Jeff Lindner, Harris County Flood Control Meteorologist just issued a heavy rainfall warning. Lindner notes that the line of strong thunderstorms currently moving across the area will drop rainfall amounts of 1-3 inches.
The good news: the leading edge of this line is becoming detached from the outflow boundary. That suggests storms will weaken as they move southward. Rainfall rates which were 2-4 inches earlier over N Waller and Montgomery Counties have lessened to near 1-2 inches. The main threat now is short duration street flooding in areas with the heaviest rainfall.
Tonight’s Forecast
Lindner points to extremely active radar out west along the Rio Grande. He says that’s where the next round of weather will be developing. He expects it to move quickly toward our area tonight. Models show this line of storms quickly reaching the area between midnight and 400 a.m. But at the speed it’s moving, he predicts only another 1-2 inches for most areas with this line.
Intercontinental Radar as of 8PM Sunday night, 5/24/2020
Monday Prediction
Continued high rain chances. The air may take much of the morning and early afternoon to recover from the early morning line of weather, but temperatures will only need to reach the low 80’s to trigger more storms. It will not take much heating to set things off, he warns. Storm motions could be fairly slow Monday afternoon and this could lead to excessive rainfall rates in a short period of time.
Tuesday-Thursday: Continued Threat
Upper level disturbances remain parked over the state with rounds of storms at nearly any time. Heavy rainfall will continue to be a threat.
Rainfall Amounts Add Up Changing Nature of Threat
Lindner concludes, “Moisture profiles certainly support heavy to excessive rainfall rates as seen today and if storms slow of train for a period of times totals could quickly add up. Grounds will saturate over time leading to increasing and eventually maximum run-off conditions…so the threat may grow from mainly street flooding to potential rises on area creeks, bayous, and rivers.”
Lindner concedes that it’s hard to pinpoint any day or time or location that has a higher flood risk than another. “So we will just have to closely watch each convective episode and be prepared to react quickly,” he says.
Impact of Today’s Rains on Elm Grove
Despite heavy rainfall this afternoon, Jeff Miller, an Elm Grove resident and frequent contributor, drove the streets of Elm Grove this evening. He notes that:
Streets still seem clear as of 8 p.m.
Taylor Gully is about half full, but water is flowing rapidly
Water level is about 2 feet from the top of the twin culverts at the Rustling Elms bridge.
Miller sees the possibility of that culvert being overflowed as a danger.
Posted by Bob Rehak on 5/24/2020 with reporting from Jeff Miller and Jeff Lindner
https://i0.wp.com/reduceflooding.com/wp-content/uploads/2020/05/Radar-524.jpg?fit=607%2C1200&ssl=11200607adminadmin2020-05-24 20:14:412020-05-25 05:31:20Heavy Rainfall Threat in Coming Days
A close analysis of swimming pools and river currents in Google Earth satellite images suggests that many San Jacinto East Fork homes were flooded by the West Fork during Hurricane Harvey. Stories from East Fork homeowners suggested as much in the months after Harvey. Many reported water flowing through their property from west to east, not north to south as one might expect. However, to my knowledge, no one presented photographic evidence to support those claims – until now.
Eagle-Eyed Geologist Interprets Satellite Photos
A retired high-level geologist for one of the world’s largest oil companies analyzed satellite images in Google Earth. The eagle-eyed geologist, R.D. Kissling, lives in the Lake Houston area and kayaks that area regularly.
Kissling noted water-borne-sediment coloration changes between the East and West Forks after the SJRA started releasing 79,000 cubic feet per second from Lake Conroe. The image from 8/30/2017 shows West Fork water pushing into the East Fork. Note how water from the East Fork (upper right) and Luce Bayou (far right) are crowded over into a narrow band running down the (east) side of Lake Houston.
Satellite image from 8/30/2017 shows West Fork water (middle left) pushing into East Fork (top right).
Cloud cover obscures images from the previous day.
Flooded Swimming Pools Tell Part of Story
Kissling also examined the color of water in swimming pools. Most homes in Royal Shores on the East Fork have swimming pools that look bright blue on satellite images. See the image below from before the storm.
Swimming pools in Royal Shores appear bright blue before the storm.
But on 8/30/2020 during the storm, many of those had turned brown. Water was starting to recede by then, but note the boat houses still underwater. Above the red line, all swimming pools still appear blue.
Royal Shores on 8/30/2017 during the storm.Note the concentration of brown swimming pools south and east of the red line.North, they are still blue (unflooded).
The photo above is a magnification of the Royal Shores area from the wider satellite image above. Below, I’ve zoomed back out to show the wider image. I’ve also highlighted the Royal Shores homes with brown swimming pools so you can see their their relationship to the West Fork water pushing into the East Fork.
Same image as above but with the part of Royal Shores highlighted that had flooded pools and that was ALSO apparently taking on WEST FORK water.
Conclusions
Of course, by themselves, the swimming pool colors don’t prove that West Fork water flooded East Fork homes. But when considered in conjunction with the first image, they suggest to me the validity of residents’ claims. At a minimum, these images do not contradict those claims, according to Kissling.
Posted by Bob Rehak on 5/23/2020 based on analysis by R.D. Kissling
998 days after Hurricane Harvey
https://i0.wp.com/reduceflooding.com/wp-content/uploads/2020/05/AOI.jpg?fit=1200%2C855&ssl=18551200adminadmin2020-05-23 15:33:052020-05-23 15:33:15Google Earth Images Suggest East Fork Swimming Pools Flooded By West Fork During Harvey
As mechanical dredging whittles down the part of the San Jacinto West Fork mouth bar that sticks up above water, it’s important to think about longer-term maintenance dredging. Remember three things:
How the sand got there in the first place
Why it will be redeposited over time
What the consequences will be of not removing it periodically
How Sand Got There
Most movement of sediment happens during floods. Sand and silt washes downstream from two main sources: natural and man-made.
The natural sources include erosion from river banks and beds.
So-called mouth bars are giant sand bars formed at the mouths of rivers. They form wherever a river enters an ocean, sea, estuary, lake, or reservoir. Whenever water slows, a river will deposit sediment. And it always slows when a moving body of water encounters a standing body of water. It’s a well understood geophysical process that occurs everywhere around the world. A prime example is the Mississippi delta.
Mouth bars are actually part of river delta formation. As they build up, they force a river to split.
Why Intervention Is Necessary In Populated Areas
As sediment builds up, if left alone, it will eventually choke the headwaters of the lake and form a flat swampy lowland. You can already see this beginning to happen on the East Fork San Jacinto.
Looking north at northern part of East Fork Mouth Bar, which has become vegetated. Note how it causes the river to split. The river is carving itself up into a maze of small channels. Photos taken 5/11/2020.Here’s the area immediately below the shot above. It is near the entrance of Luce Bayou to the East Fork. This area went from 18 feet deep to 3 feet after Imelda according to boaters.Photo taken 3/5/2020. Note how the newest mouth bar is forming in one of the channels formed by the previous mouth bar which has become anchored by vegetation.Looking west toward West Lake Houston Parkway Bridge and the West Fork of the San Jacinto. Note how this mouth bar also caused the river to split. Sediment is now being deposited on both sides, and will eventually cause another splitwithout more dredging.Photo taken 5/11/2020.Looking south toward FM1960 from north of the mouth bar. Notice how shallow this section of the river has become. The loss of conveyance contributes to flooding.Photo taken 5/11/2020.From Harris County Flood Control District’s page on the on-going Kingwood Area Drainage Assessment.
Part of the reason for the buildup of sediment behind the West Fork mouth bar is that Ben’s Branch and another major drainage ditch have been dumping sediment into the river there. Luckily, HCFCD is removing sediment from these and other ditches. That will help reduce the problem in the river, but not eliminate it.
Need for Maintenance Dredging
Erosion is relentless. We can do many things to minimize it (preserve wetlands, use best management practices in sand mining and construction, etc.). However, as long as rain falls, we can’t eliminate it.
To my knowledge, until the emergency West Fork dredging program began in 2018, the upper San Jacinto had never been dredged since the Lake Houston Dam was built in 1953. That’s 65 years. Over that time, sediment build up turned into a $100+ million dredging program. And that doesn’t even include flood damages which likely total another BILLION dollars according to a City estimate. Imagine all the heartbreak and misery that could have been avoided had the City budgeted $2 million for dredging each year.
Dredgers keep nibbling away at the mouth bar like an ear or corn, removing one row at a time.Photo taken 5/11/2020. Unfortunately, the effort to remove the portion of the bar above water may make people think the problem is solved, but it won’t reconnect the upstream river channel with the lake.
Imagine the:
Flood losses we could have avoided
Recreational opportunities we could have realized
Reservoir capacity we could have preserved
Home values we could have multiplied.
For all these reasons, we need to start a serious dialog about maintenance dredging. Even if it’s not every year, we need it after every flood. Think of it as a yearly insurance premium against the next disaster.
The Army Corps estimated this bar immediately downstream from River Grove Park blocked 90% of the West Fork. In the three months before the Corps removed it, River Grove flooded six times. Since then River Grove has not flooded at all.
Posted by Bob Rehak on 5/22/2020
997 Days after Hurricane Harvey
https://i0.wp.com/reduceflooding.com/wp-content/uploads/2020/05/20200511-RJR_2501.jpg?fit=1200%2C800&ssl=18001200adminadmin2020-05-22 17:58:532020-05-23 11:39:54Putting Mouth Bar Removal in Larger Context; Need for Maintenance Dredging
Heavy Rainfall Threat in Coming Days
Jeff Lindner, Harris County Flood Control Meteorologist just issued a heavy rainfall warning. Lindner notes that the line of strong thunderstorms currently moving across the area will drop rainfall amounts of 1-3 inches.
The good news: the leading edge of this line is becoming detached from the outflow boundary. That suggests storms will weaken as they move southward. Rainfall rates which were 2-4 inches earlier over N Waller and Montgomery Counties have lessened to near 1-2 inches. The main threat now is short duration street flooding in areas with the heaviest rainfall.
Tonight’s Forecast
Lindner points to extremely active radar out west along the Rio Grande. He says that’s where the next round of weather will be developing. He expects it to move quickly toward our area tonight. Models show this line of storms quickly reaching the area between midnight and 400 a.m. But at the speed it’s moving, he predicts only another 1-2 inches for most areas with this line.
Monday Prediction
Continued high rain chances. The air may take much of the morning and early afternoon to recover from the early morning line of weather, but temperatures will only need to reach the low 80’s to trigger more storms. It will not take much heating to set things off, he warns. Storm motions could be fairly slow Monday afternoon and this could lead to excessive rainfall rates in a short period of time.
Tuesday-Thursday: Continued Threat
Upper level disturbances remain parked over the state with rounds of storms at nearly any time. Heavy rainfall will continue to be a threat.
Rainfall Amounts Add Up Changing Nature of Threat
Lindner concludes, “Moisture profiles certainly support heavy to excessive rainfall rates as seen today and if storms slow of train for a period of times totals could quickly add up. Grounds will saturate over time leading to increasing and eventually maximum run-off conditions…so the threat may grow from mainly street flooding to potential rises on area creeks, bayous, and rivers.”
Lindner concedes that it’s hard to pinpoint any day or time or location that has a higher flood risk than another. “So we will just have to closely watch each convective episode and be prepared to react quickly,” he says.
Impact of Today’s Rains on Elm Grove
Despite heavy rainfall this afternoon, Jeff Miller, an Elm Grove resident and frequent contributor, drove the streets of Elm Grove this evening. He notes that:
Miller sees the possibility of that culvert being overflowed as a danger.
Posted by Bob Rehak on 5/24/2020 with reporting from Jeff Miller and Jeff Lindner
999 Days since Hurricane Harvey, 248 since Imelda, and four years since the last Memorial Day Flood.
Google Earth Images Suggest East Fork Swimming Pools Flooded By West Fork During Harvey
A close analysis of swimming pools and river currents in Google Earth satellite images suggests that many San Jacinto East Fork homes were flooded by the West Fork during Hurricane Harvey. Stories from East Fork homeowners suggested as much in the months after Harvey. Many reported water flowing through their property from west to east, not north to south as one might expect. However, to my knowledge, no one presented photographic evidence to support those claims – until now.
Eagle-Eyed Geologist Interprets Satellite Photos
A retired high-level geologist for one of the world’s largest oil companies analyzed satellite images in Google Earth. The eagle-eyed geologist, R.D. Kissling, lives in the Lake Houston area and kayaks that area regularly.
Kissling noted water-borne-sediment coloration changes between the East and West Forks after the SJRA started releasing 79,000 cubic feet per second from Lake Conroe. The image from 8/30/2017 shows West Fork water pushing into the East Fork. Note how water from the East Fork (upper right) and Luce Bayou (far right) are crowded over into a narrow band running down the (east) side of Lake Houston.
Cloud cover obscures images from the previous day.
Flooded Swimming Pools Tell Part of Story
Kissling also examined the color of water in swimming pools. Most homes in Royal Shores on the East Fork have swimming pools that look bright blue on satellite images. See the image below from before the storm.
But on 8/30/2020 during the storm, many of those had turned brown. Water was starting to recede by then, but note the boat houses still underwater. Above the red line, all swimming pools still appear blue.
The photo above is a magnification of the Royal Shores area from the wider satellite image above. Below, I’ve zoomed back out to show the wider image. I’ve also highlighted the Royal Shores homes with brown swimming pools so you can see their their relationship to the West Fork water pushing into the East Fork.
Conclusions
Of course, by themselves, the swimming pool colors don’t prove that West Fork water flooded East Fork homes. But when considered in conjunction with the first image, they suggest to me the validity of residents’ claims. At a minimum, these images do not contradict those claims, according to Kissling.
Posted by Bob Rehak on 5/23/2020 based on analysis by R.D. Kissling
998 days after Hurricane Harvey
Putting Mouth Bar Removal in Larger Context; Need for Maintenance Dredging
As mechanical dredging whittles down the part of the San Jacinto West Fork mouth bar that sticks up above water, it’s important to think about longer-term maintenance dredging. Remember three things:
How Sand Got There
Most movement of sediment happens during floods. Sand and silt washes downstream from two main sources: natural and man-made.
The natural sources include erosion from river banks and beds.
The man-made sources include the dirt that washes into your storm drain during a rain. They also include new developments and construction sites that disturb the soil without adequate safeguards like silt fencing. Finally, in our area, we also have an abundance of sand mines that pump and/or dump silty wastewater into rivers.
Why It Will Be Redeposited Over Time
So-called mouth bars are giant sand bars formed at the mouths of rivers. They form wherever a river enters an ocean, sea, estuary, lake, or reservoir. Whenever water slows, a river will deposit sediment. And it always slows when a moving body of water encounters a standing body of water. It’s a well understood geophysical process that occurs everywhere around the world. A prime example is the Mississippi delta.
Mouth bars are actually part of river delta formation. As they build up, they force a river to split.
Why Intervention Is Necessary In Populated Areas
As sediment builds up, if left alone, it will eventually choke the headwaters of the lake and form a flat swampy lowland. You can already see this beginning to happen on the East Fork San Jacinto.
Part of the reason for the buildup of sediment behind the West Fork mouth bar is that Ben’s Branch and another major drainage ditch have been dumping sediment into the river there. Luckily, HCFCD is removing sediment from these and other ditches. That will help reduce the problem in the river, but not eliminate it.
Need for Maintenance Dredging
Erosion is relentless. We can do many things to minimize it (preserve wetlands, use best management practices in sand mining and construction, etc.). However, as long as rain falls, we can’t eliminate it.
To my knowledge, until the emergency West Fork dredging program began in 2018, the upper San Jacinto had never been dredged since the Lake Houston Dam was built in 1953. That’s 65 years. Over that time, sediment build up turned into a $100+ million dredging program. And that doesn’t even include flood damages which likely total another BILLION dollars according to a City estimate. Imagine all the heartbreak and misery that could have been avoided had the City budgeted $2 million for dredging each year.
Imagine the:
For all these reasons, we need to start a serious dialog about maintenance dredging. Even if it’s not every year, we need it after every flood. Think of it as a yearly insurance premium against the next disaster.
Posted by Bob Rehak on 5/22/2020
997 Days after Hurricane Harvey