Investigation of basin characteristics: Implications for sub-basin-level vulnerability to flood peak generation

The potential of the sub-basins to generate peak flood plays crucial role in assessing the probable degree of damage to various exposures in hazard condition. In this study, a semi-distributed event-based hydrological model and theoretical indicator-based framework were integrated to evaluate the vulnerability of sub-basins to generate peak flood using the Geographical Information System (GIS). The flood peak discharge of each sub-basin corresponding to the 2014 extreme flood of the Jhelum river was related with different sub-basins characteristics (terrain, hydrological, land use, and soil) to assess vulnerability of flood peak which can be categorized into the class of vulnerability called “physical vulnerability”. The determined characteristics of the sub-basins from the configured hydrological model were treated as “vulnerability indicators”. The calibrated (2014) and validated (1992 and 1997) hydrological model showed Nash–Sutcliffe efficiency (NSE) of 0.96 and (0.97, 0.98), respectively, at upstream gauging station Sangam against optimized curve number (CN) scaling factor of 0.98. However, the NSE values of 0.84 and 0.78 are obtained at the other two gauging stations, i.e., RamMunshi Bagh and Asham in the downstream after the calibration process at Sangam in the upstream. The Anantnag and Kulgam districts, exhibiting multiple sub-basins contributing to the Sangam gauging station, are falling into a high vulnerable category located in the Jhelum basin's southeastern part, Greater Himalayan Range. It was also revealed that sub-basins at the upstream of the Jhelum basin are more vulnerable compared to downstream area, where sub-basin W810, Anantnag district (Greater Himalaya), draining at Sangam gauging site is the most vulnerable. Further, hydrological characteristics control the most vulnerable sub-basin peak discharge rather than other characteristics such as terrain, soil, or land use. Outcomes of the study will be helpful in prioritizing the flood mitigation planning not only with respect to the hydrological boundary (sub-basin level) but also with administrative district boundaries. The proposed method is generic and can be applied to any flood-prone river basin.