Analysis of Flood Frequencies in the Cauvery Valley

Abstract

Annual Peak flood records from ten subbasins in the upper reaches of the river Cauvery in southIndia were analysed. It was found That floods of longer return periods were correlated well with the drainage area of the subbasin. While the correlation for floods of Short return periods was poor. Correlation with normal annual rainfall in the subbasin was also found to be poor. Return periods for design floods based on empirical formulae, used in the region for small reservoirs (called ‘tanks’). were calculated using the fitted distributions. These are much too high in relation to the expected life of the tanks in all cases but one. This would suggest that while the majority to the tank Spillways were overdesigned, some would be underdesigned. This conclusion is also supported by the fact that breach due to inadequate spillway Capacity is rare.