Impact of Climate Change on combined Flood and Drought events in India

Abstract

Droughts and floods usually occur in all parts of the world. Several studies published previously have reported that climate change may exaggerate the severity and frequency of floods and droughts in different parts of the world. However, it is still unclear if the frequency of the co-occurrence of droughts and floods is being affected in the long term or not. Therefore, we analysed the changing characteristics of co occurrence of floods and droughts in India to understand “whether the co-occurrence of floods and droughts is increasing due to climate change?”. A copula-based joint probability-based approach is considered for analysing the changing nature of joint probabilities of compound drought-flood events in the same year. Also, we used the Standardised Weighted Average of Precipitation (SWAP) index to identify the drought and the flood events. We used gridded rainfall data of India Metrological Department at a 0.25-degree grid. This study revealed that the maximum number of grid points show an increase in monthly SWAP values in summer; however, the maximum number of grid points show a decrease in monthly SWAP values in all other seasons. However, in winter, the maximum number of grid points show a reduction in monthly SWAP values. The drought and flood analysis revealed that more grid points show decreasing value for both flood and drought return period corresponding to 5-year, 10-year, 25-year when each period is compared with its preceding period. This observation indicates an increase in the frequency of flood and drought in the succeeding periods. We have noticed more grid points showed considerable change in the drought return period. But fewer grid points showed a substantial shift in flood return periods. We also found an increase in the frequency of less intensity flood events in many parts of India when compared to high-intensity flood events. This analysis demonstrates an increase in the frequency of combined flood and drought events in the same year throughout India in the last three decades.