2/7/26 – According to Harris County Meteorologist Jeff Lindner, the county has had at least 31 100-year floods in the previous 100 years. That’s between 1925 and 2025. “How can that be?” you ask. “Doesn’t a 100-year flood only happen once in a 100-years?”
Short answer, NO. To increase your safety and protect your home, read on.
Main Reasons for Apparent Contradiction
Numerous reasons exist for the apparent contradiction in the headline. They fall into three broad categories.
Widespread misunderstanding of the definition of a “100-year flood”: the term means different things to hydrologists and to the public.
Physical changes to floodplains and channels since the last flood-map update: Upstream development, sedimentation, lack of maintenance, etc. can all increase your flood risk.
Evolving statistical estimates of floodplains: Reliable weather records only go back about 130 years in this region. Predicting future risk using such a small statistical base has inherent risks of its own.
Widespread Misunderstanding of Definition
Let’s address misunderstanding of the definition first. The term “100-year flood” emerged in the early part of the 1900s to describe a flood that has a 1% chance of happeningeach year at any given geographic point.
So, technically, 100-year floods could occur in back-to-back-to-back years. And they have. See Lindner’s list of Harris County’s 31 “100-year floods” below.
5/31/29: Buffalo Bayou
12/9/35: Buffalo Bayou
10/9/49: Cypress Creek
9/11/61: Sims Bayou
6/20/73: Sims Bayou
6/11/75: Sims Bayou
7/25/79: Clear Creek, Armand Bayou, Sims Bayou, Vince Bayou
9/20/79: Clear Creek, Sims Bayou
5/3/81: Vince Bayou
8/18/83: Sims Bayou, Vince Bayou, Halls Bayou
9/19/83: Sims Bayou
6/26/89: Greens Bayou
8/1/89: Sims Bayou
10/18/94: Clear Creek, Sims Bayou, San Jacinto River, Spring Creek, Little Cypress Creek, Cedar Bayou
10/18/98: South Mayde Creek, Bear Creek, Spring Creek, Little Cypress Creek
11/14/98: Little Cypress Creek, Spring Creek
6/5/01: Clear Creek, Vince Bayou
6/9/01: Clear Creek, Armand Bayou, Brays Bayou, White Oak Bayou, Hunting Bayou, Vince Bayou, Little Cypress Creek, Willow Creek, Carpenters Bayou, Greens Bayou, Halls Bayou, Buffalo Bayou
10/29/02: White Oak Bayou
8/16/07: Vince Bayou
9/13/08: Vince Bayou, Bear Creek, South Mayde Creek
4/28/09: Bear Creek, South Mayde Creek, Buffalo Bayou
7/12/12: Little Cypress Creek
5/13/15: Armand Bayou
5/26/15: Keegans Bayou, White Oak Bayou, Buffalo Bayou
10/31/15: Cedar Bayou
4/18/16: Keegans Bayou, Spring Creek, Little Cypress Creek, South Mayde Creek, Bear Creek, Horsepen Creek
5/27/16: Spring Creek, Little Cypress Creek
8/27/17: Nearly every watershed
9/19/19: San Jacinto River, Cedar Bayou
5/2/24: San Jacinto River
Many of these watersheds have seen 5 to 10 extreme floods in the last 100-years.
“100-Year Flood” is an estimate of probability and not a guarantee of frequency.
Keep that in mind if you’re shopping for a new home or considering cancelling your flood insurance.
Physical Changes to Floodplains/Channels
The other thing to keep in mind is that floodplains constantly change. You could be high above them one year and far below the next because of changes to the terrain upstream.
I once owned a home in Dallas that went from 2 feet above a 100-year floodplain to 10 feet below it in less than three years. How? One insufficiently mitigated, new development upstream. Think it can’t happen here? Look at Colony Ridge in the East Fork Watershed. It didn’t exist 15 years ago and is now 50% larger than Manhattan.
When buying a home, consider such factors as:
Subsidence from excessive groundwater withdrawals in Montgomery County (MoCo) could reduce a home’s elevation relative to the Lake Houston Dam. That would reduce the safety margin between your slab and floodwaters.
Sedimentation could reduce the conveyance of a channel or massively block it. During Harvey, sand washing downstream reduced conveyance of the West Fork by 90%, according to the Army Corps.
Much of that sand came from sand mines in MoCo. Mines have deforested 20 square miles in a 20-mile length of the river between I-45 and I-69. That exposes a swath of sediment averaging a mile wide to floodwaters.
MoCo actually gives tax breaks to those mines that encourage deforestation, rapid sedimentation and downstream flooding.
Until recently, the state didn’t require minimum setbacks from the river for mines. Because of erosion, the river now runs through mines in at least six places on the West Fork.
Complicating that, MoCo has not enforced its own floodplain regulations. I have published dozens of stories about that, including the blatant transgressions that flooded 600 homes in 2019 along Taylor Gully across the county line from Perry Homes’ Woodridge Village development.
When most of the region adopted new drainage and floodplain regulations shortly after Harvey in 2017, MoCo took until late 2025. And their new regs didn’t meet the minimum standards adopted elsewhere.
Climate change aside, such factors as those above make estimating flood risk a shifting target. Worse, the small statistical base for those estimates gives them a large margin of error.
Complete rainfall records for Harris and Montgomery Counties only go back to the early 1890s. So, we’re trying to estimate 100-year rainfalls by looking at one complete 100-year cycle out of 4.56 billion years. That’s as difficult as predicting a statewide election outcome by interviewing one person!
As a result, scientists update rainfall estimates after most major storms such as Harvey and Allison. But that can take years. FEMA is just now releasing new flood maps based on high-water marks and elevation data acquired after Harvey. And MoCo’s population has grown by about a third since then – enough to skew results significantly.
As upstream counties pursue growth, downstream counties must require higher elevations in building codes. But that won’t help already-built homes in older neighborhoods. To help those residents, we must pursue expensive flood mitigation to offset the increased flood peaks resulting from upstream growth.
There’s just no option; it will never end. We can never give up trying to offset competing interests. Or we’re sunk.
Posted by Bob Rehak on 2/7/2026
3084 Days since 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/2022/01/image.png?fit=868%2C686&ssl=1686868adminadmin2026-02-07 20:19:222026-02-08 07:53:32Why Harris County Had 31 100-Year Floods in 100 Years
2/6/26 – The project to add more gates to the Lake Houston Dam has reached the 30% design benchmark, according to Houston City Council Member Fred Flickinger. The 30% milestone is widely regarded among engineers as the point where the design becomes real enough that you can start working out the final details, including costs, geotechnical work, and permitting.
Eastern portion of Lake Houston Dam/Spillway where gates would go.
Flickinger added that the design team is already engaging with regulatory agencies, including the Texas Commission on Environmental Quality (TCEQ), United States Army Corps of Engineers (USACE-Galveston), and Texas Parks and Wildlife Department (TPWD), to discuss project details and streamline permitting review schedules.
Significance of 30% Benchmark
The 30% completion benchmark is a widely recognized milestone in engineering and infrastructure project development. It marks the transition from conceptual planning into a sufficiently defined design that supports credible cost, schedule, and constructability judgments.
Decision-makers quote it because it is the earliest point at which a project begins to behave like a real, executable asset rather than a rough idea.
While definitions vary slightly by agency, 30% usually falls at the end of preliminary engineering (PE) or schematic design.
Typical deliverables include:
Horizontal and vertical alignments
Right-of-way footprint
Identification of utility conflicts
Substantial completion of hydrology and hydraulics models
Definition of drainage pathways
Identification of jurisdictional constraints (e.g., wetlands)
Likely permitting strategy
Elimination of potential fatal flaws
Engineer’s opinion of probable costs (much tighter than possible before 30%)
In this case, according to one engineer who previously worked on the project, they would also include pre- and post inundation maps and identification of the extent of areas benefitted.
First Defensible Go/No-Go Decision Gate
Why does the 30% point get quoted so often? According to ChatGPT, it’s the first defensible “go/no go” gate. Before 30%, optimism drives a project. At 30%, physics drive it.
At the 30% point, uncomfortable truths surface and cost escalation becomes visible.
Uncertainty gives way to measurable reality
Optimism encounters hydrology, soil, and gravity
Financial exposure becomes calculable
Scope reality emerges
In professional terms, it is the first point of engineering credibility. Before 30%, you deal with selection risk (Do we have the right idea?). After 30%, project managers deal with execution risk. For instance:
Will regulators approve it?
Will available funding meet Benefit/Cost requirements?
How will it affect downstream residents?
Will it meet needs outlined in the SJRA’s Joint Reservoir Operations Study, which is still incomplete.
How will construction of new gates dovetail with dam repairs?
Flickinger Already Met with Mayor About Next Steps
The City still hasn’t released details of its 30% plans for the gates.
However, City Council Member Fred Flickinger said, “Now we know how much more money we need to find to get this project done.” He has already talked to the Mayor’s staff about going to Austin to get it.
There’s still a long way to go. But we have reached a significant milestone and, according to Flickinger, all energies are headed in the right direction.
2/5/26 – For months, Huffman residents have complained about TXDoT contractors dumping fill in the floodplain of Cedar Bayou. This morning, I caught the dumping on camera. The fill comes from two stormwater detention basin sites. One is almost complete. The other one is larger and still being excavated. Both sites are adjacent to the FM2100 reconstruction project.
Dumping Without Permit
Dumping fill in a 100-year floodplain violates county regulations.
Regulations Effective July 9, 2019
Dumping fill in unincorporated areas of Harris County, such as this one, also requires a permit, which the contractors do not have. Harris County Precinct 3 has tried to stop the illegal activity, according to Eric Mullen, Precinct 3’s head engineer.
Jason Haines, a project manager for Precinct 3, says this fill does not have a permit. He also has tried to stop the dumping. But the contractors have not complied. He says that compliance will require either: removal of the fill or removing an equivalent amount somewhere else in the floodplain.
The visual below shows where the fill is coming from and going to. In both cases, it’s coming from outside the floodplain and going into one.
Luce Bayou cuts across left, Cedar Bayou cuts across lower right. Aqua area = 100 year floodplain.
Reducing the volume of a floodplain forces stormwater to go elsewhere, i.e., into someone else’s home or business. That’s why the regulations exist.
This morning, I photographed a parade of dump trucks being filled up at the triangular site above and depositing their loads in the floodplain. The activity has been going on for months, according to local residents Max Kidd and his wife.
Below is a small sampling of hundreds of photos I took today and on two previous occasions. They have GPS coordinates embedded in them so you can verify their locations in software, such as PhotoGeoTag.
Triangular site adjacent to FM2100, which TxDOT is excavating. Approximately 26 acres.This dump truck with the blue cab was being filled up at the triangular site.
I then followed that blue truck to the dump site, a farm just south of the Luce Inter-basin Transfer Canal.
Dump siteSame truck with blue cab pulls into position to dump its fill through a door opening beneath the trailer.As it drops its load, a bulldozer immediately starts smoothing it out so the next truck can deposit its load.I watched this for hours, shuttling from Point A to Point B and back again.As one truck left, another moved in. The elevation of the fill is quite high compared to the height of the bulldozer.The presence of lights indicates the activity may continue after dark.Load after load…all in the floodplain.
And it’s not just this one mound.
Additional fill deposited on another part of the same property but not yet spread. Luce Inter-basin Transfer Canal at top.Residents say dirt from this detention basin was also deposited at the same site although I have no pictures of the actual dumping.
It’s the Principle that Counts
The dump site (l) is less than a mile from the Huffman High School and Middle School (r), making them more vulnerable to reduced floodplain capacity.
Note: all floodplains above are based on 2007 pre-Harvey data. The floodplains should get even wider and deeper when FEMA releases the new flood maps.
Posted by Bob Rehak on 2/5/2026
3082 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/2026/02/Huffman-Floodplains-copy.png?fit=1100%2C784&ssl=17841100adminadmin2026-02-05 16:03:542026-02-23 16:48:07Caught on Camera: TXDoT Contractor Dumping Fill in Floodplain
Why Harris County Had 31 100-Year Floods in 100 Years
2/7/26 – According to Harris County Meteorologist Jeff Lindner, the county has had at least 31 100-year floods in the previous 100 years. That’s between 1925 and 2025. “How can that be?” you ask. “Doesn’t a 100-year flood only happen once in a 100-years?”
Short answer, NO. To increase your safety and protect your home, read on.
Main Reasons for Apparent Contradiction
Numerous reasons exist for the apparent contradiction in the headline. They fall into three broad categories.
Widespread Misunderstanding of Definition
Let’s address misunderstanding of the definition first. The term “100-year flood” emerged in the early part of the 1900s to describe a flood that has a 1% chance of happening each year at any given geographic point.
So, technically, 100-year floods could occur in back-to-back-to-back years. And they have. See Lindner’s list of Harris County’s 31 “100-year floods” below.
Many of these watersheds have seen 5 to 10 extreme floods in the last 100-years.
Keep that in mind if you’re shopping for a new home or considering cancelling your flood insurance.
Physical Changes to Floodplains/Channels
The other thing to keep in mind is that floodplains constantly change. You could be high above them one year and far below the next because of changes to the terrain upstream.
I once owned a home in Dallas that went from 2 feet above a 100-year floodplain to 10 feet below it in less than three years. How? One insufficiently mitigated, new development upstream. Think it can’t happen here? Look at Colony Ridge in the East Fork Watershed. It didn’t exist 15 years ago and is now 50% larger than Manhattan.
When buying a home, consider such factors as:
Evolving Statistical Estimates/Building Codes
Climate change aside, such factors as those above make estimating flood risk a shifting target. Worse, the small statistical base for those estimates gives them a large margin of error.
Complete rainfall records for Harris and Montgomery Counties only go back to the early 1890s. So, we’re trying to estimate 100-year rainfalls by looking at one complete 100-year cycle out of 4.56 billion years. That’s as difficult as predicting a statewide election outcome by interviewing one person!
As a result, scientists update rainfall estimates after most major storms such as Harvey and Allison. But that can take years. FEMA is just now releasing new flood maps based on high-water marks and elevation data acquired after Harvey. And MoCo’s population has grown by about a third since then – enough to skew results significantly.
As upstream counties pursue growth, downstream counties must require higher elevations in building codes. But that won’t help already-built homes in older neighborhoods. To help those residents, we must pursue expensive flood mitigation to offset the increased flood peaks resulting from upstream growth.
There’s just no option; it will never end. We can never give up trying to offset competing interests. Or we’re sunk.
Posted by Bob Rehak on 2/7/2026
3084 Days since 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.
Lake Houston Gates Project Reaches 30% Design Benchmark
2/6/26 – The project to add more gates to the Lake Houston Dam has reached the 30% design benchmark, according to Houston City Council Member Fred Flickinger. The 30% milestone is widely regarded among engineers as the point where the design becomes real enough that you can start working out the final details, including costs, geotechnical work, and permitting.
The plan calls for adding 11 new tainter gates to the eastern, earthen portion of the dam. They could release 78,000 cubic feet per second – as much as Lake Conroe released at the peak of Hurricane Harvey.
Flickinger added that the design team is already engaging with regulatory agencies, including the Texas Commission on Environmental Quality (TCEQ), United States Army Corps of Engineers (USACE-Galveston), and Texas Parks and Wildlife Department (TPWD), to discuss project details and streamline permitting review schedules.
Significance of 30% Benchmark
The 30% completion benchmark is a widely recognized milestone in engineering and infrastructure project development. It marks the transition from conceptual planning into a sufficiently defined design that supports credible cost, schedule, and constructability judgments.
Decision-makers quote it because it is the earliest point at which a project begins to behave like a real, executable asset rather than a rough idea.
While definitions vary slightly by agency, 30% usually falls at the end of preliminary engineering (PE) or schematic design.
Typical deliverables include:
In this case, according to one engineer who previously worked on the project, they would also include pre- and post inundation maps and identification of the extent of areas benefitted.
First Defensible Go/No-Go Decision Gate
Why does the 30% point get quoted so often? According to ChatGPT, it’s the first defensible “go/no go” gate. Before 30%, optimism drives a project. At 30%, physics drive it.
At the 30% point, uncomfortable truths surface and cost escalation becomes visible.
In professional terms, it is the first point of engineering credibility. Before 30%, you deal with selection risk (Do we have the right idea?). After 30%, project managers deal with execution risk. For instance:
Flickinger Already Met with Mayor About Next Steps
The City still hasn’t released details of its 30% plans for the gates.
However, City Council Member Fred Flickinger said, “Now we know how much more money we need to find to get this project done.” He has already talked to the Mayor’s staff about going to Austin to get it.
There’s still a long way to go. But we have reached a significant milestone and, according to Flickinger, all energies are headed in the right direction.
Posted by Bob Rehak on 2/6/26
3083 Days since Hurricane Harvey
Caught on Camera: TXDoT Contractor Dumping Fill in Floodplain
2/5/26 – For months, Huffman residents have complained about TXDoT contractors dumping fill in the floodplain of Cedar Bayou. This morning, I caught the dumping on camera. The fill comes from two stormwater detention basin sites. One is almost complete. The other one is larger and still being excavated. Both sites are adjacent to the FM2100 reconstruction project.
Dumping Without Permit
Dumping fill in unincorporated areas of Harris County, such as this one, also requires a permit, which the contractors do not have. Harris County Precinct 3 has tried to stop the illegal activity, according to Eric Mullen, Precinct 3’s head engineer.
Jason Haines, a project manager for Precinct 3, says this fill does not have a permit. He also has tried to stop the dumping. But the contractors have not complied. He says that compliance will require either: removal of the fill or removing an equivalent amount somewhere else in the floodplain.
The visual below shows where the fill is coming from and going to. In both cases, it’s coming from outside the floodplain and going into one.
Reducing the volume of a floodplain forces stormwater to go elsewhere, i.e., into someone else’s home or business. That’s why the regulations exist.
This morning, I photographed a parade of dump trucks being filled up at the triangular site above and depositing their loads in the floodplain. The activity has been going on for months, according to local residents Max Kidd and his wife.
Below is a small sampling of hundreds of photos I took today and on two previous occasions. They have GPS coordinates embedded in them so you can verify their locations in software, such as PhotoGeoTag.
I then followed that blue truck to the dump site, a farm just south of the Luce Inter-basin Transfer Canal.
And it’s not just this one mound.
It’s the Principle that Counts
Note: all floodplains above are based on 2007 pre-Harvey data. The floodplains should get even wider and deeper when FEMA releases the new flood maps.
Posted by Bob Rehak on 2/5/2026
3082 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.