Projected evolution of flood hazards under global warming in the Jhelum and Chenab River Basins of Pakistan: An integrated modeling approach

Abstract

Understanding how flood magnitudes may evolve under future climate conditions is critical for Pakistan. Accordingly, this study assesses climate change impacts on extreme hydrological responses across all return periods in the Jhelum and Chenab River basins, where high-flow regimes are governed by both monsoon rainfall and cryospheric contributions. An integrated modeling framework combining the physically based Integrated Flood Analysis System (IFAS) to simulate future extreme flows under synthesized climate scenarios, and the Rainfall Runoff Inundation (RRI) model was used to evaluate inundation extents using synthetic design hydrographs as unsteady flow boundary conditions. Climate data archives, including observed and reanalysis (1971–2004), and General Circulation Model (GCM) projections (2005–2099) under RCP 4.5 and RCP 8.5 scenarios, were utilized. Results suggest a likely decrease in projected flood magnitudes across most return periods during the twenty-first century, driven by increased temperatures, enhanced evapotranspiration, and changes in monsoon precipitation. The magnitude and timing of these changes vary across scenarios and climate models, indicating that reductions in flood magnitudes are scenario-dependent rather than deterministic, and should be interpreted as plausible trends under the selected climate forcings. The flood areas were also estimated for the projected floods corresponding to return levels of 10, 25, 50, 100, 200, 500, and 1000 years. The findings offer valuable decision-support information for sustainable flood risk management, climate adaptation planning, and the design of resilient infrastructure and land-use strategies, contributing to reduced environmental degradation and economic losses under future climate conditions.