Margaret S. Petersen
Yes. Joe Tiffany became Technical Director of WES in 1940 and continued in that position
A:
until 1969, I think. He was followed by Fred Brown. Gene
was head of the WES
Hydraulics Laboratory when we arrived in 1947 until his retirement in 197 1. The head of
the Mississippi Basin Model was H.G. Dewey--he was still alive a few years ago. He left
WES in the mid-'50's to head the Corps model of San Francisco Bay in Sausalito. He was
the head of the Bay model until 1959, when he became Chief of Design and Construction for
the California Department of Water Resources until retirement in 197 1. Dewey was another
exceptional engineer. Very bright. We worked directly for H.C. McGee, Dewey's assistant.
The MBM at Jackson was a part of the WES Hydraulics Laboratory.
The Mississippi Basin Model was the first really large model the Corps built, wasn't it? I
believe a smaller one had been built before.
Yes, there was a model covering the Lower Mississippi River at WES in Vicksburg. The
A:
MBM was designed specifically to assist in developing coordinated basin-wide plans for
flood control and operation of flood-control structures. We looked at the effects of levees
on flood heights, the effects of building dams in various places, and a range of maximum
releases from dams and how the releases would affect the downstream part of a stream and,
eventually, the Mississippi River. These are all conditions that could be routed theoretically
for individual streams, but for complex systems it was more reliable to do it on a model
where we could change variables one at a time and note the results.Within the Mississippi
River Basin in the early
there were existing, authorized, or proposed, approximately
200 reservoirs, several thousand miles of levees, and numerous other flood control structures.
We verified the MBM reach by reach and stream by stream to where it would reproduce
known flood elevations and flood hydrographs. This was accomplished by varying the
roughness, the number of small rough elements in the channel bed and the density and
location of folded screen wire (representing vegetation in the overbank) and so forth until the
hydrograph in the model was approximately the same as the flood hydrograph in the
prototype. In alluvial streams, the river bed changes a lot during a flood with scour and
deposition, and in a fixed-bed model such as the
a lot of little factors are lumped
together in one factor, in the roughness.
The 1952 spring flood on the Upper Missouri was the biggest spring flood they'd had, I
think, and there was great concern that it would overtop the flood walls protecting Omaha
and Council Bluffs. Irene was in charge of the Missouri River section of the MBM at that
time. Whenever we had emergency testing on the
my research unit shut down and
all of my staff would help out on the Mississippi Basin Model, because many people were
needed to read water service elevations manually at many points. We didn't have enough
automatic gauges in the model to provide the detailed water level data needed for flood
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