Anthropogenic and climatic drivers of the 2022 mega-flood in Pakistan
Arfan Arshad, Ali Mirchi, Cenlin He, Azeem Ali Shah, Amir AghaKouchak
Abstract
The convergence of climatic and anthropogenic factors that triggered the August 2022 mega-flood in Southern Pakistan caused 1486 fatalities and approximately $30 billion in economic damages. After a multi-year drought, the pre-monsoon rainfall was 111% higher than the long-term average of 1951–2021, increasing soil moisture by 30% in the Indus Basin floodplains. Monsoon rains were 547% above average, with record-breaking cumulative weekly rainfall in July (200 mm) on already saturated soils. Upstream drainage catchments (e.g., Chenab, Jhelum, and Ravi) received 33% and 41% more rain in pre-monsoon and monsoon periods, respectively. August 2022’s streamflow at Sukur Barrage, just upstream of the floodplains, was 170% larger than the historical average, due to the compounding effects of rain-on-snow and warmer temperatures accelerating snowmelt. The magnitude of multi-day consecutive rainfall events is projected to increase in Southern Pakistan by 2099 in a high-emission scenario (SSP5-8.5), making the catastrophic 2022 flood a forewarning of elevated future flood risks.