Abstract
Abstract. Flood is one of the most the most re-occurring natural hazard in the state of Bihar, as well as in India. The major rivers responsible for flood in the state of Bihar are Kosi, Gandak, Ghagra and Bagmati, which are the tributary rivers of Ganges. The head water catchment area of these rivers lies in the Himalayan state of Nepal. The high rainfall in Nepal, siltation of hydraulic structures, rivers and low topography of North Bihar causes flood occurrence in these areas on regular basis. Remote sensing and GIS plays an important role in mapping, monitoring and providing spatial database for all flood related studies. The present work focuses on the use remote sensing based topography and images in GIS environment for integrated flood study of Bagmati River, which is one of the most flood prone rivers of North Bihar. The Digital Elevation Model (DEM) from shuttle radar topography mission (SRTM) was used to create detailed sub-basin and river network map of entire Bagmati basin. The floods of July–August 2002 were mapped using RADARSAT-1 data using threshold based method. The SRTM DEM and ground based river cross-section from Dheng to Benibad stretch of Bhagmati River were used to create 1-dimensional hydrodynamic (1-D HD) model for simulating flood water level, discharge and flood inundation. Validation of simulated flood flows was done using observed water level of central water commission (CWC) from Dheng to Runisaidpur stations, with coefficient of correlation of 0.85. Finally, an integrated framework for flood modelling and management system is proposed.
Highlights
IntroductionAbout 40 million hectares or nearly 1/8th of country’s geographical area is flood prone, and an average of 18.6 million hectares is flooded annually (MHA, 2011, NIDM-2011)
The cause of flood is mainly the peculiarity of rainfall in the country, out of the total rainfall in the country, 75% is concentrated over a short monsoon season of 4 months from June to September which is of order of 117 cm on an average
The main hydro processing operations to extract drainage network and sub-basin physical parameters for the Bagmati basin are done in ILWIS 3.3 (ITC, 2007)
Summary
About 40 million hectares or nearly 1/8th of country’s geographical area is flood prone, and an average of 18.6 million hectares is flooded annually (MHA, 2011, NIDM-2011). Average annual loss due to floods is 1,805 crore (GOI, 2006) in India. As per government of India report (2006), on an average about 7.55 million hectare of land area, 40.967 million of population, 1560 human lives, along with large number of livestock and houses are damaged annually due to flood (GOI, 2006). Flood losses in terms of life and property can be minimized, with combination of structural and non-structural measures, with short and long terms plans (UN, 2002). This can be a flood prediction, prevention, monitoring, warning, relief & rehabilitation. These activities are generally part of nonstructural approach to flood management (UN, 2002, Kumar, 2004)
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