Understanding flood regime changes of the Mahanadi River

Abstract

ABSTRACT Understanding trends in flood severity and the persistence in peak discharge timing along a vast river network is vital for basin-scale flood risk management and reinsurance purposes. The Mahanadi River Basin (MRB) in Odisha, India, is one of the largest river basin systems in Peninsular India with a drainage area of 141,600 km2, has experienced a series of catastrophic floods in its Middle reaches and Delta areas between 1969 and 2019. Leveraging gauge-based daily streamflow records (1971–2016), we analyse floods using Monsoonal (from June – September) Maxima Flood (MMF) and Peak over Threshold Flood (PTF) events. We detect potential hotspots, where up/downward trends in floods coincide with early (or delayed) dates of occurrences. We show that at upper MRB, the MMF series tends to have an earlier occurrence of floods with a (field significant) decreasing trend in its magnitude. Up to one-third of gauges show delayed flood timings with an upward trend in peak discharge magnitude, indicating delayed arrival of rare events with changes in flood footprints. The obtained insights aid in forecast efforts and devise disaster response to mitigate the impact of disaster (flood)-climate-health nexus.