TN-71 : Use of paleoflood information in frequency analysis

Abstract

The study of past or ancient flood events which occurred prior to the time of human observation or direct measurement by modern hydrologic procedures, is termed as paleoflood hydrology. Recent studies have suggested that analysis of slack water deposits and paleostage indicators alongwith techniques for using radio carbon dating and flood frequency analysis can lead to optimum use of such information in estimation of design flood. This has led to a number of studies to develop and study procedures for using historical and pale hydrologic information in flood frequency analysis.

The main objective of this report is to bring out the recent developments and status in this area. It is seen that the methodology developed for use of historical floods could be applied for paleoflood information. The USWRC Guidelines treated the historical information by using weighting procedure and adjustment of parameters. Recent developments in this area treat the observed peak flood series together with historic information as a censored sample and recommend use of maximum likelihood estimators. Most of the studies on inter comparison of different approaches for single site and regional flood frequency analysis are based upon Monte Carlo simulation experiments.

Peninsular rivers in India with deep entrenched gorges are suitable study areas for application of techniques of pale hydrology. When carefully employed with stationary flood records and appropriate and robust statistical procedures, historical information is quite useful. This critical review of literature also brings out the need for case studies including development of statistical procedures. Further research is also needed on dating techniques and error analysis of paleoflood discharge calculations.