Tag Archive for: Lake Conroe

How SJRA Set Lake Conroe Release Rates During May Storm

5/24/24 – The SJRA board reviewed a presentation yesterday about Lake Conroe release rates during the early May storm this year. Sadly, while some people flooded, far fewer flooded than in Harvey, despite the fact that the peak inflow to Lake Conroe was higher during this storm than it was in Harvey.

Better management of the temporary floodwater storage space between Lake Conroe’s normal lake level and flowage easement may have made the difference. But there may be opportunities to make an even bigger difference.

Dissecting a Disaster

In early May this year, the headwaters of Lake Conroe received half a year’s rainfall in a few days. It was extreme to say the least. At the peak of the inflow, dam operators were releasing almost 72,000 cubic feet per second, yet the lake level still rose.

That was the second highest release rate in the history of the San Jacinto River Authority (SJRA). Only during Hurricane Harvey did the SJRA release more – 79,000 CFS at the peak.

The peak inflow was greater during this event than during Hurricane Harvey, according to Bret Raley, the San Jacinto River Authority’s Lake Conroe Division Manager.

This time, hundreds of homes flooded downstream. Thousands more were threatened. But it wasn’t nearly the disaster that Harvey was.

Regardless people who flooded or nearly flooded want to know why the release rate was so high and whether it could have been lower. Raley’s after-action report to the SJRA board meeting yesterday provides some answers.

Presentation to SJRA Board on May 23, 2024

Here’s a link to Raley’s entire presentation to the SJRA Board.

You can watch it starting at 37 minutes and 40 seconds into this video. It lasts 15 minutes.

Or you can review the slides below and my summary.

Note: some slides in this presentation use slightly different time periods.

Temporary Storage Provides Partial Buffer Against Flooding

Raley began with a recitation of SJRA’s top priorities re: operation of the Lake Conroe Dam.

He stated that “Our number one priority is … to preserve and protect the structural integrity of the dam. If we did not, the ramifications would be unimaginable.”

“I contend we are protecting public safety. How? Through a vigorous inspection and maintenance program; post-event assessments; and safe spillway operations.”

The dam, he says, provides a buffer against the full brunt of floodwaters. You’ll see later in the presentation, that at times, the inflow exceeded the outflow. Even though the Lake Conroe dam wasn’t designed for flood control, it still provides a modest buffer of temporary storage that helped reduce downstream impacts.

Only 15% of Upper Basin Protected by Dam

The Lake Conroe dam controls only about 15% of the square mileage in the upper San Jacinto River Basin.

The upper San Jacinto River basin includes nine different watersheds that all drain to Lake Houston. Said Raley, “Ours is at the very, very top of what I sometimes refer to as a funnel. Tthe bottom of the funnel is Lake Houston, the Lake Conroe watershed is at the top.”

Raley continued, “The Lake Conroe watershed is only 450 square miles. But it’s also the only watershed in the entire 3000 square miles controlled by a gated structure. The other nine watersheds flow through seven different counties.”

When rain makes its way to Lake Houston depends on when and where the rain fell. In this event, the heaviest rain fell in the West Fork (Lake Conroe) and East Fork watersheds. It could have been much worse if heavy rains had also fallen in Lake, Spring, and Cypress Creek watersheds.

Permit Limits Storage Higher Than 201 Feet Above Sea Level

The Lake Conroe Dam’s operating permit imposes several limitations that operators must contend with.

Said Raley. “The dam was constructed pursuant to a permit from the State of Texas. It authorizes us to store up to an elevation of 201 feet above mean sea level permanently. We also have the authorization to store above 201 temporarily during storm flows.”

“The permit also requires us to pass the inflows once the lake level gets above 201. But any water released below 201 must be used against permitted water rights. So there must be a permittee with available water, and then that permittee can ask to use the water.”

“The City of Houston may have, from time to time, water that’s available, and if so, they can call on it.”

Storage, Mitigation and Pre-Release

Raley then discussed the three main things he wanted people to remember from his presentation. He summarizes them in this slide.

Raley says that water which rises above 201 feet above mean sea level (MSL) cannot be held back; the lake’s operation procedures mitigate peak downstream flows; and that if the City of Houston wants to lower Lake Conroe, the City must ask for the water out of the two thirds of the lake that it owns.

Raley never addressed why the SJRA discontinued its seasonal lowering program that was in effect for several years after Harvey. The existence of that program contradicted some of the points he made in his presentation. That leads one to wonder how firm the rules he describes really are in emergencies.

Water Must Be Released as it Starts to Rise

After introducing his key points, Raley goes into more detail on each.

Raley discussed the differences between water-supply and flood-control reservoirs. “Lake Conroe is a water supply reservoir,” he said. “The intent is to keep the reservoir as full as possible to maintain your supply. In a flood control reservoir, you want to maintain capacity. You want to maintain space that can accept inflows so that you can absorb that water before having to pass it.”

Normally, Only 18″ Between Top of Water and Top of Gates

The design of the tainter gaits on Lake Conroe is another constraint. They do not allow much room for water to rise.

The photo on the left shows a gate in the normal resting position with the lake at the normal level. Water can rise only 18 inches before overtopping the gate.

If that happens, operators lose control. So, as the water rises, they must elevate the gate to stay ahead of rising levels. Remember, storms often pack high winds that create waves. Water can be choppy, not placid as shown here.

“Our gates are not designed to be overtopped” said Raley. “So, we must raise them incrementally to maintain safe freeboard.” Freeboard is an engineering term that, in this context, means “safety margin.”

The second photo shows the downstream side of a gate. Sheet flow coming over the top could destroy this support structure says Raley. “They’re just not designed to withstand that kind of force.”

Six Feet of Buffer Space

A flowage easement lets the SJRA flood properties surrounding Lake Conroe during extreme events. “We’ve got six feet of buffer that we can use,” said Raley. “Our operating protocol helps balance lake-level rise upstream and outflows downstream.”

As the water in the lake rises, SJRA must raise the gates. Still, rising water indicates that more water is coming in than going out…at least temporarily.

In extreme events, SJRA could certainly use even more stormwater storage. (But that would require pre-releasing water. Raley describes the constraints on pre-release several slides further down.)

Areas north and east of Lake Conroe received about half a year’s rain in a few days, testing the limits of the system that Raley described. It wasn’t just the amount of rain. It was also the intensity.

The basin wide average for May 2nd, for instance, approached 7 inches.

The lake at at FM1375 received more than an inch (or close to) it in several 15-minute periods. At that same location, they also received three inches in one hour.

It’s also important to realize that SJRA came into this event coming off another heavy rain. Note how the solid black line below (at the left) was just starting to return to normal when it suddenly peaked.

Note also the steepness of the rise when the black line turns up. “In a ten hour period, we went from 8,000 to 72,000 cfs,” said Raley. “That is fast. Very fast.”

The backline represents the inflow and the blue line represents the outflow. The rapid rise caused operators to open the gates wide at first. However, they also reduced the outflow when the inflow dropped. The two curves follow each other.

Inflow Higher than Harvey

The peak inflow during that rapid rise exceeded the peak inflow rate during Harvey.

The map and tables on the right indicate the peak flows coming from each tributary into Lake Houston.

Note how peak inflows from Lake, Spring and Cypress Creeks on the west were fractions of the volume coming from Lake Conroe.

Pre-Release Capabilities Constrained

Raley finished his presentation with a discussion of pre-release as a possible mitigation measure. The headline below says it all. Gone are the days of seasonal lowering.

At 700 cfs, the permit limit, Raley says it would take weeks to lower the lake. But weather predictions are not accurate that far in advance.

And if the storm misses Lake Conroe, a big release from the lake could make flooding in Lake Houston worse – especially if the storm misses Lake Conroe to the south.

So the SJRA tosses the responsibility back to the City of Houston, They make the City call for the water (out of its share of the lake) if the City wants Conroe lowered

Conclusion and Insight

Raley’s presentation won’t make flood victims feel better. But it may help them understand how difficult managing floods can be.

The important thing to take away from this is that there’s room in Lake Conroe for temporary storage of stormwater. And releasing that water so that it reaches populated areas downstream before or after the peaks coming from other tributaries will be the key to minimizing flood damage.

For instance, releasing a smaller amount after a larger peak has already passed won’t flood any more homes.

Remember, flood peaks are not necessarily additive. You can’t automatically assume that all peaks will hit at the same time and pile on top of each other.

I’m sure more knowledge can be acquired from close examination of this event. For instance, one of the big differences between this storm and Harvey was the downstream representation on the SJRA board by Mark Micheletti.

But Micheletti is the only downstream representative on a seven-person board. lf that continues, you can bet no substantial changes will be made in the long-term operation and policies of Lake Conroe.

Another thing to look at is whether keeping Lake Conroe at slightly lower levels during wet seasons would give dam operators more temporary storage, and thus protect more homes and businesses both upstream and down.

Posted by Bob Rehak on 5/24/24

2460 Days since Hurricane Harvey

All River Levels Falling, Flood Danger Over, But…

May 21, 2024 – After a second round of May floods (and the third this year), all river levels are falling today. The East Fork, West Fork and main stem of the San Jacinto River are finally falling this morning. So are the water levels in Lake Conroe and Lake Houston.

But sedimentation will likely be a problem when floodwaters totally recede.

Gage Readings For Lake Conroe

The gates at Lake Conroe are still open, but only releasing 1,599 Cubic Feet per Second (CFS). That’s about a twelfth of what the San Jacinto River Authority released at the peak of this second wave of May floods.

The graph below shows that the lake level is slowly approaching its normal conservation pool of 201 feet.

Note distances to flowage easement and top of dam. Homes around lake should be built above flowage easement.

All Gage Readings on West Fork Falling

In response, the West Fork at US59 fell below flood stage yesterday evening and continues to fall.

River Grove Park is draining, but the soccer fields are not yet playable.

River Grove Park draining on 5/20/24 at 5PM after flood peak passed

At West Lake Houston Parkway, the West Fork is well within its banks and falling.

Readings on East Fork

Upstream on the East Fork at SH105, the East Fork crest has passed and the river continues to fall.

At FM2090, the East Fork is 4 feet below flood stage and falling.

The East Fork fell below flood stage yesterday afternoon at FM1485 and continues to fall.

Lake Houston and Below

At the FM1960 bridge over Lake Houston, the level continues to fall well below flood stage, but is still about a foot above normal.

At the Lake Houston dam, water levels are also falling, but the lake is also about a foot above the spillway.

Floodwaters are still being released from the lake via both the gates and spillway.

The gates can release 10,000 CFS. That means about another 7,500 CFS are going over the spillway.

Downstream, on the main stem of the San Jacinto at Highway 90, the river is well below flood stage and continuing to fall.

West Fork Still Flowing Through Abandoned Sand Pit

That’s all great news. But the West Fork is still flowing through an abandoned sand pit near the Hallett Mine. You can see the impact at the confluence of the West Fork and Spring Creek.

Confluence of Spring Creek (left) and West Fork San Jacinto (Right) on 5/20/24 at 5 PM.

Can Water Moving at 5 MPH Transport Sand?

I measured debris coming out of the pit. It was moving at approximately 5 miles per hour (MPH).

Despite what some miners claim, 5 MPH should be more than enough to carry sand downriver.

Below is an industry-standard graph that shows the speed necessary to erode, transport and deposit sand/sediment of different particle sizes. Hydrologists and geologists call it a Hjulström curve, named after Filip Hjulström (1902–1982), the man who developed it.

After converting centimeters per second to miles per hour, I superimposed the speed of the river as a blue line over the graph.

The scientific Unified Soil Classification System defines sand as particles with a diameter of 0.074 to 4.75 millimeters. I rendered that range in red at the bottom of the chart.

Blue indicates speed of water. Red indicates range of sand sizes.

Floodwater moving at 5 MPH can transport the entire range of sand sizes according to the Hjulström curve. You can see it in the photo above.

The abandoned pit captured by the river is about a mile long and a half-mile wide.

The river will need to recede before we can see exactly how much moved down to the West Fork between Humble and Kingwood, or settled at the mouth of the river near Lake Houston.

In fairness, some of the sediment deposited downstream came from natural erosion from riverbanks. But there was also unnatural erosion from development and (I have heard) other mines. It is impossible to apportion responsibility precisely.

What we can safely say is that sand mining practices have increased sedimentation downstream and few people seem eager to fight the industry … even as we get ready to launch another round of dredging that will cost taxpayers $34 million.

Posted by Bob Rehak on 5/21/24

2457 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.

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.

SJRA Reducing Lake Conroe Release Rate

May 3, 2024 – As of 10 PM last night, the level of Lake Conroe had declined slightly for several hours. That indicates inflows are now less than outflows. Accordingly, San Jacinto River Authority Board Member Mark Micheletti worked out an agreement with the SJRA General Manager to start reducing the lake’s release rate.

By midnight the release rate was down from 69,585 cubic feet per second (CFS) to 64,797. And the lake level was down from 205.13 to 204.79.

This post contains information about the new release strategy, updated river and weather forecasts, plus a list of stunning rainfall totals from yesterday.

New Lake Conroe Release Strategy

During Harvey, many downstream residents felt the SJRA released too much for too long to return the lake to normal as quickly as possible.

The new agreement reached late tonight will have dam operators lowering the release rate in 2500 CFS increments. They will then wait two hours to see if the water level is increasing or decreasing, and adjust the next increment accordingly.

This strategy lets them delay additional decreases if necessary. For instance, if new heavy rainfalls increase inflows.

Dam operators still have the flexibility to release more if necessary. But it avoids leaving the release rate too high for too long when unnecessary.

All things considered, this strategy should protect downstream residents as much as possible. It also gives Lake Conroe operators a safety margin.

No Significant Changes to Flood Forecasts Since This Afternoon

As of 9:31 PM, Harris County Meteorologist Jeff Lindner had no changes to ongoing river forecasts. He emphasized that significant flood waves will continue moving down the East and West Forks of the San Jacinto into the weekend.

New Weather Forecast Reduces Rainfall Risk

Compared to yesterday’s weather forecast, however, Lindner also revised the expected overnight rainfall downward.

“Expect a mostly calm night with a low-end chance of a few showers toward morning. With heating on Friday and the approach of another thunderstorm complex from North Texas, there will be an increasing chance of rainfall during the day,” he said. “At this time. this complex of storms looks fairly progressive during the afternoon hours, but there is some uncertainty on how the storms evolve and how fast they cross the area.”

He says that additional rainfall amounts of 1-2 inches with slightly higher isolated totals can be expected on Friday. This additional rainfall is included in the river forecast models and should not greatly alter the current river forecast.

See river forecast summaries below.

East Fork San Jacinto River at New Caney (FM 1485)

Mandatory evacuation is still in effect for the eastern side of the river from FM 1485 to Lake Houston.

“Forecasted water levels will rise 7 feet higher than earlier this week. Structures on the ground will be flooded to rooftops levels,” says Lindner. “Elevated structures will be flooded. For reference, the forecasted water level is 4 ft below Harvey.” Similar to earlier this week, the rapid rise of several feet is expected late Friday into Saturday.

Impacted subdivisions: 
  • Idle Wilde
  • Idle Glen
  • Cypress Point
  • River Terrace
  • Magnolia Point
  • Northwood Country Ests
  • Low-lying eastern portions of Kingwood, such as:
    • Riverchase
    • Woodstream
    • Woodspring Forest
As of Thursday at 9 PM

West Fork San Jacinto River at Humble (US 59)

The river will rapidly rise from upstream inflows. It will reach major flood levels and peak near 62 ft on Saturday. Widespread low-land flooding will occur. It will likely impact lower areas in West Fork subdivisions such as:

  • Belleau Woods
  • Rivercrest
  • Northshore
  • Forest Cove 
  • Kings River Estates
  • Atascocita Shores
  • Kings Point
  • Kings Harbor
  • Kings River
  • Kingwood Greens
  • Fosters Mill
  • Kingwood Lakes
  • Barrington
  • Trailwood
  • Deer Ridge Estates

Kingwood residents should expect flooding of streets and structures near the East Fork, West Fork, and their tributaries.

Harris County is revising a potential inundation map that circulated Thursday on Facebook. Lindner says to expect the type of flooding we saw during the Memorial Days storm in 2016.

The following areas will be completely flooded with several feet of water: Deerwood Country Club, Deer Ridge Park, River Grove Park, Kingwood Country Club.

Elevated residents near the river should be prepared to be cut-off through the weekend if they don’t evacuate.

As of Thursday at 9 PM

West Fork of the San Jacinto River at I-45 

Major flooding is imminent upstream and downstream of I-45 including large portions of River Plantation and portions of Woodloch downstream to SH 242 and SH 99. Flows may approach the I-45 bridge deck. The current forecast is about 1 ft below Harvey recorded levels.

As of Thursday at 9 PM

San Jacinto River Below Lake Houston 

Major flooding is expected at all locations along the lower portions of the river.

Rio Villa will be completely inundated and cut-off and well as low lying in the river bottom around Highlands and HWY 90.

High velocity flows may damage vessels and barges near I-10 and result in loss of mooring.  

Flow may approach the I-10 river bridge west of the river crossing. Additionally, high flows will result in the suspension of Ferry service.

As of Thursday at 9 PM

Spring Creek

According to Lindner, the creek is rising on the upper end due to flows from Waller and Montgomery Counties. Minor flooding is in progress along the upper portions of Spring Creek at Hegar Rd. Water levels along the creek are high, but any flooding is minor and to rural areas near the creek. 

Willow Creek 

Willow Creek has crested and is slowly falling.

Yesterday’s Storm: Gage Readings

The storm that swept through southern Montgomery and northern Harris Counties yesterday dropped impressive amounts of rainfall.

Harris County Flood Control District released the following totals at 7 PM Thursday.

  • 8.24 in. – 1050 Spring Creek @ I-45
  • 8.2 in. – 1320 Willow Creek @ Kuykendahl Road
  • 7.76 in. – 755 San Jacinto River @ Lake Houston Pkwy
  • 7.2 in. – 785 Peach Creek @ FM 2090
  • 7.12 in. – 790 East Fork San Jacinto @ FM 1485
  • 6.92 in. – 795 East Fork San Jacinto @ FM 2090
  • 6.8 in. – 765 San Jacinto River @ SH 99
  • 6.64 in. – 1745 Cedar Bayou @ FM 1960
  • 6.6 in. – 1960 Luce Bayou @ SH 321
  • 6.12 in. – 770 San Jacinto River @ SH 242
  • 5.88 in. – 780 Caney Creek @ FM 2090
  • 5.76 in. – 1040 Spring Creek @ FM 2978
  • 5.64 in. – 1940 Luce Bayou @ FM 2100
  • 5.48 in. – 1340 Willow Creek @ SH 249
  • 5.12 in. – 1056 Mill Creek @ FM 1774
  • 5.04 in. – 1950 Luce Bayou @ SH 99
  • 5.0 in. – 1080 Spring Creek @ Decker Prairie-Rosehill Road
  • 4.96 in. – 760 San Jacinto River @ US 59

Locations Out of Banks, Flooding Likely

    HCFCD also reported that the following streams/channels were out of their banks and flooding was likely.

    • 710    San Jacinto River @ Rio Villa
    • 720    San Jacinto River @ US 90
    • 740    Lake Houston @ FM 1960
    • 760    San Jacinto River @ US 59
    • 780    Caney Creek @ FM 2090
    • 785    Peach Creek @ FM 2090
    • 790    East Fork San Jacinto @ FM 1485
    • 795    East Fork San Jacinto @ FM 2090
    • 1054    Mill Creek @ FM 1486
    • 1074    Walnut Creek @ Joseph Road
    • 1084    Threemile Creek @ Joseph Road
    • 1090    Spring Creek @ Hegar Road
    • 1195    Mound Creek @ FM 362
    • 1950    Luce Bayou @ SH 99

    Flooding Possible

    The following streams were still in banks, but flooding was possible.

    • 755    San Jacinto River @ Lake Houston Pkwy
    • 765    San Jacinto River @ SH 99
    • 770    San Jacinto River @ SH 242
    • 796    East Fork San Jacinto @ SH 105
    • 1050    Spring Creek @ I-45
    • 1055    Bear Branch @ Kuykendahl
    • 1076    Birch Creek @ Riley Road
    • 1086    Threemile Creek @ FM 362
    • 1110    Cypress Creek @ Cypresswood Drive
    • 1186    Live Oak Creek @ Penick Road
    • 1190    Little Mound Creek @ Mathis Road
    • 1320    Willow Creek @ Kuykendahl Road
    • 1340    Willow Creek @ SH 249
    • 1740    Cedar Bayou @ US 90
    • 1745    Cedar Bayou @ FM 1960
    • 1960    Luce Bayou @ SH 321
    • 2200    Houston Ship Channel @ Juan Seguin Park

    Resources for More Information

    To see:

    If in doubt about whether you will flood, remember. Better safe than sorry. If you evacuate needlessly, the most you lose is a day or two. But if you don’t and you flood, you could lose everything.

    Posted by Bob Rehak on 5/3/24

    2439 Days since Hurricane Harvey

    Lake Conroe Release Rate at 90% of Harvey

    5/2/24 at 4:30 PM – The San Jacinto River Authority (SJRA) is releasing water at the rate of 69,545 cubic feet per second (CFS from Lake Conroe. That’s down a couple thousand from the 71,835 they released earlier this afternoon, the second highest release rate ever – 90% of the all-time record of 79,000 CFS during Hurricane Harvey.

    At that rate, NOAA predicted the San Jacinto West Fork at US59 would peak at 62.4 feet. Since then, they’ve reduced that back a bit to 62.2.

    However, the level of Lake Conroe is still rising slightly. It stands at 205.13 MSL (mean feet above sea level) as of 4:30 PM.

    And local leaders including Houston Mayor John Whitmire, State Rep. Charles Cunningham and City Council Member Fred Flickinger met in Kingwood to plan emergency response with first-responders.

    More Rain on Way

    The level of Lake Conroe is up significantly since this morning. And another rain storm is headed our way tonight. The National Weather Service predicts a 40% chance of more thunderstorms tonight. Anything that falls will be on top of almost 7 inches of rain received in the Kingwood area earlier today.

    Flood watches and warnings remain in effect at the present time. Any new rain will fall onto already saturated soils, resulting in rapid runoff.

    SJRA Pushing Up Against Limit

    But the SJRA is running out of room. At 207, they flood Lake Conroe homes and endanger the dam, according to Mark Micheletti, an SJRA board member who lives in Kingwood.

    Micheletti has demanded that SJRA operators throttle back releases as soon as they stabilize the Lake Conroe’s level. The SJRA hopes to keep a safety margin by not letting the lake level get above 206, but nature, not engineers will make that call.

    Meanwhile, the uncertainty has many Kingwood people in panic mode wondering whether they should evacuate. I’ve been deluged (pardon the pun) with requests for information.

    Whitmire Visits Kingwood to Plan Flood Response

    Houston Mayor John Whitmire came to Kingwood this afternoon to meet with first responders and area leaders. He wanted to personally see the situation and assess what the area needs. He met with Fire Chief Samuel Peña, first responders, State Representative Charles Cunningham and City Council Member Fred Flickinger at Fire Station 102 on West Lake Houston Parkway.

    CM Fred Flickinger (center) met with Mayor Whitmire (right), Chief Samuel Peña (left) and other first responders at Fire Station 102 this afternoon on West Lake Houston Parkway.

    Peña emphasized the need for vehicles to stay out of high water. The fire department had already made numerous high water rescues today.

    State Representative Charles Cunningham (left) also helped plan the emergency response.

    At the meeting, Whitmire also said that he had discussed evacuation orders for certain subdivisions with Harris County Judge Lina Hidalgo. After Harvey, “communication with residents” and “warning time” were identified as two of the primary things officials needed to improve.

    Current East Fork Predictions and Evacuation Orders

    According to Harris County Meteorologist Jeff Lindner, the County has issued evacuation orders for the east side of the East Fork San Jacinto from FM1485 to Lake Houston. (Lake Houston Park is on the west side.) Forecasted water levels will rise 7-8 feet higher than earlier this week. Structures on the ground will be flooded to rooftop levels. Elevated structures will be flooded.

    For reference, the forecasted East Fork water level is 3 ft below Harvey.

    Impacted subdivisions: 
    • Idle Wilde
    • Idle Glen
    • Cypress Point
    • River Terrace
    • Magnolia Point
    • Northwood Country Estates

    Current West Fork San Jacinto Predictions and Warnings

    The West Fork is rapidly rising from upstream inflows. It will reach major flood levels and will rise to near 62 ft on Saturday. Widespread low-land flooding will occur impacting the following subdivisions:

    • Belleau Woods
    • Rivercrest
    • Northshore
    • Forest Cove
    • Kings Point
    • Atasocita Shores

    In Kingwood, Lindner expects flooding of streets and the lowest structures nearest the river. He also predicts backwater impacts along the tributaries. That means high river levels could force water in channels and tributaries to back up.

    The following areas will be completely flooded with several feet of water: Deerwood Country Club, Deer Ridge Park, and Kingwood Country Club.

    Elevated residents near the river should be prepared to be cut-off through the weekend.

    I have queried HCFCD about the list of subdivisions above. It seems incomplete. But I have not yet heard back.

    San Jacinto River Below Lake Houston

    Major flooding is expected at all locations along the lower portions of the river.

    Rio Villa will be completely inundated and cut-off. 

    High velocity flows may damage vessels and barges near I-10.

    Flow may approach and potentially reach I-10 on the west side of the river.

    Real Time Inundation Monitoring

    To monitor what’s going on around you, Harris County Meteorologist Jeff Lindner suggests using the Real-Time Inundation Mapping Tool found in the Harris County Flood Warning System. From the home page, just click “Inundation Map” in the upper left tool bar, then zoom into the area of interest.

    As of 4:22 PM on 5/2/24. Note large areas already inundated.

    Easy Way to Find the Elevation of Your Home

    Don’t know the elevation of your home? Consult this post about how to find it in the USGS National Map.

    More updates later. SJRA may issue another statement at 8PM.

    Posted by Bob Rehak at 4:30 PM, Thursday, May 2, 2024

    2438 Days since Hurricane Harvey

    Lake Conroe Increasing Release Rate After Torrential Rain

    5/2/24 Noon Update: Since publishing this, Lake Conroe has continued to rise and the SJRA has increased the release rate to 66,100 CFS. – Heavy storms dumped 10-12 inches of rain in isolated areas north of Lake Conroe last night. Most areas experienced 5-7 inches. As a result, Lake Conroe has increased its release rate to 60,455 cubic feet per second and it could go higher.

    The area north of Lake Conroe has received more than 17 inches in the last week.

    Engineers are currently modeling several different scenarios. The current inflow is more than two times greater than the outflow. The current release rate is already the second highest in the history of Lake Conroe.

    Source: SJRA as of 10:00 AM 5.2.24.

    Current Situation

    According to Jeff Lindner, Harris County meteorologist, significant flash flooding is ongoing from north of HWY 105 to southern Montgomery County and the northern portions of Harris County.

    At 8:27 am, radar showed the storm had moved into northern Harris, and northern Liberty Counties.

    RadarScope Pro Screen Capture at 8:23 AM, 5.2.24, Orange indicates 5″.

    It dumped 6 inches of rain in my gauge in two hours. And the total is still climbing.

    Such high hourly rainfall rates result in street flooding. Lindner warned people not to travel unless absolutely necessary.

    According to Lindner, “There may be a break in the activity in the afternoon hours before another complex of storms arrives overnight into Friday morning with additional heavy rainfall. But confidence in the forecast is not high.”

    Impact of Rains

    “Significant rainfall has also occurred over the headwaters of the East Fork of the San Jacinto River. New flood waves will certainly be generated on both the East and West Forks of the San Jacinto River,” Lindner added. The same holds true for Lake Livingston and the Trinity River.

    The heavy runoff over already saturated grounds will migrate downstream Friday into the weekend. 

    The SJRA does not have a dam on the East Fork and can’t control it. Dam releases on the West Fork do not impact the East Fork, but do impact Lake Houston.

    Lake Conroe Release Rate Increasing, Max Uncertain

    Lake Conroe virtually quadrupled its release rate from 17,000 cubic feet per second (CFS) at 7 AM to 60,455 CFS at 9:45 AM.

    The lake level at 10:48 AM had reached 204.4 – 3.4 feet above normal.

    Mark Micheletti, San Jacinto River Authority (SJRA) board member, said that SJRA engineers are modeling several release scenarios. So the ultimate release rate is uncertain as of this writing.

    The flowage easement at Lake Conroe is 207. That’s the elevation at which homes start to flood.

    Some people will criticize the SJRA for not releasing more water sooner. However, it was not an easy call.

    Lake Houston was already flooding from the East Fork. And a massive release coming down the West Fork could have flooded homes.

    Micheletti added, “Hydrographs are useless in a situation like this because you don’t yet know what the release will be,” he added.

    During Harvey, the SJRA released 79,000 CFS. So, they are already at 75 percent of the devastating Harvey release rate.

    But even with that, the current release rate is only about one third of the estimated water coming into the lake. “So that’s our challenge,” said Micheletti. The release rate will almost certainly go higher.”

    The Harris County Flood Warning system showed that the San Jacinto West Fork is still within banks, but that likely won’t last long.

    Before the heavy rains moved south this morning, river gages on the East and West Forks were dropping slowly as floodwaters receded from earlier in the week. But we’re about to experience a second wave there.

    If you’re in a place that has flooded before, the safest course of action is to start developing an action plan now.

    River Predictions

    At 10 AM, Lindner released new hydrographs for the West Fork, East Fork, and the area below Lake Houston.

    West Fork

    As of 10 AM, 5.2.24

    A rise to flood stage will occur today with a rise above major flood levels on Friday. Widespread low land flooding near the river is expected. The forecast may need to be increased more because of the uncertainty over Lake Conroe releases.

    While there will be widespread low land flooding, the lowest structures in Kingwood are not impacted until over 60-62ft. Expect this level of water in the river to create backwater in tributaries that could lead to additional flooding.

    A reader sent in this photo of the new Northpark South development between the West Fork and Sorters-McClellan Road.

    NorthPark South already underwater from rains. 5.2.24 at 11 AM. Photo by Jody Binnion.

    East Fork

    A significant rise on the East Fork is expected as the upstream flood wave moves downstream. Forecasted water levels will reach 6-8 ft higher than earlier this week. This expected flood level will be higher than TS Imelda and will be similar to October 1994. Even elevated structures may be flooded, according to Lindner.

    Below Lake Houston

    Other Flooding

    As I write this, I have received word that Taylor Gully is flooding and parts of nearby streets are closed.

    White Oak Creek is also flooding. Royal Pines, the new development on White Oak at the northern end of West Lake Houston Parkway, has also flooded neighbors’ yards and a garage.

    Flash flooding is ongoing along Willow and Spring Creeks, which are rising rapidly. Flooding along these creeks is becoming likely. Widespread street flooding and some structure flooding is possible.

    A training band of thunderstorms will produce another 2-4 inches of rainfall on top of the already 4-6 inches that has fallen in these watersheds.

    Pardon the pun, but the situation is very fluid. Sometimes new information comes in faster than I can update it.

    I will post updates including photos when the rain lets up.

    Posted by Bob Rehak at 10:00 AM on 5/2/24

    2438 Days since Hurricane Harvey

    Phase 1 of Northeast Water Purification Plant Expansion Nears Completion

    According to a December 15 press release by the Texas Water Development Board, Phase 1 of Houston’s new Northeast Water Purification Plant expansion is nearing completion. Phase 1 will supply 80 million gallons per day of treated surface water to the residents of Harris County, Fort Bend County and City of Houston.

    Two more phases remain. Phase 2A will deliver another 80 million gallons per day to the same areas. Phase 2B will deliver 160. So the entire complex, when complete, will deliver another 320 million gallons a day. That’s in addition to the 80 million gallons per day the original plant delivered before expansion.

    Goals of Plant

    The Texas Water Development Board provided $1.9 billion for the Northeast Water Purification Plant expansion project, making it one of the largest in the country.

    The plant has two goals:

    • Provide water for a population that increases by almost a million people per decade.
    • Reduce groundwater usage and subsidence.

    Completion Estimated in 2025

    The TWDB did not provide a date for expected completion of the next two phases, but at a May 2023 community meeting, project managers estimated a completion date in 2025.

    Artist’s rendering of completed project, looking NNW. Expansion area outlined in orange.

    Satellite photo from May with substantially complete phase outlined in red.
    Phase 1 in center of plant now substantially completed. Original plant is on far right. Photographed in August 2023.
    Phases 2A and 2B still under construction. Photographed in August 2023. Looking south.
    Entire plant. Looking east across older area toward new construction. Lake Houston at top of frame.
    Plant’s new Intake Facility. Those twin pipelines are big enough to drive pickup trucks through.

    The Luce Interbasin Transfer Project is associated with the expansion of the treatment plant. The channel from the Trinity River will ensure a steady supply of water in Lake Houston as Montgomery County’s growth demands more water from Lake Conroe.

    Reducing subsidence is paramount for the region. Subsidence has been linked to flooding. In fact, a whole subdivision on Galveston Bay in Baytown became uninhabitable before the State created the Harris Galveston Subsidence District.

    Here’s its story.

    Posted By Bob Rehak on 12/18/23

    2302 Days since Hurricane Harvey

    Why Lake Houston Is So Full in a Drought

    I flew over Lake Houston this morning in a helicopter. I expected to see the barren lake bed in places like you could during the 2011 drought. However, much to my surprise, the lake was virtually full.

    Coastal Water Authority Shows Lake Down Only 6 Inches

    The Coastal Water Authority, which manages the lake for the City of Houston, shows Lake Houston is only down a half foot.

    Coastal Water Authority dashboard as of 8/12/23 at 6PM

    Water was lapping at the edge of the the spillway.

    Lake Houston Dam spillway. Photo take 8/12/23 at approximately 10am.

    SJRA Shows Lake Conroe Down About 15 Inches

    Lake Conroe is down about 15 inches from its normal conservation pool (the target level). And it hasn’t released any water downstream toward Lake Houston in months. The SJRA’s dashboard shows

    SJRA Dashboard on 8/12/23 at 6PM.

    Luce Bayou InterBasin Transfer Canal Bringing the Water

    So what’s keeping Lake Houston full? What is offsetting drought and evaporation?

    A quick check of the gages on the Harris County flood warning system shows areas far upstream have gotten small amounts of rain. But the most water we saw moving all day was coming from the Trinity River via the Luce Bayou InterBasin transfer project.

    Luce Bayou Inter-Basin transfer canal bringing water to Lake Houston from the Trinity River on 8/12/23 at 9 am.

    Gages upstream from Lake Livingston, which captures water coming down the Trinity River from Dallas/Fort Worth, recorded approximately 11 inches of rain in June, July and August (to date).

    Lake Conroe got enough rain to offset some evaporation but not enough to supply Montgomery and Harris Counties.

    It’s nice to have backups for Lake Houston in a drought, especially widely scattered backups that can capture rain moving through different parts of the region.

    Posted by Bob Rehak on 8/12/23

    2174 Days since Hurricane Harvey

    Lake Houston Gates Project Moves Closer to Reality

    The Lake Houston Gates Project is moving closer to reality with breakthroughs on the benefit/cost ratio, funding and endorsements.

    City of Houston Mayor Pro Tem Dave Martin and Chief Recovery Officer Stephen Costello provided updates on 2/27/23 at City Hall on the Lake Houston Gates Project. The wide-ranging, hour-long discussion covered several related topics. They included:

    • A critical path for construction
    • Dredging of the lake
    • Funding for gates and dredging
    • Several related engineering studies
    • A favorable ruling from FEMA on the Benefit-Cost Ratio
    • An endorsement to the area’s legislators by the Greater Houston Partnership.

    Need For Gates

    For those new to the area, the City of Houston has been pushing to add gates to the Lake Houston Dam ever since Harvey in 2017. Upstream, Lake Conroe’s gates can release 150,000 cubic feet per second (CFS). But Lake Houston’s can only release 10,000 CFS.

    The disparity in discharge capacity complicates joint-reservoir-management and pre-release strategies designed to avoid flooding by reducing the water level in Lake Houston.

    Lake Houston releases cannot keep up with Lake Conroe’s. And pre-releasing water from Lake Houston takes so long that storms can veer away during the lowering process, often resulting in wasted water. That’s an important consideration for a water-supply lake.

    According to Martin and Costello, the gate project will:

    • Serve as the first phase of a long-term effort to extend the life of the Dam
    • Enable the rapid lowering of lake levels in advance of a flood
    • Eliminate the need for a seasonal lowering of both Lake Houston and Lake Conroe
    • Provide potential water-rights savings
    • Protect an estimated 5,000 residential properties in the surrounding area
    • Yield an estimated half billion dollars in economic benefits during the life of the project

    Gates, Funding, BCR, Studies

    Preliminary engineering studies evaluated about a dozen different alternatives for adding discharge capacity to Lake Houston. The City initially favored adding crest gates to the spillway portion of the dam.

    However, the City discarded that idea as “too risky” after further study. The engineering company cautioned the City that it would have a difficult time finding contractors willing to risk modifying a 70-year old concrete dam. The potential liability was just too great. So the City then revisited adding various numbers of tainter gates to the eastern, earthen portion of the dam.

    Because tainter gates exceeded FEMA’s funding, the City had initially focused on crest gates. But after investigating the safety issues, the City decided to seek more funding for tainter gates instead.

    The City now recommends adding 11 tainter gates.

    Recommended location for new tainter gates is next to old ones, not farther east as I conjectured earlier.

    The picture below is slightly wider and shows more of how both halves of the dam come together.

    If funding comes through, new gates would go in the upper right along the earthen portion of the dam, next to the old gates.
    Funding Needs

    FEMA initially set aside $50 million for the gates. Plus Harris County committed $20 million in the 2018 Flood Bond to attract FEMA’s match. But the latest construction estimates show eleven tainter gates could cost between $200 and $250 million.

    After engineering and environmental studies, only $68.3 million in funding remains. That includes an earmark secured by Congressman Dan Crenshaw. So the City is seeking another $150 million from the State of Texas. Martin and Costello have made weekly trips to Austin so far during this session to line up support from legislators, committee chairs, and the Texas Division of Emergency Management.

    Social Benefits Improve Benefit/Cost Ratio

    All this is suddenly possible because of a favorable ruling from FEMA on the benefit-cost ratio (BCR).

    For years, Houston had struggled to get the BCR for the gate project above 1.0 (the point at which benefits exceed costs). Usually, FEMA strictly interprets benefits as “avoided damages to structures.”

    But Houston Mayor Sylvester Turner and Costello met with FEMA to argue that the problem was much bigger than damaged structures.

    As a result, FEMA allowed the City to add the value of “social benefits” to the BCR. Social benefits can include such things as avoiding lost wages when businesses are destroyed; transportation disruptions that reduce the region’s productivity; reducing negative impacts on student achievement when schools are disrupted; and more.

    The social-benefit ruling covers a number of City projects, not just the gates. It should also benefit other areas, especially rural ones.

    Said Costello, “The minute the social benefits came in, everything was great.” Instead of struggling to reach 1.0, the City is now far above it.

    Greater Houston Partnership Endorsement

    With that out of the way, the Greater Houston Partnership wrote a powerful letter to state legislators seeking their support for the gate project. See below.

    Greater Houston Partnership letter endorsing Lake Houston Gates. For a printable PDF, click here.

    The Partnership includes business leaders from 900 member companies in the 12-county Houston Region.

    Dredging Update

    While pressing ahead with the gates project, the City is also working on a long-term dredging plan for the lake and working with the SJRA on sedimentation and sand-trap pilot projects.

    The Texas Water Department Board (TWDB) has estimated sediment inflow to Lake Houston at about 380 acre-feet of material annually.

    The lake has already lost more than 20,000 acre feet of capacity due to sedimentation. That worsens flooding. While the Federal Government supports efforts to improve Lake Houston now, the chances of getting more money in the future will be reduced – unless we can show that we’re at least keeping pace with annual sediment deposits.

    Since Harvey, FEMA, the Army Corps, TWDB, and City of Houston have removed almost 4 million cubic yards of material from the lake at a cost of $226 million.

    We have to prevent more sediment from coming downstream or dredge it after it gets here.

    Stephen Costello, City of Houston Chief Recovery Officer

    The City is currently lobbying for another $50 million for maintenance dredging to add to the money secured in the last legislative session by now-retired State Representative Dan Huberty. New Representative Charles Cunningham will reportedly now carry that banner forward along with State Senator Brandon Creighton.

    Legislative News to Follow

    March 10th is the last day to file bills in the Texas Legislature this year. Please visit the legislation page on ReduceFlooding.com for updates once bills are filed and start moving forward in Austin.

    Thanks to all of our elected and appointed representatives who have pushed so hard on so many fronts for the last 2008 days to tie all the pieces of this complicated flood-mitigation puzzle together.

    Posted by Bob Rehak on 2/27/2023

    2008 Days since Hurricane Harvey

    Engineers Testifying for LCA are Electrical and Chemical, Not Civil

    Yesterday’s post cited the testimony of two “licensed professional engineers” in the State of Texas who claimed that Lake Conroe could not refill from rainfall in the Spring or Fall after being lowered one foot to provide an extra margin of safety, which helps prevent flooding homes on both sides of the dam. However, the lake did refill…and then some…within two days after the Lake Conroe Association (LCA) filed their affidavits in its lawsuit to prevent the seasonal lowering.

    Deeper investigation reveals that neither engineer is a civil engineer. One is an electrical engineer and the other a chemical engineer.

    From https://pels.texas.gov/roster/pesearch.html

    “The Engineer Shall Not…”

    Here’s why it is important. Note Paragraphs A and C below.

    From Page 84 of PDF at https://pels.texas.gov/downloads/lawrules.pdf

    Paragraph A states that engineers shall practice only in their areas of competence.

    Paragraph C states, “The engineer shall not express an engineering opinion in deposition before a court … which is contrary to generally accepted scientific and engineering principles without fully disclosing the basis and rationale for such an opinion.”

    There was no such disclosure in their affidavits.

    In fairness, the engineers also testified as residents and they had more concerns than flooding.

    However, both:

    • Cited their professional credentials at the start of their affidavits – without disclosing their areas of expertise.
    • Drew the same conclusion about the inability of the lake to refill through rainfall – without stating the basis of their conclusions.

    Mr. Elliott has retired and his license is inactive. Mr. Waitts’ license is still active.

    Background

    Only two days after LCA filed the engineers’ affidavits, rainfall raised the lake level two feet above normal, and threatened homes and businesses. SJRA had to release water at almost 10,000 CFS to avoid flooding them.

    Seasonal Release from Lake Conroe, 529 cfs from one tainter gate open six inches.
    SJRA Seasonal Release on 4/15/2020. One tainter gate open six inches released a slow, steady stream of 529 cfs.

    Without the seasonal lake lowering policy, someone on either side of the dam would likely have flooded. Dam operators would have been forced to flip a coin to see who. But the seasonal lowering – about which the chemical and electrical engineers complained – helped protect everyone. No one, to my knowledge, flooded on either side of the dam due to river flooding.

    Posted by Bob Rehak on 5/23/2021

    1363 Days after Hurricane Harvey

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