Note: We modified this post to reflect feedback from Harris County Flood Control District and the San Jacinto River Authority. HCFCD provided new information showing rainfall totals far upstream. Confusion over the main point of this article also led us to clarify that rain was a contributing factor to the flood, but not the sole cause.
The flood on the East Fork of the San Jacinto last weekend (3/31/2018) crested at 66.1 ft. in New Caney. This was the 10th highest historical crest in the last 35 years – after a relatively minor rainfall event – 4.33 inches as measured on Caney Creek at 2090. That’s the only rain gage operated by the San Jacinto River Authority on the East Fork. Last weekend’s flood was also the third highest in the last 16 years on the East Fork. In fairness, it rained more upstream than at the gauge. HCFCD provided this rainfall map to show the distribution and said that rainfall averaged five inches across the watershed.
The East Fork: The Forgotten Flooding Problem
With the bulk of Kingwood’s and Humble’s population living on the West Fork of the San Jacinto River, it’s easy to forget that we have a flooding problem on the East Fork as well. The “East Fork” also includes Peach Creek and Caney Creek watersheds as well as Luce Bayou. And there is no shortage of sand coming down the East Fork from the sand mine on Caney Creek. This sand exacerbates flooding problems in the Kingwood and Huffman areas.
Where Did All The Sand Come From?
The sand mine on Caney Creek in Porter upstream of Kingwood comprises approximately 600 acres. The area where they stockpile sand for shipment comprises approximately 34 acres. The image below, taken on 9/14/17 shows how high the sand stockpile is relative to the height of surrounding trees.
The next image shows what happened to this stockpile during Harvey. At the top right, you can see how torrential rains eroded the pile. They washed sand down to the bottom left where floodwaters carried it downstream. Note the erosion patterns in the flat area to the left (closest to Caney Creek).
Just downstream from this sand mine, one can see sand in the tree tops. It appeared there suddenly after Harvey. The sand in the trees reaches an estimated 20 feet. The giant new sand dune in the river reaches an estimated 15 feet.
Approximately 30 acres of East End Park, in the background to the right, also flooded with sand. At Eagle Point in the Park, sand dunes exceeded 10 feet and covered approximately a half mile of trails with sand that reached shoulder height at times.
Historical Satellite Images Show Increase in Sand Volume
Some people ask, “Could the sand have come from the creek itself?” Fair question. These historical satellite images help answer it. The first satellite image of this area dates to 4/28/2014. At that point, the mine largely constrained the sand within its perimeter. You see only several small white dunes between it and East End Park, outlined in red.
In January of 2017 before Harvey, Caney Creek (see below) still contained relatively little sand. So far, so good.
After Harvey, in October, 2017, we see a radical change in the volume of sand downstream from the mine. Images taken from the helicopter and from the ground (far above) show the depth of these sand dunes. They appeared immediately after Harvey. In real life, the little white streaks in the creek stretch hundreds of feet and reach tree top height. Moreover, both ground level and helicopter photos show that much sand was hidden from satellite view by the tree canopy.
Effect of Siltation on Caney Creek and East Fork
One question remains – the most important one! How has all this sand affected the flow of Caney Creek and the East Fork? The answer: much like the sand on the West Fork has.
Smaller rains have produced bigger floods because the carrying capacity of the river has been reduced.
How You Can Help
Please contact all Harris County commissioners and the county judge. Their email addresses are on the Links page. Ask them to make sure they have enough money in the upcoming bond election to dredge BOTH the East and West Forks of the San Jacinto. Currently, they are only contemplating dredging the West Fork between US59 and West Lake Houston Parkway.
Bill Fowler, co-chair of the Kingwood Grass-Roots Flood Initiative found these statistics. Our thanks to Bill.
Posted on 4/3/18, 217 days since Hurricane Harvey.
Revised 4/10/18, 224 days since Hurricane Harvey.