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.
As of 6 PM, May 19, floodwaters are declining in this reach of the river. The crest has moved downstream toward Lake Houston.
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.
At 5 PM, the soccer fields, picnic area and boat launch at River Grove Park were also partially underwater. And water was rising quickly.
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.
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.
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.
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.
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.
