Water Resources: Hydraulics and Hydrology
flood was excessive even though failure of that dam would cause large property damage
and lose of life. He wanted to design the dam for the 1 ,OOO-year flood.
flood was about 30 percent smaller than the probable maximum flood. I
The
said, "Let's determine the difference in the cost of the spillways designed for those two
floods.
In the initial design, most of the reservoir at Rafferty Dam was for irrigation and power.
Consideration was given to increasing the dam height to provide some flood control
storage in order to justify construction of the dam. The Corps of Engineers was interested
in this flood control storage because it would reduce the channel design flood in the
River at Minot, North Dakota.
The levee heights at Minot, which were initially constructed for a
flood, were
frequently overtopped by larger floods. The Corps was in the process of designing the
flood. Increasing the height of Rafferty Dam by about 20 feet would
levees for a
reduce the
flood at Minot to a
flood, and the levees would not need to
be raised. The estimated cost of raising the dam was million. The Corps estimated
cost of raising the levees at Minot, if no flood control storage was provided at the dam,
was about 2 million. The Corps agreed to pay the cost of raising the dam, thereby
saving million over raising the levees at Minot.
So in something like this, would the Corps or the U.S. Government transfer funds to
Saskatchewan Power?
A:
That's right. They would transfer funds.
To cover the difference between their original design and the one
Yes, for the difference in cost of the dam with and without flood control storage. The
A:
Corps has an agreement with Saskatchewan Power that it will start paying when dam
construction begins. The Corps wanted to review the plans before construction started.
That brings me to the second point I want to discuss, and that is also on Rafferty Dam.
It involves the hydraulic design of a fuse plug emergency spillway.
The initial design provided for construction of a concrete-lined spillway with a stilling
basin. When design for the maximum probable flood was accepted, this spillway had to
be greatly enlarged at a high increase in cost. I suggested that instead of enlarging the
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