Researchers at Texas A&M Galveston and the University of Maryland have just published a massive new study on The Growing Threat of Urban Flooding: A National Challenge. The study – a treasure trove of insights – actually started in 2016, before Harvey.
It focuses primarily on urban flooding as opposed to riverine flooding, which caused many of the Lake Houston Area’s problems. However, area residents should not dismiss it. The two types overlap and the report largely addresses issues that exacerbate both, such as inadequate governmental systems, engineered structures and growth that overwhelms both.
The report contains eight major sections that quantify the scope of the challenge. Below, a few highlights from each.
I. Urban Floods: The Nation’s Hidden Challenge
Documents the stunning extent of urban flooding and factors that continue to make it worse. Did you know for instance, that two thirds of the nation’s population living in floodplains live in just two states: Texas and New York? Or that Texas led the nation in billion-dollar water and wind disasters between 1980 and 2018?
II. Analyzing Urban Flooding
Reveals statistics on the scope of the problem. Two gems:
Nationally, 83% of respondents indicated they had experienced urban flooding in their communities. And 85% experienced urban flooding outside special flood hazard areas!
III. Where Urban Flooding Occurs
Shows that Texas ranks in the middle of the pack in terms of frequency of events, as opposed to major events. The researchers found that nationwide, approximately 25% of all flood insurance claims are submitted by policy holders whose property lies outside the 100-year flood plain. New York found that “The problem in most communities is lack of enforcement. Communities need a comprehensive plan to address development, infrastructure needs, stormwater runoff, and building codes. When a community doesn’t address these issues it only exacerbates other problems and continued urban sprawl eats up rural areas causing flooding, erosion, and infrastructure malfunction.”
IV. Why Does Urban Flooding Happen?
Examines aging and inadequate drainage systems, increases in local and regional runoff, sewage and stormwater backups, changes in local physical conditions, and failure to maintain drainage systems. Sound familiar? If you’re worried about where your drainage fee goes, be thankful that you don’t live in Detroit. That city reports that 75% of the drains citywide are covered by debris or have a blockage.
V: Consequences of Urban Flooding
Talks about the economic and social costs of urban flooding. Did you know, for instance, that almost 40% of small business never reopen their doors following a flooding disaster? And that 90% of businesses fail within two years of being struck by a disaster? However, because no single federal agency collects and evaluates flood loss information, all national flood loss estimates are considered “approximations.” Therefore, the report says, they are of marginal use in conducting accurate economic analyses to support urban flood risk reduction mitigation.
Social costs hit moderate income, the old, and those facing social challenges the hardest. “For those lacking critical resources (savings, insurance, etc.), the flood losses gnaw away at their well-being.”
In regard to Houston, the study found that, “The urban flooding that occurs in the heart of the central city is mainly attributed to existing drainage infrastructure that predates today’s design standards or insufficient pipe sizes for the now fully developed urban areas.”
VI: What Can Be Done About Urban Flooding?
Examines different strategies to mitigate flooding:
Planning
Capturing rain where it falls
Eliminating or reducing risk
Adequate maintenance
Upgrading capacity standards
Risk communication (gaining better public understanding)
Better mapping
Disclosing risks in user-friendly ways
Insuring at-risk properties.
Some key insights:
Lack of funding and lack of political will are the most significant issues.
Much of the available funding requires a cost share and significant participation in the NFIP program. Most properties outside the mapped floodplain do not carry flood insurance. This then requires localities to fund these initiatives by themselves.
New development outside the floodplain generally has limited stormwater control requirements. Local CEOs are often reluctant to require stormwater controls as they fear this would dissuade development.
VII. Major Challenges
Includes discussions of lack of resources, population/urban growth, climate change, priority setting and fragmented governance.
If you want to understand why flood mitigation and what needs to be done to fix it, read this report.
VIII. Moving Ahead: Challenges and Recommendations
The study outlines ten challenges and makes 9 recommendations. Most target government leaders and policy makers. They are much too detailed to summarize here without tripling the length of the post. But if you want to know what you should push your representatives to consider, you must read section.
Number 8 read: “Governments, at all levels, have not provided effective means to communicate risks to those in urban flood- prone areas. A significant number of these areas are not identified by maps produced under the Federal Emergency Management Agency National Flood Insurance Programs, and actions by those responsible for urban flood mitigation are needed to delineate these areas. Communication of flood risk is often seen by public officials and developers as a negative.”
In my opinion, it’s a positive. A better understanding of risk could help everyone make better decisions that prevent heartbreaking losses, such as those we saw with Harvey.
All in all, this is a must read for anyone who wants to understand urban flooding and why it is so difficult to address.
Acknowledgements:
For University of Maryland
Dr. Gerald E Galloway
Dr. Allison Reilly
Sung Ryoo
Anjanette Riley
Maggie Haslam
For Texas A&M University
Dr. Sam Brody
Dr. Wesley Highfield
Dr. Joshua Gunn
Jayton Rainey
Sherry Parker
Posted by Bob Rehak on 12/2/2018 with thanks to Jacque Havelka
460 Days since Hurricane Harvey
https://i0.wp.com/reduceflooding.com/wp-content/uploads/2018/12/TAMU-Cover.jpg?fit=1500%2C1916&ssl=119161500adminadmin2018-12-01 20:16:182018-12-01 20:27:57Growing Threat of Urban Flooding Labeled National Challenge by New Study
Riparian means “of or relating to the banks of a river.” To see the role of riparian vegetation in reducing erosion, one need only compare the two forks of the San Jacinto River. They provide a stark contrast. But the real story is the role of sand mining in reducing riparian vegetation.
After years of sand mining on the West Fork, much of the shoreline vegetation has been lost and the resulting erosion is staggering. Between I-45 and US59, sand miners have stripped vegetation from approximately 20 square miles of floodplain and floodway (the main channel of a river during a flood).
Sand Mines on West Fork of the San Jacinto form an almost continuous line from I-45 to US59. They have stripped approximately 20 square miles of ground cover.
On the East Fork above the Caney Creek confluence, however, there are no sand mines. The vegetation is lush and the erosion is negligible. Let’s start there for a look at how nature protects us.
Forests come down to the river’s edge. Grasses and cattails abound, protecting the banks.
Dense forest anchors the land. Grasses, forced to compete for sunlight, thrive along the river’s edge, protecting banks.
A perfect time and place for reflection. A nice place just to “be.”
All images so far were taken on the East Fork of the San Jacinto River above where it merges with Caney Creek. Image courtesy of Google Earth.
Red lines on left measure width of East Fork on 3/3/16, before the Tax Day Storm. They are in a separate layer. Switching the background image to 10/28/17 shows that the river is virtually unchanged, thanks in large part to the lush riparian vegetation.
Now, A Trip up the West Fork
Now, let’s look at the West Fork. It’s vastly different.
Townhomes on Marina Drive in Forest Cove. Concrete, steel and wooden walls on the West Fork were less effective at preventing erosion than blades of grass on the East Fork.
Same area. Note steepness of banks where vegetation can no longer take hold, perpetuating cycles of erosion.
Remnants of concrete retaining wall.
Site of a breach in sand mine dike on the West Fork. The mine discharged sediment directly into the river.
Two weeks after Harvey. Just north of US 59 bridge.
West Fork Sand mine complex. Note one of many dike breaches in various mines that allowed sand and sediment to pour downstream. All helicopter images taken two weeks after Harvey on 9/14/17.
Mining a point bar after Harvey. Miners are supposed to work within their dikes to avoid disrupting vegetation along the river. Photo taken 9/14/17.
Note more repairs to dikes.
The next three images form a series.
River is migrating toward pit in background at the rate of 12 feet per year, in part, due to lack of vegetation protecting banks. See next two images before for overhead views.
This is what the area above looked like in a 1995 USGS aerial photo on Google Earth. Compare the location of the red line in this image with the location in the next image. The GPS coordinates of the line are identical. But the river has migrated.
In just 23 years, the West Fork migrated 258 feet toward the dike on the right and now threatens it. The river has eaten away at the dike an average of 12.4 feet per year. The dike is now only 38 feet wide.
A bright white trail of sand leads all the way from the mines to the mouth bar which helped back water up into the highly populated Humble/Kingwood area. Fresh sand is several feet deep. Note absence of grasses. Many of the trees will also soon die.
Nearing the US59 bridge
Confluence of West Fork and Spring Creek, which also contributed sand to this event.
The next two images form a before/after pair.
West Fork of the San Jacinto over the US 59 Bridge before the Tax Day flood in 2016. River was 330 feet wide. Image courtesy of Google Earth.
GPS coordinates of the red line have not changed; the river has. After Harvey (in a little more than two years), the West Fork widened to 489 feet and shifted north by 113 feet. In part, this was due to excessive sediment that killed vegetation along the banks and accelerated erosion. Dead trees swept downriver were trapped by the bridge pilings, forming a dam that helped flood Humble businesses south of this photo. The southbound lanes of the bridge had to be replaced by TexDoT at a cost of approximately $20 million because of erosion.
Union Pacific railroad traffic was disrupted for months.
Mountains of sand may kill the remaining trees in this area, exposing it to even more erosion during the next storm.
Sand, in part, from the mines, has almost totally blocked the West Fork where it meets Lake Houston. Before/after measurements show that as much as ten feet was deposited in this area during Harvey (approximately five feet below water and five above). This forms a dam behind the dam, that backs water up into the Humble/Kingwood corridor during storms. Unless this sediment is removed, a storm smaller than Harvey could create Harvey-scale flooding.
Trees dying in Kingwood’s East End Park because of massive sediment build up around their trunks.
The website SF Gate describes how this die-back happens. “Soil added around a tree reduces the amount of oxygen available to the roots and slows the rate of gas exchange in and around the roots. There may be less moisture and nutrients available to the roots or too much moisture may remain around the tree’s roots. Inadequate oxygen reaching the roots or microorganisms in the soil around the roots can lead to an accumulation of chemicals that can injure tree roots. The tree’s bark may decay where soil is newly in contact with it. Damage or injury to the tree because of the added soil may not become apparent for several months or years and generally appears as a slow decline followed by death.” The same thing can happen with grasses and smaller trees along riverbanks. Once they die back and there is nothing left to bind the soil…
“Sediment is the primary pollutant expected from quarry operations.”
In the upcoming legislative session, the Lake Houston area needs to push for the creation of a river preservation district like the John Graves. The Graves District excludes sand mines from the 100-year flood plain and floodway where most erosion happens.
All Lake-Houston-area mines are in the FLOODWAY with the exception of one. A floodway is defined as the main channel of the river during a flood. This makes the mines more susceptible to river capture and massive erosion, which can create a downward spiral as we have seen above. Eventually it can lead to loss of property.
Our preservation district would stretch from Lake Conroe to Lake Houston, the primary sources of water for two million people.
The lives, health, homes, and businesses of two million people are certainly worth as much as protecting some scenery.
Posted by Bob Rehak on 12/1/18
449 Days after Hurricane Harvey
https://i0.wp.com/reduceflooding.com/wp-content/uploads/2018/11/SJR_504_029.jpg?fit=1800%2C1200&ssl=112001800adminadmin2018-11-30 20:06:232018-11-30 20:35:07Photo Essay on Role of Riparian Vegetation in Reducing Erosion
This is a little off topic. However, the post about Mercer Botanic Gardens generated so much interest that I thought I would follow it up with some good news for all those people still struggling to rebuild their homes after Harvey. Here’s an event at Mercer that the whole family can enjoy. It will help you take your mind off flooding for a day.
Holiday in the Gardens and Winter Plant Sale at Mercer
Celebrate the holiday season with music, food, crafts, shopping, and more during Holiday in the Gardens Saturday, Dec. 8 from 11 a.m. to 5 p.m. at Mercer Botanic Gardens.
This family-oriented event offers a holiday market, winter plant sale, and a Children’s Corner. Attractions include face painting, a visit from Santa, and holiday-themed crafts. Entrance is free, and children’s activities are available while supplies last. Food, drinks, and holiday gifts are available for purchase.
Volunteers Needed
Volunteers are needed for Holiday in the Gardens! Anyone who would like to volunteer or has questions can contact Mercer’s Volunteer Coordinator Jamie Hartwell at jhartwell@hcp4.net. New volunteers must complete a volunteer application, available at www.hcp4.net/mercer/volunteering.
Location
Mercer Botanic Gardens is a Harris County Precinct 4 Parks facility located one mile north of FM 1960 at 22306 Aldine Westfield Road in Humble, 77338. Heartfelt thanks go to Commissioner R. Jack Cagle for continuing to believe in this facility and sponsor events like Holiday in the Gardens.
Open to All
Harris County Precinct 4 programs serve people of all ages regardless of socioeconomic level, race, sex, religion, national origin, or physical ability. Anyone seeking additional information or requiring special assistance to participate in any program should contact Mercer at 713-274-4160 or online at www.hcp4.net/community/parks/mercer.
By Crystal Simmons, Harris County Precinct 4
Posted by Bob Rehak with some editorial comments on 11/30/2018
458 Days since Hurricane Harvey
https://i0.wp.com/reduceflooding.com/wp-content/uploads/2018/11/Holiday-In-Gardens-e1543594815214.jpg?fit=1200%2C652&ssl=16521200adminadmin2018-11-30 10:05:482018-11-30 10:20:57Holiday in the Gardens at Mercer Next Week
Growing Threat of Urban Flooding Labeled National Challenge by New Study
Researchers at Texas A&M Galveston and the University of Maryland have just published a massive new study on The Growing Threat of Urban Flooding: A National Challenge. The study – a treasure trove of insights – actually started in 2016, before Harvey.
It focuses primarily on urban flooding as opposed to riverine flooding, which caused many of the Lake Houston Area’s problems. However, area residents should not dismiss it. The two types overlap and the report largely addresses issues that exacerbate both, such as inadequate governmental systems, engineered structures and growth that overwhelms both.
The report contains eight major sections that quantify the scope of the challenge. Below, a few highlights from each.
I. Urban Floods: The Nation’s Hidden Challenge
Documents the stunning extent of urban flooding and factors that continue to make it worse. Did you know for instance, that two thirds of the nation’s population living in floodplains live in just two states: Texas and New York? Or that Texas led the nation in billion-dollar water and wind disasters between 1980 and 2018?
II. Analyzing Urban Flooding
Reveals statistics on the scope of the problem. Two gems:
III. Where Urban Flooding Occurs
Shows that Texas ranks in the middle of the pack in terms of frequency of events, as opposed to major events. The researchers found that nationwide, approximately 25% of all flood insurance claims are submitted by policy holders whose property lies outside the 100-year flood plain. New York found that “The problem in most communities is lack of enforcement. Communities need a comprehensive plan to address development, infrastructure needs, stormwater runoff, and building codes. When a community doesn’t address these issues it only exacerbates other problems and continued urban sprawl eats up rural areas causing flooding, erosion, and infrastructure malfunction.”
IV. Why Does Urban Flooding Happen?
Examines aging and inadequate drainage systems, increases in local and regional runoff, sewage and stormwater backups, changes in local physical conditions, and failure to maintain drainage systems. Sound familiar? If you’re worried about where your drainage fee goes, be thankful that you don’t live in Detroit. That city reports that 75% of the drains citywide are covered by debris or have a blockage.
V: Consequences of Urban Flooding
Talks about the economic and social costs of urban flooding. Did you know, for instance, that almost 40% of small business never reopen their doors following a flooding disaster? And that 90% of businesses fail within two years of being struck by a disaster? However, because no single federal agency collects and evaluates flood loss information, all national flood loss estimates are considered “approximations.” Therefore, the report says, they are of marginal use in conducting accurate economic analyses to support urban flood risk reduction mitigation.
Social costs hit moderate income, the old, and those facing social challenges the hardest. “For those lacking critical resources (savings, insurance, etc.), the flood losses gnaw away at their well-being.”
In regard to Houston, the study found that, “The urban flooding that occurs in the heart of the central city is mainly attributed to existing drainage infrastructure that predates today’s design standards or insufficient pipe sizes for the now fully developed urban areas.”
VI: What Can Be Done About Urban Flooding?
Examines different strategies to mitigate flooding:
Some key insights:
VII. Major Challenges
Includes discussions of lack of resources, population/urban growth, climate change, priority setting and fragmented governance.
If you want to understand why flood mitigation and what needs to be done to fix it, read this report.
VIII. Moving Ahead: Challenges and Recommendations
The study outlines ten challenges and makes 9 recommendations. Most target government leaders and policy makers. They are much too detailed to summarize here without tripling the length of the post. But if you want to know what you should push your representatives to consider, you must read section.
Number 8 read: “Governments, at all levels, have not provided effective means to communicate risks to those in urban flood- prone areas. A significant number of these areas are not identified by maps produced under the Federal Emergency Management Agency National Flood Insurance Programs, and actions by those responsible for urban flood mitigation are needed to delineate these areas. Communication of flood risk is often seen by public officials and developers as a negative.”
In my opinion, it’s a positive. A better understanding of risk could help everyone make better decisions that prevent heartbreaking losses, such as those we saw with Harvey.
All in all, this is a must read for anyone who wants to understand urban flooding and why it is so difficult to address.
Acknowledgements:
For University of Maryland
For Texas A&M University
Photo Essay on Role of Riparian Vegetation in Reducing Erosion
Riparian means “of or relating to the banks of a river.” To see the role of riparian vegetation in reducing erosion, one need only compare the two forks of the San Jacinto River. They provide a stark contrast. But the real story is the role of sand mining in reducing riparian vegetation.
After years of sand mining on the West Fork, much of the shoreline vegetation has been lost and the resulting erosion is staggering. Between I-45 and US59, sand miners have stripped vegetation from approximately 20 square miles of floodplain and floodway (the main channel of a river during a flood).
Sand Mines on West Fork of the San Jacinto form an almost continuous line from I-45 to US59. They have stripped approximately 20 square miles of ground cover.
On the East Fork above the Caney Creek confluence, however, there are no sand mines. The vegetation is lush and the erosion is negligible. Let’s start there for a look at how nature protects us.
Forests come down to the river’s edge. Grasses and cattails abound, protecting the banks.
Dense forest anchors the land. Grasses, forced to compete for sunlight, thrive along the river’s edge, protecting banks.
All images so far were taken on the East Fork of the San Jacinto River above where it merges with Caney Creek. Image courtesy of Google Earth.
Red lines on left measure width of East Fork on 3/3/16, before the Tax Day Storm. They are in a separate layer. Switching the background image to 10/28/17 shows that the river is virtually unchanged, thanks in large part to the lush riparian vegetation.
Now, A Trip up the West Fork
Now, let’s look at the West Fork. It’s vastly different.
Townhomes on Marina Drive in Forest Cove. Concrete, steel and wooden walls on the West Fork were less effective at preventing erosion than blades of grass on the East Fork.
Two weeks after Harvey. Just north of US 59 bridge.
West Fork Sand mine complex. Note one of many dike breaches in various mines that allowed sand and sediment to pour downstream. All helicopter images taken two weeks after Harvey on 9/14/17.
Mining a point bar after Harvey. Miners are supposed to work within their dikes to avoid disrupting vegetation along the river. Photo taken 9/14/17.
Note more repairs to dikes.
The next three images form a series.
River is migrating toward pit in background at the rate of 12 feet per year, in part, due to lack of vegetation protecting banks. See next two images before for overhead views.
This is what the area above looked like in a 1995 USGS aerial photo on Google Earth. Compare the location of the red line in this image with the location in the next image. The GPS coordinates of the line are identical. But the river has migrated.
In just 23 years, the West Fork migrated 258 feet toward the dike on the right and now threatens it. The river has eaten away at the dike an average of 12.4 feet per year. The dike is now only 38 feet wide.
A bright white trail of sand leads all the way from the mines to the mouth bar which helped back water up into the highly populated Humble/Kingwood area. Fresh sand is several feet deep. Note absence of grasses. Many of the trees will also soon die.
Nearing the US59 bridge
Confluence of West Fork and Spring Creek, which also contributed sand to this event.
The next two images form a before/after pair.
West Fork of the San Jacinto over the US 59 Bridge before the Tax Day flood in 2016. River was 330 feet wide. Image courtesy of Google Earth.
GPS coordinates of the red line have not changed; the river has. After Harvey (in a little more than two years), the West Fork widened to 489 feet and shifted north by 113 feet. In part, this was due to excessive sediment that killed vegetation along the banks and accelerated erosion. Dead trees swept downriver were trapped by the bridge pilings, forming a dam that helped flood Humble businesses south of this photo. The southbound lanes of the bridge had to be replaced by TexDoT at a cost of approximately $20 million because of erosion.
Mountains of sand may kill the remaining trees in this area, exposing it to even more erosion during the next storm.
Sand, in part, from the mines, has almost totally blocked the West Fork where it meets Lake Houston. Before/after measurements show that as much as ten feet was deposited in this area during Harvey (approximately five feet below water and five above). This forms a dam behind the dam, that backs water up into the Humble/Kingwood corridor during storms. Unless this sediment is removed, a storm smaller than Harvey could create Harvey-scale flooding.
Tree Loss in East End Park Has Already Started
Acres of trees in Kingwood’s East End Park have already started to die back as a result of being buried in dunes 10-15 high. I believe that sand, in large part, from the 750-acre mine upstream on Caney Creek is causing this. Piling as little as six inches of sediment around the base of a tree can kill it.
Trees dying in Kingwood’s East End Park because of massive sediment build up around their trunks.
The website SF Gate describes how this die-back happens. “Soil added around a tree reduces the amount of oxygen available to the roots and slows the rate of gas exchange in and around the roots. There may be less moisture and nutrients available to the roots or too much moisture may remain around the tree’s roots. Inadequate oxygen reaching the roots or microorganisms in the soil around the roots can lead to an accumulation of chemicals that can injure tree roots. The tree’s bark may decay where soil is newly in contact with it. Damage or injury to the tree because of the added soil may not become apparent for several months or years and generally appears as a slow decline followed by death.” The same thing can happen with grasses and smaller trees along riverbanks. Once they die back and there is nothing left to bind the soil…
“Sediment is the primary pollutant expected from quarry operations.”
The Texas Commission on Environmental Quality says, “Sediment is the primary pollutant expected from quarry operations.” See page 22 of this 2012 report from the Texas Commission on environmental quality about the John Graves Scenic Riverway District on the Brazos. The TCEQ also conducted experiments showing that certain types of revegetation can reduce sediment discharge from mines by 98 percent.
These findings are consistent with Louisiana Best Management Practice Guidelines for Sand Mines. They state that grasses can reduce erosion by 99%.
Conclusion
In the upcoming legislative session, the Lake Houston area needs to push for the creation of a river preservation district like the John Graves. The Graves District excludes sand mines from the 100-year flood plain and floodway where most erosion happens.
All Lake-Houston-area mines are in the FLOODWAY with the exception of one. A floodway is defined as the main channel of the river during a flood. This makes the mines more susceptible to river capture and massive erosion, which can create a downward spiral as we have seen above. Eventually it can lead to loss of property.
Our preservation district would stretch from Lake Conroe to Lake Houston, the primary sources of water for two million people.
Posted by Bob Rehak on 12/1/18
449 Days after Hurricane Harvey
Holiday in the Gardens at Mercer Next Week
This is a little off topic. However, the post about Mercer Botanic Gardens generated so much interest that I thought I would follow it up with some good news for all those people still struggling to rebuild their homes after Harvey. Here’s an event at Mercer that the whole family can enjoy. It will help you take your mind off flooding for a day.
Holiday in the Gardens and Winter Plant Sale at Mercer
Celebrate the holiday season with music, food, crafts, shopping, and more during Holiday in the Gardens Saturday, Dec. 8 from 11 a.m. to 5 p.m. at Mercer Botanic Gardens.
Volunteers Needed
Volunteers are needed for Holiday in the Gardens! Anyone who would like to volunteer or has questions can contact Mercer’s Volunteer Coordinator Jamie Hartwell at jhartwell@hcp4.net. New volunteers must complete a volunteer application, available at www.hcp4.net/mercer/volunteering.
Location
Mercer Botanic Gardens is a Harris County Precinct 4 Parks facility located one mile north of FM 1960 at 22306 Aldine Westfield Road in Humble, 77338. Heartfelt thanks go to Commissioner R. Jack Cagle for continuing to believe in this facility and sponsor events like Holiday in the Gardens.
Open to All
Harris County Precinct 4 programs serve people of all ages regardless of socioeconomic level, race, sex, religion, national origin, or physical ability. Anyone seeking additional information or requiring special assistance to participate in any program should contact Mercer at 713-274-4160 or online at www.hcp4.net/community/parks/mercer.
By Crystal Simmons, Harris County Precinct 4
Posted by Bob Rehak with some editorial comments on 11/30/2018
458 Days since Hurricane Harvey