In “$12 Million Bayou Project Based Oa A Mistake,” (17 Aug 2017) Save Buffalo Bayou point out that clays in local streams are from geologic eras hundreds of thousands of years ago!
In this type of slumping on Buffalo Bayou, water—mainly from overbank flooding after big storms but also from heavy lawn watering or even heavy rains—seeps from above and saturates the loose, permeable sandy-clay layers below, causing them to become unstable. This loose sandy clay sits on top of an impermeable layer of hard, red clay of the very old Beaumont formation. When it hits the hard Beaumont clay, water percolating down from above travels sideways into the bayou, wetting the hard clay. Water running underground laterally (groundwater) on top of the hard clay likewise loosens the unstable sandy clay and makes the hard layer slick.
The Beaumont Formation was laid down in the Pleistocene. Peruse the Internet for more info.