Flood inundation mapping under climate change scenarios: insights from CMIP6

The present research endeavors to simulate daily stream flow by employing hydrologic and hydraulic modeling techniques to comprehensively assess the impact of climate change on flood risk. This investigation was conducted within the Shekhan basin, situated in the eighth zone of Jalalabad City, Afghanistan. The efficacy of the HEC-HMS model was meticulously evaluated for each individual flood event during both calibration (Jan/2015-October/2019) and validation (November/2019-July/2022) phases using various statistical performance indicators, notably the coefficient of determination (R-2), Nash-Sutcliffe efficiency (NSE), and percent bias (PBIAS). During calibration, the HEC-HMS model yielded R-2, NSE, and PBIAS values of 0.8795, 0.86, and 12%, respectively, while during validation, these metrics stood at 0.85, 0.8, and 9%, respectively. Among the five GCM models (INM-CM4-8, INM-CM5-0, MIROC6, MPI-ESM1-2-LR, MRI-ESM-2-0) examined, the MPI-ESM1-2-LR demonstrated superior performance based on Taylor Skill Score and Rating Metric analysis. Additionally, the HEC-SSP was employed to scrutinize precipitation frequency and to fit ranking distributions for GCM SSP245 and SSP585 scenarios. Subsequently, the aforementioned GCM data were utilized in hydrologic modeling to generate hydrographs for various return periods, while hydraulic modeling via the HEC-RAS 2D model facilitated the creation of flood inundation maps for different return periods.