kidd Archives - Reduce Flooding

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.

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!

*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.

Houston City Council Member Dave Martin announced today that the Federal Emergency Management Administration (FEMA) has authorized the United States Army Corps of Engineers (USACE) to remove sand and siltation from the Lake Houston mouth bar.

History of Project

In 2018, USACE first began removing debris deposited during Hurricane Harvey from the San Jacinto River under FEMA Mission Assignment (DR 4332). The assignment directed USACE to restore the river to pre-Harvey conditions.

DR 4332 has removed debris from three out of four identified sections of the San Jacinto River. Contractors should finish the last segment (shown in blue below) in May.

Original segments identified by USACE. The orange and green segments are complete. The blue segment should be finished with another week or so. And the purple segment is the one yet to be done – including the mouth bar.

FEMA did not approve the fourth section, in the original scope of work for DR 4332. Last month, the City of Houston filed an application for mouth bar removal as well as an additional dredge material disposal site. FEMA and USACE have been reviewing it since then, according to Council Member Martin.

The State of Texas, the City of Houston, as well as multiple stakeholders from the Lake Houston area, requested FEMA to expedite authorization of a Mission Assignment for debris removal and dredging of the mouth bar while the equipment is still in the river. The hope: to save taxpayers the cost of a second mobilization effort. Mobilization for the first assignment cost approximately $18 million.

FEMA Issues Directive of Mission Assignment

At a meeting last week in Austin, FEMA issued a directive of Mission Assignment to USACE for dredging of the mouth bar at the confluence of the San Jacinto River and Lake Houston.

The City requested removal of 1.4 million cubic yards of sediment. It is unclear at this time how much FEMA will fund, exactly where it will be stored, and whether matching funds will come from other sources. FEMA, TDEM, City of Houston, and USACE are still working to determine the amount of silt deposited by Hurricane Harvey.

Dredging of Final Segment To Begin Within 30 Days

Martin hopes the calculation will be finalized next week, and expects dredging to begin within 30 days.

*The Great Lakes Dredge is still docked at the USACE Command Post while it awaits FEMA and USACE to finalize mouth bar dredging details with the City and State.*

Kudos to Mission Team

In his press release, Martin issued “a huge thank you to our federal partners Congressman Dan Crenshaw, Field Representative for Congressman Crenshaw, Kaaren Cambio, Congressman Kevin Brady, Senator Ted Cruz, and Senator John Cornyn for their support as they have all been meeting regularly with FEMA and discussing this project.”

“This is a huge project for our area,” said Martin, “and it would not be possible without the on-going support and push from Governor Greg Abbott and Chief Nim Kidd, Texas Department of Emergency Management (TDEM), as well as Mayor Sylvester Turner and Stephen Costello, Chief Recovery Officer – City of Houston.”

Martin also gave additional thanks to Jenna Armstrong and Mark Mitchell from the Lake Houston Area Chamber of Commerce for coordinating a letter writing campaign.

Breathing a Bit Easier Tonight

During floods earlier this year, I noticed a ten foot difference at times at gauges on either side of the mouth bar. It is acting like a dam behind the dam.

With the start of Hurricane season on June 1, residents of Kingwood and Humble will breathe a little easier tonight. Hopefully, the Corps and its contractors will be able to at least dredge a channel through the mouth bar area before the peak of the Atlantic season from mid-August through September.

The SJRA has agreed to continue lowering Lake Conroe during that period by 2 feet versus its normal level as an additional buffer against flooding.

My thanks to Council Member Dave Martin for pushing this project so tirelessly, and to Kaaren Cambio and Mark Micheletti for leading to effort to lower Lake Conroe again this year. Neither effort has been easy. Finally, kudos also to Tim Garfield and R.D. Kissling, two local retired geologists for their efforts in helping people understand the dangers posed by the mouth bar.

Posted by Bob Rehak on April 26, 2019

605 Days since Hurricane Harvey

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They Clearcut 533 Acres, Then Got 17 Inches of Rain