Yesterday’s second post about the wettest AND driest decade in our lifetimes helped explain something I’ve been puzzling about. Multiple mouth bars are forming around Lake Houston. The loss of tens of thousands of trees during the drought exposed soil. One massive storm after another then washed that soil toward the lake. Voila! Mouth bars.
Diversion Ditch Blockage
We already cleared the massive side bar that blocked the mouth of Kingwood’s diversion ditch.
West Fork Blockage
The Army Corps removed about a fifth of the West Fork mouth bar.
East Fork Mouth Bar
But an East Fork Mouth Bar grew 4000 feet during Harvey and Imelda. It’s now almost blocking Luce Bayou, just as the Interbasin Transfer Project is nearing completion.
And other drainage ditches are now plugging up, too, such as the one at Walden. This is symptomatic of many ditches that empty into Lake Houston.
Here’s what it looks like from a drone from a lower altitude and angle. Video courtesy of Jack and Greg Toole.
Cause of Mouth Bars
This is not surprising for a man-made lake that’s 65 years old. Dams have a tendency to hold back sediment. Sediment drops out of suspension where the moving waters in a ditch or stream slow down as they meet the still waters of a lake.
These mouth bars increase flood risk for everyone who lives near them. They form sediment damns that restrict the conveyance of the channels behind them. That forces water up and out of the channel into people’s living rooms.
Clearing the Way for Political Solutions
So how do we get rid of these mouth bars?
State Representative Dan Huberty is organizing another dredging program that should start soon. Primary targets will be the West and perhaps East Fork Mouth mouth bars. These smaller bars represent, believe it or not, a larger problem though. They fall into a jurisdictional quagmire. Does the water body they are on belong to adjacent property owners, the City, the County, or the State?
That will determine where the money for dredging comes from. And more importantly, whether the money that is already available can be used to attack the problem when a dredge is in the lake.
The bar is in an unincorporated section of Harris County. But the City owns the shoreline, and usually the first few hundred feet of channels.
Who will take ownership of problems like Walden’s? These details still need to be worked out.
HB1824 May Help
Ironically, HB1824, which I criticized because I believe it opens the door to river sand mining, may help in cases like Walden’s. The bill allows Harris County Flood Control to take sediment from the San Jacinto and its tributaries without obtaining a permit or paying a fee as long as HCFCD deposits the sediment on private land. (Remember: Lake Houston IS the San Jacinto River.)
I suspect the Walden ditch will become precedent for how such minor tributaries are treated. Walden’s nearness to the West Fork mouth bar would argue for making it part of any dredging program there.
A new year, new challenges!
Posted by Bob Rehak on 1/1/2020 with photo and video from Jack and Greg Toole, and BCAeronautics.
855 Days since Hurricane Harvey and 104 since Imelda