A 1949 map of the area now called Kingwood reveals that the homes in Elm Grove that flooded on May 7 were built in something once called the Odom Lake Swamp. It turns out, “Nature never forgets.”
Area of interest for this discussion is circled in red.
I previously posted about this map in the context of how the West Fork has shifted over time. At the end of the post, I asked readers to write me if they found anything else interesting. One did. And it was a very interesting indeed.
He pointed to the area circled in red above. When I superimposed that over the present-day image below, my jaw dropped.
Same general area that was superimposed over old map.
It’s True. Nature Never Forgets
The area labelled Odom Lake Swamp matches very closely the outline of the May 7 flood in Elm Grove that damaged almost 200 homes.
I used the county line and the confluence of the East and West Forks to align the two images, then cropped this out of the center.
The reader who reported this came up with a slightly different map that shifts the label “Odom Lake Swamp” to the west side of Village Springs. I am not sure what alignment points he used, but his work and mine closely match.
At a Houston Geological Society seminar on flooding that I attended last year, I remember several speakers talking about this phenomenon, including former Harris County Judge Ed Emmett. During heavy rainfalls, water gravitates toward its original channels.
One expert, who talked to me on condition of anonymity because of the lawsuits swirling around this issue, explained it this way. “Where old channels, swamps, meanders, etc. were filled in, during major floods, water always seeks the lowest point. Even if you fill in an area, it usually is still the lowest point of a larger area (or watershed) and during large rain storms, the water finds its way there.”
Current Flood Map Echoes 1949 Map
He attributed the Elm Grove flooding to a combination of clear cutting without mitigation upstream, heavy rainfall, and lower elevation. In fact, FEMA’s National Flood Hazard Layer Viewer shows that this part of Elm Grove is in the 100-year (aqua) and 500-year flood plains.
I’m not a lawyer and I don’t give legal advice, but it seems to me that this finding does little to change the legal lay of the land (no pun intended).
The residents south and east of Woodridge Village, despite being lower than surrounding areas, had never flooded before – even in Harvey.
Had those ponds been in place, they should have held 13 inches of rain (a 100-year) rainfall. We didn’t get that much. The gage at US59 recorded 6.24 inches on May 7 over six hours. The heaviest rain fell during the noon hour when we got 3.64 inches.
From HarrisCountyFWS.org for May 7. The other official nearby gage at West Lake Houston Parkway received less rain that day.
Harris County meteorologist Jeff Lindner characterized the May 7th event as somewhere between a two and 50-year rain. Experiment with the different possibilities on the chart below.
NOAA Atlas 14 precipitation frequency chart.
Ten Lessons of May 7th
So aside from the Odom Lake Swamp being a historical curiosity, what can readers learn from this.
Flooding doesn’t always come from the river. Streets can flood homes when the rainfall rate exceeds the capacity of storm drains.
Before you buy a home, check historical maps. Learn whether the developer filled in lakes, ponds, swamps, or wetlands and then built your home on top of them. Remember: Nature never forgets!
If the answer is yes, question how much you want the property. Use the knowledge to negotiate a discount with which you can purchase flood insurance. That’s the best way to discourage unsafe development practices.
If you live downstream of an undeveloped area, be aware that floodplains are a shifting target. Just because you’re NOT in a floodplain today is no guarantee that you won’t be tomorrow. Upstream development can cause downstream flooding. So watch carefully.
Pay no attention to anyone who says, “Oh, that area will never be developed.” The more worthless the land, the bigger the profit potential.
If you live in this area, get flood insurance.
If you buy a low-lying home, be prepared to have your life disrupted.
Buyer beware.
Pressure your elected representatives to turn areas such as Woodridge Village into park land. When it was wetlands, it protected the people downstream from flooding and provided recreation.
Buying the property north of Elm Grove could have cost less than the damage to one home. (See appraisal below). Not buying the property was a costly decision.
Ironically, the Montgomery County appraisal district values the 60+ acres of land north of Elm Grove at about a quarter million dollars.
Posted by Bob Rehak on 6/19/2019
659 Days since Hurricane Harvey
https://i0.wp.com/reduceflooding.com/wp-content/uploads/2019/06/Elm-Grove-Circled-1949.jpg?fit=1500%2C978&ssl=19781500adminadmin2019-06-19 18:25:082019-06-20 13:38:14Nature Never Forgets: Lessons of May 7th Flooding
Tonight, the Lake Houston area is under yet another flash flood watch. Residents of North Kingwood Forest and Elm Grove are wondering whether a new detention pond in Woodridge Village will be enough to protect them.
Another 1-4 Inches of Rain Possible
We may get another chance to test the engineering on the detention ponds in that new Woodridge Village under development in Montgomery County. Our area received 1-3″ of rain today and more is on the way tonight. The area remains under a flash flood watch until 7a.m. Monday morning.
Heavy rainfall and severe thunderstorms will be possible tonight into early Monday.
Jeff Lindner, Harris County Meteorologist warned at 8:30 p.m. Sunday night that, “Numerous thunderstorms are in progress over portions of Liberty, Harris, and Montgomery Counties. Heavy rainfall is the main threat with these cells with recent HCFCD gages in SE Montgomery County recording 2.60 inches in 1 hour. Additional rainfall amounts tonight of 1-2 inches with isolated totals of up to 4 inches are possible.”
The storms appear to be fast moving so the higher totals are less likely than in early May when approximately 200 homes flooded in Elm Grove and North Kingwood Forest just south and east of the area that Woodridge contractors had clearcut.
Role of Detention Pond in Reducing Flood Potential
Had the Woodridge Village S2 Detention Pond been excavated before May 7, it might have prevented much of the flooding. But despite the land being cleared for approximately six months, the pond had not yet been built. LJA Engineers designed the pond to hold 50 acre-feet of runoff. What does that mean?
How Much is An Acre Foot?
One acre foot would cover an entire acre to a depth of one foot. An acre is about the size of a football field. That means 50 acre feet would cover:
One football field to a depth of 50 feet
50 football fields to a depth of one foot
Or, in the case, of this pond, about 3.5 acres to a depth of about 15 feet.
The pictures below show what it looks like today. Very little of this area was excavated on May 7.
S2 has the shape of a hockey stick. Here’s the “face” of the stick. It took a 14mm super-wide-angle lens to get the width of this pond in the frame.This conveys its width but does not adequately convey its depth.This panoramic image was stitched together in Photoshop from seven still images taken with a normal focal length lens. It more accurately conveys the height of the sides. But there’s still nothing in the frame to communicate scale.Although the sides don’t look tall in the previous photo, this is what they look like when you turn and face them. This shot was taken while standing near the bottom. My eye level is more than six feet high and didn’t come halfway up the slope.This notch in the wall of the pond allows water from the ditch behind the grass to overflow into the pond instead of flooding North Kingwood Forest (behind the tree line. That’s the theory anyway … if the calculations are correct.The red circle shows the location of the notch between the pond and drainage ditch beyond it.
Hopefully, the amount of detention in place tonight is enough to handle the rain we get.
Posted by Bob Rehak on 6/16/2019
656 Days after Hurricane Harvey
Thoughts expressed in this post represent my opinions on 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.
https://i0.wp.com/reduceflooding.com/wp-content/uploads/2019/06/Woodridge6.17.19_01_01.jpg?fit=1500%2C1000&ssl=110001500adminadmin2019-06-16 22:40:432019-06-16 22:43:09Flash Flood Watch in Effect Until 7 a.m. Monday; Luckily, Woodridge Detention Pond Nearing Completion
Officials close to the project say actual dredging could start as early as next week. Dredgers only need more 24″ pipe to pump the sediment 10 miles back upstream to placement area #2, an old sand pit near Kingwood College. However, the City and Corps are still debating the volume deposited by Harvey. The Corps has not yet divulged where it plans to start dredging, what its objectives are for this phase of the project, or what the contributions of other partners will be.
New Drone Video of Mouth Bar by Jim Zura of Zura Productions
New drone footage of the West Fork mouth bar shows just how much the mouth bar has grown since Harvey. I took the still shot immediately below from a helicopter two weeks after Harvey. To see what it looks like today, scroll down. Kingwood-based Jim Zura of Zura Productions shot two new drone videos this morning. They show what the mouth bar looks like 22 months later. As you watch the videos shot from different elevations, consider the immensity of the bar compared to the dredge at the tail end of each video.
Five hundred thousand cubic yards will not come close to restoring the full conveyance of the West Fork. How does 500,000 cubic yards compare with what NEEDS to be dredged?
Let’s start by looking at the channel that the Corps is dredging upriver and assume that they will extend that between the mouth bar and Atascocita Point. That strategy follows the relict channel. The relict channel is also the path with the least sediment at the moment. So that would make the most efficient use of funds.
Let’s also assume that the channel needs to be dredged an average of five yards (15 feet) deeper than its current depth along that path in order to match the profile below.
Endpoint of current dredge program shows channel 22.5′ deep by 400′ wide..
A “budget” of 500,000 cubic yards would allow you to dredge a channel 133 yards (400 feet) wide 5 yards deeper and 752 yards long. That equals 500,080 cubic yards. But 752 linear yards is only about one-fourth of the 3,000+ yards to the FM1960 bridge. And we haven’t even touched the mouth bar!
West Fork Map shows difference in sedimentation between 2010 and 2017. Note the white and violet areas near the FM1960 bridge. Red/orange/yellow/green areas represent decreases in sediment. Blue, violet and white represent increases.
Clearly, dredging the rest of the way to the bridge will require more money from the State, County and/or City. Thankfully for the Lake Houston Area, all of those entities have already allocated funds.
Details Yet to Work Out
However, the City, Harris County, and State of Texas have even more hurdles to clear beyond the volume debate.
They must find a suitable storage site that can accommodate all the sediment they hope to dredge. The storage site represents the biggest obstacle at the moment and a limiting factor.
The Corps would prefer a below ground site, i.e., an abandoned sand pit. That would reduce the risk of future floods carrying sediment back into the river. Also, it would NOT encroach on the flood plain.
Finally, the closer the site is to the dredging, the faster and cheaper the project. Long pipelines lead to more breakdowns. And each additional booster pump uses 1000 gallons of diesel per day.
Latest on Madden Property
The largest property evaluated so far is a 4000-acre site owned by Berry Madden of Humble. Madden’s property is close – half the distance of the sand mine on Sorters Road. It is also large enough to accommodate all the sediment people want to remove – including sediment from maintenance dredging down the road. Permitting one property instead of several would save lots of time (perhaps years).
But storage on Madden’s property would be above ground. Until someone builds on it, that introduces an element of risk that below-ground storage does not have. Madden has conducted an environmental survey of his property and is now conducting an archeological survey required for a storage permit. The Corps has not yet approved his property.
A source close to negotiations says the Corps is considering approving half of the Madden site for now while it performs additional evaluations of the rest of the site. That might be enough to accommodate immediate needs, reduce the cost of pumping sediment ten miles upstream, and provide storage room for future maintenance dredging.
80,000 CY More Sediment Deposited Since Last Survey
Meanwhile, time and sediment march on. Sources say the Corps recently found another 80,000 cubic yards of sediment deposited in the mouth bar area since the last survey after Harvey.
This supports the theory of two top local geologists, RD Kissling and Tim Garfield, who predicted that the mouth bar would form a dam that accelerated sedimentation. That theory also explains why the mouth bar must be removed, or at least why we must dredge a channel around it ASAP.
Posted by Bob Rehak on 6/18/2019with drone footage courtesy of Jim Zura, Zura Productions
658 Days since Hurricane Harvey
https://i0.wp.com/reduceflooding.com/wp-content/uploads/2019/06/FirstDroneVideo.jpg?fit=1500%2C839&ssl=18391500adminadmin2019-06-16 12:55:552019-06-18 17:39:41Dredge Finally Reaches Mouth Bar
Nature Never Forgets: Lessons of May 7th Flooding
A 1949 map of the area now called Kingwood reveals that the homes in Elm Grove that flooded on May 7 were built in something once called the Odom Lake Swamp. It turns out, “Nature never forgets.”
I previously posted about this map in the context of how the West Fork has shifted over time. At the end of the post, I asked readers to write me if they found anything else interesting. One did. And it was a very interesting indeed.
He pointed to the area circled in red above. When I superimposed that over the present-day image below, my jaw dropped.
It’s True. Nature Never Forgets
The area labelled Odom Lake Swamp matches very closely the outline of the May 7 flood in Elm Grove that damaged almost 200 homes.
One expert, who talked to me on condition of anonymity because of the lawsuits swirling around this issue, explained it this way. “Where old channels, swamps, meanders, etc. were filled in, during major floods, water always seeks the lowest point. Even if you fill in an area, it usually is still the lowest point of a larger area (or watershed) and during large rain storms, the water finds its way there.”
Current Flood Map Echoes 1949 Map
He attributed the Elm Grove flooding to a combination of clear cutting without mitigation upstream, heavy rainfall, and lower elevation. In fact, FEMA’s National Flood Hazard Layer Viewer shows that this part of Elm Grove is in the 100-year (aqua) and 500-year flood plains.
Implications
I’m not a lawyer and I don’t give legal advice, but it seems to me that this finding does little to change the legal lay of the land (no pun intended).
The residents south and east of Woodridge Village, despite being lower than surrounding areas, had never flooded before – even in Harvey.
They didn’t flood until the developer clearcut 268 acres, filled in natural streams, eliminated wetlands that act like natural detention ponds, and graded the property toward the area that flooded. All without constructing detention ponds until AFTER people flooded.
Had those ponds been in place, they should have held 13 inches of rain (a 100-year) rainfall. We didn’t get that much. The gage at US59 recorded 6.24 inches on May 7 over six hours. The heaviest rain fell during the noon hour when we got 3.64 inches.
Harris County meteorologist Jeff Lindner characterized the May 7th event as somewhere between a two and 50-year rain. Experiment with the different possibilities on the chart below.
Ten Lessons of May 7th
So aside from the Odom Lake Swamp being a historical curiosity, what can readers learn from this.
Posted by Bob Rehak on 6/19/2019
659 Days since Hurricane Harvey
Flash Flood Watch in Effect Until 7 a.m. Monday; Luckily, Woodridge Detention Pond Nearing Completion
Tonight, the Lake Houston area is under yet another flash flood watch. Residents of North Kingwood Forest and Elm Grove are wondering whether a new detention pond in Woodridge Village will be enough to protect them.
Another 1-4 Inches of Rain Possible
We may get another chance to test the engineering on the detention ponds in that new Woodridge Village under development in Montgomery County. Our area received 1-3″ of rain today and more is on the way tonight. The area remains under a flash flood watch until 7a.m. Monday morning.
Jeff Lindner, Harris County Meteorologist warned at 8:30 p.m. Sunday night that, “Numerous thunderstorms are in progress over portions of Liberty, Harris, and Montgomery Counties. Heavy rainfall is the main threat with these cells with recent HCFCD gages in SE Montgomery County recording 2.60 inches in 1 hour. Additional rainfall amounts tonight of 1-2 inches with isolated totals of up to 4 inches are possible.”
The storms appear to be fast moving so the higher totals are less likely than in early May when approximately 200 homes flooded in Elm Grove and North Kingwood Forest just south and east of the area that Woodridge contractors had clearcut.
Role of Detention Pond in Reducing Flood Potential
Had the Woodridge Village S2 Detention Pond been excavated before May 7, it might have prevented much of the flooding. But despite the land being cleared for approximately six months, the pond had not yet been built. LJA Engineers designed the pond to hold 50 acre-feet of runoff. What does that mean?
How Much is An Acre Foot?
One acre foot would cover an entire acre to a depth of one foot. An acre is about the size of a football field. That means 50 acre feet would cover:
The pictures below show what it looks like today. Very little of this area was excavated on May 7.
Hopefully, the amount of detention in place tonight is enough to handle the rain we get.
Posted by Bob Rehak on 6/16/2019
656 Days after Hurricane Harvey
Thoughts expressed in this post represent my opinions on 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.
Dredge Finally Reaches Mouth Bar
The Army Corps of Engineers announced last week that it had received a mission assignment from FEMA to dredge 500,000 cubic yards in the area of the mouth bar of the San Jacinto West Fork. This week, the dredge operated by Great Lakes was sighted within 200 yards of the bar. (See videos below.)
Dredging Could Start Next Week
Officials close to the project say actual dredging could start as early as next week. Dredgers only need more 24″ pipe to pump the sediment 10 miles back upstream to placement area #2, an old sand pit near Kingwood College. However, the City and Corps are still debating the volume deposited by Harvey. The Corps has not yet divulged where it plans to start dredging, what its objectives are for this phase of the project, or what the contributions of other partners will be.
More Meetings Needed to Finalize Volume
All parties will meet in the coming days to finalize the volume and a plan. The City of Houston and Army Corps are still 900,000 cubic yards apart in their estimates of the amount of sediment deposited by Harvey. The City hopes to get the Corps to increase its estimate of 500,000 cubic yards. However, that hasn’t happened so far. Meanwhile everyone wants to reduce flood risk by removing as much sediment as possible before the peak of hurricane season.
New Drone Video of Mouth Bar by Jim Zura of Zura Productions
New drone footage of the West Fork mouth bar shows just how much the mouth bar has grown since Harvey. I took the still shot immediately below from a helicopter two weeks after Harvey. To see what it looks like today, scroll down. Kingwood-based Jim Zura of Zura Productions shot two new drone videos this morning. They show what the mouth bar looks like 22 months later. As you watch the videos shot from different elevations, consider the immensity of the bar compared to the dredge at the tail end of each video.
How Far Would 500,000 Cubic Yards Get Us?
Five hundred thousand cubic yards will not come close to restoring the full conveyance of the West Fork. How does 500,000 cubic yards compare with what NEEDS to be dredged?
Let’s start by looking at the channel that the Corps is dredging upriver and assume that they will extend that between the mouth bar and Atascocita Point. That strategy follows the relict channel. The relict channel is also the path with the least sediment at the moment. So that would make the most efficient use of funds.
Let’s also assume that the channel needs to be dredged an average of five yards (15 feet) deeper than its current depth along that path in order to match the profile below.
Extending the channel through the bridge is important because of the sediment built up behind it.
Clearly, dredging the rest of the way to the bridge will require more money from the State, County and/or City. Thankfully for the Lake Houston Area, all of those entities have already allocated funds.
Details Yet to Work Out
However, the City, Harris County, and State of Texas have even more hurdles to clear beyond the volume debate.
The Corps would prefer a below ground site, i.e., an abandoned sand pit. That would reduce the risk of future floods carrying sediment back into the river. Also, it would NOT encroach on the flood plain.
Finally, the closer the site is to the dredging, the faster and cheaper the project. Long pipelines lead to more breakdowns. And each additional booster pump uses 1000 gallons of diesel per day.
Latest on Madden Property
The largest property evaluated so far is a 4000-acre site owned by Berry Madden of Humble. Madden’s property is close – half the distance of the sand mine on Sorters Road. It is also large enough to accommodate all the sediment people want to remove – including sediment from maintenance dredging down the road. Permitting one property instead of several would save lots of time (perhaps years).
But storage on Madden’s property would be above ground. Until someone builds on it, that introduces an element of risk that below-ground storage does not have. Madden has conducted an environmental survey of his property and is now conducting an archeological survey required for a storage permit. The Corps has not yet approved his property.
A source close to negotiations says the Corps is considering approving half of the Madden site for now while it performs additional evaluations of the rest of the site. That might be enough to accommodate immediate needs, reduce the cost of pumping sediment ten miles upstream, and provide storage room for future maintenance dredging.
80,000 CY More Sediment Deposited Since Last Survey
Meanwhile, time and sediment march on. Sources say the Corps recently found another 80,000 cubic yards of sediment deposited in the mouth bar area since the last survey after Harvey.
This supports the theory of two top local geologists, RD Kissling and Tim Garfield, who predicted that the mouth bar would form a dam that accelerated sedimentation. That theory also explains why the mouth bar must be removed, or at least why we must dredge a channel around it ASAP.
Posted by Bob Rehak on 6/18/2019 with drone footage courtesy of Jim Zura, Zura Productions
658 Days since Hurricane Harvey