ESTIMATING FLOOD FREQUENCY AND AVERAGE ANNUAL DAMAGE

In the National Research Council (NRC) report, ''Flood Risk Management and the American River Basin-An Evaluation,'' the use of expected pro bability (accounting for sampling uncertainty) in estimating flood fre quencies and average annual flood damages, as practiced by the Carps o f Engineers, was concluded to be biased. Alternative procedures recomm ended in the report are based on studies of samples drawn from a Gauss ian population with a fixed damage function. There is no extension of the study to diverse populations (many flood locations) with different flow-damage functions, but conclusions drawn are that the recommended procedures provide frequency and damage estimates that are nearly unb iased. Rationale behind the report study is examined, and it is demons trated herein that expected-probability procedures used by the Corps a re indeed appropriate for flood-frequency estimation and for estimatio n of average annual flood damages.