodgates can only release 10,000 CFS. Increasing the discharge rate would enable the City and CWA to:

  • Coordinate pre-releases between Lakes Conroe and Houston before major storms without swamping the Lake Houston Area.
  • Discharge as much water from Lake Houston in 2-3 hours as they now do in a day.
  • Release water when approaching storms are much closer, reducing the risk of wasting water if storms veer away.
  • Create extra storage capacity in both lakes, reducing flood risk for residents around them.
  • Reduce flood peaks, helping protect residents between the lakes and downstream from the Lake Houston Dam.

Key to Active Storm Management

All these benefits are especially important because the San Jacinto River Authority (SJRA) has abandoned its seasonal lake-lowering strategy for Lake Conroe. The SJRA has gone to an as-needed lake-lowering strategy called “Active Storm Management” instead. Active storm management requires much more speed and agility than simply having extra storage capacity in the lakes ready and waiting when storm seasons begin.

Lake Houston Area residents got a taste of “Active Storm Management” without the extra gates in May this year. SJRA got surprised by a spring storm and started releasing water at 70,000 CFS. Hundreds of homes flooded downstream in Harris and Montgomery Counties. Thousands more nearly flooded.

The May floods highlighted the risks involved with ad hoc lowering of Lake Conroe. They also underscored the need for more Lake Houston floodgates to handle the extra water that SJRA may send downstream.

2556 days have now elapsed since the storm that motivated the Lake Houston floodgates project – without moving one shovel of dirt. That’s almost twice the time that it took to fight and win World War II – 1349 days.

I’m going to go way out on a limb here and say that there may be some room for improvement in the business processes surrounding flood mitigation.

Whitmire Appoints Huberty to CWA Board

On the good-news front, Mayor John Whitmire has appointed former State Representative Dan Huberty, a Lake Houston Area resident, to the CWA board. Huberty fought years for this project and helped land much of the early funding. He knows the people and already knows the project. He should be able to step in and start making an immediate impact.

Huberty has already had meetings with the CWA staff. He told me, “This will be my highest priority moving forward to meet the needs of Lake Houston Area constituents.”

Posted by Bob Rehak on 8/28/2024

2556 Days since Hurricane Harvey

West and East Forks of San Jacinto Flooding Again

May 19, 2024 – For the second time this month, the West and East Forks of the San Jacinto River are flooding. The East Fork crested last night about 1.5 feet below the prediction. However, the West Fork is still rising at US59. Parts of River Grove Park and the turnaround under US59 are already flooded. And the National Weather Service predicts floodwaters will go even higher.

Meanwhile, the West Fork continues to run through an old Hallett sand pit that was sold in January.

Here’s what you can expect if you live near the rivers.

East Fork Crest Moving Toward Lake Houston

Low-lying areas along the East Fork began flooding yesterday at FM1485. Earlier, the East Fork flooded near Cleveland and Plum Grove. As the crest moves downriver, it is affecting communities differently. Exactly how depends on many factors, such as the conveyance of the river at different points, sediment accumulations, proximity of homes to the river and more.

Yesterday, water was coming across part of FM1485 where it crosses the East Fork and parallels SH99. Today, the entire east bound section of FM1485 was blocked by floodwaters.

East Fork San Jacinto at approximately 4:30 PM on 5.16.24
East Fork San Jacinto at approximately 4:30 PM on 5.16.24

As of 6 PM, May 19, floodwaters are declining in this reach of the river. The crest has moved downstream toward Lake Houston.

Harris County’s Flood Warning System shows the river crested last night but was still well above flood stage as of noon today.

Farther upstream, at FM2090, the river has already returned to its banks.

All this is the result of another 3-5″ of rain falling earlier in the week upstream in the watershed on grounds that were already saturated from torrential rains and flooding earlier this month.

NWS Issues Flood Warning for West Fork until Tuesday Morning

While the East Fork is falling at this hour, the West Fork is still rising. At 1:34 PM Sunday, the National Weather Service issued a flood warning for the West Fork near Humble affecting Harris and Montgomery Counties.

Communities affected include: Porter, Sendera Ranch Road, Conroe, Kingwood, Humble, Sheldon.

Only minor flooding is forecast.

National Weather Service Flood Warning

NWS will issue its next statement Monday morning at 7:45 AM CDT.

The FLOOD WARNING WILL REMAIN IN EFFECT UNTIL LATE TUESDAY MORNING.

IMPACTS: At 49.3 feet, minor lowland flooding begins in the vicinity of the gauge at US59. The north side turnaround at US 59 begins to flood. Low points in surrounding areas also begin to flood.

At 12:45 PM CDT Sunday, the river had risen to 49.2 feet.

 Bankfull stage is 45.3 feet.

The river will crest at 49.7 feet just after midnight tonight. It will then fall below flood stage late tomorrow evening.

Flood stage is 49.3 feet.

This afternoon, the turnaround under US59 was just beginning to flood. The parking lots and part of the roadway were already underwater.

Far side of sandbar in middle is normally the river bank.

At 5 PM, the soccer fields, picnic area and boat launch at River Grove Park were also partially underwater. And water was rising quickly.

Picnic area and boat docks at River Grove underwater and going deeper tonight.
Soccer fields, also at around 5PM
River still rising. Minor flooding expected through Tuesday.
Sand Mine Area Upstream

Farther upstream, the West Fork was still ripping a hole through an abandoned Hallett sand pit that the company sold to a real estate developer in January.

River is now flowing through the abandoned pit (right) instead of following the normal arc of the river (left) around the pit. Note trail of foam. It moved at around 5 mph.

This breach appears to have widened significantly in recent days. If it remains open and this pit becomes the new course of the river, it’s possible that the entire pit could become public property, just like the river is now.

On the other side of the river, Hallett filled in the trench that was releasing sludge from its settling pond last Friday afternoon.

Trench on perimeter of Hallett Mine that was releasing sludge into river on Friday afternoon has been filled in.

Lake Report

As of 7 PM, the SJRA is releasing 5,325 Cubic Feet per Second (CFS) from Lake Conroe. The lake is almost back to its normal level – within .67 feet of 201. And no rain is in sight. That’s good news. Releases should continue to go down.

Screen capture from SJRA website at 7:15PM.

Throughout this event, SJRA has balanced inflows and outflows to the degree that it can. The rate they show above is about half of what they released earlier in the weekend.

Lake Houston, however, is getting more, not less water. It is still about two feet above normal and discharging water via its gates and spillway. Total discharge is 34,015 CFS. Of that, the gates can release only 10,000 CFS. The other 24,000 CFS goes over the spillway.

Screen capture from Coastal Water Authority as of 7:15 PM.

Comparing the two numbers on the right, shows us that the flood risk is shifting to the Lake Houston Area now.

Of the 11 watersheds that send water into Lake Houston, SJRA controls only Lake Conroe. The East Fork has no flood control. But that’s a story for another time.

Posted by Bob Rehak on 5/19/24 at 8PM

2455 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.

City of Houston Re-evaluating Benefit-Cost Ratio on Lake Houston Gates Project Alternatives

According to minutes of the Coastal Water Authority (CWA) February 9 board meeting posted in March, work on the project to add more gates to Lake Houston was paused in January while the City of Houston updated the project’s benefit-cost ratio.

gates for Lake Houston and Conroe
Lake Houston and Lake Conroe gates side by side. Lake Conroe’s gates (right) can release water 15 times faster.

CWA Board Minutes Give High-Level Overview of Concerns, Status

Screen capture from CWA Feb. 9, 2022, minutes approved and posted in March.

Earlier, in December, the board learned that the project team was trying to get the benefit/cost ratio above 1.0, so benefits exceed costs.

Screen capture from CWA January 12, 2022, board minutes.

At that time, the CWA hoped to receive the updated BCR later in January. But it still hadn’t happened by the February board meeting.

Martin Says “September-ish” for BCR Report

City of Houston Mayor Pro Tem Dave Martin said he hopes to have the BRC report in a “September-ish” time frame. I asked him whether the Community Impact report was accurate when it said the project had been scaled back to 500 feet of crest gates as opposed to the original 1500 feet. He said “no,” and that the engineers were looking at multiple options. He also said “1.0 is incorrect as well,” but did not elaborate.

That leaves a lot of questions regarding this project.

History of Project

After Harvey, the Lake Houston Area Task Force identified adding additional gates to Lake Houston as one of three primary strategies to reduce flood risk in the Lake Houston Area. The idea: to equalize the discharge rates of the flood gates on Lake Houston and Lake Conroe. Conroe’s is 15X greater. That makes it difficult lower both lakes quickly in advance of approaching storms.

As a temporary strategy, the City and SJRA agreed on a temporary, seasonal lake lowering strategy to create more capacity in Lake Conroe until more gates could be added to Lake Houston. But the strategy met with significant pushback from Lake Conroe residents and lawmakers. The Lake Conroe Association even took the SJRA to court to stop it.

At various times, City representatives have discussed 10 and 6 additional tainter gates, plus 1500-, 1200-, and 1000-feet of crest gates. Engineers and City officials have repeatedly emphasized the need to balance costs, downstream impacts, and flood risk reduction.

Back in October 2020, the engineers calculated that the upstream influence of the dam ended at approximately Lake Houston Parkway. But they never explained why. It would seem that if the influence extended upstream to US59 when the lake is at its normal level, that the influence should extend at least that far in a flood. However…

BCR Not Based on Harvey Damage

Much of the damage to the Humble/Kingwood Area during Harvey happened upstream of the West Lake Houston Parkway Bridge. It included:

  • $60 Million to Kingwood College
  • $70 million to Kingwood High School
  • $50 million to Kingwood County Club
  • 283 homes in Barrington
  • 218 homes in Kingwood Lakes
  • 97 apartments in Kingwood Lakes
  • 110 homes in Kings Forest
  • 100% of businesses in Kingwood Town Center
  • 225 homes in Kingwood Greens
  • 30 homes in Deer Cove
  • 3 Homes in Deer Ridge Estates
  • 32 homes in Trailwood Village
  • An unknown number of homes in Forest Cove
  • 78 townhomes in Forest Cove
  • All of the Big Box stores along 59
  • Homes and business north of Deerbrook mall
  • 40% of all businesses in the Lake Houston Chamber
  • Humble ISD admin building
  • Destruction of US59 southbound lanes
  • Union Pacific Railroad Bridge

However, Black & Veatch does not base its benefit-cost ratio calculations on another Harvey. They’re basing it on 25- and 100-year storms. Almost all homes, businesses and infrastructure near the lake are already above those levels – at least based on pre-Atlas 14 standards. That may explain the difficulty and delays with benefit/cost ratio calculations and the multitude of scenarios examined.

Time, Uncertainty: More Factors to Consider in Cost and Risk Reduction

Each flood-risk reduction alternative would reduce lake levels by a different amount during a 100-year storm and therefore require its own BCR.

Other factors to consider: How much time do dam operators really need to lower Lake Houston? And how much uncertainty are they willing to live with?

Given the desire to preserve water, these are crucial considerations. If forecasters can reliably predict a need to lower the lake two days before a storm instead of one, operators may only need half the number of new gates. That could get the cost down to the point where the benefit-cost ratio needs to be.

But don’t forget another element of uncertainty: Atlas 14. FEMA has not yet approved the new flood maps based on the higher rainfall totals. Those could put more people in or closer to the floodplains. Below is the timetable for flood map updates currently posted on the MAAPnext website.

Timetable for flood map updates from MAAPnext.

Posted by Bob Rehak on 4/4/22 and updated on 4/5/22 with MAAPnext timetable

1679 Days since Hurricane Harvey

May 2021 Gate Project Update for Lake Houston Dam

In its March 10th board meeting, the Coastal Water Authority (CWA) accepted the recommendation of a preliminary engineering report to add one thousand feet of crest gates to the uncontrolled spillway portion the Lake Houston Dam. The additional release capacity would let operators shed water faster before, during or after major storms to reduce the risk of flooding.

At the March meeting, directors also approved $4.4 million to begin Phase II of the project. Phase II calls for Black & Veatch to proceed to final engineering of the gates and a coffer dam to protect the work area during construction.

Read the minutes of the March board meeting here. The discussion of the gates starts on page 4 under Item B.

This morning, at its May board meeting, directors received an update on the progress of Phase II work to date and plans for the remainder of the project.

Start of Phase II Engineering Approved in March

In the March meeting, CWA approved funds to begin Phase 2 of the engineering which includes the final design of the selected alternative by Black & Veatch. The selected alternative was “crest gates” constructed on the uncontrolled spillway portion of the dam on its west side. (See below.)

Looking NE at the Spillway of the Lake Houston Dam is in foreground. One thousand feet (about a third) of this spillway will be replaced with crest gates. Gates will be placed at the end closest to the camera position in the image above.

Dam operators can raise or lower crest gates from a bottom hinge, much like the lid on a piano. When in the up position, gates hold water back. When lowered, they release water.

During Harvey, the peak flow over the spillway was five times the average flow over Niagra Falls. A wall of water 11 feet tall cascaded over the spillway above. Enough to fill NRG stadium in 3.5 minutes.

Scope of Phase II Design Work

Also in March, CWA and Black & Veatch completed negotiation of the scope and fee for the final design. The key deliverables during Phase II will include:

  • Plans to modify the spillway to support the 1,000 linear feet of crest gates (in five 200-foot long sections)
  • Design of the cofferdam system to protect the work areas during construction
  • Preparation of a new gate operations plan for CWA Lake Houston Dam operators.

Director Douglas Walker moved to authorize the Executive Director to issue a contract amendment with Black & Veatch Inc. in the amount of $4,465,727.00 for “Phase 2 – Final Design of the Lake Houston Dam Spillway Improvement Project.” Director Giti Zarinkelk seconded the motion. The Motion carried unanimously.

May Update

In the May board meeting this morning, directors received an update on Phase II work to date and plans.

In April, the design team held a number of workshops and coordination meetings.

Black & Veatch also completed three weeks of field surveying of the existing spillway; that’s why CWA temporarily lowered Lake Houston during that period.

In other news, for next steps CWA will:

  • Submit the permit application to the US Army Corps of Engineers by the end of May.
  • Support City of Houston in a public outreach meeting scheduled for June 17. The public outreach meeting will coincide with the public comment period for the permit application. CWA expects permitting to take nine months, i.e., through March of 2022.
  • Complete final design by the end of September 2022.
Screen capture from portion of CWA Board meeting today shows status of Phase II Design work on the dam.

Next Steps

Does all this mean construction is assured? No. The Army Corps could reject the permit or FEMA could find some fault with the plans. But at least it shows progress. If all plans and permits are approved, construction dollars have already been committed by FEMA. Originally, construction was supposed to have been completed within three years from April 8, 2020. That now looks unlikely unless the City can obtain a deadline extension from FEMA..

Posted by Bob Rehak on 5/12/2021

1352 Days after Hurricane Harvey

October 2020 Gate Update

On Friday, October 16, 2020, stakeholders in the Lake Houston Spillway Improvement Project met at the dam to review gate alternatives and progress on the project. The main item of interest: a review of options still under consideration to increase the outflow during major storms, such as Harvey.

History of Project

Shortly after Harvey, representatives from the Lake Houston Area identified “increasing outflow” as one of the main strategies to reduce flooding. Harris County Flood Control District even conducted a pilot study. Flood Control included $20 million for the project in the 2018 bond fund (CI-028). With matching funds identified, grants were then written.

FEMA approved the project. And in April of this year, the clock started ticking on the first of two phases.

Phase One Includes…

Phase One includes preliminary engineering and environmental permitting. It should take 18 months and is on schedule at this point. A key deliverable for phase one is verification of the benefit/cost ratio. But, of course, to determine that, you need to know the cost.

Alternatives Still Under Consideration

FEMA allotted 18 months for Phase 1. We’re six months into that. Work to date has focused on determining the optimal alternative. Five remain:

  1. Expanding the existing spillway by adding new tainter gates
  2. Adding a new gated spillway within the east embankment
  3. Creating a new uncontrolled spillway within the east embankment
  4. Building crest gates within the east embankment
  5. Developing crest gates within the existing spillway

Tainter gates lift up from a radial arm. The tainter gates on Lake Conroe have 15X more release capacity than the lift gates on Lake Houston.

Crest gates flop down from a bottom hinge.

Above: the current conditions at the Lake Houston Dam. Looking slightly upstream. East is on the right.

The east embankment is a solid earthen area 2800 feet long east of the spillway and existing gates. Water cannot get over it in a storm. By adding various structures in this area, engineers could widen the current spillway capacity, allowing release of more stormwater.

One main benefit: additional gates would reduce uncertainty associated with pre-releases. Operators could wait longer until they were certain an approaching storm would not veer away at the last minute. That would avoid wasting water.

Reverse angle. Note the difference in height between the east embankment (left) and the spillway (right). Looking downstream toward Galveston Bay.
Looking west toward Beltway 8. This shows the major segments of the dam.

Benefit/Cost Ratio Must Be > 1.0

The lake-level reduction benefits of these gate alternatives during major floods range up to roughly 8x. The costs also vary by roughly 4x. Those are order-of-magnitude, back-of-the-envelope estimates and far from final. Much hard work remains to develop tighter costs and tighter estimates of flood-level reductions. The latter will determine flood-prevention savings in a storm. And the benefits divided by the costs will determine the benefit/cost ratio.

In FEMA’s eyes, the benefit/cost ratio must exceed 1.0 to justify the project. Said another way, it must produce more benefits than it costs.

FEMA allotted 18 months for phase 1. We’re six months into that phase with a year left. Project partners expect results of the alternatives analysis before the end of the year.

Benefit/Cost Calculation

Given the ballpark costs of some of these gate alternatives, we will need very tight estimates of the benefits.

Potential Benefits include:
  • Upstream flood risk reduction
  • Reduced maintenance (debris management) for CWA
  • Improved Water Quality (post storm)
Potential Impacts include:
  • Increased scour and erosion potential to wetlands downstream
  • Increased water surface elevations to structures downstream
Calculating Benefits

Benefit Cost Ratio = (Net Present Value of Benefits)/(Project Costs)

Project Costs = (Capital costs) + (Net Present Value of Operations and Maintenance Costs)

Major Tasks Remaining in Phase 1

Barring surprises, the preliminary engineering report is due in February 2021 and environmental permitting should be complete by the Fall of 2021. Other tasks that must be completed by then include:

  • Hydrologic modeling of flows into and out of Lake Houston using the latest Atlas 14 data
  • Hydraulic modeling of Lake Houston, its Dam, and the San Jacinto River downstream of the dam to Galveston Bay
  • Calibration of models to historic storms
  • Examination of upstream benefits to residents/businesses removed from flood impacts
  • Examination of downstream impacts associated with additional flow release scenarios

It’s important to understand that not everyone who flooded in the Lake Houston Area did so because of the lake level. Some on the periphery of the flood flooded because water backed up in streams leading to the lake. If you got two feet of water in your living room, it doesn’t automatically mean a lake level reduction of two feet would eliminate your flooding by itself.

Congressman Dan Crenshaw (left) reviews the project with team members at the Lake Houston Dam and listens to their needs.

Phase 2 Still Not Certain

Assuming all goes well in the planning, accounting, and conceptual validation, FEMA will make a go/no go decision on construction at the end of next year or the beginning of the following year. Construction should take another 18 months.

Credits

Funding for this project comes from FEMA, Texas Division of Emergency Management, City of Houston and Harris County Flood Control. Other stakeholders include the Coastal Water Authority, Harris County, Fort Bend County, Baytown, Deer Park, and other communities adjacent to Lake Houston.

Posted by Bob Rehak on 10/17/2020

1145 Days since Hurricane Harvey and 394 since Imelda

Beta Downgraded to Tropical Depression

At 10 a.m. CDT, the National Hurricane Center (NHC) downgraded Tropical Storm Beta to a tropical depression. The NHC also cancelled the tropical storm and storm surge warnings that were in effect. However, flash flood warnings remain in effect for large parts of the seven-county Houston region, especially the southern part. A flash flood watch remains in effect for the entire region.

RadarScope split image. Left half shows track of active storms as of 9:06AM CDT. Right half shows total rainfall accumulation for Beta. Note band of extreme rainfall near Sugar Land and sharp drop-off near Kingwood.

Flash Flood Warnings and Watches

A flash flood warning means that flooding is in progress. A Flash Flood Watch means that conditions may develop that lead to Flash Flooding.

Source: National Weather Service. Updated at 10:29 a.m. 9/22/2020. Reddish area = Flash flood warning. Green = Flash flood watch.

Lake Conroe/Lake Houston Within Banks

Neither Lake Conroe, nor Lake Houston have yet been adversely affected by Beta.

The level of Lake Conroe stands at 199.63 feet. Normal conservation pool equals 201.

According to the Coastal Water Authority, Lake Houston is at:

Lake Level41.41 ft.
Normal Pool42.4 ft.
Source: Coastal Water Authority

USGS shows that even though the lake has received about 1.75 inches of rainfall to date…

…the lake level has been dropping, no doubt due to a preemptive release.

Posted by Bob Rehak at 10:50 on 9/22/2020 based on NHC, NWS, and RadarScope data

1120 Days since Hurricane Harvey and 369 since Imelda