Evaluating the influence of watershed characteristics on flood vulnerability of Markanda River basin in north-west India

Abstract

The terrain characteristics determine the hydrological response behaviour of watershed systems and have serious effect on incidence and magnitude of floods. Assessment of floods in watershed systems is one of the most complex processes in hydrological investigations. Therefore, this study evaluates the influence of watershed terrain characteristics on flood vulnerability of Markanda River basin in north-west India based on geospatial techniques coupled with field data. This basin is subjected to frequent floods during monsoons (July–September) causing heavy damage to agriculture and other infrastructure. For this study, Cartosat-1-based digital elevation model was used as input data in geographic information system to delineate the Markanda basin and its sub-basins. Subsequently, various watershed characteristics (linear, areal, shape and relief) were selected, measured, calculated and interlinked to evaluate the degree of flood vulnerability. These selected characteristics were both directly and inversely proportional to flooding behaviour. The results of these parameters were analysed and categorized into three classes using simple statistical technique, and then, rank score was assigned to each class of all selected parameters depending on its relation to flood hazard. Apart from this, flood vulnerability was recognized and categorized into high, moderate and low degree of hazard. Analysis reveals that about 7, 21 and 72% area of the basin is vulnerable to high, moderate and low degree of floods, respectively. High flood vulnerable areas are located in upper reaches where about 2.8% of human population is settled. These reaches are characterized by steep slopes, impermeable and barren surfaces and high basin relief. The accuracy of vulnerable areas was assessed through secondary data pertaining to past floods damages such as number of affected villages, households and population, economic losses, relief released, crop damages and human casualties. The findings of this study can assist disaster managers in initiating the flood mitigation measures in highly vulnerable areas of Markanda basin in north-west India.