Spatial variability assessment of river-line floods and flash floods in Himalaya

Purpose - The main objective of the study is to identify the vulnerable areas for river-line and flash flood hazard and its mitigation through GIS Database Management System (DBMS) of geo-hydrometeorological parameters. The Dabka watershed constitutes a part of the Kosi Basin in the Lesser Himalaya, India in district Nainital has been selected for the case illustration.Design methodology approach - The Dabka DBMS is constituted of three GIS (Geographic Information System) modules, i.e. geo-informatics (consists of geomorphology, soils, geology and land use pattern, slope analysis, drainage density and drainage frequency), weather informatics (consists of daily, monthly and annual weather data about temperature, rainfall, humidity and evaporation) and hydro-informatics (consist of runoff, sediment delivery, and denudation). The geo-informatics and weather informatics modules carried out by comprehensive field work and GIS mapping than both modules used to carry out hydro-informatics module. Through the integration and superimposing of spatial data and attribute data with their GIS layers of all these modules prepared Flood Hazard Index (FHI) to identify the level of vulnerability for flood hazards and their socio-economic and environmental risks.Findings - The results suggest that geo-environmentally most stressed areas of barren land (i.e. river-beds, flood plain, denudational hills, sites of debris flow, gullies, landslide prone areas etc.) have extreme vulnerability for flood hazard due to high rate of runoff, sediment load delivery and denudation during rainy season (i.e. respectively 84.56 l s km2, 78.60 t km2 and 1.21 mm year) whereas in geo-environmentally least stressed dense forest areas (i.e. oak, pine and mixed forests) have low vulnerability due to low rate of stream runoff, sediment load delivery and denudation (i.e. respectively 20.67 l s km2, 19.50 t km2 and 0.20 mm year). The other frazzled geo-environment which also found high vulnerable for flood hazard and their risks is agricultural land areas due to high rate of stream runoff, sediment load delivery and denudation rates (i.e. respectively 53.15 l s km2, 90.00 t km2 and 0.92 mm year).Research limitations implications - For hydro-informatics module it is quite difficult to monitor water and sediment discharge data from each and every stream of the Himalayan terrain due the steep and rugged topography. It requires strategic planning and trained man power as well as sufficient funds; theref