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<p>Flood inundation mapping is the pre-requisite and integral aspect in the formulation of effective flood mitigation strategies. The utilization of open access satellite-based products and validating with field-based information are the crucial steps for enhancing the practicality of flood simulation in data scarce region. This study employed the recent HEC-RAS v6.4 model to simulate 2D flood inundation and developed risk scenarios within the ArcGIS environment in downstream of West Rapti River Basin (WRB) in Nepal Himalaya. Gumbel’s model was utilized to produce the discharge for 2-, 5-, 10-, 25-, 50-, 100-, and 200-year return periods at Kusum hydrological station. The ALOS-PALSAR Digital Elevation Model, 100&#xa0;m mesh size, Shallow Water Equation-Local Inertial Approximation, Manning’s minimum ‘<i>n</i>’ value, were found the best-fit parameters. Land use map prepared utilizing the Landsat 9 imageries. Model calibration and validation yielded better performance omitting breaklines and terrain modifications overall. However, better results were achieved with their inclusion only in low-flow conditions. Inundated areas were mapped for each return period across different risk zones. The simulated model shows maximum crop land loss and reveals the inadequacy of existing levees and flood walls to safeguard lives and properties beyond five-year return period flood. The economic losses of crop found increased from USD 5.25 million to USD 12.02 million in 2-year to 200-year return periods. The study comprehensively integrated the flood inundation simulations, risk scenario and loss estimation to address real-world problem particularly in the data scarce region.</p>

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Appraising flood risk and inundation extent using GIS-aided 2D hydraulic modeling in Nepal Himalaya: a case of West Rapti River Basin

  • 期刊论文

  • 发表日期：

    2025年3月15日

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  • Amrit Prasad Sharma,
  • Xudong Fu,
  • Giri R. Kattel,
  • Tirtha Raj Adhikari,
  • Marwan A. Hassan

摘要

Flood inundation mapping is the pre-requisite and integral aspect in the formulation of effective flood mitigation strategies. The utilization of open access satellite-based products and validating with field-based information are the crucial steps for enhancing the practicality of flood simulation in data scarce region. This study employed the recent HEC-RAS v6.4 model to simulate 2D flood inundation and developed risk scenarios within the ArcGIS environment in downstream of West Rapti River Basin (WRB) in Nepal Himalaya. Gumbel’s model was utilized to produce the discharge for 2-, 5-, 10-, 25-, 50-, 100-, and 200-year return periods at Kusum hydrological station. The ALOS-PALSAR Digital Elevation Model, 100 m mesh size, Shallow Water Equation-Local Inertial Approximation, Manning’s minimum ‘n’ value, were found the best-fit parameters. Land use map prepared utilizing the Landsat 9 imageries. Model calibration and validation yielded better performance omitting breaklines and terrain modifications overall. However, better results were achieved with their inclusion only in low-flow conditions. Inundated areas were mapped for each return period across different risk zones. The simulated model shows maximum crop land loss and reveals the inadequacy of existing levees and flood walls to safeguard lives and properties beyond five-year return period flood. The economic losses of crop found increased from USD 5.25 million to USD 12.02 million in 2-year to 200-year return periods. The study comprehensively integrated the flood inundation simulations, risk scenario and loss estimation to address real-world problem particularly in the data scarce region.