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.

Sand Island Dredging Profile.

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