Tag Archive for: USGS National Map

Royal Pines Clearcutting Floods Neighbor on Less Than 1″ of Rain

As proof of how dangerous clearcutting without sufficient mitigation can be, the controversial Royal Pines development has flooded a neighbor on a rain that was less than 1″ – even as the Lake Houston area flirts with drought.

Royal Pines sits at the northern end of West Lake Houston Parkway in Montgomery County. Looking SE from NW corner on 10.31.22.

The circumstances are similar to those of a nearby development – Woodridge Village. There, clearcutting flooded Elm Grove Village and North Kingwood Forest twice in 2019. Without sufficient detention basins, sheet flow from approximately 268 acres swept through hundreds of homes. But those incidents weren’t during a drought. And the rainfalls were much heavier.

Less than an Inch of Rain

In this case, the rain fell on October 28, 2022. Harris County’s Flood Warning System recorded a peak of .72 inches of rain in an hour at the nearest gage. To put that in perspective, .72 inches is so slight that it would have had to have fallen in five minutes to qualify as a five-year rain or ten minutes to qualify as a one-year rain.

atlas 14 rainfall probabilities
NOAA’s Atlas 14 rainfall probabilities

However, the rain was spread out over about a half hour.

From Harris County Flood Warning System for West Lake Houston Parkway gage on 10/28/22.

And the soils were not saturated either. The Lake Houston Area has been in drought for much of the year. As of 11/5/22, the US Drought Monitor rated this area “abnormally dry.”

From US Drought Monitor

During the entire month before October 28, the area had received only a little more than a half inch of rain.

From Harris County Flood Warning System for month before rain in question.

Sloping Land Toward Neighbor’s House

The flooding occurred in the northwest corner of the new development. From pictures and emails supplied by the neighbor, aerial photos taken during the last several months, elevation profiles obtained from the USGS national map, and construction plans obtained via a FOIA Request, I’ve been able to piece together the following. It appears that:

  • Montgomery County asked the developer to revise its plans for a detention basin.
  • Before approval of the revisions, contractors clearcut 200+ acres.
  • Contractors filled in a natural depression that channeled runoff toward White Oak Creek and sloped the development toward the neighbor’s home.
  • Runoff from the .72-inch rain rushed toward the northwest corner of the development.
  • Silt fences funneled most of the runoff toward the corner, where it broke through the fence.
  • Runoff also seeped under the fence.
  • The runoff washed sediment across the back of the neighbor’s property toward White Oak Creek.

See the YouTube video below.

Video shot by resident on 10/28/22
Sloping mudline on silt fence shows how land had been angled toward this corner. The lower elevation used to be to the right. See discussion below.
Water and muck running onto neighbor’s property through break in corner. Water also ran underneath silt fence.
Aerial photo taken five days later on 11/2/22. Notice all the muck still in the corner and the silt deposited in the woods.

The neighbor’s property extends on a straight line beyond the left fence. Water flowed from bottom of frame toward corner.

Wider shot taken after the rain on 11.2.22 shows contractor tried to fill in trench eroded by runoff.
On 11.5.22, contractors repaired the silt fence and installed additional silt fences to slow and block runoff.

Luckily, the neighbor’s house did not flood. But a heavier rain might have flooded it.

Development Now Slopes Toward Neighbor Instead of Away

The USGS National Map shows that this area used to slope AWAY from their property, NOT TOWARD it.

Left side of image shows contour (brown line) from USGS National Map before land was cleared. Right side shows area east of the resident’s home used to slope down more than 7 feet in about 250 feet.

In this area water flows from the bottom of the frame toward the top where White Oak Creek is. Comparing the contours on the left above and depression on the right with the direction the water actually travelled confirm that contractors altered the slope of the land.

Yet Chapter 11.086 of the Texas Water Code begins “No person way divert … the natural flow of surface waters in this state, or permit a diversion … that damages the property of another …”

Missing Detention Basin

Construction plans show that the developer was supposed to have built a detention basin in the corner that flooded.

Royal Pines
Royal Pines construction plan shows detention basin in northwest corner. Also note same contour shown on USGS map above.

However, the Montgomery County Engineer’s Office has reportedly asked for changes to the design of the detention basin. A sound business practice would have been to avoid clearcutting that area until the basin could have been excavated immediately.

Montgomery County does not require the approval of construction plans before clearcutting. This story shows why that should change. Delays expose people to more flood risk.

Normally, October is the second rainiest month in Houston. We average 5.46 inches.

Clearly, the flooding shown in the pictures below could have been much worse in a normal year.

Let’s hope they get that stormwater detention basin built before heavier rains return! And let’s also hope that other contractors learn this clearcutting lesson.

Posted by Bob Rehak on 11/6/2022

1895 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.