Spatial variability assessment of river‐line floods and flash floods in Himalaya : A case study using GIS

Abstract

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; therefore representative micro‐watershed approach of varied ecosystem followed for a three years (2006‐2008) period.

Practical implications

The study will have great scientific relevance in the field of river‐line flood and flash flood hazard and its socio‐economic and environmental risks prevention and management in Himalaya and other mountainous terrain of the world.

Originality/value

This study generated primary data on hydro‐informatics and weather informatics to integrate with geo‐informatics data for flood hazard assessment and mitigation as constitutes a part of multidisciplinary project, Department of Science and Technology (D.S.T.) Government of India.

Citation

Rawat, P.K., Pant, C.C., Tiwari, P.C., Pant, P.D. and Sharma, A.K. (2012), "Spatial variability assessment of river‐line floods and flash floods in Himalaya : A case study using GIS", Disaster Prevention and Management, Vol. 21 No. 2, pp. 135-159. https://doi.org/10.1108/09653561211219955