Water Resources: Hydraulics and Hydrology
Q ..
You've mentioned cavitation erosion repeatedly as being a major problem in high-velocity
spillways, and with destructive consequences. What other kind of problems do you
in high-velocity spillways that are destructive as that?
A:
Sometimes there is a destructive problem with high-velocity spillways that have a concrete
stilling basin. For example, if a high dam having four spillway crest gates discharges with
only two gates on one side of the spillway, most of the water enters the stilling basin in
that side. The hydraulic jump would be very erratic with considerable return flow on the
other side of the stilling basin where there is no flow from the spillway. The return flow
on that side was caused by higher tailwater downstream of the stilling basin. When the
river bed and banks downstream of the stilling basin consisted of loose gravel and rock,
return flows would carry that gravel and rock into the stilling basin where it would erode
the concrete floor of the stilling basin.
The Corps had this problem occur at quite a few stilling basins. The solution was, after
the flood was gone, remove all the gravel and rock from the stilling basin, repair any
concrete erosion, remove gravel and loose rock in the downstream river channel, and, in
some cases, place some concrete or large stone protection downstream of the stilling basin.
Despite all of the modeling, some of this correction only came from practical experience
with the design.
That's right, after operation of the project.
Design Considerations: Spillway Gates
We talked about this before, but was this a matter of experimenting with various
configurations of the gates?
A:
Yes.
Q ..
It sounds like an exotic science. Let me ask you about some key projects and see if you
have any particular memories of some of these. The Arkansas-Red-White project. Were
there any particular hydraulic design problems in that project that caused you any
consternation?
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