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New Drone and Helicopter Footage Reveals How Elm Grove Disaster Unfolded

In the world of process quality-control, a consulting company named Kepner-Tregoe built a reputation for itself with a simple methodology. The foundation? When a problem appears, look for something different you did. Chances are, you’ll find the cause there.

Applying that same methodology to Elm Grove, an area that never flooded before May 7th, but which has flooded twice since then, one would have to look at the clearcut area immediately to the north, home of a new development called Woodridge Village.

Shortly after Perry Homes, its subsidiaries and contractors clearcut approximately 268 acres the problems started. But that wasn’t all the Perry gang did.

Before Harvey

They also filled in all the natural streams and wetlands that wound through the dense forest, slowing down runoff. Here’s what the area looked like before Harvey.

This is where the wetlands were (past tense).

Source: USGS. According to the Army Corps of Engineers, no one requested a jurisdictional delineation for the wetlands on this site. Normally, engineering companies request such a ruling to see if the Corps will object to the loss of valuable wetlands. So this project could have required a Corps permit that the developer never obtained.

After Clearcutting

Here’s what the same area looks like today from a helicopter facing south.

Shot taken on 9/21/19 two days after Imelda. Land slopes generally from NW to SE, funneling toward Taylor Gully at the tip of the arrow. Note the ponding water on the northwest side of the dirt pile near the base of the arrow. Depending on where rain falls within this area, it could take a different path, but the destination remains the same – Taylor Gully.

The LJA engineer who authored the Woodridge hydrology report characterized the slope on the northern section as 1% or greater. That’s confirmed by this contour map. And that slope is enough to make water move.

For the full report, click here.
This map shows that LJA Engineering knew all drainage funneled into Taylor Gully. For the full report, click here.
LJA also knew that the areas on either side of Taylor Gully in North Kingwood Forest and Elm Grove were vulnerable. Large areas were classified within the 100-year flood plain. For the full report, click here.

Post Hoc Ergo Propter Hoc

Kepner-Tregoe aside, just because something happened after something else does not automatically mean that A caused B. In logic, that assumption is called the Post hoc ergo propter hoc fallacy.  (Latin for “after this, therefore because of this.”)

Even though the Kepner-Tregoe methodology strongly suggests a linkage, do we have more direct proof that runoff from this subdivision caused the Elm Grove/North Kingwood Forest Flood on 9/19/19? Yes.

Clue #1

Well, for one thing, 75% of the detention pond capacity was supposed to be installed on that steep northern section, which is twice as big as the souther section. But none was. Or at least, none of it was fully functional.

Here’s where LJA intended it to go. It virtually ringed the western, southern and eastern sides.

This illustration shows that 234 acre feet of detention capacity should have been built on the northern section. But before Imelda, only 75.7 acre feet were actually built, all on the southern section. Less than 25% of the detention was fully functional when Imelda hit.

Out of the promised 309 acre feet of detention, only 75 acre feet actually existed before Imelda, about 25% of the eventual total. All of that was on the southern section. Despite the fact that the northern section contained far more land.

N1 detention in NW corner missing. Looking SW.
N2 Detention only partially available in SW corner. Montgomery County excavated this to a depth of approximately three feet between 2006-2008. But it needs to go much deeper to reach its detention goal. Looking West.
Where the top part of the missing N3 detention pond should be on the NE corner. Looking SE.
Where the bottom part of the missing N3 should be. A shallow trench channeled water toward Taylor Gully (out of frame in the upper right), without the benefit of any detention on the northern section to slow it down. Also looking SE.

Clue #2

When all that water reached the tree line that separates Elm Grove from Woodless Village (sic), it pushed the silt fence over. Notice the giant chunks of wood slammed up against the fence.

Silt fence that separates Woodridge Village from Elm Grove now leans toward Elm Grove.
The same thing happened on the border with Taylor Gully. When the rainfall exceeded the capacity of the detention pond, water came up out of it and pushed the silt fence near the culvert outward.
The same thing happened with the silt fence that borders North Kingwood Forest to the East. It leans toward the damaged area.

Water pushed the silt fence outward in all directions, like an exploding water balloon. This indicates the S2 pond exceeded its capacity.

Clue 3

If all this inferential evidence isn’t enough, we have direct evidence – video shot by Allyssa Harris during the flood. It shows water streaming out of the development in the background, directly into the streets of Elm Grove.

What it looked like from the Elm Grove side of the silt fence during the storm. Video courtesy of Allyssa Harris. Video looks north toward S2 detention pond from Village Springs.

This is what happened to the 75% of the runoff that the two southern detention ponds could not hold.

Clue #4

When the flood subsided, there was muck in streets, driveways, yards and homes. This was not just rainwater; it was runoff from 268 clearcut acres.

Abel Vera had to grab his car to avoid slipping in ankle-deep sediment on Village Springs.
What Village Springs looked like the day after Imelda.

Clue 5

According to the USGS gage at US59, a foot of rain fell on this 268 clearcut area on 9/19. All of it had to squeeze through the two tiny box culverts circled in the lower right. It was like aiming firehoses into a kitchen sink. Note: it’s worse than it looks. Additional acreage exists out of frame on left and right.

Likely Path of Water

As in May, water that should have been detained elsewhere rushed to S2. S2 overflowed and added to already heavy rainfall.

Broken fences, leaning grass, the location of ponding water, and erosion patterns all suggest that water followed the same routes on May 7.

It rushed to the SE corner of Woodridge, couldn’t get through the culvert, backed up, and sought ways around – via the streets of Elm Grove and North Kingwood Forest.

Likely path of water in May and September floods. Background image is from February, before S2 pond was completed.

What Should Happen Next?

In my opinion, for all the reasons listed above, as a result of clearcutting all this land without installing required detention, hundreds of families flooded for a second time in four months. Worse, the threat remains.

Perry, its subsidiaries and contractors had ideal construction weather during that time yet construction activity ground to a half almost a month ago.

That exposed hundreds of people to needless flood risk. Again. Worse, more than two months remain in hurricane season. And lawyers for the defendants in the lawsuit are dragging the case out by stonewalling production of evidence. They refuse to answer even simple questions like, “Who was in charge of this project on the day of the flood?” And “Who is your insurance company?”

Water Six Feet Deep in Places

What started as a dispute over negligence has turned into a massive public safety issue. Residents estimated water in the streets of Elm Grove reached six feet in places. That’s deep enough to sweep people away and drown them.

My Wishes for Elm Grove and North Kingwood Forest

  1. That Perry Homes settles these lawsuits immediately and makes people whole, or…
  2. That Perry Homes fast-tracks construction and completes the promised detention ponds, or…
  3. That Perry Homes puts a conservation easement on the land, donates it to the County or a conservation organization, and converts the property back to its natural state or a giant lake/detention pond.
  4. Failing any of the above, that the City of Houston or Montgomery County pulls construction permits for this property and renders it useless and valueless.

But before any of those things happen, the judge in this case may need to throw some lawyers and CEO’s in jail. If someone walked into a 7-11 and stole a loaf of bread, he would get jail time.

But steal the lives and destroy the homes of hundreds of people and what do you get? Delays.

It’s time to put a stop to this nonsense and hold people accountable.

These are my opinions on matters of public safety and concern. They are protected by the First Amendment of the US Constitution and the Anti-SLAPP statute of the Great State of Texas.

Posted by Bob Rehak on 9/23/2019 with grateful thanks to Matt Swint for his drone images, Jeff Miller for his reporting, Allyssa Harris for her video, and Daryl Palmer for arranging the helicopter from National Helicopter Service, Inc.

755 Days since Hurricane Harvey and 3 since Imelda