Water Resources:
So you'd see if that dam needs some modification so it will pass the present day standard
of a probable maximum flood. Trying to convey the real need for doing that was a lot
harder than showing somebody that it was physically crumbling. You`d say, "Well, we've
got a bigger flood than we had before. If that big flood comes it will be overtopped and
might drown everybody downstream. The response would be "But that's rare, though--it's
not going to happen, the chances of that hitting this particular dam are rare.
We'd say, "Yes, you can do that kind of a manipulation if you want and decide how
infrequently that big flood would hit this dam if you knew how to do it, which you don't
know how to do. You can do some studies and say, "Well, this is so rare we don't need
to worry about it. The answer to that is, "Yes, but there are many dams in the United
States.
They're all over the country. Everywhere where there is a stream almost, there's a dam.
Maybe it won't hit the one you were interested in, but it's going to hit some of them
somewhere. If you don't design them all for a high level of protection, sooner or later,
some of them are going to start failing because those big floods happen here, there, and
everywhere. But it's hard to convince people. That's always been a big battle.
You'd get the economist-type people who would say, "Well, we need to do a benefit/cost
type analysis on everything we do.
That's always been the vogue in the Federal
Government. How much are we going to get back for what we spend? They force people
to do that type of an economic approach on almost everything they do, even though they
can't do it with any degree of accuracy. They require some sort of an estimate of that sort
of thing.
I used to get upset when people would start saying, "Well, they're going to do probability
estimates of floods out to the probable maximum flood which is the biggest one
Nobody knows what the probability of that is because, as we talked earlier, you only have
at most about a hundred years of records at any one location. Maybe a few hundred years
at rare places, but that won't tell you what is going to happen in terms of thousands of
years, and that's where you're dealing. I argued with them again and I said, "Suppose it's
a l0,000-year flood, as opposed to a
5 0 , 0 0 0 -flood. Which difference does it make
to you? I mean how can you tell.
If somebody tells you that that dam was designed for a l0,000-year flood and someone
else says, "Well, this other one is a better dam because this was designed for a
year flood, does that mean anything to you. It doesn't mean anything to me, so I don't
see how it can mean anything to you. But if they tell me it's designed for a bigger flood,
which can happen, then I have some feeling for the need to do that. But when they start
throwing these rare numbers at me, they don't tell you anything really.
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