A front moving into the region could bring high hourly rainfall rates and rapid street flooding, according to Jeff Lindner, Harris County’s meteorologist. He says, “A weak front will move into the area today and tonight, and stall near the coast or just offshore on Tuesday and Wednesday.”
Weather Live radar composite as of noon CDT, 8.2.21.
Slow-Moving Front, Training Cells, Possible Street Flooding
“The slow-moving front is moving southward across north and central TX. Numerous showers and thunderstorms have already formed along it. The air mass in the Houston region will become increasingly unstable this afternoon. Expect numerous, slow-moving showers and thunderstorms to develop across the region,” says Lindner.
“The combination of slow movement, deep tropical moisture, and the potential for training all points toward a heavy rainfall threat this afternoon,” he said.
“The main threat will likely be short-term rainfall rates of 2-3 inches per hour leading to rapid onset street flooding.”
Jeff Lindner, Harris County meteorologist
Mainly South of I-10 and Offshore by Tomorrow
Lindner continued, “The front will push toward the coast tonight and may even move offshore on Tuesday. A slightly drier air mass will build into the region behind the front with rain chances focusing near the coast and across Gulf waters later today and tomorrow.”
He sees the main rain chances on Tuesday for areas south of I-10. However, he also predicts much of the activity will be offshore.
Enjoy the slightly drier air mass and “cooler” temperatures behind the front as it washes out by late week. After that, onshore flow will return along with humidity. “By next weekend, heat index values could near advisory levels,” Lindner warns.
Tropics to Pick Up by Mid-August
On an unrelated topic, Lindner sees no concerns for the next 5 days for tropical development in the Atlantic basin. However, Lindner sees signals that the Atlantic basin will become increasingly favorable for development toward mid August.
Posted by Bob Rehak on 8.2.21based on information provided by HCFCD
1434 Days since Hurricane Harvey
https://i0.wp.com/reduceflooding.com/wp-content/uploads/2021/08/Radar-8.2.21-noon.jpg?fit=1200%2C1677&ssl=116771200adminadmin2021-08-02 12:26:042021-08-02 12:27:55Possible Street Flooding Later Today
Tyson’s Sponge City article focused on recent Chinese floods from July 17-21, 2021. They hit a large manufacturing center called Zhengzhou with a population of more than 10 million especially hard. Rains there were eerily reminiscent of Hurricane Harvey.
While the Sponge City investments didn’t save Zhengzhou from a 5000-year flood, they did provide many benefits. And many lessons.
Sponge Cities and Green vs. Gray Infrastructure
The title of Tyson’s article is, “To curb urban flooding, China is building ‘sponge cities.’ Do they work?” Answer: Not by themselves. At least not yet. And not for a 5000-year storm.
The Sponge Cities concept has a large green component as opposed to being all gray. Think of gray infrastructure as dams and other concrete based solutions. China has constructed 97,000 dams since the 1950s, says Tyson. That doesn’t even include the dikes and levees also built to prevent riverine flooding in cities built on floodplains. But those alone were not preventing flooding.
China has had a large urban migration in the last 40 years. Since 1978, the country’s urban population expanded fivefold. As concrete replaced green space, urban drainage systems in most Chinese cities proved insufficient to cope with rising flood risk, says Tyson. Hence, a push for more green solutions
Says Tyson, “China’s Sponge City program aims to use pervious pavements, rain gardens, green roofs, urban wetlands, and other innovations to absorb water during storms. The soil then purifies that water and gradually releases it – much like a sponge. The government has invested more than $12 billion in the program since 2014 to help cities create sponge features on 20% of their land, with the goal of retaining or reusing 80% of annual precipitation by the 2030s.”
But the Sponge City idea involves more than just green features. Guy Carpenter, who models climate risks for insurance companies, points out that the concept also includes construction of large capacity drainpipe networks, underground stormwater storage tanks, and other flood-control facilities.
One-Hundred-Year Level of Protection Inadequate for Record Rains
Says Carpenter, “The aim of the Sponge City project is to protect the city from floods with return periods up to about 1-in-100 years (1% annual chance). Both the peak rate of precipitation and the total rainfall amount of this event far exceeded the tolerance of the design scope of the Sponge City.”
Zhengzhou in Mainland China’s Henan Province was struck by tropical cyclones Cempaka and In-fa. They dumped more rain on Zhengzhou in a day – 28 inches – than it usually receives in a year. From start to finish, Zhengzhou received 32.5 inches. The one hour peak was 7.9 inches.
The Sponge City investments were not wasted. Despite the severity of the rainfall, they eliminated 125 previous flood-prone locations (77% of total). They have also proven effective with light to medium precipitation, reducing flood peaks, promoting the sustainable circulation, and recovery of rainwater.
The South China Morning Post reported that the flood caused at least 66 deaths, including 14 in the local subway system and six in a tunnel.
Extreme flooding in Zhengzhou, China, on July 20, 2021, after 28 inches of rain fell in 24 hours. (Image credit: UN Climate Change Twitter feed)
The heavy rainfall almost caused several reservoirs to breach. More than 230,000 people in surrounding areas had to be evacuated as a precaution. Workers are still shoring up the reservoirs.
The severity of this event simply exceeded the flood control and storm-water drainage facilities in the city including the ‘sponge city’ additions. The event had knocked out transportation, communications, water supply, power and other industries.
Zhengzhou’s Hurricane Harvey
Sounds a lot like Houston during Harvey. And it was, relatively speaking.
The following tables from Harris County Flood Control District’s final report on Tropical Storm Imelda compare rainfall totals for different durations during several recent storms including Harvey and Allison. These are the max totals recorded inside Harris County. In some cases, the storms produced higher totals in neighboring counties.
Max rainfall rates recorded in Harris County during different durations three major storms.
Remember, Zhengzhou got 28 inches in a day, 7.9 inches in an hour and 32.5 inches for the storm. So their totals are comparable to Harvey’s.
The South China Morning Post also describes the chaos that reigned in Zhengzhou, much as it did in Houston after Harvey. The Chinese government had invested heavily not just in Sponge Cities, but in Smart Cities. The latter were supposed to provide people with extra evacuation time. However, the Post reported Zhengzhou was cast back into the “digital dark ages” when the disaster knocked out the Internet and electricity. Warnings did not get from officials to the people who needed them.
According to its lake lowering policy adopted last year, the San Jacinto River Authority (SJRA) should start to drop the level of Lake Conroe this weekend.
Text of Lake-Lowering Policy
The lake-lowering policy states:
“Beginning August 1, release only an amount of water from Lake Conroe to create a one foot capacity to catch rainfall and storm runoff (from 201’ msl to 200’ msl). After September 1, increase capacity an additional six inches (from 200’ msl to 199.5’ msl). If a named storm is predicted to impact our region, the COH may initiate an additional release of six inches (to 199’ msl) by notifying SJRA in writing of their call for release. Recapture beginning October 1.”
As of 5PM Friday, 7/30/21, Lake Conroe stood at 200.87 feet. The only release from the lake was the water feeding the SJRA water treatment plant to supply drinking water to area customers (GRP Diversion).
Before the SJRA can lower the lake, however, the City of Houston (COH) must call for the lowering to start. And according to a spokesman in Mayor Pro Tem Dave Martin’s office, the City has called for the release to start.
The City owns two thirds of the water in the Lake and the release will come out of the City’s portion. When the numbers in the box labeled “COH diversion” on the SJRA’s dashboard increase, you’ll know the seasonal release has started.
Judge Mike Mays set a hearing date for Tuesday, August 24, 2021 at 2PM.
Approaching Peak of Hurricane Season
So how is this hurricane season going so far?
The National Hurricane Center (NHC) predicts no tropical activity anywhere in the Atlantic basin for the next five days. That includes the Gulf of Mexico.
However, we’ve already had five named storms this year. And NHC observes…
This chart shows the distribution of storms throughout the season. The peak happens from mid-August to late October.Galveston, Harris, Brazoria, and Chambers Counties get the most hurricane strikes in Texas.Hurricane Strikes in Continental US by State and By Year since 1950
All in all, the Atlantic this time of year is like a casino. You have to play the odds. And that’s what the temporary seasonal lake lowering policy is designed to do – reduce the risk of huge property losses by creating extra capacity in Lake Conroe to help offset heavy rainfall and the need for large releases.
Posted by Bob Rehak on 7/30/21
1431 Days since Hurricane Harvey
The thoughts expressed in this post represent opinions on matters of public concern and safety. They are protected by the First Amendment of the US Constitution and the Anti-SLAPP Statute of the Great State of Texas.
https://i0.wp.com/reduceflooding.com/wp-content/uploads/2021/07/cum-average_Atl_1966-2009.gif?fit=1350%2C791&ssl=17911350adminadmin2021-07-30 17:20:522021-07-30 17:47:21Lake Lowering to Start as Peak of Hurricane Season Nears
Possible Street Flooding Later Today
A front moving into the region could bring high hourly rainfall rates and rapid street flooding, according to Jeff Lindner, Harris County’s meteorologist. He says, “A weak front will move into the area today and tonight, and stall near the coast or just offshore on Tuesday and Wednesday.”
Slow-Moving Front, Training Cells, Possible Street Flooding
“The slow-moving front is moving southward across north and central TX. Numerous showers and thunderstorms have already formed along it. The air mass in the Houston region will become increasingly unstable this afternoon. Expect numerous, slow-moving showers and thunderstorms to develop across the region,” says Lindner.
“The combination of slow movement, deep tropical moisture, and the potential for training all points toward a heavy rainfall threat this afternoon,” he said.
Mainly South of I-10 and Offshore by Tomorrow
Lindner continued, “The front will push toward the coast tonight and may even move offshore on Tuesday. A slightly drier air mass will build into the region behind the front with rain chances focusing near the coast and across Gulf waters later today and tomorrow.”
He sees the main rain chances on Tuesday for areas south of I-10. However, he also predicts much of the activity will be offshore.
Enjoy the slightly drier air mass and “cooler” temperatures behind the front as it washes out by late week. After that, onshore flow will return along with humidity. “By next weekend, heat index values could near advisory levels,” Lindner warns.
Tropics to Pick Up by Mid-August
On an unrelated topic, Lindner sees no concerns for the next 5 days for tropical development in the Atlantic basin. However, Lindner sees signals that the Atlantic basin will become increasingly favorable for development toward mid August.
Posted by Bob Rehak on 8.2.21 based on information provided by HCFCD
1434 Days since Hurricane Harvey
China’s “Sponge Cities”
A reader sent me a link to a fascinating article by Ann Scott Tyson in the Christian Science Monitor about China’s “sponge cities.” It reminded me of a recent study by Dr. Matthew Berg about the need for conservation to be a component of all flood solutions.
Tyson’s Sponge City article focused on recent Chinese floods from July 17-21, 2021. They hit a large manufacturing center called Zhengzhou with a population of more than 10 million especially hard. Rains there were eerily reminiscent of Hurricane Harvey.
While the Sponge City investments didn’t save Zhengzhou from a 5000-year flood, they did provide many benefits. And many lessons.
Sponge Cities and Green vs. Gray Infrastructure
The title of Tyson’s article is, “To curb urban flooding, China is building ‘sponge cities.’ Do they work?” Answer: Not by themselves. At least not yet. And not for a 5000-year storm.
The Sponge Cities concept has a large green component as opposed to being all gray. Think of gray infrastructure as dams and other concrete based solutions. China has constructed 97,000 dams since the 1950s, says Tyson. That doesn’t even include the dikes and levees also built to prevent riverine flooding in cities built on floodplains. But those alone were not preventing flooding.
China has had a large urban migration in the last 40 years. Since 1978, the country’s urban population expanded fivefold. As concrete replaced green space, urban drainage systems in most Chinese cities proved insufficient to cope with rising flood risk, says Tyson. Hence, a push for more green solutions
Says Tyson, “China’s Sponge City program aims to use pervious pavements, rain gardens, green roofs, urban wetlands, and other innovations to absorb water during storms. The soil then purifies that water and gradually releases it – much like a sponge. The government has invested more than $12 billion in the program since 2014 to help cities create sponge features on 20% of their land, with the goal of retaining or reusing 80% of annual precipitation by the 2030s.”
But the Sponge City idea involves more than just green features. Guy Carpenter, who models climate risks for insurance companies, points out that the concept also includes construction of large capacity drainpipe networks, underground stormwater storage tanks, and other flood-control facilities.
One-Hundred-Year Level of Protection Inadequate for Record Rains
Says Carpenter, “The aim of the Sponge City project is to protect the city from floods with return periods up to about 1-in-100 years (1% annual chance). Both the peak rate of precipitation and the total rainfall amount of this event far exceeded the tolerance of the design scope of the Sponge City.”
Zhengzhou in Mainland China’s Henan Province was struck by tropical cyclones Cempaka and In-fa. They dumped more rain on Zhengzhou in a day – 28 inches – than it usually receives in a year. From start to finish, Zhengzhou received 32.5 inches. The one hour peak was 7.9 inches.
According to Guy Carpenter, who models climate risks for insurance companies, $7.7 billion of those $12 billion “sponge city” dollars were invested in Zhengzhou. Zhengzhou is one of China’s major manufacturing centers and where Apple manufacturers most iPhones.
The Sponge City investments were not wasted. Despite the severity of the rainfall, they eliminated 125 previous flood-prone locations (77% of total). They have also proven effective with light to medium precipitation, reducing flood peaks, promoting the sustainable circulation, and recovery of rainwater.
Damage
Yale Climate Connections reported that preliminary damage estimates exceed $10 billion.
The South China Morning Post reported that the flood caused at least 66 deaths, including 14 in the local subway system and six in a tunnel.
The heavy rainfall almost caused several reservoirs to breach. More than 230,000 people in surrounding areas had to be evacuated as a precaution. Workers are still shoring up the reservoirs.
The severity of this event simply exceeded the flood control and storm-water drainage facilities in the city including the ‘sponge city’ additions. The event had knocked out transportation, communications, water supply, power and other industries.
Zhengzhou’s Hurricane Harvey
Sounds a lot like Houston during Harvey. And it was, relatively speaking.
The following tables from Harris County Flood Control District’s final report on Tropical Storm Imelda compare rainfall totals for different durations during several recent storms including Harvey and Allison. These are the max totals recorded inside Harris County. In some cases, the storms produced higher totals in neighboring counties.
Remember, Zhengzhou got 28 inches in a day, 7.9 inches in an hour and 32.5 inches for the storm. So their totals are comparable to Harvey’s.
Yet Zhengzhou gets 40% less rain on average than Houston. Zhengzhou’s annual rainfall is 29.7 inches. In contrast, Houston averages 49.77 inches.
So you can see how the Zhengzhou flood totally overwhelmed the city’s defenses. The Wall Street Journal reported that the food had a recurrence interval of 5000 years. This was China’s Hurricane Harvey!
Lessons from Sponge Cities and Smart Cities
The South China Morning Post also describes the chaos that reigned in Zhengzhou, much as it did in Houston after Harvey. The Chinese government had invested heavily not just in Sponge Cities, but in Smart Cities. The latter were supposed to provide people with extra evacuation time. However, the Post reported Zhengzhou was cast back into the “digital dark ages” when the disaster knocked out the Internet and electricity. Warnings did not get from officials to the people who needed them.
“Millions of people in Zhengzhou struggled with basic communication, transport, buying food and even keeping people alive,” says the Post.
In my opinion, this story underscores the need to:
Posted by Bob Rehak on 7/31/2021
1432 Days after Hurricane Harvey
Lake Lowering to Start as Peak of Hurricane Season Nears
According to its lake lowering policy adopted last year, the San Jacinto River Authority (SJRA) should start to drop the level of Lake Conroe this weekend.
Text of Lake-Lowering Policy
The lake-lowering policy states:
“Beginning August 1, release only an amount of water from Lake Conroe to create a one foot capacity to catch rainfall and storm runoff (from 201’ msl to 200’ msl). After September 1, increase capacity an additional six inches (from 200’ msl to 199.5’ msl). If a named storm is predicted to impact our region, the COH may initiate an additional release of six inches (to 199’ msl) by notifying SJRA in writing of their call for release. Recapture beginning October 1.”
Before the SJRA can lower the lake, however, the City of Houston (COH) must call for the lowering to start. And according to a spokesman in Mayor Pro Tem Dave Martin’s office, the City has called for the release to start.
The City owns two thirds of the water in the Lake and the release will come out of the City’s portion. When the numbers in the box labeled “COH diversion” on the SJRA’s dashboard increase, you’ll know the seasonal release has started.
Lake Conroe Association Still Fighting
In the past, releases have been hotly debated. The Lake Conroe Association has sued the City and SJRA in Montgomery County District Court. The litigants have filed 80 documents totaling more than 2800 pages in the last 121 days. That’s more than 23 pages per day! Some of the plaintiff’s arguments border on ridiculous in my opinion.
Isn’t that kind of like a neighbor of a bank alleging fraud when a depositor makes a withdrawal?
To read all the documents yourself, go to the Montgomery County District Clerk’s website.
Judge Mike Mays set a hearing date for Tuesday, August 24, 2021 at 2PM.
Approaching Peak of Hurricane Season
So how is this hurricane season going so far?
The National Hurricane Center (NHC) predicts no tropical activity anywhere in the Atlantic basin for the next five days. That includes the Gulf of Mexico.
However, we’ve already had five named storms this year. And NHC observes…
If history is a guide, the four charts below from the NHC Climatology Page hint at what we can likely expect in the coming months.
The fact that we only had one named storm in July (Elsa) is not unusual; it’s average. But keep in mind that Elsa was the earliest named “E” storm on record.
All in all, the Atlantic this time of year is like a casino. You have to play the odds. And that’s what the temporary seasonal lake lowering policy is designed to do – reduce the risk of huge property losses by creating extra capacity in Lake Conroe to help offset heavy rainfall and the need for large releases.
Posted by Bob Rehak on 7/30/21
1431 Days since Hurricane Harvey
The thoughts expressed in this post represent opinions on matters of public concern and safety. They are protected by the First Amendment of the US Constitution and the Anti-SLAPP Statute of the Great State of Texas.