Tag Archive for: river flooding

NWS Says Chance of San Jacinto River Flooding in Next Three Months is Minor

The National Weather Service (NWS) predicts only minor flood risk for both the West and East Forks of the San Jacinto through the end of May. That’s the good news.

NWS predicts only minor long range flood risk for the East (38.85%) and West Forks (26.22%) of the San Jacinto.

Drought Conditions Expanding Across Texas

But there is a downside: potential drought.

The reason for the low risk has to do with a below-average rainfall pattern across much of Texas. The Texas Water Development board posted two stories in the Texas Water Newsroom last week about the potential for drought. Large parts of the state are already severely behind on rainfall for the year and the pattern is expected to continue through May when weakening La Niña conditions could return us to normal.

Source: Texas Water Development Board as of end of February 2021.

The map above shows that most of the Houston area has received about 90% of expected rainfall year to date. But large parts of the state have received less than 20%. TWDB predicts those dark areas on the map will expand at least through May. At that point, TWDB predicts only the extreme eastern part of the state will not be in some kind of drought condition.

At the end of February, drought covered just over half the state, according to the TWDB. Statewide storage in our water-supply reservoirs is at 82 percent of capacity, about three and a half percentage points less than normal for this time of year. 

Drought Relief Could Come as La Niña Fades

Says Dr. Mark Wentzel, Texas Water Development Board Hydrologist, “The National Weather Service anticipates drought expansion across all but the eastern edge of the state by the end of May. Looking a little farther out there is some good news. La Niña conditions, that are at least partially responsible for drought in Texas, are expected to dissipate after April.”

So, the river flooding outlook could be very different by Hurricane season this year.

Did snow in February not help? Not really. Wentzel points out that snow is mostly air. It takes up to a foot of snow to equal and inch of rain.

Posted by Bob Rehak on 3/14/2021

1293 Days since Hurricane Harvey

Excessive Rainfall Threat from Beta Spreads Inland

As of mid-day Sunday, all of East Texas now faces some level of excessive rainfall and flash flood risk from Tropical Storm Beta.

The projected path of the storm has shifted inland, so rainfall will reach father north. The latest track now takes the storm on a path right up US59 from Sugar Land to Humble and Kingwood. However, Beta likely be a tropical depression by the time it reaches the north side.

Kingwood is the blue dot next to Spring.

Six to 15 Inches of Rain Now Predicted

According to the local National Weather Service office and the National Hurricane Center, most of the Houston region can expect 6 to 15 inches with the highest totals closer to the coast.

Harris, Montgomery and Liberty Counties (and the whole Houston region) face a high to moderate threat of flooding rains. The first rainbands from Beta have already started to move onshore today, but the heaviest rain will not occur until Monday into Tuesday.

North Houston Under Moderate Flooding Rain Threat

Flash Flood Watch in Effect

The entire region is under a flash flood watch. Coastal areas also face storm surge and tropical storm warnings.

Slow Moving Storm Will Produce Prolonged Rains

Beta is meandering slowly at about 3 mph northwest toward the coastline west of Houston and will then curl back over Houston. It should move inland sometime Monday or Monday night and turn from a storm into a depression by the time it reaches Houston.

However, Beta could dump rain on us from later today all the way through Wednesday.

40-50% Chance of Tropical Storm Force Winds Reaching North Houston

The North Houston Area has a 40-50% chance of seeing tropical storm force winds from Beta.

If the high winds reach this far inland, they would likely arrive Monday evening. Winds extend outward from the center for 195 miles as of Sunday morning.

Feeder Bands Extend Outward 190 Miles

In fact, at 11 a.m. Sunday morning, the first feeder band was approaching the eastern side of Houston, as you can see in the radar image below.

This image shows how the wind and rain from Beta could remain with us for days as the storm’s center wanders around the Gulf.

These feeder bands reach out 190 miles. That is roughly the distance from Houston to San Antonio. So Beta will produce long-duration rainfall from the middle Texas coast to southern Louisiana. 

Flash, Urban, and River Flooding Likely 

The National Weather Service warns that coastal flooding will remain a threat through midweek with the worst of the storm surge anticipated on Monday and Tuesday. 

Elsewhere impacts from the excessive rain include:

  • Rainfall flooding may prompt evacuations and rescues.
  • Rivers and tributaries may rapidly overflow their banks.
  • Small streams, creeks, canals, and ditches may become dangerous rivers.
  • Flood control systems and barriers may become stressed. 
  • Flood waters may cover escape routes. 
  • Streets and parking lots may become rivers of moving water with underpasses submerged.
  • Driving conditions may become dangerous. 
  • Many roads and bridges may close with some weakened or washed out.

Lake-Level Situation

According to the SJRA, Beta has the potential to dump up to 8 inches of rain in Montgomery County. 

SJRA is operating under standard protocols for a severe weather event and will be onsite at Lake Conroe throughout the duration of Tropical Storm Beta.  

Lake Conroe remains 18 inches low, and based on the current forecast, no reservoir releases are expected. 

SJRA

Real-time information on lake level can be found on the SJRA homepage at the “Lake Operations and Rainfall Dashboard” link.

At of this writing, Lake Houston is down a foot compared to its normal pool level (41.38 vs 42.4). You can monitor Lake Houston levels via the Coastal Water Authority website.

Monitor Downstream River Levels

You can monitor stream and river levels in near-real time at Harris County Flood Warning System. Make sure you check out the inundation mapping feature.

Posted by Bob Rehak on 9/20/2020 based on information from the National Weather Service and National Hurricane Center

1118 Days after Hurricane Harvey

East and West Forks Out of Banks Already, Flash Flood Watch Extended to 2 a.m. Wednesday

My friend, John Knoerzer, owner of Uniserve Air Conditioning, sent me this video from East End Park around sunset tonight. It shows the East Fork of the San Jacinto River has already come out of its banks. This was at about 6:22 p.m. Tuesday.

Even Gus the Poodle knows to stay away from the raging East Fork. Shown here: the North Loop Trail in East End Park.

I have no pictures from the West Fork, so this graph will have to do. It shows that the West Fork at US59 is already out of its banks and in the moderate flooding stage.

Flash Flood Watch Extended to 2AM Wednesday

Meanwhile, the National Weather Service has extended the Flash Flood Watch for Houston until 2 a.m. Wednesday.  This means conditions are favorable for flooding to occur. A nearly stationary weak boundary is focusing training showers and thunderstorms across the watch area. Very heavy rainfall is occurring in a short time period, which can cause flooding of streets, creeks and bayous. With the loss of daytime heating, precipitation should begin to gradually weaken as we head into the overnight hours. 

Said Jeff Lindner of Harris County Flood Control, “Rainfall amounts of 5-9 inches occurred this afternoon over NE Harris County in the Kingwood/Humble area resulting in significant street flooding. Water is taking time to go down due to the large volume of water that fell in such a short period of time.”

Areas under flash flood watch as of 8:30PM Tuesday night.

Romerica Land Going Under for 7th Time in 14 Months

Harris County’s Real Time Inundation Mapping System shows that the area below the Barrington where Romerica hopes to build it’s residential, commercial and hotel high rises is largely under water as of this writing. That will make the seventh flood in the last 14 months. At times like these, I wish people, i.e., developers with dreams, would learn to listen to nature.

Take Protective Action

Be Prepared.  People should bring their pets inside and delay travel or outdoor activities during periods of heavy rainfall.  If travel is unavoidable, reduce your speed to avoid hydroplaning.  If a Flash Flood Warning is issued for your area, DO NOT travel.  

Turn Around, Don’t Drown®:  Do not drive through flooded areas.  If you see water covering the road, do not attempt to cross it.  Only a few inches of water can float a vehicle . If you find yourself in a dangerous situation where your vehicle is taking on water, get out of the vehicle, get to a higher position, and call 911.   

Monitor Official Sources for Current Information:  Harris County Flood Warning System (harriscountyfws.org), Houston TranStar (houstontranstar.org), and the National Weather Service Houston/Galveston Forecast Office (weather.gov/hgx).

Monitor Stream, Bayou, and Creek Conditions:  Rain may move repeatedly across the same area, causing creeks and bayous to rise and possibly exceed their banks.  Stay informed of current conditions and avoid traveling near creeks and bayous.

Avoid Traveling during Periods of Heavy Rain:  Rain can reduce visibility and prevent you from seeing the road ahead, which could lead to accidents.

Posted by Bob Rehak on 5/7/19 at 8:30 PM

616 Days since Hurricane Harvey