Gilbert F. White
the floodplain thoroughly actuarial, taking into account prospective changes
in frequency of floods, which is, we now know, likely in most urban areas.
And third, encouraging the municipalities that have responsibility for the land-
use regulations to develop these regulations in connection with plans for the
use of the floodplain rather than just being obliged to meet a relatively simple
requirement from the Federal Insurance Administration. They should have
regulations that satisfy a few criteria about frequency and about rise in flood
stages as a result of encroachment.
Q: How do you take into account the so-called catastrophic flood-the once-in-
l00-years flood?
A: There was a very interesting development of the notion that there could be a
flood of sufficiently low frequency that no effort should be made to cope with
it. The Federal Insurance Administration picked one percent of a recurrence
interval of a hundred years. And some of us were involved in that because
we recognized they initially had to have some figure to use. The one-percent
flood was chosen. I think Jim Goddard and TVA colleagues would be
considered parties to the crime. With the lack of any other figure, the
concept taken from TVA's "intermediate regional flood" seemed a moderately
reasonable figure. We generally use the term "catastrophic flood" for events
of much lesser frequency.
This goes back to my earlier criticism of the FIA and its determination to
cover the country promptly. In covering the country promptly they
established one criterion--the 100-year flood. I think it would have been
much more satisfactory if they had not tried to impose a single criterion but
had recognized that there could be different criteria for different situations.
This could have been practicable administratively even though a federal
administrator would say it's far easier, cleaner, to have a single criterion that
blankets the country as a whole.
What's the effect of having a single criterion of 100 years if in doing so a
local community is encouraged to regulate any development up to that line and
then to say we don't care what happens above that line? We know that in a
community like Rapid City [South Dakota] the floods were of a lesser
frequency than 100 years, and a community ought to be aware of this
possibility.
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