High Resolution Remote Sensing Data & GIS Techniques in Updation of Infrastructure Details for Flood Damage Assessment - A Case Study

There are several natural disasters occurring throughout the world round the year and causing huge loss to the lives, property and natural resources. Assessment of damage caused by these disasters needs to be carried out accurately in minimum possible time frame. Space technology is one of the best-suited means for the assessment of damage brought about by natural disasters. Remote sensing satellites provide synoptic view, repetitive coverage and high-resolution images. This advanced high-resolution sensor technology has provided immense scope to the earth resource scientists world-wide for mapping and analysis of earth surface feature details using Remote Sensing and Geographic Information System (RS & GIS). India is among several countries in the world, which face severe problem of floods every year particularly in the river basin of Ganga-Brahmaputra.

Considering the seriousness of the flood problem, Department of Space / Govt. of India has taken very important step to develop and implement an effective Disaster Management System (DMS). One of major activities under DMS is to provide flood damage assessment and to assist in flood mitigation/ protection work. North - Eastern part of India and especially the Assam State is most prone to flood due to its delicate geographic location in the Bramhaputra valley. The mighty river Brahmaputra travels approximately 720 km in Assam from east to west with its perennial flood menace during monsoon that affects almost 20 districts out of a total 24 districts in the state of Assam. Marigaon district of Assam, which is taken as the case study is one of the worst affected districts. Almost 60 % of the district get inundated during flood season causing untold human sufferings and heavy loss to animal lives, property and natural resources worth several million rupees. Indian Remote Sensing Satellite (IRS) - 1C / 1D high resolution PAN, LISS- III, WiFS data and topographic maps on 1: 50,000 scale are used in carrying out this study. Initially digital map database is prepared for geometric rectification of PAN, LISS- III and WiFS data. Further this map database is utilised in digitizing infrastructure details. Merged products of PAN+LISS- III are generated and used for extraction of infrastructure details in GIS environment, i.e., settlements, metal and unmetal roads/ cart tracks, rails, embankments/ dykes and causeway. Apart from infrastructure details, natural features were also digitized, i.e., drainage, ox-bow lakes, streams, river, river islands, tanks and reserve forests boundaries. WiFS data is used for extraction of flood layer and the resultant flood layer is used along with all infrastructure layers to intersect the inundated area and assess the damage. Classified landuse/ landcover (level III) map generated from LISS - III data is used to assess the damage to agricultural crops.