Tag Archive for: overflow

Woodridge Village Pre-Cristobal Detention Pond Update

Perry Home’s new contractors have excavated the vast majority of virtually all three detention ponds on the north section of Woodridge Village. That means they have almost completed 77% of the detention pond capacity for the whole site in two months. The previous contractors completed only 23% in approximately twenty months.

That represents approximately a 30x increase in productivity.

Overview of Woodridge Village Detention Pond Capacity

The pie chart below shows how that capacity breaks down. And the map shows where it is.

Percentage of detention pond capacity in acre feet for each of the five Woodridge Village ponds. Source: LJA Drainage Addendum.
General layout of detention ponds on Perry Homes’ property.

Contractors Scurry as Cristobal Churns in Gulf

Tropical Storm Cristobal could be a game changer next week if it hits Houston. It’s track is far from certain at this point, but the National Hurricane Center still puts Houston within the cone of uncertainty.

Cristobal has the potential to create massive erosion and set the work schedule back. The aerial photos below taken on 6/2/2020 show the current “pre-storm” status of construction for the three northern detention ponds. The two southern detention ponds were completed earlier this year.

N1 Nearing Completion of Excavation

N1 Starts at the northern boundary of the site and runs halfway down the western edge to Mace Street.

Looking north at N1 from Mace Street in Porter to the northern boundary.
The area between the culverts will eventually become an extension of Mace Street (top of photo) which will traverse the entire subdivision to Ford Road on the eastern side.
While some contractors continue excavating, others work on installing concrete pilot channels. Shown here, the pilot channel near Ivy Ridge in Porter.
The northern part of N1 is not yet complete. Contractors still use the Webb Street entrance (upper left as their main access point to the site. Note how height of road dwarfs excavator in pit.

Still Widening and Deepening N2 Pond

The area left of the diagonal road is the expansion of N2. The area near the diagonal embankment is deep enough to conceal trucks and excavators. However, the grassy triangle in the middle left was a previous detention pond constructed my Montgomery County in the early 2000s.
Contractors are deepening the MoCo pond a small amount to create additional storage capacity. The dirt is being used to build up other portions of the site.
Looking north along the western boundary from the southern part of the grassy triangle. Much work remains to extend the N1 channel south to N2. Jeff Miller reported today that contractors started working on this this morning.
On 6.3.20, contractors were removing dirt from the northward extention of N2 with three dump trucks running in a relay fashion. Photo courtesy of Jeff Miller.
Twin culverts installed in Taylor Gully will control outflow rates from N1 and N2.

N3 All Excavated

N3 cuts down the eastern side of Woodridge Village and joins Taylor Gully right above S2.

Looking north. Excavation of N3 appears complete although few of the finishing touches have yet been installed.
Looking south at the main body of N3.
N3 widens out about halfway down the eastern border.
Then it narrows down again to help control outflow speed as it approaches the junction with Taylor Gully.
Water from the entire site converges here. Erosion patterns, fence damage and grass matting show this is where the overflow started that contributed to the flooding of Elm Grove (right) and North Kingwood Forest (left) twice last year.

The pile of dirt in the picture above could be shoved into the connecting channel in the event that Cristobal should strike Houston. That would then help retain water in N3 until after the storm.

All the runoff from the approximately 200-acre northern portion of the site converges here and tries to make its way through a 3-foot culvert at the end of the concrete channel.

Uncertain Still Surrounds Corner of Chaos

Some Elm Grove and North Kingwood Forest residents have called the complex flow patterns in the photo above “The Corner of Chaos.”

Overflow from the concrete lined channel is supposed to go into the kite-shaped S2 pond, and then through the twin culverts into Taylor Gully. However, a hydrology consultant for the plaintiffs in flooding lawsuits contends that floodwaters went the other way. They escaped out of the inflow channel, he says. He further claims that LJA Engineering failed to model the performance of that connecting channel.

Diagram from consultant’s report.

If the design of the flow at this “Corner of Chaos” is flawed, there’s little contractors can do to fix that at this point without some major re-engineering.

In that regard, we should also remember that LJA designed these ponds before Atlas 14, so they will only hold approximately 60% of a 100-year rainfall as defined by Atlas 14 standards adopted in Harris County.

How Contractors are Temporarily Funneling Water into Ponds

Because storm drains are not yet installed, contractors are relying on temporary channels to intercept runoff and direct it to detention ponds.

Small ditches like one on right catch runoff and direct it to ponds for the time being.

Next Steps in Completing Detention Ponds

A modest amount of excavation remains to complete the full detention pond capacity.

But the capacity already in place should reduce flood risk compared to last year by more than 3X for storms equivalent to May 7 and September 19, 2019.

As some crews focus on completing excavation, others are putting the finishing touches on ponds. Those include concrete pilot channels, backslope interceptor swales, drain pipes, and culverts to control the rate of outflow.

Racing Against Hurricane Season

At this point, contractors are racing against time and the hurricane season. Cristobal underscores the risk of having waited for months to begin the three northern detention ponds in April. Had they begun them immediately after J. Carey Gray’s letter to Mayor Turn in October, they could easily have finished by now.

Posted by Bob Rehak on 6/4/2020 with thanks to Jeff Miller

1010 Days after Hurricane Harvey and 258 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.

Law on “Overflow Caused by Diversion of Water” and Photographic Analysis of Recent Elm Grove Flood

As I interviewed flood victims in Elm Grove last week, I constantly heard different versions of the same story. “We never flooded before. Then they changed the drainage on that land to the north of us and we flooded.” Another common theme: “Water was flowing right out of the new subdivision through our street.”

“You Can’t Flood Neighbors”

An acquaintance at Harris County Flood Control told me that its a basic tenet of Texas law that you can’t flood your neighbors. I asked him for a legal reference. He said, “Check the Texas State Water Code.” I did. It’s more than 2200 pages long. Just as I was falling asleep reading the requirements for inter-basin transfers, I stumbled on Sec. 11.086. Quite interesting, that section! It reads (in part):

“OVERFLOW CAUSED BY DIVERSION OF WATER”

(a) No person may divert or impound the natural flow of surface waters in this state, or permit a diversion or impounding by him to continue, in a manner that damages the property of another by the overflow of the water diverted or impounded.

(b) A person whose property is injured by an overflow of water caused by an unlawful diversion or impounding has remedies at law and in equity and may recover damages occasioned by the overflow.

(c) The prohibition of Subsection (a) of this section does not in any way affect the construction and maintenance of levees and other improvements to control floods, overflows, and freshets in rivers, creeks, and streams or the construction of canals for conveying water for irrigation or other purposes authorized by this code. However, this subsection does not authorize any person to construct a canal, lateral canal, or ditch that obstructs a river, creek, bayou, gully, slough, ditch, or other well-defined natural drainage.

(d) (Not applicable to Elm Grove)

Amended by Acts 1977, 65th Leg., p. 2207, ch. 870, Sec. 1, eff. Sept. 1, 1977.

In Plain Language

I’m not a lawyer and I don’t offer legal advice, but it sounds to me as if the law says:

(a) You can’t divert water in a way that damages others.

(b) Someone whose property is harmed by an overflow may recover damages.

(c) People (such as developers) can make improvements in drainage to control flooding. However, they can’t make improvements that obstruct well-defined natural drainage features such as creeks, gullies or ditches.

That last point is crucial because the developer north of Elm Grove (Figure Four Partners, LTD), reportedly filled in natural ditches or streams that worked well for generations. The replacements? Those didn’t work out so well in heavy rains last week.

A Photographic Examination of Flood Pathways

Abel Vera, the resident closest to the new development on Village Springs Drive was flooded from the street, not Taylor Gully. How can you be sure? Compare these two pictures on the inside and outside of the fence between his house and Taylor Gully.

Inside back yard fence, facing Village Springs Drive. Taylor Gully is on the other side. Photo taken on 4/8/19, two days after flood.
Outside of same fence facing gully shows no debris line. Grass is standing tall, not matted down by flood waters. These two photos in combination suggest that the primary direction of flow came from the street, not the drainage ditch.
Warning sign at end of Village Springs Drive caught flood debris rushing down the street from developer’s property. This was not just a case of water backing up from storm drains.
Vera’s vehicle was parked high on his driveway. This side faced water flowing out of the new development. The side facing away from the new development did not trap any debris. This indicates flow came from the new development. The flood was not simply from water rising in the street. It was from water flowing from the developer’s property where changes to drainage had been made.
Vera’s house is behind the trees on the right. Notice how much higher the developer’s new culvert is compared to the land around it. The height and the constriction diverted water toward Vera’s house on the right behind the trees and down Village Springs Drive.

Where Did The Water Come From?

I believe the floodwater came from rainfall on approximately 267 acres being clear cut by the developer. Had a foot of rain fallen on Vera’s property, with none coming from anywhere else, the water level would not have risen past the bottom of his driveway. His home would likely be whole today.

However, clear cutting, filling in old channels, constricting new channels and changing the slope of the land on those 267 acres all appear to have diverted water. Below is a satellite image showing the outlines of the developer’s property.

Approximate outline of land owned by Figure Four Partners LTD. This satellite image is dated 2/23/19. More land has been clear cut since then.

Let’s zoom in on the area above the culvert where the drainage ditch coming down the east side of the property makes a 120-degree turn, just above Same Way and Right Way.

Use the image below to understand the location of the images that follow.

The photo below compared to the satellite image above shows that the developer appears to have extended the ditch straight up. However, the ditch extension also appears to be clogged with debris from the clear cutting. Whether the developer stacked it there or the storm swept it there is unknown.

Facing north. The main ditch makes a 120-degree turn by the tire. You can see what appears to be a new ditch that helps drain the northern section of land in the upper right.
Here’s a telephoto shot showing the same blockage in the ditch.
Immediately to the left of the shot above, you can see how far clear cutting has progressed toward the ditch.
Turning 180 degrees and looking the other way down the ditch, toward Taylor Gully, you can see that it dead-ends halfway down the eastern boundary of the property.
At the end of the shot above, this is what you find. The entire flow of the ditch must go through what appears to be a 2-foot pipe covered with debris..

Compared to the volume of the ditch, that two-foot pipe will not carry much water in a flood. It may have been adequate when surrounded by woodlands and wetlands to sponge up any overflow. Right now though, it doesn’t feel up to the task of draining hundreds of acres of clear-cut land.

Shot while standing on edge of ditch above the pipe entrance, looking south and a little west. When water came out of the ditch above, it headed back west toward the Vera House on Village Springs Drive to find another way out.
Here you can see the force of large volume of water came out of the ditch above the pipe during the flood.

Consequences

This sequence of pictures suggests that a large volume of water coming down from the clear-cut parcel to the north, wound up being channeled back across the southern parcel and into Elm Grove. A portion of the flood also channeled through the subdivision to the east. Restrictions in both outflow channels forced water into streets and homes.

Here’s what Abel Vera’s home looked like yesterday.

There are 400 more just like it in Elm Grove.

Posted by Bob Rehak on 5/13/2019

622 Days since Hurricane Harvey

All thoughts above are opinions regarding matters of public policy and safety. They are protected by the First Amendment of the US Constitution and the Anti-SLAPP statute of the great State of Texas.