We have neglected to highlight an important component of a spillway - the stilling basin. Today, we'd like to generate a little love for stilling basins.
A stilling basin is a structure that dissipates the energy
of the water rushing down the spillway. Without a stilling basin, water
coming out of the spillway could scour out the foundation of the dam, the base
of the spillway, and nearby creek beds. In short, the stilling basin is a sort
of bodyguard for the dam.
Stilling basins come in a variety of types, but generally
fall into two categories: a straight drop for lower elevations, or an inclined
chute. The stilling basin at the new Calaveras Dam is an example of the
latter category. To be specific, it is a United States Bureau of Reclamation (USBR)
Type II stilling basin. Our stilling basin is approximately 200 feet
long, 45 feet high and 80 feet wide.
Water flowing down the new spillway of the new Calaveras Dam
will drop 200 feet in elevation before it reaches
the stilling basin at the bottom.The stilling basin creates a hydraulic jump to
slow down the high velocity water before it slowly, and safely, discharges
into Calaveras Creek.
A view of the new stilling basin at the Calaveras Dam Replacement Project
So, let's hear it for the humble stilling basin!
See you around the Valley!
