HYDRODYNAMIC MODELLING OF BHAGIRATHI RIVER USING GEOMATICS TECHNIQUES

Abstract

In India, flood is the most devastating and frequently occurring natural hazard event. In 1976 Government of India constituted Rashtriya Barh Ayog (RBA- National Flood Commission). It was reported that More than 12 % of geographical area is flood prone. It is important and necessary to take up flood studies and improve the technique to understand the flood dynamics so as to facilitate planning appropriate remedial measures. Though remote sensing imageries have proven their potential in the flood plain mapping and in some situations these images are used as a powerful tool to monitor the live floods. RADARSAT SAR images are widely used to develop flood plain maps on the basis of water depths and continuously monitor the progress of floods. Flood plain mapping using geo information has many limitations. Data obtained from optical remote sensing is considered better for digital classifications but due to cloud cover it is difficult to use optical remote sensing data. Microwave remote sensing distinguish water and land very clearly but it is difficult to perform digital classification with microwave remote sensing data. Data obtained from remote sensing source does not provide detailed information about flood parameters and it is not possible to predict the future scenario of water level and flood inundation. To overcome these limitations, the simulation of flood event using MIKE 1 1 hydrodynamic model is carried out in this study. Digital representation of the terrain with desired level of accuracy is the primary input for hydrodynamic model. Uttarkashi district in Uttrakhand state, located close to Gangotri, origin of Bhagirathi River, experiences flood almost every year. During June —August 2013 one of the flood events occurred in the Uttrakhand state which also struck the Uttarkashi district. By using MIKE 1 1 hydrodynamic model, longitudinal profile of the study area, velocity of flow, water level and routed discharge along the river at different reaches were obtained to know the flood inundation scenario. ASTER DEM was used in the study to derive the cross sections in the flood plain.