TxDOT’s Grand Parkway extension (a.k.a. State Highway 99) is rapidly moving east and south toward I-10. As it arcs around the northeast quadrant of the Houston Metro Area, it will open up vast new areas to development. Below is a map showing several already under development.
Yesterday, as I was photographing different areas near Huffman and New Caney near the San Jacinto East Fork, I captured these shots of the Grand Parkway extension and FM1485. The Grand Parkway is still under construction in this area, but it’s rapidly getting there.
SH99 and FM 1485, looking northeast toward Colony Ridge and Liberty County.SH 99 and FM 1485 looking north with San Jacinto East Fork running through middle of frame from top to bottom.SH 99 and FM 1485 Looking east over San Jacinto East Fork
I’ve taken shots of this area before and am fascinated by the difference in the spans of the bridges. Part of what you’re seeing is the difference between standards for Farm-to-Market Roads and State Highways. But you’re also looking at the consequence of an increase in expected rainfall rates, more upstream development, and learning from experience. FM1485 frequently goes under water nowadays.
Detention Pond under Bridge: Permanent?
One of the curious things I noticed yesterday was a large detention or sediment retention pond under the bridge. TxDOT has rerouted the East Fork around it as you can see in the first and second photos. I wonder if they will keep it as a large detention pond under the freeway when they complete construction. Or whether they will return the river to its normal course and plant trees between the two roads as you see in the distance.
Stay Away During Construction
Traffic detours through this area are a nightmare. Stay away if you can. It took me an hour to get from here to Kingwood yesterday via 1485, 494 and US59 at 2:30 pm. The distance: only 7 miles as the crow flies.
Posted by Bob Rehak on 12/4/2021
1558 Days since Hurricane Harvey and 776 since Imelda
https://i0.wp.com/reduceflooding.com/wp-content/uploads/2021/12/20211203-DJI_0936.jpg?fit=1200%2C799&ssl=17991200adminadmin2021-12-04 21:06:442021-12-04 21:06:47Grand Parkway Extension is Getting There
Dredging Location as of 10/12/2021. East Fork at Mouth of Luce Bayou on right.From here, pontoons ferry the spoils back to the West Fork opposite Kingwood’s River Grove Park.East Fork Dredging as of 12/3/2021. Photo taken from Huffman side of river looking SW toward Royal Shores and the FM 1960 Bridge in the distance.
Since then, the dredgers have managed to remove about 300 feet of the tip of one sandbar blocking the mouth of Luce Bayou and Red Gully (on the left in the shot above).
Looking upstream. Lots of dredging left to do. Between Harvey and Imelda, the sandbars in this area grew approximately 4000 feet.
Note the sediment plume in the middle of the boat’s wake above. That indicates the shallowness of the river.
According to boater Josh Alberson, the depth through this reach of the river was reduced from 17 feet to about three feet between Harvey and Imelda.
Dredging: A Conveyance Issue
The dredging is far more than a recreational issue. The decreased conveyance of the river creates a sediment dam than backs water up and contributes to the flooding of homes. In fact, I passed by dozens of flooded and abandoned homes while looking for a place to launch my drone.
Mechanical Vs. Hydraulic Dredging
One can only wonder whether the City of Houston is using the right tools for the job. Even Stephen Costello, Houston’s Chief Recovery Officer, called mechanical dredging “unsustainable in the long run” when he addressed a crowd at the Kingwood Community Center on July 9.
But it may come down to a case of slow-go or no-go.
I asked a friend in the dredging business to estimate the costs of mechanical vs. hydraulic dredging. He qualified the discussion by saying that:
To even consider hydraulic dredging you need a pit to pump the material into.
He also suggested that to reduce long-term overhead costs, you want to be able to use the equipment year round and create a perpetual dredging program.
He said the ideal would be to go once around the lake and arrive back at the beginning when it was time to start all over again.
That said, he estimated that hydraulic dredging was 10X faster and one third to one fourth the cost of mechanical dredging.
With hydraulic dredging, the upfront equipment and setup costs are far higher. Mechanical dredging is far slower and more expensive.
I won’t pretend that I have the answer to the question of which is better in this case: mechanical or hydraulic.
Vendor for Long-Range Dredging Plan Due to Be Selected This Month
The submission deadline for vendors bidding on a long range dredging plan for Lake Houston was 9/23. The Request for Qualifications stated that the City hoped to put contract approval on the City Council Agenda for December and start the contract in January. The selected vendor will have two years to complete the dredging plan.
It could easily take that long to finish the East Fork Mouth Bar at the current rate.
Posted by Bob Rehak on 12/3/2021
1557 Days since Hurricane Harvey and 775 since Imelda
https://i0.wp.com/reduceflooding.com/wp-content/uploads/2021/12/20211203-DJI_0925.jpg?fit=1200%2C799&ssl=17991200adminadmin2021-12-03 18:28:162021-12-04 07:27:39Slow-Go: East Fork Dredging Still at Mouth of Luce Bayou
Stormwater detention basins work by storing excess stormwater temporarily until channels can safely carry it away. Water enters the basin quickly during heavy downpours. But the basin releases it slowly at a steady rate that channels are designed to carry. This helps reduce the risk of flooding.
Harris County is so flat that dams are not often options. Therefore, virtually all of our stormwater storage has to be excavated.
Harris County Flood Control District
Willow Water Hole Example
The Harris County Flood Control District (HCFCD) detention basins typically cover several hundred acres and service regions. Willow Water Hole just outside the southwest corner of Loop 610 on a tributary of Brays Bayou is an excellent example.
The 279-acre Willow Waterhole has six compartments. Willow is part of the Brays Bayou Federal Flood Damage Reduction Project (Project Brays), a multi-year, $550 million project that substantially reduces flooding risk in the Brays Bayou watershed. The project is a cooperative effort between the Harris County Flood Control District and the U.S. Army Corps of Engineers.
Willow Waterhole Detention Basin Complex in SW Houston has six compartments.
Why the Need?
As areas develop, buildings and concrete cover up soil, so stormwater can’t sink into the ground. Water runs off concrete faster than it does from native grasslands. When that water all hits channels, streams and bayous simultaneously from different directions, it exceeds the carrying capacity of the channel. And homes flood.
Many, but not all, new developments use stormwater detention basins to offset that negative effect.
When full, detention basins often resemble lakes. When dry, detention basins look like large excavated open space areas. The Willow Water Hole is normally dry. Yesterday, however, it contained water from recent rains and the low (seasonal rate of evaporation).
Two of the compartments bracket South Willow Drive. See location above. Note the weir (discussed below) leading to the channel.
Some systems have water in them permanently, so they resemble small lakes. These provide flood storage between the normal surface of the lake and the top of the bank. See the difference in the photograph below.
Willow Water Hole southwestern pond. Note extra capacity between the top of the water and the top of the banks.
Detention? Retention? Which is It?
A detention basin normally has a dry bottom. It holds excess stormwater temporarily.
A retention basin always has a wet bottom. It stores water indefinitely. Retention basis normally have no outlet. Evaporation and infiltration usually keep the lake levels manageable.
The Harris County Flood Control District always builds and uses detention basins. Developers more likely will use retention ponds and market the resulting “lakes” as residential amenities.
HCFCD owns approximately 70 large regional detention basin sites throughout Harris County. They supplement hundreds of smaller developer-built basins. Countywide, these basins hold billions of gallons of stormwater during heavy rainstorms.
Two northeastern retention ponds within Willow Water Hole complexon either side of South Post Oak Road.
How Water Gets In
Sometimes HCFCD designs stormwater detention basins with a weir (visible in the first and second drone photos above). The weir, or low dam, lets stormwater rising in the channel spill into the detention basin when it reaches a certain height. Other detention basins have no weirs. They are simply open to a channel. In this case, stormwater fills the basin as it rises in the channel.
But there’s also a third alternative for stormwater detention basins, i.e., those not near a channel. Storm sewers and/or sheet flow fill these detention basins. “Big pipes in – little pipes out” is the rule in this instance. The basin gets the water away from streets and homes quickly. Then lets it drain off slowly.
How Water Gets Out
HCFCD typically designs detention basins to drain by gravity, as opposed to using pumps. This lets basins function when power goes out, a frequent occurrence during floods.
In ponds that drain by gravity, depth of the drain (outfall) is dictated by the depth of the receiving channel. The rate at which stormwater drains depends on the stormwater level in the receiving channel. Typically, stormwater drains out of the detention basin after channel levels recede.
Complex engineering calculations determine the volume of stormwater that a detention basin must hold to protect surrounding homes and businesses. That volume, usually measured in acre-feet, determines the width, length and depth of a basin. The amount of time stormwater stays in a basin depends on levels in the receiving channel and how full the basin got. In Harris County, detention time is usually measured in hours, not days.
How the Process Works
Normal Flow
When there is normal flow in a bayou or channel, the detention basin is generally empty.
Initial Storm Effects
Basins begin to fill as bayous or channels rise, or as surrounding developments drain into them through storm sewers.
Capturing the Flow of a Heavy Storm
As water continues to fill the detention basin, it spreads out into the excavated area. Often culverts connect multiple “compartments” within a larger basin, as above.
Detaining the Flow
By holding water in the detention basin, it does not flood homes and businesses downstream.
Draining Detained Water
As the level of the channel recedes, the channel water level drops and lets the basin drain, but only as fast as the channel can handle it.
Back to Normal Flow
With the water level in the channel normal, the basin is once again empty and ready for the next rainstorm.
End Result
Often, HCFCD partners with local groups, such as the Houston Parks Board, to build trails around these ponds that provide a retreat from busy city life. Areas such as Willow Water Hole also provide habitat for birds. People out for a stroll or a jog may think they are in a beautiful park and not even realize the role it plays in reducing flood risk.
Grand Parkway Extension is Getting There
TxDOT’s Grand Parkway extension (a.k.a. State Highway 99) is rapidly moving east and south toward I-10. As it arcs around the northeast quadrant of the Houston Metro Area, it will open up vast new areas to development. Below is a map showing several already under development.
New Developments Already Under Way
East Fork Crossing: Tale of Two Bridges
Yesterday, as I was photographing different areas near Huffman and New Caney near the San Jacinto East Fork, I captured these shots of the Grand Parkway extension and FM1485. The Grand Parkway is still under construction in this area, but it’s rapidly getting there.
In March, this Grand Parkway in this area was nothing but dirt. By June, they were clearing land down to the Luce Bayou InterBasin Transfer Canal. Now it’s concrete as far as the eye can see. At least from the East Fork.
I’ve taken shots of this area before and am fascinated by the difference in the spans of the bridges. Part of what you’re seeing is the difference between standards for Farm-to-Market Roads and State Highways. But you’re also looking at the consequence of an increase in expected rainfall rates, more upstream development, and learning from experience. FM1485 frequently goes under water nowadays.
Detention Pond under Bridge: Permanent?
One of the curious things I noticed yesterday was a large detention or sediment retention pond under the bridge. TxDOT has rerouted the East Fork around it as you can see in the first and second photos. I wonder if they will keep it as a large detention pond under the freeway when they complete construction. Or whether they will return the river to its normal course and plant trees between the two roads as you see in the distance.
Stay Away During Construction
Traffic detours through this area are a nightmare. Stay away if you can. It took me an hour to get from here to Kingwood yesterday via 1485, 494 and US59 at 2:30 pm. The distance: only 7 miles as the crow flies.
Posted by Bob Rehak on 12/4/2021
1558 Days since Hurricane Harvey and 776 since Imelda
Slow-Go: East Fork Dredging Still at Mouth of Luce Bayou
In July, the City announced it was wrapping up West Fork dredging and starting on East Fork dredging. It took three months for the dredgers to dredge their way through the Royal Shores channel before they could even start on the East Fork. Since then, it’s been a slow-go as round trip travel times to the placement area get longer.
Since then, the dredgers have managed to remove about 300 feet of the tip of one sandbar blocking the mouth of Luce Bayou and Red Gully (on the left in the shot above).
Note the sediment plume in the middle of the boat’s wake above. That indicates the shallowness of the river.
According to boater Josh Alberson, the depth through this reach of the river was reduced from 17 feet to about three feet between Harvey and Imelda.
Dredging: A Conveyance Issue
The dredging is far more than a recreational issue. The decreased conveyance of the river creates a sediment dam than backs water up and contributes to the flooding of homes. In fact, I passed by dozens of flooded and abandoned homes while looking for a place to launch my drone.
Mechanical Vs. Hydraulic Dredging
One can only wonder whether the City of Houston is using the right tools for the job. Even Stephen Costello, Houston’s Chief Recovery Officer, called mechanical dredging “unsustainable in the long run” when he addressed a crowd at the Kingwood Community Center on July 9.
But it may come down to a case of slow-go or no-go.
I asked a friend in the dredging business to estimate the costs of mechanical vs. hydraulic dredging. He qualified the discussion by saying that:
He said the ideal would be to go once around the lake and arrive back at the beginning when it was time to start all over again.
With hydraulic dredging, the upfront equipment and setup costs are far higher. Mechanical dredging is far slower and more expensive.
This website has an excellent discussion about seven factors that drive dredging costs.
I won’t pretend that I have the answer to the question of which is better in this case: mechanical or hydraulic.
Vendor for Long-Range Dredging Plan Due to Be Selected This Month
The submission deadline for vendors bidding on a long range dredging plan for Lake Houston was 9/23. The Request for Qualifications stated that the City hoped to put contract approval on the City Council Agenda for December and start the contract in January. The selected vendor will have two years to complete the dredging plan.
It could easily take that long to finish the East Fork Mouth Bar at the current rate.
Posted by Bob Rehak on 12/3/2021
1557 Days since Hurricane Harvey and 775 since Imelda
How Stormwater Detention Basins Work
Stormwater detention basins work by storing excess stormwater temporarily until channels can safely carry it away. Water enters the basin quickly during heavy downpours. But the basin releases it slowly at a steady rate that channels are designed to carry. This helps reduce the risk of flooding.
Willow Water Hole Example
The Harris County Flood Control District (HCFCD) detention basins typically cover several hundred acres and service regions. Willow Water Hole just outside the southwest corner of Loop 610 on a tributary of Brays Bayou is an excellent example.
The 279-acre Willow Waterhole has six compartments. Willow is part of the Brays Bayou Federal Flood Damage Reduction Project (Project Brays), a multi-year, $550 million project that substantially reduces flooding risk in the Brays Bayou watershed. The project is a cooperative effort between the Harris County Flood Control District and the U.S. Army Corps of Engineers.
Why the Need?
As areas develop, buildings and concrete cover up soil, so stormwater can’t sink into the ground. Water runs off concrete faster than it does from native grasslands. When that water all hits channels, streams and bayous simultaneously from different directions, it exceeds the carrying capacity of the channel. And homes flood.
Many, but not all, new developments use stormwater detention basins to offset that negative effect.
When full, detention basins often resemble lakes. When dry, detention basins look like large excavated open space areas. The Willow Water Hole is normally dry. Yesterday, however, it contained water from recent rains and the low (seasonal rate of evaporation).
Some systems have water in them permanently, so they resemble small lakes. These provide flood storage between the normal surface of the lake and the top of the bank. See the difference in the photograph below.
Detention? Retention? Which is It?
A detention basin normally has a dry bottom. It holds excess stormwater temporarily.
A retention basin always has a wet bottom. It stores water indefinitely. Retention basis normally have no outlet. Evaporation and infiltration usually keep the lake levels manageable.
The Harris County Flood Control District always builds and uses detention basins. Developers more likely will use retention ponds and market the resulting “lakes” as residential amenities.
HCFCD owns approximately 70 large regional detention basin sites throughout Harris County. They supplement hundreds of smaller developer-built basins. Countywide, these basins hold billions of gallons of stormwater during heavy rainstorms.
How Water Gets In
Sometimes HCFCD designs stormwater detention basins with a weir (visible in the first and second drone photos above). The weir, or low dam, lets stormwater rising in the channel spill into the detention basin when it reaches a certain height. Other detention basins have no weirs. They are simply open to a channel. In this case, stormwater fills the basin as it rises in the channel.
But there’s also a third alternative for stormwater detention basins, i.e., those not near a channel. Storm sewers and/or sheet flow fill these detention basins. “Big pipes in – little pipes out” is the rule in this instance. The basin gets the water away from streets and homes quickly. Then lets it drain off slowly.
How Water Gets Out
HCFCD typically designs detention basins to drain by gravity, as opposed to using pumps. This lets basins function when power goes out, a frequent occurrence during floods.
In ponds that drain by gravity, depth of the drain (outfall) is dictated by the depth of the receiving channel. The rate at which stormwater drains depends on the stormwater level in the receiving channel. Typically, stormwater drains out of the detention basin after channel levels recede.
Complex engineering calculations determine the volume of stormwater that a detention basin must hold to protect surrounding homes and businesses. That volume, usually measured in acre-feet, determines the width, length and depth of a basin. The amount of time stormwater stays in a basin depends on levels in the receiving channel and how full the basin got. In Harris County, detention time is usually measured in hours, not days.
How the Process Works
Normal Flow
When there is normal flow in a bayou or channel, the detention basin is generally empty.
Initial Storm Effects
Basins begin to fill as bayous or channels rise, or as surrounding developments drain into them through storm sewers.
Capturing the Flow of a Heavy Storm
As water continues to fill the detention basin, it spreads out into the excavated area. Often culverts connect multiple “compartments” within a larger basin, as above.
Detaining the Flow
By holding water in the detention basin, it does not flood homes and businesses downstream.
Draining Detained Water
As the level of the channel recedes, the channel water level drops and lets the basin drain, but only as fast as the channel can handle it.
Back to Normal Flow
With the water level in the channel normal, the basin is once again empty and ready for the next rainstorm.
End Result
Often, HCFCD partners with local groups, such as the Houston Parks Board, to build trails around these ponds that provide a retreat from busy city life. Areas such as Willow Water Hole also provide habitat for birds. People out for a stroll or a jog may think they are in a beautiful park and not even realize the role it plays in reducing flood risk.
Posted by Bob Rehak on 12/2/2021 based on information provided by HCFCD
1556 Days since Hurricane Harvey