sand island Archives - Reduce Flooding

San Jacinto West Fork Before-After Photos Show Dramatic Conveyance Improvements from Dredging

After a year of dredging, the Army Corps and its contractors are gone. Even though they didn’t get all of the West Fork Mouth Bar, they made dramatic conveyance improvements on the West Fork as these before/after photos show.

Sand Island Before Dredging

The first was a blockage that dredging contractors nicknamed “Sand Island.” It sat in the middle of the river just downstream from River Grove Park in Kingwood. According to the Corps, it blocked 90% of the river.

*Sand Island formed during Hurricane Harvey. Boats that drew 18 inches of water could not navigate upstream past this giant sandbar.* *Photo taken 9/14/2019.*

Sand Island After Dredging

*Sand Island is now Gone Island.* *Photo taken 12/3/2019.*

The Corps removed approximately 15 feet of sand over a 15 acre area that was 566.7 feet wide at its widest point. An acre is about the size of a football field. So this would be like stacking sand on a football field 225 feet high (15×15)! And that doesn’t even include the sand they removed from the channels on either side of the island in the background.

Diversion Ditch Bar Before Dredging

A second huge sand bar deposited by Harvey blocked the Kingwood Diversion Ditch, also at River Grove Park. The Diversion Ditch empties the western third of Kingwood. Approximately 600 homes flooded above this one blockage. They were in Barrington, Kingwood Cove, Trailwood, Kingwood Lakes and Kings Forest.

*Diversion Ditch (center left) was virtually closed off by a new sandbar deposited by Harvey.* *Photo taken 9/14/2017.*

Army Corps measurements show that at its highest point this bar measured 10 feet about the water surface. It forced water coming out of the ditch to make a 90 degree left turn where it then hit another downstream blockage.

Diversion Ditch Bar After Dredging

*Photo taken 10/2/2019 after dredging opened up the channel and reduced the downstream bar.*

*Photo of same area taken on 11/4/2019, but looking upstream.*

The Corps dredged a channel 150 feet wide through this bar to a depth of 35 feet above sea level. That’s about 7.5 feet below the normal water surface elevation of the Lake. The channel narrowed to 50 feet wide where it meets the mouth of the ditch.

From the highest point on the bar to the target depth, the Corps removed 17.5 vertical feet of sand. From the mouth of the channel to the outer edge of the bar measured 750 feet.

Comparison in Satellite Images from Google Earth

Here’s how this section of the river looked from a satellite BEFORE dredging. The numbers refer to the discussions above.

Here’s how it looked AFTER. (Note this image was taken on 2/23/19 and the dredge was still removing sand island.

Altogether, the Corps removed approximately 2.3 million cubic yards of sediment. Even if the Corps didn’t finish the mouth bar, that’s a lot to be grateful for. Thank you, FEMA, Army Corps, Great Lakes Dredge and Dock and Callan Marine.

Have a merry Christmas!

Posted by Bob Rehak on 12/24/2019

847 Days after Hurricane Harvey

Now You See It; Now You Don’t. Second Biggest Blockage on West Fork GONE!

These two images, taken almost two years apart, show one of the most dramatic improvements to West Fork conveyance – the removal of a giant blockage that the Army Corps nicknamed Sand Island.

Sand Island mysteriously appeared during Harvey almost overnight and virtually blocked the entire West Fork of the San Jacinto. Today, the blockage is gone as the before/after photos below show.

Taking Time to Reflect on Accomplishments

This is what Sand Island looked like two weeks after Harvey. It appeared virtually overnight. I took this shot from a helicopter.

*Facing east. Sand Island blocks the entire west fork of the San Jacinto. The Kingwood Country Club is in the upper left portion of the photo. Shot from a helicopter on 9/14/2017.*

Bayou Land Conservancy Provides the “After” Photo

Suzanne Simpson, Land Stewardship Director for the Bayou Land Conservancy, was doing a wetlands inventory with her drone near River Grove Park this morning. She captured a similar shot below of the same area.

After more than a year of dredging, Sand Island is finally gone. The Army Corps and Great Lakes have restored conveyance on this portion of the San Jacinto West Fork, immediately downstream from River Grove Park. *Shot by Suzanne Simpson with a drone on 7/18/2019.*

A Job Well Done

This pair of images shows the dramatic improvement in conveyance to this portion of the river. Kudos to the Army Corps and their contractors, especially Great Lakes, which managed this portion of dredging.

Clearing the river of blockages like these should have a dramatic impact on conveyance and help reduce future flooding.

Great Lakes is now working on the mouth bar farther downriver, while Callan Marine is dredging the area near Kings Harbor. Only the mouth bar was/is a bigger blockage on the West Fork than Sand Island.

Additional thanks go to FEMA for funding the project, the Texas Division of Emergency Management, former Congressmen Ted Poe, and the City of Houston.

Since dredging started almost a year ago, the Corps has removed 1.8 million cubic yards of sediment. That’s enough sand to fill the Astrodome.

Posted by Bob Rehak on 7/18/2019

688 Days After Hurricane Harvey

Photo of the Day #285

South of Where Romerica wants to build high rises and a marina for 640 40-boats,, Hurricane Harvey deposited this giant island that virtually blocks the West Fork of the San Jacinto River. Dredgers nicknamed this area Sand Island. It was six feet tall and backed water up into River Grove Park six times in the last year. The island has since been removed by the Army Corps.

Before and After Harvey Images Show Impact of Sediment on West Fork Flooding

Below are two videos taken by Jim Zura of Zura Productions before and after Harvey. Together with other still images, flooding statistics and the Army Corps’ Value Engineering report, they demonstrate how radically Harvey transformed the West Fork. As you review these, keep in mind that the proposed new high-rise development in this area based its engineering on pre-Harvey assumptions.

Zura, a videographer and local drone pilot, shot this first video in 2016. River Grove Park looked pristine. Beyond it, a massive clear cut area surrounds an idyllic little lake. This is where a developer plans to build a high-rise resort around a marina. The drone then rotates to reveal a river without blockages downstream, or in front of the boat docks. In just 18 months, everything would radically change.

River Grove Before Harvey and the Sand

Hurricane Harvey brought with it massive rainfalls that washed sediment downstream, clogging the West Fork. Onshore, they reached up to five feet and stretched 450 feet inland.

*Still frame from Jim’s video compared to a shot I took from a helicopter two weeks after Harvey. The angles are slightly different but they show the same location.*

Result: a park that normally floods once every over year flooded six times in one year – three times in the last month alone – 12X greater than normal.

The Reason for Increased Flooding Frequency

It’s called reduced conveyance of the river. The Army Corps documented this in its Value Engineering Study. Here are some shots I took after Harvey from a helicopter. Consider them within the context of the videos above and below. You will understand why River Grove has been near-continuously inundated for a month. I wonder how the owners of luxury high-rise condos would feel about not being able to access their property for that long.

*To get a feeling for how much sand was left in the river by Harvey, see how much lined both shores of the West Fork.*

*Sand on both side of the river stretched 450 inland after Harvey. Nearest the river, it reached 5 feet in height through this reach of the West Fork.*

A giant sand bar 12 feet high and 1500 feet long was deposited in one event: Harvey. It blocked the drainage ditch that empties the western third of Kingwood. The proposed new high-rise development would also depend on this ditch.

I fail to see how the high-rise developer filling in hundreds of additional acres of floodplain with 12-feet of fill could have zero net impact. If every engineering survey ever submitted for a flood plain development were correct, the world would have no flooding problems.

River Grove after the Christmas flood. Water went down briefly then came back up during the next flood in early January. As of today, the soccer fields were still flooded. See the area that compares to the first video at the end of this one.

Posted by Bob Rehak on 1/8/2018

497 Days after Hurricane Harvey

Sand Island Losing Ground to Army Corps

Before

After

Keith Jordan, a resident of Kingwood Lake Estates, sent me the pictures below today. They show how quickly Great Lakes Dredge and Dock and the Army Corps are reducing the giant blockage nicknamed “Sand Island” south of Kingwood Country Club. Keith generously consented to let share his pictures with you. He says that much of the island has already been brought down to the water line. It used to jut up 6-10 feet. Still, much dredging remains to reduce the portion below water and restore the conveyance of the West Fork. Progress may look greater than it actually is at the moment because of persistent flooding. As of this posting, the river is still at 46.07 feet according to the USGS gage at US59. That’s about 3.5 feet above normal.

This booster pump keeps sand moving upstream to placement area #2, an old sand mine on Sorters Road south of Kingwood College.

Dredge #2 from Great Lakes Dredge & Dock has been eating away that Sand Island since moving downstream from River Grove Park.

Much of Sand Island is now at the water level.

This wider shot gives you a good feeling for how little is left.

Hopefully, we will get more recent aerial shots from our local drone pilots soon. As the West Fork returns to its normal level, we will see exactly how much of Sand Island remains.

Posted by Bob Rehak on January 6, 2019

496 Days since Hurricane Harvey

How Government Shutdown Affects All Lake Houston Area Flood Mitigation Projects

Good news: The Emergency West Fork Dredging Project is still active. The government allocated funds for the project before the shutdown. Also, because FEMA designated it an emergency, it enjoys preferred status. Dredges are still dredging.

Bad news: Every other Lake Houston area flood mitigation project that depends on federal dollars is on hold.

Watershed study? 10 months and still waiting for approval.
Additional gates for Lake Houston? Hit the pause button.
More upstream detention. Deep freeze.
Additional dredging? Why rush it?

The Really Bad News

I’d say that’s the end of the story, but it’s not. Tonight the Associated Press reports that President Trump warns the shutdown could continue for months or years. Even considering the obvious hyperbole, I shudder to think of employees’ reactions. At a certain point, people put families and futures in front of jobs that pay zero. Maybe Trump could hold out for years. But a GS-7 with a bachelor’s degree and student loans to pay off? Someone making $35K per year?

The reason most people take a pay cut to go into government service is because it’s a steady gig. But yank that paycheck out from under them. Woooooosh! That’s the sound of talent and institutional knowledge creating a vacuum as it sprints out the door.

Rebraining Projects

A prolonged government shutdown will turn the Mo down Low. Lose momentum and you have to spend more energy to regain it. You lose time. You lose money. You lose talent. And when it’s over, you have to rebrain projects. Recruitment. Training. Getting people back up to speed. Clearing out backlogs…that could really last years.

Sweating Details and Bullets

So while the mouth bar project is on hold, dredging behind the mouth bar continues. Officials hoped they could save $18 million in demobilization and remobilization fees by having the mouth bar project ready to start when the Emergency Project finished. But that window is rapidly narrowing. Back in October, when we thought we had six months to work out details, everyone felt comfy and confident. Now with three months left, officials are sweating the details while residents sweat bullets. Here’s why.

Problems Likely to Migrate Downstream

As I discussed in yesterday’s post, River Grove Park has experienced greater-than-usual flooding. Crests usually experienced every other year now happen once every other month. The river has crested over 50 feet six times in 11 months. That’s likely due to the backwater effect created by “Sand Island” (as dredgers have named it). Sand Island virtually blocks off the river creating a backwater effect. See its location relative to River Grove below.

*The Army Corps has nicknamed the giant blockage immediately downstream from River Grove Park “Sand Island.”*

The next picture shows how this massive dune virtually blocks the entire West Fork. I took the picture two weeks after Harvey. During floods, when water moves quickly, Sand Island has created a ten-foot difference between water upstream and downstream.

*Sand Island causes higher-than-normal floods at greater -than -normal frequencies because of backwater effects.*

Great Lakes Dredge and Dock, the Corps’ prime contractor on this job has finished dredging through the side bar at River Grove . Now they are attacking Sand Island (see below).

*The focus of dredging has moved from the side bar at River Grove to Sand Island. Once removed, the flooding problems at River Grove will likely migrate downstream.*

As they remove this blockage, downstream residents in Atascocita Point have reported water rising higher in their yards during floods. Once dredgers completely remove Sand Island, flooding problems will likely migrate downstream to the next major blockage, the mouth bar.

The mouth bar virtually blocks the West Fork where it enters Lake Houston. It stretches from Kings Point to Atascocita Point, but is not within the scope of the current dredging project. Expansion of the scope has been halted by the government shutdown.

However, there’s a big difference between Sand Island and the Mouth Bar.

Parks, vacant land, and golf courses surround Sand Island.
People, kids and homes surround the Mouth Bar.

Let’s pray that the government shutdown ends quickly. In this area, government can really make a huge and important difference – immediately.

Posted by Bob Rehak on 1/5/2019

494 Days since Hurricane Harvey

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