Above-Water Portion of Mouth Bar Could Be Gone by Christmas

At the current rate that crews are removing sand from the West Fork San Jacinto Mouth Bar, the remainder of the above-water portion of this once-behemoth sand bar could be gone by Christmas. See the two pictures below. The first taken after Harvey and the second taken today.

These two shots show the West Fork mouth bar two weeks after Harvey and todaymore than three years later.

Much Yet to Dredge

Of course, even when the above water portion of the Mouth Bar is removed, that will still leave a huge portion below the surface. However, all progress is welcome.

Like an iceberg, most of a sand bar exists below the waterline. Photo taken 10/26/2020. I can’t say with certainty that this is submerged sand, or water stirred up by dredging. It seems too uniform to be the latter. Compare the picture below looking toward the WLHP bridge from a slightly different position and note how irregular the stirred-up sediment looks. Also note that the picture above was taken upstream from the current dredging.

At the start of October, the above-water (sub-aerial) extent of the mouth bar was down to the width of one excavator. Two excavators are now working toward the middle from each end. See below.

Looking WNW toward the West Lake Houston Parkway Bridge and Kings Harbor. Taken 10/26/2020.
From the wet mark on this excavator’s arm, it looks as though they are excavating up to 10 feet below the waterline. The 10-foot estimate closely agrees with the profile chart below. Taken 10/26/2020.

Like an Iceberg, Most of a Sand Bar Exists Below Water

That’s significant progress given what we started with. But much sand remains below the surface.

Tim Garfield and RD Kissling, two leading geologists now retired from one of the world’s largest oil companies, mapped the depth of the river using sonar and depth poles. They found an underwater plateau exists in this region of the river. See chart below.

The blue line represents the water surface. The gold line indicates the deepest part of the channel as you move downstream from the WLHP bridge to the FM1960 bridge. Numbers on the left scale indicate water depth. Numbers on the bottom scale indicate distance in feet downstream from the WLHP bridge.

Plans for Next Phase Still Not Revealed

FEMA has approved dredging another million cubic yards. And Dan Huberty’s amendment to SB500 in the last legislature dedicated $30 million for dredging the West Fork Mouth Bar. The City is drawing up plans, but they have not been announced yet. The last time I talked to Stephen Costello about this, he said the City was leaning toward dredging a channel somewhere south of the mouth bar. But many details remained to be worked out, such as:

  • Method of dredging (hydraulic vs. mechanical)
  • Exact location
  • Channel width
  • Finding qualified contractors
  • Bidding
  • Determining a suitable placement area, etc.

More news when its available.

Posted by Bob Rehak on 10/26/2020

1154 Days after Hurricane Harvey

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