East Fork Flooding at FM1485

East Fork Flooding Migrates Downstream

Two days ago, I wrote about San Jacinto East Fork Flooding at FM2090 in Plum Grove. Yesterday, floodwaters were peaking downstream at FM1485/SH99. No homes were threatened that I saw, but at least one vehicle stalled and was abandoned.

Pictures Taken on 4/10/23 Just After Peak

See the pictures below that I took Monday afternoon when the river was at 63 feet.

Looking west along SH99 at the San Jacinto East Fork where FM1485 parallels the Grand Parkway.

Note the difference in the width of the spans in these bridges. The newer bridge is at least 5X wider. Because water flows right to left, this creates a bottleneck that causes the roads in this area to go underwater frequently. TxDoT probably needs to widen the 1485 bridge or elevate the roadway or both.

Looking east. Upstream (left) of the 1485 bridge, the East Fork remained placid. But downstream, you can actually see the currents in the rushing water.
Looking east from over eastbound FM1485 as vehicles attempted to plough through water. Note the black car stalled at the side of the road farther up. That one didn’t make it.
Looking west at same location. Despite the dangers, vehicles persisted through the water. There was no room for them to turn around.

All this was caused by rain falling 20 or more miles upstream last week.

According to the stream elevation table below, the floodwaters at FM1485 have since receded.

From Harris County Flood Warning System.

The floodwaters are moving even farther downstream toward the headwaters of Lake Houston. According to the Harris County Flood Warning System, the lake elevation is still about a half to a full foot above the spillway. According to USGS, the top of the spillway is at 42.4 feet above sea level.

From Harris County Flood Warning System.

As of this writing (noon on 4/11/23), SJRA has scaled back its releases from Lake Conroe to about 1000 cubic feet per second (CFS).

Caution to Swimmers and Waders

Swimming or wading in floodwater can endanger your life. A cubic foot of freshwater weighs about 62 pounds. Rapidly moving water that rises above knee level has enough force to easily knock adults over and sweep them downstream.

The East Fork at FM1485 is still moving at more than 4000 CFS!


So swimmers and waders beware. This morning a reader wrote me about a woman and her daughter who were killed in the East Fork after Harvey. The woman could not battle the current. Her daughter tried to save her and both died.

Understand also that floodwaters can easily scour the riverbed to create drop-offs in unexpected places. Even if you could safely wade in areas before the flood, after the flood, you could easily step into holes over your head.

If you find yourself swept up in a strong current, don’t try to swim against it. Swim perpendicular to it or with it to reach shore.

Posted by Bob Rehak on 4/11/2023

2051 Days since Hurricane Harvey