As mechanical dredging whittles down the part of the San Jacinto West Fork mouth bar that sticks up above water, it’s important to think about longer-term maintenance dredging. Remember three things:
How the sand got there in the first place
Why it will be redeposited over time
What the consequences will be of not removing it periodically
How Sand Got There
Most movement of sediment happens during floods. Sand and silt washes downstream from two main sources: natural and man-made.
The natural sources include erosion from river banks and beds.
So-called mouth bars are giant sand bars formed at the mouths of rivers. They form wherever a river enters an ocean, sea, estuary, lake, or reservoir. Whenever water slows, a river will deposit sediment. And it always slows when a moving body of water encounters a standing body of water. It’s a well understood geophysical process that occurs everywhere around the world. A prime example is the Mississippi delta.
Mouth bars are actually part of river delta formation. As they build up, they force a river to split.
Why Intervention Is Necessary In Populated Areas
As sediment builds up, if left alone, it will eventually choke the headwaters of the lake and form a flat swampy lowland. You can already see this beginning to happen on the East Fork San Jacinto.
Looking north at northern part of East Fork Mouth Bar, which has become vegetated. Note how it causes the river to split. The river is carving itself up into a maze of small channels. Photos taken 5/11/2020.Here’s the area immediately below the shot above. It is near the entrance of Luce Bayou to the East Fork. This area went from 18 feet deep to 3 feet after Imelda according to boaters.Photo taken 3/5/2020. Note how the newest mouth bar is forming in one of the channels formed by the previous mouth bar which has become anchored by vegetation.Looking west toward West Lake Houston Parkway Bridge and the West Fork of the San Jacinto. Note how this mouth bar also caused the river to split. Sediment is now being deposited on both sides, and will eventually cause another splitwithout more dredging.Photo taken 5/11/2020.Looking south toward FM1960 from north of the mouth bar. Notice how shallow this section of the river has become. The loss of conveyance contributes to flooding.Photo taken 5/11/2020.From Harris County Flood Control District’s page on the on-going Kingwood Area Drainage Assessment.
Part of the reason for the buildup of sediment behind the West Fork mouth bar is that Ben’s Branch and another major drainage ditch have been dumping sediment into the river there. Luckily, HCFCD is removing sediment from these and other ditches. That will help reduce the problem in the river, but not eliminate it.
Need for Maintenance Dredging
Erosion is relentless. We can do many things to minimize it (preserve wetlands, use best management practices in sand mining and construction, etc.). However, as long as rain falls, we can’t eliminate it.
To my knowledge, until the emergency West Fork dredging program began in 2018, the upper San Jacinto had never been dredged since the Lake Houston Dam was built in 1953. That’s 65 years. Over that time, sediment build up turned into a $100+ million dredging program. And that doesn’t even include flood damages which likely total another BILLION dollars according to a City estimate. Imagine all the heartbreak and misery that could have been avoided had the City budgeted $2 million for dredging each year.
Dredgers keep nibbling away at the mouth bar like an ear or corn, removing one row at a time.Photo taken 5/11/2020. Unfortunately, the effort to remove the portion of the bar above water may make people think the problem is solved, but it won’t reconnect the upstream river channel with the lake.
Imagine the:
Flood losses we could have avoided
Recreational opportunities we could have realized
Reservoir capacity we could have preserved
Home values we could have multiplied.
For all these reasons, we need to start a serious dialog about maintenance dredging. Even if it’s not every year, we need it after every flood. Think of it as a yearly insurance premium against the next disaster.
The Army Corps estimated this bar immediately downstream from River Grove Park blocked 90% of the West Fork. In the three months before the Corps removed it, River Grove flooded six times. Since then River Grove has not flooded at all.
Posted by Bob Rehak on 5/22/2020
997 Days after Hurricane Harvey
https://i0.wp.com/reduceflooding.com/wp-content/uploads/2020/05/20200511-RJR_2501.jpg?fit=1200%2C800&ssl=18001200adminadmin2020-05-22 17:58:532020-05-23 11:39:54Putting Mouth Bar Removal in Larger Context; Need for Maintenance Dredging
This is off topic, but it does affect thousands of readers, hence I’m posting this release from the City of Houston solid waste department. Please note: If your community association has private trash pickup, your schedule will vary. These dates and times affect only those with City pickup.
Solid Waste Schedule for Memorial Day/Week
Monday, May 25, 2020 (Memorial Day) CITY HOLIDAY: NO COLLECTION SERVICES. All Facilities and services closed.
Tuesday, May 26, 2020 Monday’s garbage collected, B-Week Curbside Recycling, Yard Waste and 4th Monday’s & 4th Tuesday’s Tree Waste collected. Westpark Recycling Center and Reuse Warehouse re-open. Neighborhood Depositories remain closed.
For more information about solid waste schedules, contact: Jessica Beemer at (832) 393-3008 or email districte@houstontx.gov.
Posted by Bob Rehak on 5/22/2020
997 Days after Hurricane Harvey
https://i0.wp.com/reduceflooding.com/wp-content/uploads/2020/05/Trash.jpg?fit=900%2C1200&ssl=11200900adminadmin2020-05-22 16:24:082020-05-22 16:24:33City Announces Trash Pickup Schedule for Memorial Day Week
Two days ago, Harris County Commissioner’s voted to heap another demand on the Perry Homes’ Woodridge Village purchase offer. Even though they had already sent a formal offer to Perry last week! Now, before Commissioners cut a check for $14 million to Perry Homes, they want the City of Houston to contribute up to half the construction costs of a regional detention basin, not just half the purchase price of the land. So the City’s costs went from half of $14 million to half of (potentially) $44 million. In other words, they tripled.
Despite the hiccup, however, construction crews at Woodridge Village are back in high gear. After a short rain delay, they continue to excavate all three detention ponds on the northern section.
Martin Provides Text of County’s Original Offer to Perry
“If the parties are unable to execute a mutually agreeable earnest money contract within 75 days after the date of this letter then this offer will be considered withdrawn and void.”
“If this proposed transaction is successful, the City and District (HCFCD) will work together to secure partnership funding from others to include, but not be limited to, the state and federal government in order to build the maximum flood risk reduction benefits at this site.”
The 75-day limit may be ambitious now that the City has to come up with more land (in lieu of cash) – and transfer it to the county before the deal becomes effective. (See below.)
And if other levels of government get involved, such as the State and Federal governments, that could create more delays. It took approximately 950 days to get all levels of government to the point where preliminary engineering could begin on more gates for the Lake Houston Dam. And it will take at least another three years to complete the project, assuming FEMA approves construction.
Conditions Must be Met Before Deal
Time is crucial because Commissioners made it clear Tuesday night that they want to see the City meet conditions on the sale before writing a check. They are not taking the City’s word that the City will fulfill its end of the bargain at some unspecified point in the future. They worry that could take 20 years. This was yet another crucial change in the offer that will require more time.
The County wants the money or land upfront so that it can begin work immediately and limit its potential liability.
Martin Insists Conditions are “No Problem”
Mayor Pro Tem Dave Martin insists that the City has no problem with updating drainage and floodplain regulations related to Atlas 14. Nor, he insists, will the City have a problem coming up with land in lieu of cash. However, the City Council has not yet approved either.
“It’s not necessary to take up any issue with this through a City Council vote as there is no Interlocal Agreement to vote on,” says Martin. “Until Harris County Flood Control sends us an Interlocal Agreement to vote on, we don’t take action. We understand HCFC is working on this document as we have daily communication with them.”
Perry Plows Ahead
Meanwhile, Perry contractors continue to excavate detention ponds. Here’s where things stand as of this afternoon.
N1 Pond – Contractors are excavating in a northerly direction to connect the tail of N1 to the main body of the pond.
N2 Pond – Contractors continue to expand and deepen it.
N3 Pond – Contractors are extending it south to where it connects to Taylor Gully. They’re also sloping edges.
Contractors excavating the N3 pond on the northeastern border of Woodridge. Photo taken 4/21/2020 by Jeff Miller.Miller estimates that, weather permitting, they may finish excavating N3 early next month.Of course, it will take longer than that to make the pond fully functional.Contractors excavating the N1 pond in the northwestern corner of Woodridge Village.General layout of detention ponds on Perry Homes’ property.
In addition, contractors are:
Lining more of Taylor Gully with concrete
Getting ready to connect N1 and N2
Using dirt excavated from ponds to raise other areas.
Posted by Bob Rehak on 5/21/2020with thanks to Jeff Miller for reporting and photography
996 Days since Hurricane Harvey
https://i0.wp.com/reduceflooding.com/wp-content/uploads/2020/05/20200521-RJR_3015.jpg?fit=1200%2C800&ssl=18001200adminadmin2020-05-21 21:46:382020-05-21 22:06:15Detention Pond Work Continues at Woodridge Village Despite Change in County Purchase Offer
Putting Mouth Bar Removal in Larger Context; Need for Maintenance Dredging
As mechanical dredging whittles down the part of the San Jacinto West Fork mouth bar that sticks up above water, it’s important to think about longer-term maintenance dredging. Remember three things:
How Sand Got There
Most movement of sediment happens during floods. Sand and silt washes downstream from two main sources: natural and man-made.
The natural sources include erosion from river banks and beds.
The man-made sources include the dirt that washes into your storm drain during a rain. They also include new developments and construction sites that disturb the soil without adequate safeguards like silt fencing. Finally, in our area, we also have an abundance of sand mines that pump and/or dump silty wastewater into rivers.
Why It Will Be Redeposited Over Time
So-called mouth bars are giant sand bars formed at the mouths of rivers. They form wherever a river enters an ocean, sea, estuary, lake, or reservoir. Whenever water slows, a river will deposit sediment. And it always slows when a moving body of water encounters a standing body of water. It’s a well understood geophysical process that occurs everywhere around the world. A prime example is the Mississippi delta.
Mouth bars are actually part of river delta formation. As they build up, they force a river to split.
Why Intervention Is Necessary In Populated Areas
As sediment builds up, if left alone, it will eventually choke the headwaters of the lake and form a flat swampy lowland. You can already see this beginning to happen on the East Fork San Jacinto.
Part of the reason for the buildup of sediment behind the West Fork mouth bar is that Ben’s Branch and another major drainage ditch have been dumping sediment into the river there. Luckily, HCFCD is removing sediment from these and other ditches. That will help reduce the problem in the river, but not eliminate it.
Need for Maintenance Dredging
Erosion is relentless. We can do many things to minimize it (preserve wetlands, use best management practices in sand mining and construction, etc.). However, as long as rain falls, we can’t eliminate it.
To my knowledge, until the emergency West Fork dredging program began in 2018, the upper San Jacinto had never been dredged since the Lake Houston Dam was built in 1953. That’s 65 years. Over that time, sediment build up turned into a $100+ million dredging program. And that doesn’t even include flood damages which likely total another BILLION dollars according to a City estimate. Imagine all the heartbreak and misery that could have been avoided had the City budgeted $2 million for dredging each year.
Imagine the:
For all these reasons, we need to start a serious dialog about maintenance dredging. Even if it’s not every year, we need it after every flood. Think of it as a yearly insurance premium against the next disaster.
Posted by Bob Rehak on 5/22/2020
997 Days after Hurricane Harvey
City Announces Trash Pickup Schedule for Memorial Day Week
This is off topic, but it does affect thousands of readers, hence I’m posting this release from the City of Houston solid waste department. Please note: If your community association has private trash pickup, your schedule will vary. These dates and times affect only those with City pickup.
Solid Waste Schedule for Memorial Day/Week
Monday, May 25, 2020 (Memorial Day)
CITY HOLIDAY: NO COLLECTION SERVICES. All Facilities and services closed.
Tuesday, May 26, 2020
Monday’s garbage collected, B-Week Curbside Recycling, Yard Waste and 4th Monday’s & 4th Tuesday’s Tree Waste collected. Westpark Recycling Center and Reuse Warehouse re-open. Neighborhood Depositories remain closed.
Wednesday, May 27, 2020
Tuesday’s garbage collected, B-Week Curbside Recycling, Yard Waste & 4th Wednesday’s Tree Waste collected. Neighborhood Depositories re-open.
Thursday, May 28, 2020
Thursday’s garbage collected, B-Week Curbside Recycling, Yard Waste & 4th Thursday’s Tree Waste collected.
Friday, May 29, 2020
Friday’s garbage collected, B-Week Curbside Recycling & Yard Waste collected.
For more information about solid waste schedules, contact: Jessica Beemer at (832) 393-3008 or email districte@houstontx.gov.
Posted by Bob Rehak on 5/22/2020
997 Days after Hurricane Harvey
Detention Pond Work Continues at Woodridge Village Despite Change in County Purchase Offer
Two days ago, Harris County Commissioner’s voted to heap another demand on the Perry Homes’ Woodridge Village purchase offer. Even though they had already sent a formal offer to Perry last week! Now, before Commissioners cut a check for $14 million to Perry Homes, they want the City of Houston to contribute up to half the construction costs of a regional detention basin, not just half the purchase price of the land. So the City’s costs went from half of $14 million to half of (potentially) $44 million. In other words, they tripled.
Despite the hiccup, however, construction crews at Woodridge Village are back in high gear. After a short rain delay, they continue to excavate all three detention ponds on the northern section.
Martin Provides Text of County’s Original Offer to Perry
Separately, City of Houston Mayor Pro Tem Dave Martin sent ReduceFlooding.com the County’s original offer letter on the property dated 5/14/2020. Even though the letter has been superseded by changes made in Commissioner’s Court last Tuesday, it’s interesting to note two provisions in the original purchase offer.
The 75-day limit may be ambitious now that the City has to come up with more land (in lieu of cash) – and transfer it to the county before the deal becomes effective. (See below.)
And if other levels of government get involved, such as the State and Federal governments, that could create more delays. It took approximately 950 days to get all levels of government to the point where preliminary engineering could begin on more gates for the Lake Houston Dam. And it will take at least another three years to complete the project, assuming FEMA approves construction.
Conditions Must be Met Before Deal
Time is crucial because Commissioners made it clear Tuesday night that they want to see the City meet conditions on the sale before writing a check. They are not taking the City’s word that the City will fulfill its end of the bargain at some unspecified point in the future. They worry that could take 20 years. This was yet another crucial change in the offer that will require more time.
Martin Insists Conditions are “No Problem”
Mayor Pro Tem Dave Martin insists that the City has no problem with updating drainage and floodplain regulations related to Atlas 14. Nor, he insists, will the City have a problem coming up with land in lieu of cash. However, the City Council has not yet approved either.
“It’s not necessary to take up any issue with this through a City Council vote as there is no Interlocal Agreement to vote on,” says Martin. “Until Harris County Flood Control sends us an Interlocal Agreement to vote on, we don’t take action. We understand HCFC is working on this document as we have daily communication with them.”
Perry Plows Ahead
Meanwhile, Perry contractors continue to excavate detention ponds. Here’s where things stand as of this afternoon.
In addition, contractors are:
This afternoon, Perry had approximately two dozen pieces of earth-moving equipment hard at work on the site. Perry has said that if the County and City couldn’t come up with a deal by its May 15th deadline, they would continue to try to sell the property on the private market or finish developing it themselves.
Posted by Bob Rehak on 5/21/2020 with thanks to Jeff Miller for reporting and photography
996 Days since Hurricane Harvey