Infrastructure bottlenecks reveal themselves during extreme events. This is a universal phenomenon. Bridges, culverts, and channel constrictions control flood elevations behind them.
You see this everywhere around the world. It’s a well studied phenomenon. Let’s look at two areas.
Openings then catch debris floating downstream, further reducing the conveyance of the river. Forested basins supply large wood during storms. Inlet plugging is common. Debris blockage can reduce culvert capacity by 30–80%.
This is especially acute in Appalachia because of steep basins susceptible to flash flooding and the fact that roads usually follow streams. They can have many crossings per mile.
Older culverts and bridges may have been designed in previous eras when engineers anticipated smaller storms. You see scour at outlets where water churns, trying to get under the bridge. You also see jetting on the downstream side. Both lead to channel instability.
In June 2016, West Virginia experienced one of the worst floods in its history. After the event, U.S. Geological Survey, Federal Highway Administration and West Virginia Department of Transportation documented:
Hundreds of culvert and small bridge failures
Widespread road overtopping and washouts
Extensive debris blockage at inlets
Excessive erosion and sedimentation downstream.
NOAA photo from 2016 West Virginia Flood
Houston-Area Examples
In the Houston area, we see the same hydraulic constraint issues.
FM1010 culverts could not handle the drainage from new upstream development larger than Manhattan.
I-69 Bridge Over West Fork
TxDot had to replace part of the I-69 bridge over the San Jacinto West Fork while residents endure massive traffic jams because of scouring under the supports for the southbound lanes.
Replacement took almost a year.
UPRR Bridge over West Fork
Union Pacific’s Bridge over the San Jacinto West Fork was destroyed by Harvey. Trees washing downstream formed a dam that raised the flood level.
Tree Lane Bridge
Multiple floods backed water up behind the Tree Lane Bridge over Bens Branch in Kingwood. They raised water levels upstream as jetting scoured bridge supports on the downstream side. The bridge has been repaired several times since Harvey.
Tree Lane bridge after Imelda in 2019.
Given upstream development, the width was insufficient. Engineers ultimately had to widen the opening of the bridge to let high peak flows pass through.
Rustic Elms Bridge
Up to 600 homes flooded twice in Kingwood’s Elm Grove Village in 2019. The bridge below was one of the problems. The culverts convey less water than the open span design of the West Lake Houston Parkway Bridge over Taylor Gully in the background.
The bridge will soon be replaced as part of a HUD/GLO/HCFCD project.Rustling Elms Bridge underwater as school bus tries to cross it in May 2019.
West Fork Mouth Bar
Eroded sediment washed downstream during Harvey and dropped out of suspension where water slowed as it met Lake Houston. Thousands of homes and businesses flooded behind this sediment dam, which reached more than 10 feet about normal water level.
West Fork mouth bar after Harvey and before dredging. Note the openings under the FM1960 bridge in the background.
FM 1960 Bridge
Post-Harvey analyses revealed a significant constriction in the San Jacinto near the headwaters of Lake Houston. The openings in the FM 1960 causeway across the lake are half the width of upstream and downstream bridges.
John Blount, Harris County Engineer at the time of Hurricane Harvey said he noticed a difference in the water surface elevations on the upstream and downstream sides of the bridge. Downstream was lower by 1-2 feet.
During Harvey, one hundred and ten homes in Kings Forest flooded behind these culverts half clogged with sediment. The City of Houston cleaned them out in 2025.
HCFCD 2019 photo of blocked culverts under Kingwood Drive
Lake Houston Dam
The single biggest blockage in the Lake Houston Area is the Lake Houston Dam. While the dam has a spillway to handle high-water events, it does not have gates with a sufficient release capacity to lower water levels immediately before storms. The City of Houston is designing additional gates that will allow greater coordination with pre-releases from Lake Conroe. And the San Jacinto River Authority is studying ways to coordinate pre-releases.
Earthen portion of Lake Houston Dam where new gates will be added.
I-45 Bridge at Cypress Creek
Harvey’s floodwaters in Cypress Creek were so strong that they literally picked up parts of the southbound I-45 lanes and shifted the bridge. The constriction caused by the bridge backed water up into hundreds of homes.
I-45 southbound feeder over Cypress Creek showing cattywumpus bridge panels
I could go on. But you get the idea. Bridges and culverts restrict flow in large events, creating dangerous backwater. Those bridges and culverts may have been adequate early in their lives, but upstream growth rendered them inadequate.
For more information about other factors that contribute to flooding, see the Lessons page of this website.
Posted by Bob Rehak on 4/3/26
3139 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/2018/05/I69Damage-e1775243525276.jpg?fit=1100%2C733&ssl=17331100adminadmin2026-04-03 14:15:142026-04-03 14:42:25How Infrastructure Bottlenecks Constrain Peak Flows, Cause Local Flooding
4/2/2026 – Across the U.S., fragmented governance increases flood risk by creating a patchwork quilt of local interests that makes regulation, compliance and enforcement difficult.
One might think that our multi-level system of government – federal, state, county, city, improvement districts, etc. – creates defense in depth. In reality, each governmental entity plays by its own rules and is responsible to different groups of voters with different priorities and interests.
The problem is especially visible in large metro regions that involve numerous cities and counties with upstream/downstream conflicts of interest. Watersheds fragment into jurisdictional silos.
People downstream may experience flooding issues decades before upstream residents. And those upstream residents have no incentive to increase their taxes to pay for downstream mitigation.
Fragmented governance, therefore pits groups against each other as development spreads outward.
It also creates an accountability gap – “Not our job!”
And regulatory inconsistency (different rules for detention, rainfall and fill) make it almost impossible to measure the cumulative impact of hydrological changes throughout the watershed.
In any given river basin, we may all be part of the solution. But we don’t all feel the problem. At least, not yet.
Denver’s South Platte Basin
Fragmented governance in the Denver metro—especially in the South Platte River basin—has been a persistent, structural driver of flood risk. A patchwork of cities, counties, special districts, and state/federal agencies manage the basin. The result: coordination gaps that translate directly into flood risk.
Special districts like the Mile High Flood District (MHFD)
MHFD develops regional drainage criteria.However, it does not regulate land use; local governments do. As a result:
Different jurisdictions adopt different stormwater standards, detention requirements, and update cycles
Upstream communities can:
Allow higher impervious cover
Use less conservative rainfall assumptions
Provide insufficient detention
Flows arriving at Denver often stack on top of each other and higher in volume
Cumulative peak flows exceed what any one jurisdiction modeled
No entity is responsible for system-wide flood control.
Need for Basin-Wide Master Planning
According to the EPA, each jurisdiction optimizes locally, not basin-wide. Upstream cities capture the tax base from new development and export their runoff downstream. Meanwhile, downstream, Denver bears the flood risk and mitigation costs.
Denver has acknowledged the need for basin-wide master planning. But historically, many tributaries fell outside FEMA mapping and were handled locally. Imagine every city along a freeway each designing the freeway to meet its own needs. That’s the system in flood control.
Storm sewers, channels, and detention systems do not align across boundaries and have mismatched capacities.
Encroaching development has already narrowed the South Platte floodplain. But no single entity has tracked the loss of floodplain storage.
Furthermore, no one jurisdiction coordinates infrastructure development of bridges and highways where they intersect drainage. Undersized crossings create system-wide backwater effects.
In addition, the South Platte is heavily regulated by upstream reservoirs, which the Army Corps operates. But urban stormwater systems are operated locally and not fully synchronized. Sound familiar?
In Chicago, suburban expansion has increased runoff, but regional drainage capacity has not kept pace.
The Chicago area has even more extreme jurisdictional fragmentation than Denver. Cook County and three surrounding counties have more than 200 municipalities, plus a variety of state and federal agencies all sharing responsibilities for parts of the drainage.
Historically, each county has had different design storms, release rates, and detention requirements. Previously developed areas have had trouble keeping pace with upstream expansion.
The Chicago Area Waterway System also has three main rivers: the Chicago, Des Plaines and Calumet rivers. No single authority controls basin-wide runoff timing, impervious cover, or development in flood-prone areas.
But after several early successes, the program seems to have quietly dropped out of the headlines.
Likewise, the San Jacinto Region 6 Flood Planning Group proposed minimum floodplain management practices throughout the river basin in 2025. But it is strictly an advisory group.
Texas 2036 and the American Flood Coalition hosted an informative seminar on 2/17/26. It emphasized lessons learned from other states about the need for river-basin-wide flood control to help ensure flood resilience.
Everyone seems to recognize the need. But no one seems to have the power to address fragmented governance.
In Texas, we even have a state agency charged with flood mitigation investing in the development of property in floodplains and floodways…and denying FOIA requests to keep the investment secret. That’s how entrenched the problem of fragmented governance has become.
To see how fragmented governance compounds other factors that contribute to flooding, see the Lessons Page of this website.
Posted by Bob Rehak on 4/2/2026
3138 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.
4/1/26 – In my quest to summarize the most important “lessons learned” since Hurricane Harvey, here’s Lesson #3: Floodplain Encroachment. Floodplain encroachment is consistently rated one of the most important drivers of flooding worldwide. Think about it. If people didn’t build in floodplains, no one would flood. But that’s only part of the story. Floodplain development also changes flood assumptions for communities downstream.
Why People Build in Floodplains
Despite the risks, people worldwide build in floodplains. The land usually costs less. And it can yield extraordinary profits to developers lucky or persistent enough to obtain building permits.
After all, people pay premiums to live near water. Water views are prestigious, beautiful and soothing. Plus, historically, living near water translated to “security.” Water sustains life. The need for water is hard-wired into our DNA, our culture, and even our economy.
Once a thriving community. Destruction on Bolivar Peninsula in 2008. Storm surge 15 feet high during Hurricane Ike washed away homes and ripped storm sewers right out of the ground.
Yet during Hurricane Ike in 2008, storm surge reached 30 miles inland in places. And despite being leveled, within 10 years, homes on the vulnerable Bolivar Peninsula had built back.
While I have focused primarily on the Houston Area, floodplain encroachment is a global problem. Nearly all growing metro areas encroach on floodplains – coastal or riverine.
Loss of Natural Storage Can Increase Downstream Flood Elevations
The problem isn’t just “putting people in harm’s way.” It’s also about the loss of natural floodplain storage. In riverine systems, floodplains function as temporary storage reservoirs during overbank flows.
Insufficiently mitigated development can remove that storage volume or prevent it from being accessed.
Apartments and commercial development along Houston’s Brays Bayou
That’s why after Harvey, Houston and Harris County changed floodplain regulations so developers couldn’t bring fill into floodplains. Fill displaces water. Nature compensates for the fill by increasing water surface elevations elsewhere.
Floodplain development can also reduce the duration of floodplain storage, resulting in faster, higher peaks downstream.
See examples below.
Mississippi Floodplain Development
Historically, the Mississippi River occupied a broad alluvial valley tens of miles across in places. It inundated seasonally . Floodplains functioned as massive, temporary storage reservoirs.
Encroachment occurred primarily through federal levee construction under the U.S. Army Corps of Engineers and urban/industrial development that occurred later behind the levees.
As a result, floodplain width narrowed dramatically. The levees confined the river’s flow into a narrower channel where floods moved higher and faster, often breaking through levees with devastating consequences.
Levee failure also played a major role in the inundation of New Orleans during Hurricane Katrina in 2005.
Floodplain encroachment can turn into a vicious feedback loop. Levees reduce frequent flooding. That attracts more investment and development behind the levees. But as the consequences of levee failure increase, there’s more pressure to build higher, stronger levees.
West Fork San Jacinto/Spring Creek Confluence
Closer to home for most of my readers, developers have recently been trying to figure out ways to develop 5,300 acres between the West Fork San Jacinto River and Spring Creek. Virtually the entire area is in floodplain or floodway. Though current flood maps don’t fully reflect the danger, FEMA’s new draft flood maps for the area show part of the property. See below.
Dark blue/gray = floodway. Dark green = 100-year floodplain. Light green = 500-year floodplain.From HCFCD MAAPnext.
A leading hydrologist in the area told me that developing this area would be like “aiming a fire hose at the Humble/Kingwood Area.”
It’s not clear yet what the developer has planned for the site. Both the Texas General Land Office (GLO) and the Texas Attorney General have denied FOIA requests for the plans.
An “externality problem” occurs when the production or consumption of a good, such as housing, imposes unintended costs or benefits on third parties not involved in the transaction. In economic terms, this leads to market inefficiencies. It is a form of market failure. Private costs/benefits differ from social costs/benefits.
For instance, sand mines help produce a raw material needed for concrete. It generates profit for producers. But in their zeal to maximize their profit, they mine too close to rivers and in a manner that exacerbates erosion and sedimentation.
It’s the same way with flooding. Developers profit from building in floodplains. And the vast majority try to do it safely.
Regardless, in 2023, the Joint Economic Committee of Congress estimates that each year flooding costs Americans between $179.8 and $496.0 billion. The total depends on the types of damage included, i.e., structural, lost economic output, infrastructure repairs, insurance losses, decreased tax revenues, transit, deaths, etc.
Assuming the higher flood-damage estimate of nearly half of a trillion dollars, that represents 7% of last year’s entire federal budget. I’d sure like a 7% tax cut. April 15th is two weeks away!
For More Information
For more “lessons learned” about flooding since Harvey, see this website’s Lessons Page.
Posted by Bob Rehak on 4/1/2026
3137 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/2020/11/Hurricane-Ike-363.jpg?fit=1500%2C993&ssl=19931500adminadmin2026-04-01 19:10:362026-04-02 08:47:26Floodplain Encroachment: Another Consistent Driver of Flooding Worldwide
3/31/26 – Since Hurricane Harvey, one of the dominant themes of more than 3,000 posts on this website has been outdated rainfall assumptions and how flood-infrastructure design lags those assumptions. That design lag contributes to flooding nationwide.
How Infrastructure Design Lags Rainfall Estimates
Almost nine years after Harvey, Harris County finally has new “draft” flood maps issued by FEMA based on Atlas-14 rainfall assumptions. But they won’t take effect for another two to three years. Meanwhile, parts of the region have built and will continue to build infrastructure, homes and businesses based on long-outdated rainfall predictions.
Different regulatory agencies and jurisdictions update at different speeds.
Imagine members of a choir each singing from different songbooks.
These rainfall predictions affect many aspects of flood control and building codes, including:
Stormwater detention basin sizing
Floodplain mapping
Subdivision drainage criteria, i.e., size of storm sewers
Elevation of homes and businesses above the 100-year floodplain and street level
Acceptable foundation types in flood- hazard areas
Building in floodways including width, depth, bracing and other requirements for piers
Where fill can and cannot be used
In 2009, Harris County revised its floodplain development standards. After Harvey, Harris County Engineering compared damage found in subdivisions built before and after the new standards.
Subdivisions built with the updated standards experienced one twentieth the amount of damage.
EVA and the Difficulty of Developing Rainfall Estimates
So getting the rainfall right is important. But why do we get it wrong so often? Rainfall predictions stem from an obscure branch of mathematics, known as EVA (Extreme Value Analysis). With EVA, forecasters try to predict the probability of unobserved future events based on the frequency of somewhat smaller past events.
But there’s a problem. All predictions (500-year storms, etc.) are based on extremely small data sets. EVA may produce the best numbers possible, but predicting 500-years into the future based on 100 years of data takes a lot of guess-work. And we design entire cities based on these probabilities!
And that’s what I mean by the “design lag” problem based on outdated rainfall assumptions. Assumptions change with major new storms, such as Harvey. But we can’t just wave a major wand and change trillions of dollars of infrastructure already in the ground. We are systematically under-designed for current rainfall statistics.
This isn’t just a Houston problem. And it’s not just “in the ground” infrastructure. For example…
Mississippi Levees
Engineers typically design levees to contain a 100-year (1% annual chance) storm. Even small increases in in rainfall when levees constrain a river can produce huge increases in water surface elevation and push crests above levees. We’ve seen this happen recently in 2008 and 2019.
Design lag manifested itself as systemic underestimation of river stage, leading to overtopping of levee defenses.
Street Flooding in New York City
In 2023, extreme rainfall (up to 2.5 inches per hour) snarled the New York metropolitan area. It knocked out subways, commuter rail lines, flooded basements and closed a terminal at LaGuardia. It was the City’s wettest day since 1960 and came just two years after Hurricane Ida killed at least 13 people.
Engineers from previous generations designed storm sewers for much lower peak intensities. Usually, they design urban systems around peak intensities for short time periods (minutes to a few hours). But pre-Atlas 14 standards underestimated those short duration bursts.
Storm sewers were simply designed for much lower peak intensities. Systems failed almost instantly. Subway entrances became inlets for street flooding.
The Lesson Learned
Flooding results not just from rainfall. It results from under-designed infrastructure for rain that falls. For example:
Homes not high enough.
Channels not wide enough.
Storm sewers not big enough.
As a result, NOAA hopes to update rainfall frequency estimates much more frequently in the future. NOAA developed Atlas 14 region-by-region from approximately 2000–2018.
Texas lagged other regions by years. Before Atlas 14, the prior standard (TP-40) dated to 1961. And during that time, Houston grew exponentially. So most of our infrastructure is built to older standards.
NOAA is trying to eliminate the “outdated by the time it’s adopted” issue. But:
Local adoption will still likely lag availability
Regulatory inertia will remain the bottleneck.
See Lessons Page For More Information
For more information about other causes of flooding, see the Lessons page of this website.
Posted by Bob Rehak on 3/31/26
3136 Days since Harvey
https://i0.wp.com/reduceflooding.com/wp-content/uploads/2024/05/NOAA-Atlas-14-Rainfall-Rates-for-Kingwood.png?fit=976%2C828&ssl=1828976adminadmin2026-03-31 17:07:382026-03-31 17:28:03Outdated Rainfall Assumptions: A Systemic Design-Lag Problem
3/30/31 – According to numerous engineering studies, the single most consistent, anthropogenic (human-created) driver of flooding worldwide is expansion of impervious cover related to urbanization.
How Impervious Cover Contributes to Flooding
Any area growing in population adds roads and rooftops. When stormwater falls on them, it runs off quickly, unlike when forests or grass covered the land. Engineers talk of friction coefficients. Less friction with concrete increases the speed of runoff.
But it’s not just the speed, it’s also the volume of runoff. Engineers also measure the permeability of different land surfaces and soil types. Is the surface clay or sand, for instance. One holds water; the other lets it sink in.
Regardless, replacing either with concrete and shingles increases the speed and volume of runoff. Think of water running off a roof and down a gutter during a torrential rain.
Quantitative example calculated by ChatGPT.
Note how volume peaks higher and faster after development.
Pre-development: CN 68, Time of concentration 2.5 hr
Post-development: CN 90, Time of concentration 0.8 hr
Results:
Pre-development peak flow: about 81 cfs
Post-development peak flow: about 402 cfs
Pre-development time to peak: about 1.75 hr
Post-development time to peak: about 0.73 hr
Runoff volume: increases from about 21.6 ac-ft to 44.8 ac-ft
This example is not site specific. It is an example for illustrative purposes only. While the numbers would change depending on soil types, slope and native ground cover, something similar happens everywhere urban growth occurs. You see:
Increased runoff volume
Faster time of concentration (peaking)
Higher peak discharges.
You see similar, though not identical, responses worldwide. For example…
Atlanta: Faster, Higher Peaks after Urbanization
A widely cited Georgia State University study of eight metro-Atlanta streams correlated population increases with flooding frequency and severity from 1986 to 2010. During that time, developed land and high-flow days (flood-like conditions) roughly doubled.
Urbanization led to a 26 percent increase in annual stream flow. The increase was not rainfall driven; the study controlled for precipitation.
It reflected: increased impervious cover, reduced infiltration, and faster concentration in channels.
“This means that during a storm event, you’ll now see more runoff, more extreme flows and more flooding than you would have seen for a similar storm event in 1986,” said Jeremy Diem, the study’s lead author and associate professor in the Department of Geosciences at Georgia State.
Another study, “The Influence of Urban Development Patterns on Streamflow Characteristics in the Charlanta Megaregion,” found similar results. “The statistical analysis revealed that increasing the extent of urban development enhanced high and low flow frequency as well as annual peak unit discharge,” said the authors. “Impervious surfaces in source areas distant from streams increased the frequency of high flows.”
“Flashiness” also increased. USGS found that urbanization increased flood magnitude most strongly for moderate storms (e.g., 2–10 year events). The difference narrowed for very large storms because everything becomes saturated and behaves as impervious cover anyway.
The American Meteorological Society found that flood severity was driven as much by runoff efficiency as rainfall magnitude. In other words, in urban areas, rainfalls that aren’t historically extreme can produce exceptional stream rises and flooding.
Dallas and the Trinity River
Studies by the U.S. Geological Survey and U.S. Army Corps of Engineers documented similar problems in Dallas. As the city expanded after World War II, an explosion of impervious cover dramatically increased the speed of runoff. Storm sewers carried water to the river much faster so the city saw steeper and earlier flood peaks.
Peak flows from tributaries stacked on top of each other rather than arriving at staggered intervals. This created higher peaks on the Trinity and more frequent “bank full” conditions. It also put greater stress on levees.
The levees enabled economic development in floodplains, but narrowed channel width, increasing water surface elevation and speed.
As a result, the system became efficient at passing moderate floods—but more vulnerable to extreme ones.
Conclusion
In city after city, hydrologists find that the growth of impervious cover creates more intense, faster, and higher peak flooding. Soil differences affect infiltration and runoff rates. But it is not uncommon to find pre-/post-development differences of approximately 2X.
The two pictures below taken within a few miles of each other in the north Houston Area speak volumes.
Part of the 5,300 acres owned by Scarborough west of Kingwoodin Montgomery County is currently being studied for development.The Preserve at Woodridge was carved out of similar forest. The developer’s plans show it was supposed to be 65% impervious cover.
All those dots in the pavement above are storm drains that act as superhighways for rainfall. They channel it straight to the nearest stream.
According to a recent New York Times article, nine of the 20 counties in the U.S. that have experienced the most development the last decade are in Texas.
Posted by Bob Rehak on 3/30/2026
3135 Days since Hurricane Harvey
https://i0.wp.com/reduceflooding.com/wp-content/uploads/2026/03/DJI_20241025151910_0036_D.jpg?fit=1100%2C619&ssl=16191100adminadmin2026-03-30 17:00:172026-03-30 17:20:19Growth of Impervious Cover: Most Consistent Driver of Flooding Worldwide
3/28/26 – At the San Jacinto River Authority (SJRA) Board Meeting on 3/26/26, HCFCD Executive Director Tina Petersen updated the board on a number of Lake Houston Area projects including the Kingwood Diversion Ditch. She confirmed it is fully funded – through construction.
However, design of the Diversion Ditch Project has not yet started. It should begin in April and finish by the end of 2027.
A year ago, the preliminary engineering study estimated the cost of the project at $40.7 million. Current estimates put the cost at $43 million, according to Petersen.
Looking N at the Kingwoodwood Diversion Ditch from over the Walnut Lane Bridge
Relationship to Bens Branch Flooding
The Diversion Ditch splits off of Bens Branch near St. Martha Catholic Church north of Northpark Drive.
Stormwater flow to Bens Branch will be restricted by pipes. That will force more stormwater into the expanded Diversion Ditch. In the process, that would take enough stormwater out of Bens Branch to improve it from a 2-year level of service to a 100-year level.
Red Diagonal = Bens Branch. White = Kingwood Diversion Ditch. Green = new outfall to river.
Diverting water from Bens Branch is important because Bens Branch runs through Kingwood Town Center where 12 people died from Harvey flooding.
Crenshaw Connection
Ironically, funding obtained by US Congressman Dan Crenshaw back in 2024 to widen the bridge shown above at Walnut Lane saved this project from the chopping block – even though it was ranked the most important project in Kingwood by the Kingwood Area Drainage Analysis.
At the time, Precinct 3 Commissioner Tom Ramsey PE warned that killing projects in Quartiles 2, 3 and 4 could have dire unintended consequences. The Diversion Ditch project fell into Quartile 3.
After the Democrats saw how much partnership funding they would lose by killing projects in the lower quartiles, they relented. In their next meeting, they voted to exempt projects in the lower quartiles that already had partnership funds committed.
That breathed new life into the Kingwood Diversion Ditch project because it included widening of the Walnut Lane Bridge which Crenshaw had already secured funding for.
HCFCD spokesperson Emily Woodell confirmed the Diversion Ditch funding today. “It was categorized as a partnership project during the bond update presented to commissioners court in August [2025] which means it is fully funded through construction.”
For Updates on Other San Jacinto Watershed Projects
It covers a lot of territory including the history of HCFCD, status of the bond program, partnership funding, maintenance programs, gauges, the flood-warning system, and more.
Other capital improvement projects in the Lake Houston Area that she discusses include:
Woodridge Village/Taylor Gully – Construction starting in April.
Jackson Bayou Detention Basin – Construction starting Q3/2026.
Barrett Station Drainage Improvements – Currently in Design Stage.
Lake Houston/East Fork/West Fork Dredging – Completed.
Lake Houston Gates – Engineering should finish by end of this year.
3/27/26 – On 3/26/26, the San Jacinto River Authority (SJRA) board heard the results of a feasibility study about creating “dry-bottom dams” on Birch and Walnut Creeks. The creeks are far upstream in the Spring Creek watershed in Waller County and were being studied for potential flood-mitigation benefits.
The board made no decision in the meeting on whether to pursue recommendations from the study. However, they did agree to discuss several issues with study partners. Other sponsors included the City of Humble, Harris County Flood Control District and five municipal utility districts in Harris and Montgomery Counties.
Chief among the concerns discussed:
Whether funding is available given low Benefit-Cost Ratios (BCR)
Whether land is still available to build the projects
Finding a party that could take “ownership” the projects.
But before the presentation even started, Kaaren Cambio, a former director, laid down a fiery challenge to the board. Let’s look at the study first. It will provide a context for Cambio.
Benefit/Cost Ratio Concerns
Matt Barrett, PE, SJRA’s Water Resources and Flood Management Division Director, gave a presentation that summarized the results of the 661-page feasibility study.
The feasibility study came out of the larger San Jacinto Master Drainage Plan study which identified 16 projects costing more than $3 billion in a 3000 square mile area upstream from Lake Houston.
Birch Creek had an estimated BCR of .55 to .83. That means costs exceeded benefits by almost as much as 2 to 1.
Walnut Creek had an estimated BCR of .77 to 1.04. In the best case scenario, benefits barely exceeded costs.
See estimated BCRs in blue boxes. Date of BCR calculations is not listed, but they came from 2020 Master Drainage Plan, not Feasibility Study, according to Barrett.
Design and Operation
Barrett identified the construction as something akin to detention basins. The dams would feature a long barrier that trapped water with a small opening that let water out at a slow rate.
He next described how such construction would work in four different scenarios.
On a sunny day with no rain, water in the creeks would simply pass through them unobstructed.In a small storm, not likely to cause flooding, water would still pass through the opening unobstructed.But in a moderate storm that could cause minor flooding, water would pool behind the dam faster than it could go through.In a major storm, water would also pass over the spillway at the top of the dam.
Barrett then talked about the exact locations of the dams, their widths, and land-use conflicts. The latter include a solar farm and new developments in the project footprints.
Benefits of Project(s)
Next, Barrett addressed the flood reduction benefits of the two dams in 10-, 50-, 100-, and 500-year storms.
He discussed the benefits of both dams together and individually. Below are the combined benefits of both dams.
They produce benefits measured in feet upstream and inches downstream.
Upstream, near the dams, the benefits exceed 3 to 4 feet. But downstream, near the confluence with the West Fork at the US59 bridge, benefits would only be 3 to 4 inches. That’s because the dams have a large effect on the small watersheds they directly control. But they exert no influence over the rest of the San Jacinto River Basin draining to that point.
Location of Structures Benefitted
The study found that more structures in Montgomery County Precinct 3 would benefit than anywhere else – by a factor of almost 4X compared to other jurisdictions.
Social Benefits Needed to Justify Funding
Near the end, Barrett showed what happens to the BCRs if you include “social benefits,” such as time lost from work during and after a flood. When you factor those in, the benefits exceed costs. However, Barrett also pointed out that as of 2025, the federal government no longer allows social benefits in BCR calculations.
In my opinion, this makes federal support unlikely in the current environment. And the state is unlikely to be able to make up the difference. The cost of the dams comprises a huge percentage of the balance in the Texas Flood Infrastructure Fund.
Significantly, while Barrett addressed the BCR, he did not call out total current costs. He did mention 2020 costs of $200 million in his narration. But total current estimates from the study put the cost at $298 million. And even $298 million assumes property can be acquired at market rates.
Conclusions
Barrett’s concluding slide focused on the challenges ahead based on the findings of his feasibility study. He implies the projects are still worthwhile if you consider social benefits. However, he acknowledges several additional hurdles ahead. And they are high hurdles.
For instance:
Who will take ownership of this project when the dams are in Waller County? (Editorial comment: the largest beneficiary is Montgomery County Precinct 3)
Where will the money come from when social benefits no longer apply?
For a high-resolution PDF of Barrett’s complete slide deck, click here.
Cambio Comments
You may also want to watch Kaaren Cambio during the public comment period before Barrett took the floor. Cambio starts at 11:10 into the video. She is a former SJRA director appointed by Governor Abbott.
Cambio began by reminding the board that after Harvey, the governor charged the SJRA with developing short, medium, and long range plans to ensure another Harvey would never produce so much damage again.
Time it has taken the SJRA flood management division to produce studies
Management of the studies
Absence of any benefits produced to date in any of the SJRA studies since Harvey
Pursuit of the Spring Creek study even after it became clear the land was not available
Cost per structure pulled out of the floodplain in the Spring Creek study – more than $800,000 each
SJRA’s inability to examine less expensive options, such as buyouts or elevation of those structures
Cambio closed her remarks by urging the board to “Please go back and look at the goals that this division had and make sure you’re meeting those goals. And redirect your efforts, so that we are seeing manageable solutions.”
An outspoken leader, Cambio raised some great points.
You could sense the urgency in her voice as she pled with the board to implement solutions, not just studies.
Plea for Involvement
More people from downstream areas need to testify at SJRA board meetings. We should never let the SJRA board – now heavily dominated by Lake Conroe residents – forget the destruction of lives and property caused by the massive release from Lake Conroe during Hurricane Harvey.
Posted by Bob Rehak on 3/27/26
3132 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/2026/03/5.3_Spring-Creek-Rev2_Page_10.jpg?fit=2000%2C1125&ssl=111252000adminadmin2026-03-27 19:00:522026-03-29 09:07:18SJRA Board Takes No Action on Birch, Walnut Creek Dams Feasibility Study
3/26/26 – A $29,387,654 bid from Bryce Construction & Design, LLC has been approved by the county purchasing agent to construct the Woodridge and Taylor Gully flood mitigation projects in Kingwood. See Item 45 on the agenda. Here is their bid transmitted to Commissioners Court. It was the low bid.
To streamline approval of US Housing and Urban Development Department Community Development Block Grants (CDBG), several months ago Commissioners Court approved a proposal to let the County Purchasing Agent approve CDBG projects. They all have tight deadlines.
The contractor will mobilize within two weeks according to Emily Woodell, a Harris County Flood Control District (HCFCD) spokesperson. We should see dirt flying this Spring.
History of Project
Up to 600 families in Kingwood flooded twice in 2019 when Perry Homes’ contractors cleared approximately 268 acres for Woodridge Village just north of the Harris County line. Then they sloped the land toward Taylor Gully. Many of the families had just recovered from the first flood on May 7th when they flooded again in September before the stormwater detention basins had been built.
Subsequently, in 2020, Harris County and the City of Houston purchased the land so that it couldn’t be developed and flood Kingwood again. Before the purchase, Perry Homes built five stormwater detention basins on the Woodridge property. However, Montgomery County regulations at the time required much less detention capacity that Harris County – about 40% less.
That was because Harris County had already adopted Atlas 14 and because Montgomery County averaged rainfall estimates across the entire county, even though annual rainfall increases as you move south toward the county line.
Elements of Solution
So, Harris County Flood Control set out to study what it would take to properly reduce flood risk using Atlas 14 data near the county line. The studies recommended:
More upstream detention
Increasing conveyance of Taylor Gully
Replacing a culvert bridge at Rustic Elms with a clear-span bridge
Project overview from construction plans
The project limits of the proposed Taylor Gully Channel Improvements stretch from the Montgomery County boundary on the west to approximately 700 feet upstream of the confluence with White Oak Creek – a length of approximately 12,630 linear feet.
This portion of the project includes replacing the bridge at Rustling Elms.
At Rustling Elms, HCFCD will replace a culvert bridge with a clear-span bridge to remove a bottleneck.
HCFCD also plans to finish one more large stormwater detention basin upstream from Taylor Gully in Montgomery County.
HCFCD started work on the pond in January 2022 under an Excavation and Removal contract with Sprint Sand & Clay. The contract to remove up to 500,000 cubic yards of soil would have more than doubled the previous detention capacity on the site and more than made up for the 40% Atlas 14 shortfall.
However, HCFCD paused the Sprint contract when it applied for a U.S. Department of Housing and Urban Development (HUD) grant. That’s because HUD rules stipulate that a project cannot change during the grant application period.
HCFCD later terminated the contract in November 2023 when it became clear the project would qualify for the grant. At that point, Sprint had already removed 160,000 cubic yards, an amount equivalent to approximately 100 acre feet. So if the figures in the construction drawing are accurate, the capacity of the basin will quadruple compared to what you see below.
Woodridge Village on May 31, 2025. The final basin will extend down past the trees near the end of the entry road.
Expected Impact
Contractually, work must finish within 552 days from the notice to proceed – approximately 18 months. That would make a great 2027 Christmas present for a lot of Kingwood families.
Under HUD’s Community Development Block Grant for Mitigation, all work must finish and billing must be completed by March 31, 2028. That should be doable.
The project will give Taylor Gully a 100-year level of service.
HCFCD
That means it should only come out of its banks in a hundred-year storm.
The improvements would reduce water-surface elevation (WSE) along Taylor Gully up to 6.9 feet in places and 4 to 5 feet on average for a 100-year storm event.
Also, this project will remove approximately 276 structures from a 100-year flood plain. Without the project, area residents would continue to flood in lesser storms.
Taylor Gully bridge at Rustling Elms during May 7, 2019, storm.
That means we should NOT see many more scenes like the one above until Noah’s comeback tour.
Thanks to Precinct 3 Commissioner Tom Ramsey PE, for continuing to push this project when things seemed bleak.
Posted by Bob Rehak on 3/26/26
3131 Days since Hurricane Harvey
https://i0.wp.com/reduceflooding.com/wp-content/uploads/2026/03/Overview.jpg?fit=2550%2C1650&ssl=116502550adminadmin2026-03-26 16:35:252026-03-27 08:08:45$29 Million Construction Contract for Woodridge, Taylor Gully Project Approved
3/25/26 – On 3/24/26, I photographed partially cleared property owned by HS Tejas LTD on West Lake Houston Parkway (WLHP) between the Kingwood YMCA and Kings Harbor.
Approximate area of partially cleared landcircled in red.
According to Dustin Hodges, Chief of Staff for District E City Council Member Fred Flickinger, the City has received no permit applications for developing the property yet.
To be clear, an owner does not need a permit to survey his property. But the survey may be required as preparation for:
Subdividing land/plat approval
Developing in floodplains
Title companies or lenders
So, this is an early sign that something could soon happen with the property. However, it’s not yet clear what HS Tejas plans.
Who Is HS Tejas?
HS Tejas is a company owned in part by Kingwood developer Ron Holley. Holley sold floodplain/floodway property on South Woodland Hills to a company affiliated with Romerica back in 2012. Since then, Romerica has tried repeatedly to develop the property with little luck using various concepts including:
Currently, Holley is also trying to develop Royal Shores Estates in the floodway and floodplain of the San Jacinto East Fork south of Kings Point.
Shifting Floodplain Maps
New flood maps show the floodway has expanded and now encompasses virtually all of Holley’s property. From a flooding perspective, a floodway is more hazardous than a floodplain because of the speed of water. To see how large the floodway has grown, compare the two images below.
Once the new draft maps become effective, Holley will have a much harder time developing the property because of restrictions on building in floodways. So, the impending map change may have something to do with the surveying.
Pictures Showing Recent Activity
Below are several pictures taken on 3/24/26 that show the partial clearing.
Note Deerwood golf course and Bens Branch in upper left. Looking slightly east and south from over WLHP.Looking S toward Self Storage and Memory Care facility in upper right.Memory Care facility in lower right.Looking E toward Deerwood. Looking W toward WLHP from over Bens Branch in bottom of frame.
Putting Flood Risk Into Perspective
The areas shown above are about a half mile from the San Jacinto West Fork along Bens Branch.
As a result of Harvey flooding, 12 residents of Kingwood Village Estates died. KVE is an assisted living facility more than a half mile north (farther from the West Fork).
Moreover, ALL of the adjacent businesses, townhomes, apartments and homes flooded in:
A floodway is not only defined by the speed of floodwaters. In Houston, the floodway is regulated as the portion of the floodplain required to convey the 100-year flood with no increase in water surface elevation. However, FEMA-mapped floodways may have been delineated assuming up to a 1-foot rise.
Developers cannot bring fill into a floodway. So, doing anything on this property will likely mean stilts, structural analyses, and more. Chapter 19 of the City’s floodplain regulations lays out the requirements.
Current activity is not visible from WLHP. So, please contact me if you hear or see anything.
Posted by Bob Rehak on 3/25/26
3130 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/2026/03/HS-Tejas-.jpg?fit=1100%2C707&ssl=17071100adminadmin2026-03-25 15:56:022026-03-26 06:22:30Surveyors Staking Out Property on WLHP in New Floodway
3/23/26 – The Texas Water Development Board recently issued a press release about the State’s Geographic Information Office (TxGIO) and Department of Information Resources (DIR) contracts. The concepts discussed in the article affect many growing areas in the San Jacinto watershed, which is plagued by political fragmentation.
Dozens of counties, cities, and utility districts share responsibility for development, drainage, and flood-control. But they update their flood maps infrequently and irregularly. So, engineers and hydrologists often have trouble planning. They have a fragmented, incomplete picture of what’s going on around them.
But these state systems help to change that. Two key takeaways:
They pre-qualify a pool of vendors. That shortens the qualification and bidding processes for services they may need, such as LIDAR.
Upon completion, studies become part of the public domain – available to everyone who can benefit from them.
The press release, reprinted below, talks about many synergies already discovered with these ingenious systems. They increase collaboration, speed, and cost sharing to improve planning and reduce flood risk.
From TWDB’s Texas Water Newsroom
Left to right: Lidar image of downtown Austin, Texas, aerial view of a neighborhood in Bexar County, and an elevation image of Canyon Lake
Imagine two neighboring communities facing the same challenge.
A small watershed authority in East Texas needs high-resolution elevation data. Recent storms have rewritten floodplain maps, and the old topography simply doesn’t match what residents now experience during heavy rains. Engineers need accurate models. Emergency managers need better evacuation planning. The watershed authority has the expertise to specify the data but lacks the budget to acquire it.
Forty miles away, a county engineering department faces the same problem. New development pressures require updated drainage studies. The county’s flood maps show their age. Engineers spend hours adjusting for known errors rather than designing solutions. They have budget allocated but procurement rules demand a competitive bidding process that will take a year or more to complete.
Both entities will acquire elevation data eventually, but they’ll pay different prices and receive deliverables that may not align at their shared boundaries. This fragmentation describes how Texas communities acquired geospatial data for decades—a siloed process that was slow and inefficient, with few opportunities for collaboration. The old way treated every project as a fresh start rather than a contribution to shared infrastructure.
StratMap Contracts
The Texas Geographic Information Office (TxGIO) and the Department of Information Resources (DIR) Geographic Information Systems (GIS) & Digital Land Surveying Products and Services contracts—known collectively as the StratMap contracts—were developed to be a far more streamlined procurement model.
The StratMap program was originally established in 1997 by Senate Bill 1 to develop consistent statewide digital data layers. Since then, its primary goal has been to acquire and improve digital geographic data for statewide mapping applications, and the program also maintains comprehensive data standard specifications to ensure consistent, high-quality data products across Texas. The TxGIO StratMap program administers and promotes the StratMap contracts, and TxGIO uses those contracts to get the data it needs to develop and maintain consistent statewide digital data layers.
For hydrologists modeling flood risks, engineers designing infrastructure, GIS professionals building applications, and citizens depending on sound governance, the StratMap contracts deliver what communities need most: quality geospatial services, software, and hardware at competitive prices.
How StratMap contracts work
The genius of the StratMap Contracts lies in their simplicity—generally, the state negotiates GIS contracts every five years so that individual communities and governmental entities don’t have to do it themselves. Before signing any potential StratMap vendor contracts, a team of GIS technical experts from TxGIO and DIR contract specialists evaluate every company seeking a StratMap contract based upon their project experience, technology innovation, professional staff, and available resources.
Companies that pass this review earn a place on the DIR Master Contracts list as qualified providers. These pre-approved providers serve Texas state, regional, and local government offices, including river and water authorities, and public education entities. Each approved vendor maintains a Pricing Index on their DIR contract page that lists available products, services, and software alongside pre-negotiated percentage discounts.
The three-step procurement process
Once a community identifies a need, the typical path forward contains three steps:
Review the Pricing Index on the vendor’s DIR contract page to confirm available offerings and discounts.
Obtain a quote directly from the vendor’s listed contact. The quote must reflect the contract’s pre-negotiated discount percentage. If the project is for a state agency and is over $50,000 or requires customization, the community provides a statement of work with the quote and must go through the DIR statement of work process for review and approval—which can take a couple of months.
Issue a purchase order listing the company’s DIR contract number.
That’s it. No months spent drafting and reviewing contracts. The master contracts already satisfy procurement requirements and enable entities to quickly obtain competitive bids from multiple pre-qualified vendors in one place. For state agencies, additional thresholds govern statement of work requirements and processes. But for most local governments, these three steps represent all the administrative requirements.
Complete geospatial coverage
StratMap Contracts cover the full spectrum of GIS:
Whether a community needs new data, help managing a project, or software to analyze existing information, the contracts provide access to quality vendors who can provide what they need. This streamlined procurement process alone is a huge benefit, but incredible strategic value emerges when communities start collaborating.
TxGIO is a collaboration facilitator
No single city or county sees the full map of geospatial activity across Texas, but TxGIO does. Through quarterly community meetings, TxGIO maintains visibility into which projects are being planned, where overlap may exist, and potential partnerships. When a community notifies TxGIO about a potential project, they don’t simply file the information. TxGIO scans for matches and considers who else might need the data to uncover opportunities that isolated communities may not find on their own. This approach allows communities to discover shared challenges and data requirements and combine their budgets to expand the scope of projects and meet their needs more effectively.
Cost sharing as standard practice
StratMap actively cultivates collaboration. Communities that use StratMap learn to start every project conversation with a simple question: “Who else might need this?”
Sometimes the answer reveals unexpected partners. A city planning some new parks might connect with a county assessing conservation easements. A groundwater district modeling aquifers might align with a utility mapping critical infrastructure. A school district planning new facilities might coordinate with emergency services designing evacuation routes. Each partnership multiplies the value of every dollar spent and builds relationships that endure beyond individual projects. Collaboration normalizes the idea that geospatial data serves regional needs.
The specification dividend
Partnerships under StratMap deliver another hidden benefit: better specifications.
When multiple entities collaborate on a statement of work, each brings distinct requirements to the table. The watershed authority prioritizes vertical accuracy for flood modeling. The county emphasizes land cover classification for drainage analysis. A participating city cares about planimetric features for infrastructure management.
Vendors receive requirements that reflect diverse, real-world needs rather than a single department’s perspective. The resulting data serves more purposes, satisfies more stakeholders, and delivers greater return on investment. TxGIO staff facilitate these conversations, helping partners balance competing priorities and arrive at specifications that work for everyone. Their experience across dozens of projects informs recommendations that communities couldn’t develop independently. This collaboration pays in immediate cost savings, in better data, and in regional relationships that strengthen Texas communities for years to come.
The compounding value of data in the public domain
For TxGIO StratMap projects, after vendors deliver final products and independent quality assurance confirms their accuracy, the data enters the public domain. TxGIO staff verify deliverables, integrate them into statewide collections, and make them available to everyone.
Traditional procurement treats data as a consumable. A community pays for it, uses it, and eventually replaces it, so its value degrades over time. The StratMap program inverts this model. TxGIO projects add to a growing public repository. Each new dataset increases the repository’s utility, and new users discover applications for that data that the original sponsors never imagined.
And because TxGIO maintains all StratMap deliverables, staff understand what works and what doesn’t. They have worked with more than 80 different agencies in Texas, from river authorities to municipalities, counties, and councils of government. So, TxGIO sees which specifications produce reliable results. They track which vendors consistently deliver quality and can identify emerging technologies that improve accuracy or reduce costs.
This experience informs future statements of work. When the next community plans a project, TxGIO staff recommend specifications refined through dozens of previous efforts. They warn against approaches that failed elsewhere and can suggest others that succeeded. Each project learns from every project that came before, which ensures that every Texas community, regardless of size or budget, can build on the best available information.
StratMap prepares Texas communities for the future
Texas faces challenges in the coming decades, from population growth to flood risks that will require sophisticated modeling and environmental needs that will demand informed management. Communities need accurate geospatial information to navigate these challenges effectively.
The StratMap contracts can help provide the foundational data upon which solutions to those challenges depend.
Posted by Bob Rehak on 3/23/26
3128 Days since Hurricane Harvey
https://i0.wp.com/reduceflooding.com/wp-content/uploads/2026/03/gis_imagecollage.jpg?fit=999%2C670&ssl=1670999adminadmin2026-03-23 13:40:492026-03-24 17:02:14TxGIO, DIR StratMap Contracts: Strategic Asset for Texas Communities
