Confluence of East Fork and Caney Creek after Heavy Weekend Rains

Despite Heavy Weekend Rains, Most Area Channels and Streams Stayed Within Banks

Despite heavy weekend rains, with a few exceptions, streams and channels stayed within their banks. There are several possible explanations.

  • Soil was dry before the rains.
  • Rainfall came in two waves separated by several hours, allowing the first peak to start working its way through the system before the second hit.
  • The amount of rainfall was within the designed capacity of most channels.
  • The heaviest storms occurred under relatively narrow bands of training supercells.
  • Harris County Flood Control has been actively working on channels!

Rainfall Map of Heavy Weekend Rains

In the image below, note how much higher the rainfall totals are near the red line compared to areas farther away. Most upstream areas received less than an inch or two, limiting the amount that traveled downstream.

Red line indicated path of supercells that tracked across the center of the county last weekend. Note how highest rainfall totals parallel line.

Heavy But Not Harvey

If you were under one of those supercells, you probably received 5-8 inches of rain between Saturday afternoon and Sunday morning – a little more than a 12-hour time span. Consulting NOAA’s Atlas-14 Rainfall Probability table for this area, you can see that those totals correspond to 2- to 10-year storms. Heavy! But not Harvey!

atlas 14 rainfall probabilities
NOAA’s Atlas-14 rainfall probabilities for the Lake Houston Area

Storms Tracked Perpendicular to Most Watersheds

In Harris County most watersheds track from NW to SE. But the storms tracked perpendicular to that. That limited the amount of water dumped in most watersheds. It might have been very different had the storms tracked parallel with bayous.

Here was the channel status report from Harris County Flood Control on Sunday shortly after noon. It shows that virtually all channels were well within their banks. Only the gage at Luce Bayou and SH321 in Liberty County indicated flooding was a possibility near Lake Houston (warning triangle in upper right).

Despite receiving the highest rainfall total in the area (8.56 inches)…

…Luce Bayou never did come out of its banks at that location. See below. As of today, Luce is falling.

Halls Bayou near 45 briefly came out of its banks, but no structures were reported flooded. Same for Greens Bayou at 59. Water briefly got up to the feeder road there.

Brickhouse Gully, White Oak and Buffalo Bayous were also briefly in danger of coming out of banks in places, but receded quickly according to a HCFCD source. They were all back in banks before I could get there with a camera.

Photos of Area Streams and Bayous

At the East Fork and FM1485, I found a high water caution sign on the road Sunday afternoon. But again, the river was well within its banks. The closest it came to flooding was 2 feet from the top of bank three hours before I took this photo.

Here’s how some other local streams and channels fared in the heavy weekend rains.

A tributary channel of Bens Branch between Woodridge Forest and Northpark Drive next to Kingwood Park High School. That cleared area is the new Preserve at Woodridge that will offer 660 SF homes.
Bens Branch looking E (downstream toward Woodland Hills Drive. CVS on Northpark Drive (left). This was the highest part of the highest stream I found. Notice how it’s almost coming out on the left.
St. Martha’s School Parking lot flooded again a little farther downstream on Bens Branch.
Looking west at Bens Branch toward West Lake Houston Parkway. Note debris line on the left bank in the sun.
The debris line in Taylor Gully shows water never got more than halfway up the bank. Looking upstream from the Maple Bend bridge.
Kingwood Diversion Ditch north of Walnut Lane in distance just hours after tornado ripped through area.
Confluence of East Fork San Jacinto (right) and Caney Creek (left). Note docks still above water on right.

No Reports of Flooded Structures in Harris County

As of 8 PM Monday, Harris County Flood Control had not received any reports of structures flooding from the heavy weekend rains.

Storms of this magnitude are common in Houston, but not for January. Jeff Lindner, Harris County’s meteorologist remembered two in the last decade.

“We had comparable totals on 1-9-2012 in the Brays Bayou watershed (6.6 inches peak in 12 hours). On 1-18-2017, we also had several 4-7 inch gage readings on Brays and 7.0 inches in 12 hours on Lower White Oak Bayou.”

For now, most Harris County residents can chalk this one up in the “close-call” column. But let’s remember that people in Plum Grove DID flood. And pray for the tornado victims in Humble, Kingwood and Forest Cove.

Posted by Bob Rehak on 1/10/2021

1595 Days since Hurricane Harvey