The April 2022 South Africa Flood event

Abstract

Over April 2022, heavy rain in KwaZulu-Natal province in South Africa, followed by intense flooding and mudslides, caused one of the deadliest natural disasters in the country, mostly hard-hitting the areas in and around Durban. The intense rainfall was caused by a cut-of-low mid-latitude depression, known as Storm Issa, which is a common weather system in South Africa, particularly in the spring and summer months. In this study we present an analysis which investigates 1) the reasons why this event has been so impactful in terms of damage and loss compared to other similar events in South Africa and 2) if the intensity and frequency of such a storm is increasing as a result of a changing climate.  The analysis has been carried out at different levels: ERA-5 reanalysis data and rain gauge data have been used to characterize at different temporal and spatial scales the precipitation relative to the event and compared to other similar events; DWS discharge data have been used to analyse the event in terms of hydrological response and flow; and finally the footprint of the event has been reconstructed, following the flow analysis and by means of UNOSAT satellite-detected flood, landslide and damaged structures taken as reference. Among the major outcomes of the analysis we found that the duration and antecedent conditions, most probably also exacerbated by La Nina effect, made the event exceptional, resulting in a flash flood among the highest recorded in the last 70 years. The reconstructed event footprint whilst could be improved in the areas which were mostly affected by landslides, captures well the flooding in the major floodplain.