Drought can delay or speed-up riverine flooding

Abstract

Abstract Flooding during or after droughts poses significant challenges to disaster risk management. However, interactions between droughts and floods are often overlooked by studying these events individually, with potential under- or overestimation of flood risk. Here we analyse global datasets of hydrometeorological and biophysical variables for 8255 catchments worldwide, showing that more than 20% of floods globally are preceded by, or happen during, drought conditions. In most cases, these compound or consecutive events do not strongly affect flood timing. However, almost a quarter of drought-flood events exhibits a substantially altered flood timing, with a majority (80%) occurring later than expected. These shifts in flood timing suggest potential effects of drought processes on flood generation processes. As both drought and flood occurrences are projected to increase in a warming climate, interactions between them need to be accounted for in flood risk assessment and management.