Paleoflood Hydrology and Flood Frequency Analysis

Techniques recently developed in paleohydrology enable the estimation of discharges and dates of occurrence of flood events which occurred thousands of years ago. We use computer simulation to assess whether a single paleoflood estimate, when included in a single‐site or regional flood frequency analysis procedure, gives a worthwhile increase in the accuracy of estimates of extreme floods. We find that the main factors affecting the utility of this kind of paleological information are the specification of the fitted flood frequency distribution (whether it has two or three unknown parameters) and the size of the measurement error of paleodischarge estimates. Errors in estimating the date of the paleoflood are of minor importance. We conclude that paleological information is most useful when estimating a three‐parameter flood frequency distribution for a single site possessing only a short gauged record. When several independent and homogeneous gauged records from different sites are used in a regional flood frequency analysis, the value of paleological information is, within the limits of this study, negligible.