Tag Archive for: Time of Accumulation

How Soon We Forget!

How soon we forget. Hurricane Harvey was just 4.5 years ago. Since then I have documented dozens, if not hundreds of questionable practices that erode margins of flood safety.

It Didn’t Have to Be That Bad

Harvey was the largest rainfall event in the history of North America. However, with better regulations and construction practices, it didn’t have to be as destructive as it was.

  • Lax regulations;
  • Willful blindness;
  • Development and construction practices that pushed the safety envelope;
  • Relentless destruction of forests and wetlands near rivers and streams;
  • And homebuyers who didn’t realize their true flood risk…

…made Harvey’s destruction worse than it otherwise would have been.

No one factor by itself would explain Harvey’s destruction. But put them all together, and it’s like “death of a thousand cuts.”

The sheer volume of material – more than 1,000,000 words on this site – makes it difficult for people to see the big picture sometimes. To put 1,000,000 words into perspective, the average novel contains only about 100,000. So I’m condensing the website into a book that includes the themes below.

No One Wins Arguments with Mother Nature

During an interview with Milan Saunders and his daughter Lori, Milan said, “No one wins arguments with Mother Nature.” How profound! It doesn’t matter how many surveys, studies and engineer stamps you have on your home’s title. If you don’t:

  • Respect the rivers.
  • Give them room to roam.
  • Protect wetlands.
  • Allow plenty of margin for safety…

…you will flood.

Thought courtesy of Milan Saunders, Chairman/CEO of Plains State Bank. That’s his daughter Lori’s house during Harvey.

Understanding the Causes of Flooding

Excess sedimentation is one of them. Sediment pollution is the single most common source of pollution in U.S. waters. Approximately 30% is caused by natural erosion, and the remaining 70% is caused by human activity.

Large islands built up during Harvey blocked both drainage ditches and rivers. Below, you can see a large sand island (top) built up at the confluence of the Kingwood Diversion Ditch where it reaches the San Jacinto West Fork at River Grove Park. This sand bar reached 10-12 feet in height above the waterline and helped back water up into Trailwood, the Barrington and Kingwood Lakes and Kings Forest. Before the Army Corps dredged this island, River Grove flooded five times in six months. It hasn’t flooded since.

The Kingwood Diversion Ditch and West Fork San Jacinto were almost totally blocked by sediment dams deposited during Harvey.

The second photo above was taken a few hundred yards downstream on the West Fork from the first. It shows “Sand Island” – so nicknamed by the Army Corps. It took the Corps months to dredge this island which they say had blocked the West Fork by 90%.

A certain amount of this sedimentation can be explained by natural erosion. But mankind also contributed to the sheer volume by other practices which I will discuss below.

Respect the Rivers

The red polygons in the satellite image below surround 20-square miles of sand mines on the West Fork of the San Jacinto in a 20 mile reach of river between I-45 and I-69. That exposes a mile-wide swath of sediment to erosion during floods and increases the potential for erosion by 33x compared the river’s normal width.

Even without floods, mines sometimes flush their waste into the rivers. The shot below on the top right shows the day the West Fork turned white. The TCEQ found the source of the pollution upstream: a sand mine that had flushed 56 million gallons of sludge into the West Fork (bottom right).

Influence of sand mines of West Fork San Jacinto water quality.

End the War on Wetlands

Wetlands are nature’s detention ponds. During storms, they hold water back so it won’t flood people downstream. But we seem to want to eradicate wetlands. The images below show the Colony Ridge development in Liberty County. Wetlands (right) are being cleared (left) to make way for the world’s largest trailer park. The acceleration of runoff wiped out FM1010 during Harvey. The road still has not been repaired.

Colony Ridge in Liberty County.

Conservation Costs Much Less than Mitigation

Halls Bayou at I-69 near Fiesta. Image on left shows whole subdivisions that that to be bought out before detention ponds on right could be built.

All across Harris County, especially in older areas inside Beltway 8, apartment complexes, homes and businesses are built right next to bayous and channels. This makes it difficult to enlarge streams or build detention ponds when necessary. One study showed that preservation of floodplains is 5X more cost effective than mitigation after homes flood. Yet private developers keep crowding bayous and residents keep demanding public solutions.

Respecting Individuals’ Property Rights While Protecting Others’

In Texas, it sometimes feels that an individual’s right to do what he/she wants with property trumps others’ rights NOT to flood. You may think you’re protected by all those public servants reviewing and approving plans. But what happens when developers and contractors decide to ignore the approved plans? Here’s a prime example: the Laurel Springs RV Resort near Lakewood Cove.

The approved plans said that “Stormwater runoff shall not cross property lines.” So what did the contractors do? They pumped their stormwater over the development’s detention pond wall. When that took too long, they dug a trench through the wall. Then they laid pipes through the wall to permanently empty the sludge into the wetlands of Harris County’s new Edgewater Park.

This apparently violated the developer’s City of Houston permit, the Texas Water Code, TCEQ’s construction permit and the developer’s stormwater pollution prevention plan. Four investigations are currently swirling around this development. The contractor also cut down approximately 50 feet of trees in Edgewater Park along the entire boundary line and received a cease-and-desist letter from the Harris County Attorney. But the damage is done.

Balance Upstream and Downstream Interests

About 10% of all the water coming down the West Fork at the peak of Harvey came from Crystal Creek in Montgomery County. But the wetlands near the headwaters of Crystal Creek are currently under development. And the developer is avoiding building detention ponds with a “beat-the-peak” survey. This loophole allowed by Montgomery County says that if you get your stormwater to the river faster than the peak of a flood arrives, then you’re not adding to the peak of a flood and you don’t have to build detention ponds. So developers conduct timing surveys to reduce costs and maximize salable land.

What happens when upstream areas develop without consideration for the impact on downstream property owners.

Of course, speeding up the flow of water in a flood is the opposite of what you want to do. To reduce flooding, you should hold back as much water as possible.

The slide above shows part of a new development called Madera at SH242 and FM1314 being built on wetlands near Crystal Creek.

The graph on the right shows what happened on Brays Bayou without suitable detention upstream. Floodwaters peak higher, sooner. Harris County has spent more than $700 million in the last 20 years to remediate flooding problems along Brays.

How much will we need to spend when more areas like Madera get built upstream on the West Fork?

How Quickly We Forget!

FEMA’s Base-Flood-Elevation Viewer shows that in that same area, developers have already built homes that could go under 1-5 feet of water in a 100-year flood. These homes are actually in a ten-year flood zone. And yet more homes are being built nearby. On even more marginal land!

In recent years, the price of land as a percent of a new home’s cost has risen from a historical average of 25% to approximately 40% today. This puts pressure on developers to seek out cheaper land in floodplains, reduce costs by avoiding detention pond requirements, pave over wetlands, and reduce lot sizes resulting in more impervious cover. All contribute to flooding.

Of course, smart homebuyers would not make such risky investments. But few lack the expertise to gauge flood risk. Educating such homebuyers will be one of the major objectives of the book I hope to write.

Posted by Bob Rehak on 2/23/2022

1639 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.

Rapid Runoff from World’s Largest Trailer Park Wipes Out Plum Grove Road in Liberty County and More

Rapid runoff from Colony Ridge, perhaps the world’s largest trailer park, in Liberty County contributed to a washout of FM1010. Nearby residents in Plum Grove say it also contributed to the flooding of their homes. Moreover, erosion from the development has contributed to the buildup of sedimentation in the East Fork.

Nine years ago, this area was mostly forested wetlands. Today, it’s mostly mobil homes, many on barren lots, stretching mile after mile.

World’s Largest Trailer Park?

There is no definitive source ranking the size of trailer parks, but multiple references to Sun Valley in Nevada come up when you Google “world’s largest trailer park.” That development is one third the size of this one!

Nine years ago, Colony Ridge didn’t exist.

Satellite image from 2011. The land that would become Colony Ridge was covered with forests, wetlands and rice fields. Paper companies owned most of this land for decades and periodically harvested timber.
Colony Ridge today. This is just the southern section. Two more sections are out of frame on the north.

By the end of 2019, Colony Ridge had grown to cover approximately 10,000 acres and it’s still expanding. It has transformed the landscape massively, and it’s not clear whether the development has provided sufficient detention to keep runoff at its predevelopment rate. Judging by the frequency of flood damage to surrounding homes and roads since Colony Ridge was developed, many local residents believe the answer is no.

Documentation about the design and effectiveness of the drainage systems is hard to come by. Authorities in Liberty County have not returned emails or phone calls. And the information is not posted online.

Entire Population Growth of Liberty County in Last Decade

Colony Ridge alone can account for all of the population growth in Liberty County in the last decade. The U.S. Census Bureau officially estimates that Liberty County’s population grew from 75,000 to 88,000 between 2010 and 2019. Unofficially, one local politician estimates the population of Colony Ridge to be about 20,000. Firm numbers are difficult to come by because many residents are undocumented and uncounted.

Contributing to Flooding?

Thousands of acres of trailer homes with open-ditch drainage and no deed restrictions.
Typical landscape in Colony Ridge is highly susceptible to erosion and rapid runoff.

The lack of deed restrictions means many have not planted grass. That accelerates runoff.

Also consider that the developer created many of the lots by filling in wetlands and clearing trees that used to retain water in storms. The absence of wetlands and trees also accelerates runoff.

Wetlands drained by Colony Ridge from USGS National Wetlands Inventory.

Contributing to Road Blow Out

FM1010 lies in the path of a drainage ditch more than 2.5 miles long and 60 yards wide in places. It cuts like a butcher knife through the heart of Colony Ridge.

Satellite image shows massive erosion in straight-line drainage ditch that stretches for 2.5 miles toward Plum Grove Road, out of frame on the left.

The straight line nature of such ditches accelerates water and erosion even more. During Harvey, a combination of factors (population growth, lack of ground cover and deed restrictions, design of drainage, loss of forests and wetlands, impervious cover and extreme rainfall) all contributed to washing out FM1010. (See images below.)

Acceleration of runoff also shortens the time of accumulation during floods which heightens flood peaks.

Effect of Urbanization on Peak Stream Flows” by Dr. William Dupre, professor emeritus from the University of Houston.

One Person’s Dream Turns into Another’s Nightmare

The developer of Colony Ridge had an attractive vision for a niche market: to provide affordable plots of land without deed restrictions (at least in the early stages) to low-income families trying to escape the City. He marketed mainly to Hispanics who dreamed of owning their own land in America. The result may be a dream for some, but it’s turning into a nightmare for others.

A low-altitude shot looking west toward Plum Grove Road (concealed in tree line in distance).

Unintended Consequences or Foreseeable Tragedy

The giant ditch shown above leads directly to where FM1010 washed out. Along the way, there’s little to slow water down. The developer has installed twin culverts under a road that crosses the ditch. They may help. But judging by the results, they’re not working very well.

Cropped and enlarged from wide image above of Colony ditch.

From the bridge above, the elevation drops more than 27 feet in three quarters of a mile before stormwater goes into a strip of woods between FM1010 and the development. There, it gathered the momentum to blow out the road.

In the last part of its journey across Colony Ridge to the East Fork (left), water drops 27 feet with only a strip of woods to slow it down before it reaches the part of Plum Grove Road that washed out.
FM1010, Plum Grove Road has been impassible since Hurricane Harvey 1020 days ago.
Looking upstream toward Colony Ridge out of frame in the background (upper left)
Looking downstream toward the East Fork about 200 yards to the east.

Detours and Delays

More than 2.5 years after Harvey, this road has yet to be repaired.

The loss of FM1010 makes northbound traffic detour through Colony Ridge or up US59 and then back east. As a result, residents say that it can now take an hour during rush hour to go the five miles from US59 to Plum Grove on FM 2090. But that’s not the only problem.

Rapid Sedimentation Downstream

Downstream from Colony Ridge, we’re now getting rapid sand build ups on the East Fork, much like we have on the West Fork from sand mines. According to boaters, the area shown below was 18 feet deep before Imelda. The deepest point in the channel when this picture was taken last December was 3 feet.

Growing East Fork Mouth Bar

A massive development, such as Colony Ridge, without appropriate safeguards against erosion, contributes to this buildup. They certainly aren’t the only contributors. Sand mines that provided the aggregate for the roads in Colony Ridge have certainly helped.

Posted by Bob Rehak on 6/14/2020

1020 Days since Hurricane Harvey and 269 since Imelda

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.