Tag Archive for: Sila

How Solving Problems of the Past Can Create Problems of the Future

12/1/25 – Sometimes, solving problems of the past creates problems of the future. Consider the elevation of homes above floodplains.

During Hurricane Harvey, 154,170 homes in Harris County flooded, according to the Harris County Flood Control District. Of that number:

  • 48,850 were within the 1% (100-yr) floodplain
  • 105,340 were outside it.

Said another way, more than 100,000 homes flooded because building codes did not recognize the need to build to higher standards.

Accordingly, in the wake of Harvey, Harris County, Houston and many surrounding areas increased building code requirements. Now, most jurisdictions require that the minimum finished floor elevation be established at (or waterproofed to) the 500-year flood elevation “shown on the effective flood insurance study.”

But as builders started elevating foundations with dirt they excavated from stormwater detention basins, water started running downhill. And not always toward the detention basins. Sometimes it flows toward pre-existing neighboring homes built at lower elevations.

The problem can most often be seen during construction after forests are cleared next to existing subdivisions.

I was driving north on the US59 feeder the other day and saw this near E. Wallis Drive in Porter.

New development has been built up almost to the roofline of adjoining homes.

And less any doubt exists about how the contractors sloped the built-up area, note the erosion on that hillside in the photo below.

Note water ponding in yard and along fence line of corner home.

Also note the amount of sediment washed out to the feeder road and running into the storm drain. Contractor has installed no silt fences as best practices dictate.

As I was developing a post about the new development above, I received an email from Eric Unger who lives next to another new development several blocks south. He said that contractor raised the ground level at least a foot relative to his and his neighbors’ yards, “which results in their entire acreage now sitting higher than our yards.”

Then he said, “A recent 2-inch rain fall caused a flow of silty water to invade our yard and come dangerously close to our back porch.” He sent this image taken more than day later to me.

Photo courtesy of Eric Unger

Erosion and ponding water in the photo below make it easier to see the slope of the land toward his and his neighbors’ homes.

Note ponding next to fence line of Unger home (bottom left) and erosion next to road.

A Disturbing Pattern

I see this same problem in development after development. In Woodridge Village, contractors clearcut 270 acres and sloped the land toward Elm Grove Village in Kingwood. Up to 600 homes then flooded twice in 2019 before the City of Houston and Harris County stepped in and purchased the land from Perry Homes.

Flooded homeowners pursued a class action lawsuit that was ultimately settled in the homeowners’ favor.

During discovery, it became apparent that contractors had shaved down a berm protecting Elm Grove and that they had not followed the engineering plans. Specifically, they were supposed to install stormwater detention basins in one section before clearcutting the next. See below what that policy resulted in.

Car submerged during Imelda at the end of Village Springs adjacent to Woodridge Village. Note the sediment laden water from the development. Photo courtesy of Allyssa Harris.

In Huffman, a developer clearcut 533 acres uphill from Northwoods Country Estates right before they got 17 inches of rain.

Sila in Huffman
Friendswood’s Sila Development in Huffman flooding neighbors in 2024

Meritage cleared 40 acres for 255 homes in Atascocita on both sides of Pinehurst Trail Drive. Then on 4/5/25, they got 2.6 inches of rain in 2 hours.

Meritage site floods neighbors after heavy rain
Meritage neighbors paid the price.

During eight years of blogging about flooding, I’ve seen this problem repeatedly.

Chapter 11.086 of the Texas Water Code prohibits altering drainage in ways that flood neighbors. But it tells developers what they should not do, not what they should do.

In my opinion, developers should force contractors to build berms shielding neighbors as soon as clearing is complete. They should also build detention basins as soon as possible after clearing. Instead, many wait a year or more.

Silt fences are not enough…as you can clearly see in the photo above.

I don’t wish to tar all developers and contractors. Many are both reputable and responsible.

But as we try to avoid problems in the future, we also need to define practices that protect homes built in the past.

Posted by Bob Rehak on 12/1/25

3016 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.

They Clearcut 533 Acres, Then Got 17 Inches of Rain

Construction is always the riskiest period during a development project. Especially when you clearcut 533 acres and get 17 inches of rain … in a week. However, thanks to best practices and luck, most people surrounding the Sila development in Huffman narrowly escaped what could have become a major disaster.

As the people in Woodridge Village learned repeatedly on far less rain, best practices can make all the difference. They lived near a development where stormwater detention basins were not built before the rain; the people near Sila did.

The new 553-acre Sila Project in Huffman on the East Fork of the San Jacinto seems to have had considerably less impact on neighbors. This is a story of people caught between a rising river and sheet flow coming down a slope.

Sila’s Similarities, Differences with Woodridge

Several similarities with the Woodridge project exist. Sila is big. Built on an identical slope. And clearcut. But after 17 inches of rain last week, the outcome was dramatically different.

Instead of flooding hundreds of homes below the development as Woodridge did, most residents near Sila only got water in their yards. One fish pond was ruined. At least two vehicles flooded. And at least one garage flooded.

The big differences between Sila and Woodridge?

Sila had already built stormwater detention basins. When the rain hit, a series of berms and ditches helped funnel runoff to the basins and away from neighbors. Silt fences intercepted much of the runoff. And crews replaced the fences when silt started to spill over the top.

Before looking at pictures, first let’s look at some stats that put the rainfall in perspective.

5- To 25-Year Rainfall

After Sila weathered this year’s January rains, it got slammed again in the week between April 29 and May 5 with almost 17 inches of rainfall.

Nearest official Harris County gage at FM1485 on East Fork San Jacinto showed 16.68 inches of rain fell in the seven days from April 29 to May 5.

That included 7 inches in one day. And half of that fell in one hour.

Of the 17 inches, 7.12 inches fell on 5/2/24 alone, with 3.48 inches in one hour.

NOAA defines a 7-day/17.1 inch rain in this area as a 25-year rainfall. Ditto for a one-hour 3.88 inch rain. Seven inches in one day, however, is only a 5-year event.

However, the East Fork peaked at FM1485 at a level equal to a 500-year flood according to Harris County Flood Control’s Flood Warning System. That’s because even heavier rain fell upstream in less time. It then reached FM1485 when heavy rains were falling there.

East Fork peaked over 77 feet at FM1485 on May 5.
According to HCFCD, 77 feet is more than a 500-year rain.

Also, according to HCFCD, to date, the area near FM1485 has received more than two thirds of a year’s average annual rainfall in about one third of the year – 34.72 inches!

Pictures Taken During Week of Heavy Rains

Northwood Country Estates resident Max Kidd provided many of the following photos taken at ground level during the flood.

They show mainly severe street flooding. Thankfully, Harris County Precinct 3 Commissioner Tom Ramsey’s crews had just finished cleaning roadside ditches. Otherwise these photos might have told a much worse story.

Water poured out of Sila across Northwood Country Road on 5/2, the day before the big rain.

On 5/3 and 5/4/24, Kidd took these photos.

Flooded home and vehicles.

Kidd believes the home above likely flooded from the East Fork. However, Sila runoff may have added to the flood depth.

Photos Taken After the Storm

Sila is so big that it’s hard to get it all in one shot. The aerial shots below were all taken on 5/6/24 after the rain ended.

Looking E across the southern portion of Sila. St. Tropez, a separate development is at very top of frame across FM2100. But Sila drains to the East Fork, and St. Tropez drains to Luce Bayou. Luce later re-enters the East Fork near its mouth at the headwaters of Lake Houston.
Sila had a swale behind the erosion to slow water running down a hill out of frame to the left. However, that swale filled in with sediment, according to Kidd. And water then flowed into a ditch behind the fence filling it with sediment, too.
Still, some sediment flooded into the backyards of neighbors.
A series of detention basins caught and channeled runoff through the development.
Shortly after the rain ended, it appears that bulldozers graded perpendicular to slopes to help retain or slow down any additional rain that might fall.

In the photo below, also note the forested corridors that break up Sila runoff. While large portions have been clear cut, those that haven’t help retain sediment.

Detention basin was holding water and emptying it slowly, presumably at the pre-development runoff rate.
Still, some sediment escaped the development. Note roadside ditch filling in at peak of triangle.

As I left after this photo session, I noticed workers replacing and reinforcing the silt fence above. But the photo below shows the volume of the sediment that escaped despite their efforts. A lot!

Drainage had filled in completely.
Kidd’s fish pond is no longer habitable by fish due to Sila runoff that polluted it.
Lowest of the detention basins at southwestern edge of development was sending stormwater into a wetland mitigation bank before it reached the East Fork.
Contractors had put silt fence at the outfall of the detention basin to help retain sediment.
But then they pumped water toward the river, through a mass of muck, creating more erosion. (Can’t win ’em all.)
Along the way to the river, some of the dirt will get a chance to settle out in the wetland mitigation bank.
Regardless, the East Fork was running orange on 5/6/24.

No doubt, several sources contributed to the discoloration. They include Sila, other upstream developments, sand mines and natural, river-bank erosion.

Few developments that I have observed go to as much trouble to control runoff as Sila. And few bother to leave trees these days. I wish more did. We might have less sediment clogging our rivers and contributing to downstream flooding.

Posted by Bob Rehak on 5/9/24

2445 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.

Why Flood Risk Increases During Construction

Pictures taken of a new Huffman development after a 3.75-inch, 2-year rain last week illustrate why flood risk increases during construction compared to other phases of a project.

Aerial images taken over Sila, west of the Huffman-Cleveland Road, show:

  • Cleared land that accelerates runoff and decreases infiltration
  • Partially constructed stormwater detention basins
  • Trenches not yet consistently sloped
  • Rampant erosion
  • Workers pumping water out of one flooded area under construction only to flood another

Friendswood took more precautions with the 553-acre Sila than most developers take with their projects.

Regardless, despite their best intentions, a 2-year rain still overwhelmed them in places. Let’s look at examples of each point above.

Accelerating Runoff, Decreasing Infiltration

Natural ground cover slows the rate of runoff. Removing the ground cover lets stormwater flow faster.

Contractors also grade the land to create consistent slopes for roads and storms drains. That can eliminate little ponds, pockets of wetlands, and other natural catchments that slow water down.

Construction clearing for Sila in Huffman
First phase of Friendswood’s Sila Development in Huffman. Looking east toward St. Tropez at top of frame across Huffman-Cleveland Road.

I took these pictures just hours after the rain stopped. Notice how fast the runoff accumulated, even without storm drains.

Reverse angle looking west. Note water rapidly collecting and running off cleared area compared to forested area.

Partially Constructed Mitigation Facilities

Stormwater detention basins collect accumulated runoff and later release it at slower pre-development rates. Thus post-development runoff rates equal pre-development rates. At least if everything is done correctly.

But what happens when a large rain slams you before you complete the detention basins?

Partially completed Sila detention basin.

Trenches Not Yet Consistently Sloped

During work in progress, like this, trenches may not be consistently sloped. In the picture below, water flowed downhill from left to right. A swale caught most of the runoff. And a silt fence backstopped it. Regardless…

Because the swale was not consistently sloped toward the top of the frame, stormwater overflowed onto a neighbor’s property.

Rampant Erosion

Backslope interceptor systems that reduce erosion on the sides of ditches and basins have not yet been built here. Neither has grass been planted on the side slopes of those ditches and basins. The result: rampant erosion that can clog ditches and streams, and reduce the capacity of basins.

Note silt in stormwater detention basin.

Workers Saving One Area Only to Endanger Another

The first three shots below show the partially completed detention basin and workers scrambling to expel the rapidly accumulating runoff.

Workers pump water out of the pond into a ditch.
Note the pumps washing dirt into the ditch.

From there, water raced downslope toward the East Fork of the San Jacinto.

But the high flow from the pumped water found a way around one set of rock gabions and destroyed another.

That turned the outfall for a neighboring ditch (right of greenish pond above) into a mass of muck. From there, the muck flowed toward the river.

Muck moves toward East Fork San Jacinto beyond top of frame.

Could Have Been Worse

I didn’t see any homes that flooded on this day. Muck did flow into a few yards and across roads. And the outfall to a neighborhood drainage ditch, which was just cleaned out, will have to be cleaned out again.

But no doubt, it could have been much worse. See below.

Contractors created a slight depression to keep water from rushing downhill into neighboring homes (top of frame).

It’s also worth noting that runoff from Sila must go through more than a half mile of forested wetlands before reaching the East Fork. That will slow the water down, capture some of the erosion before it reaches the river, and keep the sediment from reducing the conveyance of the river channel.

Construction always entails flood risk, especially large scale construction that can take years. But with the right precautions, large rains don’t have to spell disaster.

Posted by Bob Rehak on 4/14/2024

2420 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.

Friendswood Clearing 553 Acres in Huffman

Friendswood Development Company has started clearing 553 acres west of Huffman-Cleveland Road. It will eventually extend from Northwood County Estates on the north to Cypress Point on the south. Plat records show that Friendswood has named the development “Sila.”

Long, Narrow, Dense Homesites

The new residential community will contain an unspecified number of homesites, most long and narrow. This will certainly increase the percentage of impervious cover relative to the surrounding area.

Detail from Sila Section 3 plat approved by Houston Planning Commission in 2023.

Existing homes sit on larger, heavily wooded lots. So, this and other new, nearby developments will change the character of the area considerably. Along with that will come more traffic and congestion.

To put that in perspective, I talked to one homeowner in nearby Northwood Country Estates who owns a five-acre lot.

Forty-five of the lots indicated above could fit on his property.

Drainage Plans

Friendswood appears to be almost halfway done with clearing land for Sila. Consistent with best practices and construction plans, contractors appear to be clearing one section at a time, installing perimeter catchment ditches, erecting silt fence, and stabilizing land before moving on to the next area.

Detail from Sila drainage impact analysis.

The drainage analysis also claims that the development will provide more than the minimum amount of required detention-basin capacity. The minimum required is .65 acre feet per acre. But the engineering firm BGE says it will provide .67.

The minimum requirement was established by Harris County Flood Control District in 2019 after Hurricane Harvey. So, it should accommodate 100-year rainfalls projected under Atlas 14, NOAA’s current standard for rainfall estimates.

Approximately the northern half of this area has been cleared to date.

Approximately Half of Land Cleared So Far

The pictures below, all taken on 2/3/24, show the areas cleared so far.

Looking west over Huffman-Cleveland Road at extent of clearing. Curvature in road is caused by wide-angle-lens distortion.

The yellowish runoff in the foreground of the photo above is from Saint Tropez another new, but different development seen in the background of two pictures below.

Note the ditches that channel runoff away from homes in Northwood County Estates in upper right.

A 1.5 inch rain the night before I took these photos caused the ponding water you see.

Reverse angle. A series of three connected stormwater retention basins will flank the main entry road. Area to right (south) has not yet been cleared.
Looking east toward Saint Tropez across Huffman-Cleveland Road. Friendswood appears to have planted grass in foreground to reduce erosion.
Silt fence protects neighbors in other areas cleared earlier.

Proposed Lake Houston Mitigation Bank

The Sila property will drain into hundreds of acres that are part of the proposed Lake Houston Mitigation Bank.

Looking W at wetlands and floodplain between Sila and the East Fork San Jacinto.

LH Ranch has proposed creation of the wetlands mitigation bank here.

East Fork San Jacinto River and Lake Houston Park beyond.

The preservation of so much land will help protect homebuyers from flooding. It will also provide wildlife habitat and an exceptional recreational amenity. Here’s the prospectus for the mitigation bank presented to the Army Corps. Corps approval still appears to be pending as of this writing.

Areas of Concern

Two areas of concern, however, exist near the land most recently cleared. Contractors have not yet erected silt fence or dug protective ditches behind some of the neighboring homes on Davidson Lane in Northwood County Estates.

Looking S. Neighboring homes in upper right were still unprotected from runoff when I took this picture on 2/3/24. Water flows from left to right toward East Fork San Jacinto out of frame on the right.
Looking W. Note how runoff is draining across neighbor’s property. A larger rain could have caused damage.

Neighbors in Northwood County Estates are also concerned with how existing drainage will tie into Sila’s drainage. Elevations on county drawings and Sila’s drawings differ in places. So residents are asking for confirmation that existing ditches will continue to drain properly.

Ditch at end of Davidson Lane in Northwood Country Estates.

For the most part, with the exceptions noted above, Friendswood seems to be responsibly navigating the perilous early phase of development between clearing and the installation of drainage.

Posted by Bob Rehak on 2/4/24

2250 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.