5/11/25 – A study published in the November 2024 edition of the Journal of Applied Meteorology and Climatology by researchers from Louisiana State University and Texas A&M examined stalling and rapidly intensifying tropical cyclones.
After analyzing 1,274 storms going back to 1900, they found one of the primary areas for such storms to strike is along the central Gulf Coast. They also found that, the estimated annual frequency of stalls significantly increased from 1966 – 2020 – by 1.5% year.
Lead author of the study, called Stalling North Atlantic Tropical Cyclones, is Jill C. Trepanier of LSU. Others include: John Nielsen-Gammon of Texas A&M; and Vincent Brown, Derek Thompson and Barry Keim, all of LSU.
Stalling Storms More Damaging
The authors found that, “Storms that stall tend to have a longer average duration than those that do not stall in all categories.” By that they mean levels of intensity (Cat 1 through 5).
They say stalling storms increase rainfall rates, storm surge heights and exposure to high winds including tornado activity. “Storms that slow down or stall can increase total damage by prolonging the exposure time to intense conditions,” they say.
Stalling Storms Clustered in Central Gulf, Late in Season
They also found that stalls tend to cluster in certain places. Those include, but are not limited to the central Gulf Coast.
And they happen more often late in the season during September and October.
“Stalls tend to occur in similar places over time and happen more frequently later in the hurricane season (October) when compared to the middle (August). Emergency managers can use this information to identify the likely location and timing for stalls throughout the North Atlantic tropical cyclone season,” say the authors.
Definition of Stalling
The researchers define a stalling cyclone as one that moves less than 200 km in 72 hours. “Potentially most devastating are those stalls within 200 km of the coast, but even more so, those that stall over or partially over land.”
“This is important for emergency managers to realize,” they say, “as those stalling near the coast will have a higher potential to inflict more damage to a population.” And storms that also rapidly intensify also give:
Emergency managers less time to evacuate people.
Residents less time to prepare.
The researchers also found that Category 3+ storms such as Hurricane Harvey persist longer than weaker tropical cyclones, providing more stall opportunities. Harvey, they say, dumped more rain than any stalling storm in recorded history. They examined the historical record going back to 1899.
Harvey track in 2017. Notice how dots get closer together as storm stalled over Texas.Each dot represents 6 hours.
Rapidly Intensifying Storms Also Becoming More Frequent
These studies suggest that rapidly intensifying storms have become more frequent and are occurring closer to the coast in recent years. Rapidly intensifying storms make evacuations more difficult. More people must move in less time and with less warning.
Coastal Areas More Densely Populated
According to NOAA, coastal areas are notably more densely populated than inland regions. For instance, coastal shoreline counties have a population density more than five times greater than the U.S. average.
Approximately 39% of the U.S. population lives in coastal shoreline counties, which comprise less than 10% of the nation’s land area (excluding Alaska).
Additional Research
Before concluding, the authors called for more research on the rainfall recurrence intervals associated with stalling cyclones. They also say future analysis should include a deeper dive on rapid intensification.
Individuals Should Research Preparation
In the meantime, the best thing people living in coastal areas can do is prepare. Forecasters predict an above-average hurricane season, which starts in about two weeks. The National Hurricane Center has produced an excellent series of videos to help you protect your family and property.
5/9/2025 – Houston has 3,900 miles of storm sewers and 2,500 miles of roadside ditches. When it comes to reducing flooding, roadside ditches and storm sewers each have their pros and cons. But before looking at the strengths and limitations of each, let’s consider some basic capacity and performance differences.
Capacity and Performance
A typical grass ditch 3.5 feet deep and 1,000 feet long can hold 325,000 gallons of runoff before overtopping – more than ten times the volume than that of a 24-inch storm sewer of equal length. In essence, the ditch itself acts as a long, linear detention basin, reducing flood peaks downstream.
While open ditches by themselves may have more storage capacity than storm sewers, streets with storm sewers are often depressed. Thus, the streets themselves can provide additional temporary storage until the storm sewers drain. Even if the street floods for a period of time, the street may provide enough extra capacity to keep homes from flooding.
Plus, storm sewers move water faster because of their smoothness. They offer less friction. And that offsets the capacity of ditches somewhat. But speed can also have a downside. Water can rush all at once to an already swollen bayou.
Open ditches also provide infiltration and filtration opportunities, improving water quality before reaching waterways. For this reason, the U.S. Environmental Protection Agency has noted that well-designed vegetated swales can improve stormwater quality.
The natural processes in a ditch – absorption by soil, uptake by plants, evaporation – can mitigate flooding and provide environmental co-benefits that storm sewers lack. But…
Maintenance Challenges with Ditches
To maintain their effectiveness, ditches require frequent maintenance including regrading, de-silting, unblocking, and flushing driveway culverts. Few homeowners can handle such tasks. Thus, lack of routine maintenance has been a major limitation of open ditch systems in Houston.
Many older suburban neighborhoods with ditches have seen capacity decline over time due to infrequent maintenance, leading residents to complain of street flooding from what should be a fixable drainage issue.
Quickly funneling runoff to bayous can contribute to higher downstream flood peaks. If not mitigated, they trade street flood risk for potentially greater flooding in waterways.
Blocked roadside ditches in several north Houston neighborhoods.
Strengths and Limitations of Each
Below is a summary of the strengths and limitations of storm sewers and ditches.
Storm Sewers – Strengths:
Space Efficiency: Underground pipes free up surface space for roads, sidewalks, and landscaping, crucial in dense areas.
Urban Compatibility: Curb and gutter streets are better for traffic and pedestrian safety in cities.
Rapid Drainage: Can quickly carry water away during and after small to moderate storms, clearing streets faster once rain ends.
Low Profile Maintenance: No open water at surface so safer for children. No marshy ditches in front yards. No need for mowing or weed control.
Less Obstruction: Less prone to large debris blockage (covered inlets keep out big trash, though they can clog with litter/leaves).
Storm Sewers – Limitations:
Limited Capacity/Volume: Pipes have restricted diameter; they carry less water volume than an equivalent open channel. In heavy rain, they fill up quickly, then excess water floods the street.
High Cost: Expensive to install and upgrade. Retrofitting a larger pipe is a major construction project. Economics may limit their size (designers balance capacity vs. cost, often resulting in designs that handle only smaller storms).
Out-of-Sight Failures: Problems (sediment buildup, collapse, clogs) are hidden underground. Maintenance requires specialized crews and equipment (vacuum trucks, confined-space entry). Issues may go unnoticed until flooding occurs.
Fast Runoff Discharge: Quickly funneling runoff to bayous can contribute to higher downstream floods.
Dependency on Outfalls: If the receiving channel is high (e.g., bayou at flood stage), storm sewers can’t drain and may even backflow. They have little resiliency in such conditions.
Open Drainage Ditches – Strengths:
Large Capacity & Storage: Can convey and hold significantly more water than buried pipes for the same length. Acts as built-in detention, reducing peak flow and helping attenuate floods.
Cost-Effective Installation: Cheaper to construct initially – essentially just grading earth – making them feasible in new lower-density developments or where budgets constrain.
Natural Drainage Benefits: Encourages infiltration and evaporation, uptake by grasses. Vegetation filters pollutants, improving water quality.
Easy Problem Identification: Problems like blockages or erosion are visible and simple to fix without heavy, expensive underground work and ripping up streets.
Flood Mitigation Role: By slowing runoff, they reduce the likelihood of sudden flash flooding. Streets with roadside swales often avoid deep inundation in moderate storms.
Open Drainage Ditches – Limitations:
Land Use and Aesthetics: Require wider rights-of-way and reduce useable yard space. Some consider them unsightly or “rural-looking.” They complicate driveway design (need culverts) and can be obstacles for pedestrians (few sidewalks in ditch neighborhoods).
High Maintenance Demand: Must be kept clear of silt, trash, and overgrowth to function. Neglected ditches lose capacity and can cause flooding worse than if a proper sewer were in place. Maintenance is continuous (mowing, dredging every few years), which can be a burden on residents or cash-strapped city programs.
Slower Drainage & Standing Water: Water may stand for days in flat areas. Poorly graded ditches can have sections that never fully drain. Standing ditch water is a common complaint.
Limited Applicability in Dense Areas: Not suitable for high-density urban neighborhoods. Physically impractical on narrow streets or where buildings are close to the road.
Potential Safety Hazards: Open water and drop-offs pose risks – vehicles can end up in ditches during accidents or flooding. Also, eroded ditches can undermine road edges if not fixed.
Which is Better?
There is no one-size-fits-all; Houston’s vast size means both systems will continue to be used.
In low-density residential areas of Houston, enhanced and well-maintained drainage ditches are often better suited to reduce street and property flooding (thanks to their storage capacity and slower release of stormwater).
However, in high-density areas, storm sewers with curbs are more appropriate despite their limits, as they fit the space and usage needs, such as on-street parking.
We should use the volume capacity of open ditches AND the efficient conveyance of storm sewers as complementary pieces of Houston’s complex drainage puzzle.
For More Information
See this illuminating, footnoted and annotated 7,000 word deep dive into ditches and storm sewers by ChatGPT 40. I borrowed heavily from it for this post.
Posted by Bob Rehak on 5/9/25
2810 Days since Hurricane Harvey
https://i0.wp.com/reduceflooding.com/wp-content/uploads/2021/06/MultiBlockages.jpg?fit=1440%2C960&ssl=19601440adminadmin2025-05-09 19:05:382025-05-10 16:58:53Are Ditches or Storm Sewers More Effective at Reducing Flooding?
5/8/25 – Several crucial operations that are part of the Northpark expansion project should soon begin in the quest to create the first all-weather evacuation route from Kingwood. Contractors are about to begin:
Boring under the the UnionPacific Railroad (UPRR) tracks to connect the drainage on either side
Installing two junction boxes west of Loop 494 on the south side of Northpark to convey stormwater to the north side.
Relocating an electrical distribution box next to Exxon at US59.
Modifying the Exxon station itself.
Separately, contractors have already started clearing surface lanes on the south side of Northpark between Loop 494 and Marco’s Pizza. The lanes will carry traffic next to the bridge going over 494 and the UPRR tracks.
This post will also discuss utility-related delays to date and the timetable for completing project components. Those include Phase II, a new detention basin, and widening of the northernmost portion of the Kingwood Diversion ditch.
Prep for Bore Under Tracks Started Today
Preparation for the bore under the tracks started today. An auger started drilling holes that will define the edges of the bore pit.
Auger drilling first hole.
The pit will contain a steel framework to protect contractors from cave-ins as they work.
See line of holes dug by auger and covered by boards.
Junction Boxes for Drainage West of Loop 494
The Northpark expansion plan calls for two junction boxes to link culverts on both sides of Northpark – one by Sonic, the other by the dry cleaners on the corner of Loop 494.
Looking west toward 59. The junction boxes will collect stormwater from the south (left) side of Northpark and convey it under the street to the north side.
Contractors will build the junction boxes first. Then they will link 6′ x 6′ reinforced concrete culverts by digging trenches across Northpark in stages. Each stage will disrupt traffic on one side of the road while traffic is routed to the other.
Changes near Exxon Station
There are two major operations closer to 59 in the Northpark expansion plan. First, Entergy must move an electrical junction box out of the right of way near the Exxon station.
Second, Exxon will lose part of its canopy and one pump island. Both encroach on the right of way.
Electrical box is circled. Dotted line shows approximateright-of-way.Setback appears wider in the foreground because of wide-angle-lens distortion.
Surface Lanes East of 494 on South Side of Northpark
In the last few days, contractors have begun clearing underbrush for what will become two surface lanes on the south side of the bridge over 494 and the railroad tracks. See below.
The tall pine trees are too large to move and will likely go to a sawmill.
Perhaps for the first time, one can truly appreciate how wide Northpark expansion will be compared to the four lanes we had. See below.
Looking E. A six-lane bridge will taper down to ground level through this area with two surface lanes on each side.Reverse angle.Looking W toward 59.
This road will move some traffic!
194 Days of Delays to Date
Due to multiple utility-related delays, the Phase I Northpark expansion project has slipped 194 days to date. The Lake Houston Redevelopment Authority/TIRZ 10 board reviewed that this morning.
The screen capture below shows the financial impact of LHRA/TIRZ 10 projects on the City of Houston’s Capital Improvement Plan.
It also shows expected completion dates. Phase I should wrap up next year.
Phase II should finish in 2028. It includes the portion of Northpark expansion that extends past Woodland Hills.
A detention basin, previously part of Phase II has become its own project to accelerate it. That will reduce flood risk sooner for residents along Bens Branch and the Diversion Ditch.
The detention basin project includes widening of the northernmost portion of the diversion ditch. It should start next year and finish in 2027.
https://i0.wp.com/reduceflooding.com/wp-content/uploads/2025/05/20250508-DJI_20250508123557_0485_D.jpg?fit=1100%2C619&ssl=16191100adminadmin2025-05-08 19:08:102025-05-09 09:17:58Crucial Operations Begin In Northpark Expansion
Study Finds Stalling Cyclones Increasing
5/11/25 – A study published in the November 2024 edition of the Journal of Applied Meteorology and Climatology by researchers from Louisiana State University and Texas A&M examined stalling and rapidly intensifying tropical cyclones.
After analyzing 1,274 storms going back to 1900, they found one of the primary areas for such storms to strike is along the central Gulf Coast. They also found that, the estimated annual frequency of stalls significantly increased from 1966 – 2020 – by 1.5% year.
Lead author of the study, called Stalling North Atlantic Tropical Cyclones, is Jill C. Trepanier of LSU. Others include: John Nielsen-Gammon of Texas A&M; and Vincent Brown, Derek Thompson and Barry Keim, all of LSU.
Stalling Storms More Damaging
The authors found that, “Storms that stall tend to have a longer average duration than those that do not stall in all categories.” By that they mean levels of intensity (Cat 1 through 5).
They say stalling storms increase rainfall rates, storm surge heights and exposure to high winds including tornado activity. “Storms that slow down or stall can increase total damage by prolonging the exposure time to intense conditions,” they say.
Stalling Storms Clustered in Central Gulf, Late in Season
They also found that stalls tend to cluster in certain places. Those include, but are not limited to the central Gulf Coast.
And they happen more often late in the season during September and October.
“Stalls tend to occur in similar places over time and happen more frequently later in the hurricane season (October) when compared to the middle (August). Emergency managers can use this information to identify the likely location and timing for stalls throughout the North Atlantic tropical cyclone season,” say the authors.
Definition of Stalling
The researchers define a stalling cyclone as one that moves less than 200 km in 72 hours. “Potentially most devastating are those stalls within 200 km of the coast, but even more so, those that stall over or partially over land.”
“This is important for emergency managers to realize,” they say, “as those stalling near the coast will have a higher potential to inflict more damage to a population.” And storms that also rapidly intensify also give:
The researchers also found that Category 3+ storms such as Hurricane Harvey persist longer than weaker tropical cyclones, providing more stall opportunities. Harvey, they say, dumped more rain than any stalling storm in recorded history. They examined the historical record going back to 1899.
Rapidly Intensifying Storms Also Becoming More Frequent
The authors of the “stalling” study also reviewed other studies such as Kaplan et al. (2015) and Benedetto and Trepanier (2020).
These studies suggest that rapidly intensifying storms have become more frequent and are occurring closer to the coast in recent years. Rapidly intensifying storms make evacuations more difficult. More people must move in less time and with less warning.
Coastal Areas More Densely Populated
According to NOAA, coastal areas are notably more densely populated than inland regions. For instance, coastal shoreline counties have a population density more than five times greater than the U.S. average.
Approximately 39% of the U.S. population lives in coastal shoreline counties, which comprise less than 10% of the nation’s land area (excluding Alaska).
Additional Research
Before concluding, the authors called for more research on the rainfall recurrence intervals associated with stalling cyclones. They also say future analysis should include a deeper dive on rapid intensification.
Individuals Should Research Preparation
In the meantime, the best thing people living in coastal areas can do is prepare. Forecasters predict an above-average hurricane season, which starts in about two weeks. The National Hurricane Center has produced an excellent series of videos to help you protect your family and property.
Posted by Bob Rehak on 5/11/25
2812 Days since Hurricane Harvey
Are Ditches or Storm Sewers More Effective at Reducing Flooding?
5/9/2025 – Houston has 3,900 miles of storm sewers and 2,500 miles of roadside ditches. When it comes to reducing flooding, roadside ditches and storm sewers each have their pros and cons. But before looking at the strengths and limitations of each, let’s consider some basic capacity and performance differences.
Capacity and Performance
A typical grass ditch 3.5 feet deep and 1,000 feet long can hold 325,000 gallons of runoff before overtopping – more than ten times the volume than that of a 24-inch storm sewer of equal length. In essence, the ditch itself acts as a long, linear detention basin, reducing flood peaks downstream.
While open ditches by themselves may have more storage capacity than storm sewers, streets with storm sewers are often depressed. Thus, the streets themselves can provide additional temporary storage until the storm sewers drain. Even if the street floods for a period of time, the street may provide enough extra capacity to keep homes from flooding.
Plus, storm sewers move water faster because of their smoothness. They offer less friction. And that offsets the capacity of ditches somewhat. But speed can also have a downside. Water can rush all at once to an already swollen bayou.
Open ditches also provide infiltration and filtration opportunities, improving water quality before reaching waterways. For this reason, the U.S. Environmental Protection Agency has noted that well-designed vegetated swales can improve stormwater quality.
The natural processes in a ditch – absorption by soil, uptake by plants, evaporation – can mitigate flooding and provide environmental co-benefits that storm sewers lack. But…
Maintenance Challenges with Ditches
To maintain their effectiveness, ditches require frequent maintenance including regrading, de-silting, unblocking, and flushing driveway culverts. Few homeowners can handle such tasks. Thus, lack of routine maintenance has been a major limitation of open ditch systems in Houston.
Many older suburban neighborhoods with ditches have seen capacity decline over time due to infrequent maintenance, leading residents to complain of street flooding from what should be a fixable drainage issue.
Quickly funneling runoff to bayous can contribute to higher downstream flood peaks. If not mitigated, they trade street flood risk for potentially greater flooding in waterways.
Strengths and Limitations of Each
Below is a summary of the strengths and limitations of storm sewers and ditches.
Storm Sewers – Strengths:
Storm Sewers – Limitations:
Open Drainage Ditches – Strengths:
Open Drainage Ditches – Limitations:
Which is Better?
There is no one-size-fits-all; Houston’s vast size means both systems will continue to be used.
In low-density residential areas of Houston, enhanced and well-maintained drainage ditches are often better suited to reduce street and property flooding (thanks to their storage capacity and slower release of stormwater).
However, in high-density areas, storm sewers with curbs are more appropriate despite their limits, as they fit the space and usage needs, such as on-street parking.
We should use the volume capacity of open ditches AND the efficient conveyance of storm sewers as complementary pieces of Houston’s complex drainage puzzle.
For More Information
See this illuminating, footnoted and annotated 7,000 word deep dive into ditches and storm sewers by ChatGPT 40. I borrowed heavily from it for this post.
Posted by Bob Rehak on 5/9/25
2810 Days since Hurricane Harvey
Crucial Operations Begin In Northpark Expansion
5/8/25 – Several crucial operations that are part of the Northpark expansion project should soon begin in the quest to create the first all-weather evacuation route from Kingwood. Contractors are about to begin:
Separately, contractors have already started clearing surface lanes on the south side of Northpark between Loop 494 and Marco’s Pizza. The lanes will carry traffic next to the bridge going over 494 and the UPRR tracks.
This post will also discuss utility-related delays to date and the timetable for completing project components. Those include Phase II, a new detention basin, and widening of the northernmost portion of the Kingwood Diversion ditch.
Prep for Bore Under Tracks Started Today
Preparation for the bore under the tracks started today. An auger started drilling holes that will define the edges of the bore pit.
The pit will contain a steel framework to protect contractors from cave-ins as they work.
Junction Boxes for Drainage West of Loop 494
The Northpark expansion plan calls for two junction boxes to link culverts on both sides of Northpark – one by Sonic, the other by the dry cleaners on the corner of Loop 494.
Contractors will build the junction boxes first. Then they will link 6′ x 6′ reinforced concrete culverts by digging trenches across Northpark in stages. Each stage will disrupt traffic on one side of the road while traffic is routed to the other.
Changes near Exxon Station
There are two major operations closer to 59 in the Northpark expansion plan. First, Entergy must move an electrical junction box out of the right of way near the Exxon station.
Second, Exxon will lose part of its canopy and one pump island. Both encroach on the right of way.
Surface Lanes East of 494 on South Side of Northpark
In the last few days, contractors have begun clearing underbrush for what will become two surface lanes on the south side of the bridge over 494 and the railroad tracks. See below.
Perhaps for the first time, one can truly appreciate how wide Northpark expansion will be compared to the four lanes we had. See below.
This road will move some traffic!
194 Days of Delays to Date
Due to multiple utility-related delays, the Phase I Northpark expansion project has slipped 194 days to date. The Lake Houston Redevelopment Authority/TIRZ 10 board reviewed that this morning.
I extracted the 18 relevant pages from the 473-page board packet for you. They detail hundreds of unexpected utility delays.
The screen capture below shows the financial impact of LHRA/TIRZ 10 projects on the City of Houston’s Capital Improvement Plan.
It also shows expected completion dates. Phase I should wrap up next year.
Phase II should finish in 2028. It includes the portion of Northpark expansion that extends past Woodland Hills.
A detention basin, previously part of Phase II has become its own project to accelerate it. That will reduce flood risk sooner for residents along Bens Branch and the Diversion Ditch.
The detention basin project includes widening of the northernmost portion of the diversion ditch. It should start next year and finish in 2027.
For More Information
See the Lake Houston Redevelopment Authority project web pages or these posts on ReduceFlooding:
UPRR:
Evacuation Route:
Plan Details:
Phase II:
Posted by Bob Rehak on 5/8/25
2809 Days since Hurricane Harvey