Tag Archive for: Friendswood

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.

3738-Acre Property Developing Near Huffman

On 7/22/22, I photographed two new developments at different stages of completion east of Huffman-Cleveland Road and south of the Grand Parkway. Both are being carved out of a 3,738-ac tract owned by LH Ranch LTD.

A third part of that tract, west of Huffman-Cleveland Road, is in the planning stages and submitting plats for approval.

General Location

The first two developments are immediately east of Huffman-Cleveland Road and south of Meyer Road. See red area below.

Red outlined area contains the two new developments. The third area is to the west (left) of the red box.

One of the new developments will become a “lagoon community” called Saint Tropez. Another will become a residential community called Los Pinos. The third will also become a residential community.

Saint Tropez

Megatel Homes has begun clearing land for what it says will become a $2 billion lagoon community spanning 1,000 acres.

Looking SW from over Meyer Road at the first part of what will become Saint Tropez.

According to Megatel, the development will eventually feature 4,500 homes, an enormous manmade lagoon with white sand beaches, paddle-boarding, kayaking, a swim-up bar, surf simulator, a water slide tower, a playground, cabanas, soundstage, splash park, and more.

An entertainment district will offer a restaurant, bar, teen arcade, bowling alley, and a children’s immersive indoor play area. That will certainly change the character of the rural Huffman area.

The development will feature both single and multi-family housing. Single-family homes will range in size from 1,500 square feet to 4,000 square feet and sell for between $350,000 to $700,000 each.

Full construction plans and a drainage analysis are not yet available. At this time, the Harris County Engineering Department has only issued a permit for clearing the land, but it shows a general layout.

Plan submitted to Harris County Engineering to obtain clearing permit. Intersection of Meyer Rd. and FM2100 in upper left.

Los Pinos

South of Saint Tropez, the second development is much further along. For it, I have obtained both construction plans and a drainage analysis via a FOIA Request.

Looking SE from over FM 2100. Note the large, linear detention basin in the foreground running diagonally through the frame.
Drainage Features

Phase One of the 130-acre Los Pinos Project will have approximately 250 single-family residential lots. The 1/3rd-acre lots will have about 30% impervious cover.

Plans claim that the total detention storage will exceed Harris County Flood Control District’s (HCFCD) minimum storage requirements. They require 270.4 acre feet, but the developer will provide 366.3 – 26% more.

Phase One sits in the FEMA’s unshaded X zone (higher than the 500-year flood plain). So there is no requirement for floodplain mitigation.

Preston Hydrologic, Inc., which conducted the drainage analysis, says, “The proposed detention basin will reduce the maximum sheet flow depths downstream of the development, for storm events up to and including the 1% AEP storm.” AEP means annual exceedance probability. And 1% refers to a 100-year storm.

The tract drains to Key Gully and two unnamed tributaries within the Luce Bayou watershed. This development falls outside Houston’s city limits in unincorporated Harris County.

Looking east from over FM 2100. Note a second large linear detention pond on the right bracketing the development.

Water in this area naturally flows toward the southeast where it enters Luce Bayou. The detention ponds that bracket the development are designed to contain rain falling on the development and water trying to flow across it.

Map from Preston Hydrologic’s drainage analysis shows layout of detention basins.

Six interconnected, dry-bottom detention basins will mitigate the impacts of development, according to hydrologists. The lots in proposed Phase 1 will drain into Ponds 2 and 6. Ponds 1, 3, 4, and 5 will intercept runoff from undeveloped land.

Peak flow estimate indicates ponds should hold a 100-year rainfall and cut peak outflow roughly in half (red vs. blue curve)
Claims No Adverse Impact

Hydrologists claim the development will cause “no adverse impacts” compared to the pre-project drainage conditions of the receiving streams in the Luce Bayou watershed. That includes downstream properties within the City of Houston.

They also estimate that overland sheet flow will not cause any adverse impacts downstream of the project site. In fact, the hydrologists claim that the proposed project will reduce peak flow rates and runoff volumes to areas downstream. That, they say, will result in reduced ponding depths in the Huffman Hills subdivision and adjacent properties.

Small Part of Future Development

The 130-acre Los Pinos Phase One tract represents only 0.34% of the larger LH Ranch Tract from which it is carved. The hydrologists caution that future phases will require future studies of their own. They indicate that future uses of the LH Ranch tract may include additional single-family residential development, commercial development, and a wetlands mitigation bank.

Wetlands Mitigation

Plans considered by the Army Corps in January of 2021 show wetland mitigation areas on both the west and east.

The mitigation bank proposal showed that 25% of the LH Ranch tract would be set aside for mitigation.

The LH Ranch tract bridges two watersheds. The western portion drains to the East Fork. The eastern portion drains to Luce Bayou. Both eventually drain into Lake Houston. Much of the land was originally wetlands.

Image from same general area taken on January 2021 when tree canopy did not obscure ground. Note standing water.
Will Increased Runoff Increase Erosion?

The side slopes of the ponds will be grass lined and have backslope interceptor swales to reduce erosion.

Preston Hydrologic believes that the increased runoff from Los Pinos Phase One will not increase erosion in Key Gully. They base that opinion on three factors: a USGS estimate of soil-erosion potential in the area, reduced peak flow, and slower water velocity at the peak.

Potential Problems

Section 5.3 of the drainage analysis cites an inventory of potential problems. Among them: Colony Ridge. Preston’s report says, “Currently, a large developing area adjacent to the Harris-Liberty County line may create problems for water quantity and quality. This development is large-lot rural and uses underground septic systems located in the effective floodplain area of Luce Bayou. Additionally, it is possible that inadequate drainage infrastructure is being provided in the area, which could lead to a possible increase of floodwater peak flow rates downstream in Harris County.”

For the complete drainage analysis, click here.

Other LH Ranch Property West of FM 2100

West of FM 2100, LH Ranch LTD and Friendswood Development applied to the Houston Planning Commission for plat approval of a 927-acre parcel on 8/4/22. This parcel is immediately west of the two projects discussed above. It drains into the East Fork on the left edge of the map below.

No further details are available at this time. I will watch it closely in the future months. One thing is clear: Huffman will never be the same.

Posted by Bob Rehak on 8/9/22

1806 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.

Text of Ben’s Branch Agreement Between Bear Branch Trail Association, Friendswood and HCFCD

Rumors of a Ben’s Branch agreement between Bear Branch Trail Association, Friendswood and Harris County Flood Control District have circulated for weeks. On Wednesday, November 13, 2019, the deal became official when Diane Trautman, the Harris County Clerk, recorded the easement. Here is exactly what the easement does and doesn’t allow the various parties to do along Ben’s Branch.

Ben’s Branch below St. Martha’s Catholic School is characterized by hairpin turns and trees growing right down to and into the stream.

49-Page Ben’s Branch Easement Finally Signed

The easement is like a contract that spells out the rights, obligations and limitations of each party.

Here is the complete text of the 49-page document. Below is a summary.

Bear Branch Trail Association Rights and Obligations

This is an agreement between three parties that modifies the original deed of gift between Friendswood and the Bear Branch Trail Association (BBTA).

BBTA:

  • Gives Harris County Flood Control the right to operate in an area 100 feet wide, 50 feet on either side of the creek’s centerline.
  • Retains the right to maintain and operate existing trails, bridges, low water crossings.
  • May construct, install, maintain and operate new trails in the easement area as long as they don’t obstruct water flow, cause erosion or hinder HCFCD’s “de-snagging” efforts. De-snagging is the removal of trees that have fallen or are falling into the creek.
  • Must share plans for new trails, bridges, etc. with HCFCD and HCFCD must approve them before any construction begins.
  • Acknowledges that HCFCD equipment may damage trails and agrees not to hold HCFCD liable for repairs.
  • Remains solely responsible for the safe condition and maintenance within the easement area and for repairs to any damage.
This low water crossing north of Bear Branch Elementary may not be removed according to the terms of the easement. Some observers have noted trees “spearing” into the narrow culverts and backing water up. But HCFCD cuts trees into small enough sections to let them pass through such openings.

Harris County Flood Control Rights and Obligations

HCFCD may:

  • Perform de-snagging operations related to flood control and drainage.
  • Clear, cut, drop, stack and stockpile trees, shrubs, vines, and vegetation for the sole purpose of flood control.
  • Grade and stabilize banks to protect against erosion and maintain drainage.
  • Plant grass, or use rip rap or man-made materials to reduce bank erosion.
Trees constantly fall into Ben’s Branch because of bank erosion. When floating trees catch on other trees or roots during floods in the narrow channel, they can form “beaver dams” that back water up into adjoining streets, homes and businesses.

HCFCD can/will NOT:

  • Widen, deepen, enlarge, straighten or smooth the channel in such a way as to increase channel capacity.
  • Maintain or repair trails or bridges, but may repair erosion that threatens them.

HCFCD has no responsibility to repair or replace storm sewer outfalls or to repair erosion around them.

Friendswood Agrees to All of Above Plus…

Friendswood agrees to all of the above. Friendswood also agrees that the terms of the easement will not trigger the automatic reversion of ownership from BBTA to Friendswood that the original deed of gift specified.

Signatories

John Hammond of Friendswood signed the easement on Monday, November 11, 2019.

Kathryn Palmer, president of BBTA signed it on Tuesday, November 12, 2019.

Diane Trautman, the Harris County Clerk signed and recorded it on November 13, 2019.

Roadblocks to Flood Control Maintenance Now Removed

This means that Flood Control can now begin de-snagging and other maintenance activities within 50 feet of either side of Ben’s Branch. The area affected lies between Woodland Hills Drive and Kingwood Drive.

Geographic Limitations

North Park, Woodland Hills, Kingwood Drive and West Lake Houston Parkway define the boundaries of BBTA.

Other community and commercial associations control the creek outside of those boundaries. But those areas are already channelized and maintained by HCFCD for the most part.

Note: Those who don’t live within these boundaries may be confused by the names. Ben’s Branch is the name of the creek that runs through Bear Branch Village, Kings Forest and Hunters Ridge. The Bear Branch Trail Association overlaps all three of the community associations, but technically has nothing to do with them. BBTA is solely responsible for the greenbelts and greenbelt trails. It has nothing to do with swimming pools or deed restrictions. This can differ in other parts of Kingwood.

Compromise Between Natural Aesthetics and Flood-Risk Reduction

Everyone should realize that this easement represents a compromise. Any loss of natural aesthetics is the price of reducing flood risk to their neighbors. The three parties worked on this for more than a year.

Parts of the greenbelt will be thinned out, but you shouldn’t see wholesale widening of the creek into a massive channel. As a consequence, people who live along the creek should realize that this doesn’t offer the highest degree of flood protection. But it does help protect both greenbelts and property owners much more than before.

St. Martha Catholic School, Kids In Action, and homes on either side of the creek that flooded should be optimistic about this agreement.

The densely forested nature of the preserve along each side of the creek will look less dense. However…

The Ben’s Branch greenbelt is a minimum of 300 feet wide. In most places, it’s 400-600 feet wide. And in some places, it measures as much as 800 feet wide. This agreement affects only 100-feet.

Thus, two-thirds to seven-eighths of the natural area will remain the way it looks now. That sounds like a reasonable price to pay for helping to protect neighbors and property values in the entire neighborhood.

Posted by Bob Rehak on 11/17/2019

810 Days since Hurricane Harvey and 59 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.