Author(s)

A. K. Gopinath & T. Radhakrishnan

Abstract

Uninstrumented watersheds pose a problem to the practising engineers when attempts to mitigate the flood waters of these watersheds are taken up. The problems become complex when one encounters a situation where there is no demarcation available for the watersheds in a region, nor historic data available for any meteorological factors of the region. Practising engineers usually adopt unscientific rational or empirical methods for estimating the design flood. But these approaches lead to overestimation or under estimation of floods, since such approaches do not take into account the hydro-meteorological factors of the watershed under consideration. Hence a more scientific approach for flood estimation is required for a cost effective design of the stream networks. This aspect is taken up through this study. The case study pertains to mitigation of flood waters in the Onattukara region of Kerala State, India which encompasses all these complexities. Twelve micro watersheds in this region were identified and this was made possible through identification of drainage networks in the area and digitization of the same on GIS platform. A scientific approach which takes into account all the above mentioned factors for ungauged catchments and developed by Central Water Commission (CWC), Govt of India was applied for this region. To bring out the effectiveness of this method, a comparison of this method with the conventional method on estimation of flood discharge is made. The flood discharge values are estimated with the existing empirical and rational formulae (Conventional method) for this region. The comparison with that obtained from the CWC model has considerable deviation. Keywords: uninstrumented watershed, rational and empirical formulae, central water commission (CWC), drainage, geographical information system (GIS).

Keywords

uninstrumented watershed, rational and empirical formulae, central water commission (CWC), drainage, geographical information system (GIS)