Comprehensive flood risk evaluation with climate change study for the Bagmati River Basin in Nepal

Abstract

In recent times, the Bagmati River Basin has faced flooding as its most significant environmental challenge. This study aims to develop a flood risk map that incorporates climate change projections using the EC-Earth 3 model for the SSP 2-4.5 and SSP 5-8.5 scenarios. By integrating hazard, vulnerability, and exposure components, the study creates a comprehensive flood risk map for the Bagmati River Basin. The flood hazard map is generated using HEC-RAS with projected future precipitation data while model performance indicates strong predictive skill using Nash-Sutcliffe Efficiency (NSE), Coefficient of Determination (R²), and Percent Bias (PBIAS) for calibration and validation and model selection. The vulnerability map assesses flood damage risk by considering land use and land cover (LULC) types, soil characteristics, hydrometeorological, and topographical features, employing the Frequency Ratio (FR) method. The exposure map identifies at-risk elements within flood zones, such as population density, infrastructure, and building assets. Results indicate that across all periods, the EC-Earth 3 5-8.5 Scenario consistently predicts a larger flood risk area, suggesting a more significant impact associated with higher emissions, with a total area of 495 km² from 2071 to 2100. This highlights Kathmandu, Lalitpur, Rautahat, and Sarlahi as some of the most affected districts, with Kathmandu having the largest area at risk of flooding. The study underscores the necessity of integrating climate change factors into flood risk assessment methods, marking a significant advancement over previous studies.

Keywords

Flood risk / Hazards / Vulnerability / Exposure / Nepal

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Funding

MEXT(223705)

RIGHTS & PERMISSIONS

The Author(s)