West Fork

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