involved in the flood insurance working with HUD [Housing and Urban Development].
We did some of that, too, because flood insurance people didn't have much experience in
hydrology and hydraulics. They had a few people but very few. They weren't really
tasked to do technical studies. They were expected to use the advice and counsel of other
agencies that had the technical capability.
So they called on the Corps for a lot of the assistance. They ended up making up their
own minds, of course, what they were going to do on things. But they would ask us and
often I got involved in it because I had been close to the program. There would be
discussions on levee design and all kinds of things like that--expected probability and the
statistical array--and that's been a controversial subject between the two agencies for a
long time--about whether you use expected probability or not, and it still is. Right now,
it's raising it's head again.
But that concept was that, given that you come out with your computed probability based
on the record you have, there is a statistical technique for adjusting the results of that
analysis based on the length of your record. The length of record is a measure of the
accuracy of the results. If you get a gauge with a lot of years of record, you automatically
assume that that is better than the gauge with a shorter period of record. That may not
always be true, but over the long run that's true, of course.
So the Corps' concept was we use expected probability because if we get new data and it
changes, it's more likely to change the frequency curve one way than the other way. It's
almost assured that if you get enough additional data, the curve is going to move in one
direction. The Corps uses that because they build projects and they do economic analysis
based on what is going to happen in the future.
They try to apply all the things that they can reasonably estimate in the future to their
analysis. When they design levees, the economics, the design level, and all that sort of
thing is based on the expected probability. Even though the flood insurance people agreed
that that was a good concept, they had some practical considerations that they couldn't let
technical things get in the way of. That was, if you have people living in the floodplain,
how do you define t.he floodplain.
If you use
that may or may not change the answer, it's a question about
whether it is going to change the answer or not, they wouldn't be treating these people
fairly. Because if they say, "We moved the floodplain way out here because we think that
when we get new, more information, it's going to move out there. The people would
say,
it's not there yet so why am I penalized, I can't build in this floodplain on my
land because you've said the floodplain is here, I can't build anything. [You've] limited
use of that land, you've restricted my use, and you don't have evidence that good to prove
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