On May 7th and September 19th, sediment-laden runoff from Perry Homes’ Woodridge Village development in Montgomery County flooded the streets and homes of Elm Grove Village and North Kingwood Forest. On September 26, the City of Houston wrote a cease and desist letter to Perry Homes, its subsidiaries and contractors. The letter alleged that runoff damaged the City’s sewer system and residents’ homes. It demanded that Perry Homes’ proxies stop sending sediment into the City.
After Imelda, Abel Versa had to grab his car to avoid slipping in ankle-deep sediment on Village Springs. The sediment came from Woodridge Village right behind him.
Sediment Control Measures Not Followed in Subdivision Rules and Regs
If Perry Homes and its contractors had followed all the construction regulations affecting drainage, the flooding of Elm Grove would not have happened and the letter would not have been necessary. So what went wrong? I previously reviewed the sediment control measures in the Montgomery County Subdivision Rules and Regulations. Perry Homes received seven strikes. Among the worst apparent violations:
They clearcut 268 acres when the rules say no more than 10.
They are supposed to plant temporary vegetation but haven’t.
They were supposed to make provisions for increased runoff during construction, but didn’t.
The southern section of Woodridge Village has been cleared, filled and graded since last summer. Grass could have reduced the runoff during Imelda.Photo taken on 11/4/2019.The northern section has also been mostly cleared for months, though workers are still removing piles of dead trees. This shows the area where they filled wetlands.Because no detention exist for the northern section, runoff from 188 acres is supposed to funnel through a 3′ pipe. That’s not working well in heavy rains.You can see how much loose sediment is exposed to floodwaters.
More Regulations in Drainage Criteria Manual Not Followed
Perry Homes also overlooked many provisions in the Montgomery County Drainage Criteria Manual. Twenty-two of the 175 pages also discuss erosion and sediment control (see Section 6 starting on page 85). Among the more serious omissions:
Channel Slopes Severely Eroding
Section 6.2.1 on Grass Establishment states that: “A good grass cover must be established on all areas within the right-of-way (except the channel bottom) disturbed by channel improvements or by any type of construction. An adequate grass stand on the banks helps stabilize the channel and minimize erosion caused by overbank flow and high velocities in the channel. Establishing a good grass cover requires preparing the seedbed, seeding properly. keeping the seed in place, fertilizing, and watering regularly.
The LJA Engineering report never mentions erosion or sediment control by those words. However, it does mention grass-lined and concrete-lined channels and spillways. Only one problem. The channels are not grass lined and most of the areas designated for concrete lining have yet to be lined.
The banks of detention ponds should be lined with grass. They are not. As a result, sediment is slumping to the bottom of the ponds where it is carried downstream by floodwaters.This closeup shows how severe the erosion is.
Channel Turns Not Protected
Section 6.2.3 on Minimum Erosion Protection Requirements for Bends specifies that bends in drainage ditches must be protected from erosion by grass, rip-rap, or concrete. The material depends on the radius of the curve, the type of soil, average water velocity and maximum water velocity.
Despite funneling 188 acres of sheet flow into Taylor Gulley, which narrows down into a 3-foot pipe, Perry Homes has done little to increase the channel capacity or detention for that area. Worse, the channel design which may have been adequate for forested wetlands, can no longer handle high volume overland sheet flow.
The most obvious needs are on the eastern side of the development. There, Taylor Gully makes a 120-degree turn, then two quick 90 degree turns and two 45-degree turns, all within two hundred yards. Getting dizzy? The floodwater turns 390 degrees in this area!
At each turn the banks take a beating. The full force of the floodwater slams against the far bank and erodes it.
Photo taken on 11/4/2019 along eastern boundary of the southern section of Woodridge Village. That’s North Kingwood Forest on the rightand Elm Grove on the bottom.Little wonder that this was the area hardest hit by floodingin May and September.Where the channel on the right narrows down into the black 3-foot pipe, contractors built an overflow channel into the detention pond on the left but still have not lined it with concrete. Note the severe erosion. Also note the erosion and sediment coming into the pond on the left just below the flow-constricting device in Taylor Gully. Clearly, there isn’t enough channel capacity to handle the volume of water. Photo taken on 11/4/2019, looking north.
Straight Drop Spillway Not Installed
Section 6.2.5.3 states that a straight-drop spillway should be installed in drainage channels to adjust channel gradients which are too steep for design conditions.
LJA specifies one between where detention pond N3 will be and the 120-degree turn shown above. However, neither the detention pond, nor the spillway have yet been installed. So water from the north comes barreling down the ditch on the right unchecked. The high velocity increases erosion. Here’s what it looked like after May 7th.
Same area shown above but from ground level and looking south toward Elm Grove.Rain did a lot of the excavating for Perry Homes. But unfortunately, the sediment wound up in flood victims’ homes and the City storm drains.
More Things Perry Homes Didn’t Do in the Montgomery County Drainage Manual
Contradictions in Perry Homes’ Plans
The Dirt on Perry Homes’ Soil Test
The Floodplain that Wasn’t
Posted by Bob Rehak on 11/20/2019 with help from Jeff Miller
813 Days since Hurricane Harvey and 62 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.
https://i0.wp.com/reduceflooding.com/wp-content/uploads/2019/11/RJR_4881.jpg?fit=1500%2C1000&ssl=110001500adminadmin2019-11-20 15:48:182019-11-20 16:02:51What Went Wrong, Part II: Lack of Erosion and Sediment Control Worsen Elm Grove Flooding
On May 7th and September 19th, floodwater poured out of the 268 clearcut acres of the Woodridge Village development in Montgomery County. It poured into the streets and homes of people who lived in Kingwood’s Elm Grove Village and North Kingwood Forest. That should not have happened if everything had gone according to plan and by the book. This is the first in a series about what went wrong.
In it, LJA promised that PHASE 1 would only include 30 acres on the northern part of the site. But contractors clearcut the ENTIRE northern section instead. That was approximately 188 acres. Without installing any detention ponds there.
The 30-acre mention is buried in the middle of a long paragraph. Frankly I read it several times and never snapped to its significance until Jeff Miller, an Elm Grove activist, rubbed my nose in it.
And, by the way, the 30 acres should have had 12.1 acre feet of detention, according to the plan. (See bottom of page 2 of the letter.) That equals the triangular area in the bottom left of the northern section. But in the May flood, there was nothing there to detain the water. That triangle is actually owned by Montgomery County and was excavated in 2006. One flood expert suggested that the area was already counted as detention for some other area, so it really shouldn’t count for Woodridge.
Of the three Woodridge sections outlined below, Phase One was supposed to include 58 acres in the southern (middle) section and 30 in the northern. The northern section dwarfs the others.
Gone: Everything that Could Have Slowed Runoff
Gone were the trees, underbrush and wetlands to soak up and slow down runoff. Contractors cleared six times more than LJA Engineering planned. That was a game changer. Plus those 188 clearcut acres had the steepest grade on the property. And the drainage all funneled toward the homes that flooded. Oops! Or should I say, “Duh”?
Map of original drainage on site shows which way water funneled.
It might have been a good plan. But you have to follow the plan for it to work.
Things Perry Homes Didn’t Do in the Montgomery County Drainage Manual
The Dirt on Perry Homes’ Soil Test
The Floodplain that Wasn’t
Posted by Bob Rehak on 11/19/2019, with thanks to Jeff Miller
812 Days after Hurricane Harvey and 61 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.
https://i0.wp.com/reduceflooding.com/wp-content/uploads/2019/11/RJR_4365.jpg?fit=1500%2C1000&ssl=110001500adminadmin2019-11-19 18:59:022019-11-20 15:13:50What Went Wrong: First in a Five Part Series about Woodridge Village and Elm Grove Flooding
At its November meeting, the Kingwood Service Association (KSA) Parks Committee voted to dredge the boardwalk and boat ramp areas of River Grove Park. The work, when done, will finally restore the park to full function.
Harvey Nearly Destroyed Park
Hurricane Harvey nearly destroyed River Grove Park. Thanks to KSA, the park has made a remarkable comeback. Harvey deposited sand five feet high in the parking lot. It left a wall of sand 12 feet high and a quarter mile long that blocked the drainage ditch that runs through the park and empties the western third of Kingwood. In the process, it also blocked the park’s boat ramp, only one on the West Fork. Finally, the storm deposited sand in the lagoon by the boardwalk and across the southern end of the soccer fields.
By the time the park is fully restored, repairs will have taken more than two and a half years.
Boat Ramp After Harvey
The Army Corps spent weeks opening up the drainage ditch that contains the boat ramp. Contractors dredged a 250-foot wide opening in the bar. Here’s how that area looked then and now from a satellite and helicopter.
Google Earth image from October 2017 shows the massive sand bar blocking the boat ramp and drainage ditch that empties the western third of Kingwood.How the sandbar looked from a helicopter two weeks after Harvey.
Sand Bar After Dredging
Image from 2/2019.Boats can now get through the bar, but the area immediately in front of the boat ramp is still filled with sediment.Photo taken October 2, 2019.
Even though boats can get by the sand bar now, they can’t get in and out of the water. Sediment remains around the ramp area and must be dredged. The Corps dredge was too big to maneuver in the tight space around the dock.
The Corps asked KSA not to open its boat docks in the name of safety while dredgers were still working the West Fork. Now, with dredging done and all the dredge pipe removed, KSA can work on reopening the dock.
Lagoon Also Filled with Sediment
The lagoon opposite the boardwalk filled with sediment during Harvey, too. Here’s what it looked like two weeks after Harvey.
The lagoon next to the boardwalk totally filled in with sand deposited by Hurricane Harvey. Photo also taken two weeks after Harvey.
The Association has already located a placement area for the spoils far from the river and any flood plain.
If permitted, removal of the sediment around the dock and boardwalk would begin in January.
Removal should take 6-8 weeks. Sediment will be placed on the parking lot to drain and dry. Then it will be trucked to the placement area in Humble.
The park could be fully functional again as early as March next year.
Public Soccer Fields Now Available
While working to prepare this project, KSA also restored the soccer fields which had been covered with sand several feet thick. All fields are now playable and KSA has designated two as public fields.
All in all, it’s been a remarkable comeback for a park that Harvey all but destroyed.
Posted by Bob Rehak on 11/19/2019, with grateful thanks to Dee Price and KSA
812 Days since Hurricane Harvey
https://i0.wp.com/reduceflooding.com/wp-content/uploads/2019/11/RJR_4052.jpg?fit=1500%2C1000&ssl=110001500adminadmin2019-11-18 22:11:042019-11-18 22:54:25KSA Parks Committee Votes to Dredge River Grove Park Boat Ramp and Boardwalk
What Went Wrong, Part II: Lack of Erosion and Sediment Control Worsen Elm Grove Flooding
On May 7th and September 19th, sediment-laden runoff from Perry Homes’ Woodridge Village development in Montgomery County flooded the streets and homes of Elm Grove Village and North Kingwood Forest. On September 26, the City of Houston wrote a cease and desist letter to Perry Homes, its subsidiaries and contractors. The letter alleged that runoff damaged the City’s sewer system and residents’ homes. It demanded that Perry Homes’ proxies stop sending sediment into the City.
Sediment Control Measures Not Followed in Subdivision Rules and Regs
If Perry Homes and its contractors had followed all the construction regulations affecting drainage, the flooding of Elm Grove would not have happened and the letter would not have been necessary. So what went wrong? I previously reviewed the sediment control measures in the Montgomery County Subdivision Rules and Regulations. Perry Homes received seven strikes. Among the worst apparent violations:
In fact, they have substantially completed only 23% of the permanent detention ponds for the whole subdivision despite clearcutting all 268 acres.
More Regulations in Drainage Criteria Manual Not Followed
Perry Homes also overlooked many provisions in the Montgomery County Drainage Criteria Manual. Twenty-two of the 175 pages also discuss erosion and sediment control (see Section 6 starting on page 85). Among the more serious omissions:
Channel Slopes Severely Eroding
Section 6.2.1 on Grass Establishment states that: “A good grass cover must be established on all areas within the right-of-way (except the channel bottom) disturbed by channel improvements or by any type of construction. An adequate grass stand on the banks helps stabilize the channel and minimize erosion caused by overbank flow and high velocities in the channel. Establishing a good grass cover requires preparing the seedbed, seeding properly. keeping the seed in place, fertilizing, and watering regularly.
The LJA Engineering report never mentions erosion or sediment control by those words. However, it does mention grass-lined and concrete-lined channels and spillways. Only one problem. The channels are not grass lined and most of the areas designated for concrete lining have yet to be lined.
Channel Turns Not Protected
Section 6.2.3 on Minimum Erosion Protection Requirements for Bends specifies that bends in drainage ditches must be protected from erosion by grass, rip-rap, or concrete. The material depends on the radius of the curve, the type of soil, average water velocity and maximum water velocity.
Despite funneling 188 acres of sheet flow into Taylor Gulley, which narrows down into a 3-foot pipe, Perry Homes has done little to increase the channel capacity or detention for that area. Worse, the channel design which may have been adequate for forested wetlands, can no longer handle high volume overland sheet flow.
The most obvious needs are on the eastern side of the development. There, Taylor Gully makes a 120-degree turn, then two quick 90 degree turns and two 45-degree turns, all within two hundred yards. Getting dizzy? The floodwater turns 390 degrees in this area!
At each turn the banks take a beating. The full force of the floodwater slams against the far bank and erodes it.
Straight Drop Spillway Not Installed
Section 6.2.5.3 states that a straight-drop spillway should be installed in drainage channels to adjust channel gradients which are too steep for design conditions.
LJA specifies one between where detention pond N3 will be and the 120-degree turn shown above. However, neither the detention pond, nor the spillway have yet been installed. So water from the north comes barreling down the ditch on the right unchecked. The high velocity increases erosion. Here’s what it looked like after May 7th.
Yesterday I posted about how Perry Homes was supposed to cut only 30 acres of trees on the northern section but cut 188. Still to come in this “What Went Wrong” Series:
Posted by Bob Rehak on 11/20/2019 with help from Jeff Miller
813 Days since Hurricane Harvey and 62 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.
What Went Wrong: First in a Five Part Series about Woodridge Village and Elm Grove Flooding
On May 7th and September 19th, floodwater poured out of the 268 clearcut acres of the Woodridge Village development in Montgomery County. It poured into the streets and homes of people who lived in Kingwood’s Elm Grove Village and North Kingwood Forest. That should not have happened if everything had gone according to plan and by the book. This is the first in a series about what went wrong.
Clearcutting 188 Acres Instead of 30
Let’s start with paragraph 2 of the Drainage Impact Analysis letter from LJA Engineering to the Montgomery County Engineering Department.
The 30-acre mention is buried in the middle of a long paragraph. Frankly I read it several times and never snapped to its significance until Jeff Miller, an Elm Grove activist, rubbed my nose in it.
And, by the way, the 30 acres should have had 12.1 acre feet of detention, according to the plan. (See bottom of page 2 of the letter.) That equals the triangular area in the bottom left of the northern section. But in the May flood, there was nothing there to detain the water. That triangle is actually owned by Montgomery County and was excavated in 2006. One flood expert suggested that the area was already counted as detention for some other area, so it really shouldn’t count for Woodridge.
Gone: Everything that Could Have Slowed Runoff
Gone were the trees, underbrush and wetlands to soak up and slow down runoff. Contractors cleared six times more than LJA Engineering planned. That was a game changer. Plus those 188 clearcut acres had the steepest grade on the property. And the drainage all funneled toward the homes that flooded. Oops! Or should I say, “Duh”?
It might have been a good plan. But you have to follow the plan for it to work.
Act of God or Act of Man?
Next in “What Went Wrong” Series
Next up in this series:
Posted by Bob Rehak on 11/19/2019, with thanks to Jeff Miller
812 Days after Hurricane Harvey and 61 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.
KSA Parks Committee Votes to Dredge River Grove Park Boat Ramp and Boardwalk
At its November meeting, the Kingwood Service Association (KSA) Parks Committee voted to dredge the boardwalk and boat ramp areas of River Grove Park. The work, when done, will finally restore the park to full function.
Harvey Nearly Destroyed Park
Hurricane Harvey nearly destroyed River Grove Park. Thanks to KSA, the park has made a remarkable comeback. Harvey deposited sand five feet high in the parking lot. It left a wall of sand 12 feet high and a quarter mile long that blocked the drainage ditch that runs through the park and empties the western third of Kingwood. In the process, it also blocked the park’s boat ramp, only one on the West Fork. Finally, the storm deposited sand in the lagoon by the boardwalk and across the southern end of the soccer fields.
By the time the park is fully restored, repairs will have taken more than two and a half years.
Boat Ramp After Harvey
The Army Corps spent weeks opening up the drainage ditch that contains the boat ramp. Contractors dredged a 250-foot wide opening in the bar. Here’s how that area looked then and now from a satellite and helicopter.
Sand Bar After Dredging
Even though boats can get by the sand bar now, they can’t get in and out of the water. Sediment remains around the ramp area and must be dredged. The Corps dredge was too big to maneuver in the tight space around the dock.
The Corps asked KSA not to open its boat docks in the name of safety while dredgers were still working the West Fork. Now, with dredging done and all the dredge pipe removed, KSA can work on reopening the dock.
Lagoon Also Filled with Sediment
The lagoon opposite the boardwalk filled with sediment during Harvey, too. Here’s what it looked like two weeks after Harvey.
Since then, vegetation has grown on the sand.
Timetable for Dredging
KSA is now applying for a permit to remove the sediment from both the boat dock and boardwalk areas. KSA will use mechanical rather than hydraulic dredges.
The Association has already located a placement area for the spoils far from the river and any flood plain.
If permitted, removal of the sediment around the dock and boardwalk would begin in January.
Removal should take 6-8 weeks. Sediment will be placed on the parking lot to drain and dry. Then it will be trucked to the placement area in Humble.
The park could be fully functional again as early as March next year.
Public Soccer Fields Now Available
While working to prepare this project, KSA also restored the soccer fields which had been covered with sand several feet thick. All fields are now playable and KSA has designated two as public fields.
All in all, it’s been a remarkable comeback for a park that Harvey all but destroyed.
Posted by Bob Rehak on 11/19/2019, with grateful thanks to Dee Price and KSA
812 Days since Hurricane Harvey