Status: this discussion paper is a preprint. It has been under review for the journal Hydrology and Earth System Sciences (HESS). The manuscript was not accepted for further review after discussion.
Co-incidence Analysis of Changes in Flood Magnitude and Shifts in Flood Timing in a Large Tropical Pluvial River Basin
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. While earlier studies have primarily focused on analysis of either trends in floods or its seasonality independently, here for the first time, we assess coincidence of changes in peak discharge and shifts in its timing in one of the largest peninsular rivers (drainage area of 141 589 km2), Mahanadi River Basin (MRB), in India during 1970–2016. Our research is motivated by the recent six major consecutive floods over MRB during the years 2001, 2003, 2006, 2008, 2011, and 2013. We analyze flood properties using peak fluvial discharge indicators, Monsoonal (from June 1–end of September, during the Indian summer monsoon period), Maxima Flood (MMF) and Peak over Threshold Flood (POTF) events. While we find a blend of (insignificant) up/downward trends in flood magnitude at Upper MRB (Region I), the middle reaches of the basin (Region II) showed an upward trend in flood magnitude with a larger number of sites detect significant trends in floods for the POTF events. Although the average dates of peak discharge in the basin are concentrated in August, notwithstanding the nature of flood samplings, a delayed (or earlier) shift in flood timing is apparent for most of sites. Further, we detect potential hotspots, where up/downward trends in flood magnitude coincide with early (or delayed) dates of flood occurrences. Based on observational evidence, here we show that up to one-third of sites show an up/downward trend in peak discharge with a distinct shift in the flood timing throughout the MRB. The outcomes of the study call for developing efficient adaptation strategies to ensure regional flood resilience since variations in the peak discharge timing should not be confounded with (insignificant) changes in its magnitude.
Received: 04 Feb 2020 – Discussion started: 31 Mar 2020
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While earlier literature analyzes either change in severity or timing of floods independently, we for the first time detect coincidence in changes in peak discharge and timing of floods in a large tropical pluvial basin in peninsular India. We find up to one-third of sites show coincidence of up/downward trends in floods with shifts in peak discharge timing. The outcomes of research can be extended to any river basins globally to aid in flood resilient strategies, such as flood warnings.
While earlier literature analyzes either change in severity or timing of floods independently,...
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