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<p>Flood is one of the most common hazards in Nepal that have a severe socio-economic effect especially in Himalayan basins that are dominated by monsoons. In this study, we constructed the rainfall thresholds of flood early warning in the Babai River Basin (BRB) by using a calibrated and validated Hydrologic Engineering Center’s Hydrologic Modeling System (HEC-HMS) rainfall-runoff model. The model showed good performance, with the calibration values of NSE = 0.84, R² = 0.87, and PBIAS = − 5.6%, and validation values of NSE = 0.78, R² = 0.81, and PBIAS = − 7.9%. The historical flood occurrences and rain data (1990–2018) were examined at Chepang (mid-basin) and Bhada Bridge (basin outlet). The findings indicate that cumulative rainfall and peak discharge have a significant positive association, and amplified downstream runoff is by virtue of integrated basin runoff. The rainfall thresholds were calculated to obtain bankfull, warning, and danger levels of the river for 1-day, 3-day, and 5-day accumulations. Chepang had 105–110&#xa0;mm of bankfull, 135–140&#xa0;mm of warning, and 200–205&#xa0;mm of danger levels, and the Bhada Bridge needed higher thresholds of 140–145&#xa0;mm, 185–190&#xa0;mm, and 240–245&#xa0;mm for bankfull, warning, and danger, respectively. These thresholds provide a practical advice on anticipatory flood management in addition to current stage-based monitoring. Although the downstream discharge information is not well known and there may be some land-use and climate shifts, the study provides a feasible model of improving early warning of floods in the Himalayan basins. Communities at floods risk are ensured safer and more resilient with real time monitoring combined with risk-based planning.</p>

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Rainfall thresholds for flood early warning in the Babai River Basin, Nepal using rainfall-runoff modelling

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年7月9日

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  • Deepa Pradhan,
  • Madhav Adhikari,
  • Dibash Shrestha,
  • Sudeep Thakuri

摘要

Flood is one of the most common hazards in Nepal that have a severe socio-economic effect especially in Himalayan basins that are dominated by monsoons. In this study, we constructed the rainfall thresholds of flood early warning in the Babai River Basin (BRB) by using a calibrated and validated Hydrologic Engineering Center’s Hydrologic Modeling System (HEC-HMS) rainfall-runoff model. The model showed good performance, with the calibration values of NSE = 0.84, R² = 0.87, and PBIAS = − 5.6%, and validation values of NSE = 0.78, R² = 0.81, and PBIAS = − 7.9%. The historical flood occurrences and rain data (1990–2018) were examined at Chepang (mid-basin) and Bhada Bridge (basin outlet). The findings indicate that cumulative rainfall and peak discharge have a significant positive association, and amplified downstream runoff is by virtue of integrated basin runoff. The rainfall thresholds were calculated to obtain bankfull, warning, and danger levels of the river for 1-day, 3-day, and 5-day accumulations. Chepang had 105–110 mm of bankfull, 135–140 mm of warning, and 200–205 mm of danger levels, and the Bhada Bridge needed higher thresholds of 140–145 mm, 185–190 mm, and 240–245 mm for bankfull, warning, and danger, respectively. These thresholds provide a practical advice on anticipatory flood management in addition to current stage-based monitoring. Although the downstream discharge information is not well known and there may be some land-use and climate shifts, the study provides a feasible model of improving early warning of floods in the Himalayan basins. Communities at floods risk are ensured safer and more resilient with real time monitoring combined with risk-based planning.