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<p>Geomorphometric assessment of the Himalayan watersheds is challenging due to its topographic heterogeneity and frequent catastrophic hydrological events brought by the significant rainfall during the monsoon season. The digital elevation model (DEM) resolution influences drainage representation’s intricacy, where the flow accumulation threshold (FAT) regulates stream start, optimizing network density and distribution. Both must correspond with the study’s objectives and the terrain’s intricacy. This study aims to prepare a drainage density map and quantify the morphometric parameters with the proposed optimal FAT value (FAT ≥ 1394; i.e., the mean value of the flow accumulation raster) of selected DEM for the Ranikhola watershed, Gangtok, India. Furthermore, the present study involves land use land cover (LULC) analysis by processing high-resolution Linear Imaging Self Scanning Sensor-IV (LISS-IV) satellite images. According to this analysis, a 14.5% decrease in forest cover area was observed from 2008 to 2020, with the rapidly increasing urban area (97.7% increase) being the primary concern for hydrological and environmental vulnerabilities. A distinctive procedure, i.e., topographic position index (TPI)-based landform classification, involves identifying landforms for the topographically harsh, ungagged watershed. The regional land use land cover change (LULCC) analysis indicates that the overall forest area decreases significantly on open slopes, followed by the mid-slope ridges. In contrast, the urban area increases on open slopes, followed by the U-shaped valley. The LULCC between 2008 and 2020, with combined geomorphological analysis output, provides crucial information for various applications, including water resource management, land-use planning, environmental assessment, and natural hazard mitigation.</p>

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A GIS-based integrated assessment of geomorphometry with land use dynamics for topographically harsh ungauged watershed

  • 期刊论文

  • 发表日期：

    2025年4月29日

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  • Dibyandu Roy,
  • Venkappayya R Desai,
  • Bharath H Aithal

摘要

Geomorphometric assessment of the Himalayan watersheds is challenging due to its topographic heterogeneity and frequent catastrophic hydrological events brought by the significant rainfall during the monsoon season. The digital elevation model (DEM) resolution influences drainage representation’s intricacy, where the flow accumulation threshold (FAT) regulates stream start, optimizing network density and distribution. Both must correspond with the study’s objectives and the terrain’s intricacy. This study aims to prepare a drainage density map and quantify the morphometric parameters with the proposed optimal FAT value (FAT ≥ 1394; i.e., the mean value of the flow accumulation raster) of selected DEM for the Ranikhola watershed, Gangtok, India. Furthermore, the present study involves land use land cover (LULC) analysis by processing high-resolution Linear Imaging Self Scanning Sensor-IV (LISS-IV) satellite images. According to this analysis, a 14.5% decrease in forest cover area was observed from 2008 to 2020, with the rapidly increasing urban area (97.7% increase) being the primary concern for hydrological and environmental vulnerabilities. A distinctive procedure, i.e., topographic position index (TPI)-based landform classification, involves identifying landforms for the topographically harsh, ungagged watershed. The regional land use land cover change (LULCC) analysis indicates that the overall forest area decreases significantly on open slopes, followed by the mid-slope ridges. In contrast, the urban area increases on open slopes, followed by the U-shaped valley. The LULCC between 2008 and 2020, with combined geomorphological analysis output, provides crucial information for various applications, including water resource management, land-use planning, environmental assessment, and natural hazard mitigation.