Riparian means “of or relating to the banks of a river.” To see the role of riparian vegetation in reducing erosion, one need only compare the two forks of the San Jacinto River. They provide a stark contrast. But the real story is the role of sand mining in reducing riparian vegetation.
After years of sand mining on the West Fork, much of the shoreline vegetation has been lost and the resulting erosion is staggering. Between I-45 and US59, sand miners have stripped vegetation from approximately 20 square miles of floodplain and floodway (the main channel of a river during a flood).
On the East Fork above the Caney Creek confluence, however, there are no sand mines. The vegetation is lush and the erosion is negligible. Let’s start there for a look at how nature protects us.
A perfect time and place for reflection. A nice place just to “be.”
Now, A Trip up the West Fork
Now, let’s look at the West Fork. It’s vastly different.
Same area. Note steepness of banks where vegetation can no longer take hold, perpetuating cycles of erosion.
Remnants of concrete retaining wall.
Site of a breach in sand mine dike on the West Fork. The mine discharged sediment directly into the river.
The next three images form a series.
The next two images form a before/after pair.
Union Pacific railroad traffic was disrupted for months.
Tree Loss in East End Park Has Already Started
Acres of trees in Kingwood’s East End Park have already started to die back as a result of being buried in dunes 10-15 high. I believe that sand, in large part, from the 750-acre mine upstream on Caney Creek is causing this. Piling as little as six inches of sediment around the base of a tree can kill it.
The website SF Gate describes how this die-back happens. “Soil added around a tree reduces the amount of oxygen available to the roots and slows the rate of gas exchange in and around the roots. There may be less moisture and nutrients available to the roots or too much moisture may remain around the tree’s roots. Inadequate oxygen reaching the roots or microorganisms in the soil around the roots can lead to an accumulation of chemicals that can injure tree roots. The tree’s bark may decay where soil is newly in contact with it. Damage or injury to the tree because of the added soil may not become apparent for several months or years and generally appears as a slow decline followed by death.” The same thing can happen with grasses and smaller trees along riverbanks. Once they die back and there is nothing left to bind the soil…
“Sediment is the primary pollutant expected from quarry operations.”
The Texas Commission on Environmental Quality says, “Sediment is the primary pollutant expected from quarry operations.” See page 22 of this 2012 report from the Texas Commission on environmental quality about the John Graves Scenic Riverway District on the Brazos. The TCEQ also conducted experiments showing that certain types of revegetation can reduce sediment discharge from mines by 98 percent.
These findings are consistent with Louisiana Best Management Practice Guidelines for Sand Mines. They state that grasses can reduce erosion by 99%.
In the upcoming legislative session, the Lake Houston area needs to push for the creation of a river preservation district like the John Graves. The Graves District excludes sand mines from the 100-year flood plain and floodway where most erosion happens.
All Lake-Houston-area mines are in the FLOODWAY with the exception of one. A floodway is defined as the main channel of the river during a flood. This makes the mines more susceptible to river capture and massive erosion, which can create a downward spiral as we have seen above. Eventually it can lead to loss of property.
Our preservation district would stretch from Lake Conroe to Lake Houston, the primary sources of water for two million people.
The lives, health, homes, and businesses of two million people are certainly worth as much as protecting some scenery.
Posted by Bob Rehak on 12/1/18
449 Days after Hurricane Harvey