Hydrological and Engineering Relevance of Flood Frequency Analysis

Abstract

The mainstream of contemporary flood frequency analysis (FFA) qualifies neither as a hydrological science nor as an engineering discipline. It is not a hydrological science because it does not analyze the frequencies of floods — it merely postulates that flood records are random samples from simple probability distributions. It is not an engineering discipline because it pays most attention to, and exerts most energy on, formal polishing of concepts which are crude by their very nature and whose basic assumptions, which have an overriding influence on design parameters, are arbitrary and are dictated by expediency rather than scientific knowledge. At best, much of flood frequency analysis is just a part of small sample theory in disguise, the term “flood” being used merely as a name for the numbers employed; at worst, it is a pretentious game draining resources both from hydrology and engineering research, and a cheap opportunity to satisfy the need of academics to publish papers and supply easy topics for graduate students who know little beyond elementary statistics, probability theory, and computer programming.

“The engineer may be asked to evaluate the risks involved in a certain project and to take effective measures for the protection of lives and property in a catastrophic eventuality. To do this intelligently, the very basis for the design is often missing or hard to obtain: this is an adequate knowledge of the mechanics of the feared phenomena. It is indeed not the engineer’s task to study natural phenomena as such: this is the task of the scientist.”

Adrian E. Scheidegger (1975)