Vernon K.
rain to take place and all that kind of stuff.
So they got all kinds of good data from the storm study program. There were a lot of
storms studied, and the rain distribution intensity and all that stuff was developed for all
the storms. The Weather Service used that, then, as a base for working on maximum
probable floods--at the time they called them maximum possible storm. They finally
changed the name to probable maximum because they wanted to get across the idea that
it wasn't necessarily absolute you could get it but something that was reasonably possible.
So they called it probable maximum. The Weather Service worked up generalized
procedures for coming up with that rainfall.
Well, here is another area of difference between the Corps and the Bureau. The Bureau
was having a tough time supporting the cost of their projects. Doing something like this
and coming up with extreme storms to design their spillways for them or something like
that, it's going to make their projects a lot more costly.
So they weren't so sure they wanted to just go into this with everybody else and let the
Weather Service make all the decisions on the storm. So they did their own analysis of
storms out in their area. They said, "We'll do our own storm analysis and decide what
the probable maximum flood should be out here. The Weather Service has ever since
then been doing the probable maximum storms for the Corps. Then the Corps takes that
probable maximum storm and turns it into a probable maximum flood which in turn is then
used to design major dams. The whole concept of that has been questioned by people
since then but this is just what happened early on.
So what happened is that the Corps and the Bureau were working in the same area and
were getting much difference in their probable maximum floods. The Bureau's were much
smaller than the Corps'. Primarily motivated, I'm sure, by cost. They didn't want to
spend the extra money for the big spillways, so they argued that they would use all of the
logic that they could come up with to say that the storms couldn't be that big.
Whereas the Weather Service, they didn't care one way or the other what the cost was.
They just said, "Well, based on our experience and knowledge about storms, we could
move them around and the storm that happens here can happen over there and so forth."
They would maximize the storm. They moved the biggest storm in the area over to this
other location and then they would decide what this transposition did to the storm. Would
it make it rain more or less and so forth, depending on the elevation and all or the
geography of the area and all that kind of stuff. They have published a lot of documents
on how you do this sort of thing.
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