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.
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!
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.
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
