Hydrometeorological dynamics of monsoon floods on the Kaveri River, Southern India

Abstract

This study aims to investigate the hydrometeorological dynamics of monsoon floods on the Kaveri River, Southern India. It encompasses the analysis of interannual rainfall variability and its correlation with floods, characterization of flood-inducing low-pressure systems (LPS), depth-area-duration (DAD) evaluation, assessment of the relationship between annual rainfall totals and flood frequencies, application of the normalized accumulated departure from mean (NADM) method to identify flood-linked anomalies, and investigation of the interplay between El Niño southern oscillation (ENSO) phenomena and monsoon rainfall patterns governing flood dynamics. The study employs a 121-year rainfall dataset, coupled with a 45-year annual maximum series for two hydrological monitoring stations, enabling long-term statistical analysis of rainfall variability and flood dynamics. The results indicate that the interannual variability in the basin is characterized by a notable increase in the frequency and magnitude of floods, particularly post-1960s. Moreover, substantial flood events coincided with periods of above-average rainfall, underscoring the significant role of rainfall anomalies in modulating flood dynamics. Intense LPS predominantly drive major floods in the basin, especially in the deltaic zone. DAD curve of 23-25 July 1924 event has contributed the highest average depth of rainfall over the basin for 1-day, 2-day and 3-day duration. Analysis of synoptic conditions associated with major floods indicate that most of the floods were associated with positive departure from mean rainfall in the basin. The NADM graphs show epochal behaviour of high and low rainfall and therefore, floods. The frequency of floods is generally high in years with normal or weak ENSO conditions.