Storm Report: Flooding Delayed Because of Rainfall Distribution
4/29/24 – The rainfall distribution in last night’s storm was very uneven. It ranged from a tenth of an inch in some places to more than 10 inches in others.
Totals to the north and east of Houston approached 8-10 inches in places. But most of Harris County received less than 2 inches.
Regardless, the heaviest rainfall in the upper reaches of the East Fork San Jacinto watershed will migrate downstream in the next 2-3 days and cause flooding in low-lying areas near New Caney. The West Fork should only be moderately affected.
After three hours of driving around this morning, all ditches and minor streams that I saw appeared to be within their banks.
Very Uneven Rainfall Distribution
The farther north and east you went, rainfall increased. The gage at US59 and the West Fork received only 1.76 inches.
My rain gage by Kingwood High School recorded 3.11 inches. And a friend who lives by the Montgomery County line recorded a little more than 4 inches.
The Trinity River Authority recorded 10.92 inches on Caney Creek at a small town called Fryday north of Lake Livingston. That gage recorded a whopping 6 inches in one hour between 8 and 9 PM last night.
A gage in Mont Belvieu recorded almost 9 inches. Almost 5 inches of that fell in one hour between 2 and 3 AM.
Most of the higher totals occurred in watersheds that will not drain directly into Harris County. At 1PM on Monday, only six gages in and around the county showed danger signals (meaning a stream was in danger of coming out of its banks).
Most Streams in Banks
The good news: Only one stream at this hour is in danger of coming out of its banks upstream from Lake Houston. That’s Peach Creek near 2090. Peach Creek forms the western boundary of Lake Houston Park.
The bad news: SJRA is releasing almost 10,800 cubic feet per second from Lake Conroe at noon due to heavy rains north of the lake.
Farther south, however, totals dropped off rapidly. Parts of western and southern Harris received only a tenth of an inch!
Flood Forecasts
Because of the rainfall distribution, you need to look upstream from where you are to see whether your area is in danger of flooding. You also need to factor in travel time for the floodwaters. Due to the distance of the heaviest rainfall, flood impacts will be delayed.
Lake Houston
Inflows from the East Fork, Peach and Caney Creeks, and Luce Bayou will result in a rise in the lake level Tuesday into Thursday. Elevated water levels and flows will be likely through Lake Houston for much of this week, according to Jeff Lindner, Harris County Meteorologist.
West Fork San Jacinto
Lindner expects no flooding at this time…again due to the very uneven rainfall distribution.
Much of the rainfall overnight fell above (north) of Lake Conroe. That will buffer some of this inflow. Additionally heavy rainfall largely missed Spring and Cypress Creeks and only modest amounts occurred along middle and upper Lake Creek. So, additional inflows below Lake Conroe look to be minimal.
The river is not expected to reach flood stage at US 59. However, you should continue to monitor the situation for any changes.
This morning, the West Fork was up slightly. Large amounts of foam and debris were moving downstream. But even low-lying areas such as River Grove Park and the area under the US59 bridge were well above water.
That could change by tomorrow morning.
Worst Flooding Will Be on East Fork at New Caney
A significant rise in the East Fork will start on Tuesday into Wednesday. The river will rise just below major flood level later this week.
At the forecasted levels, FM 1485 will be impassable on the west approaches and several roads downstream of FM 1485 will become flooded and impassable on the west side of the channel. Additionally low lying areas along the river in River Terrace will experience high water, according to Lindner.
Stay tuned for more updates tomorrow and Wednesday.
Posted by Bob Rehak on 4/29/24 based on information provided by Harris County Meteorologist Jeff Lindner
2435 Days since Hurricane Harvey
