Flood inundation mapping and damage assessment of Lakhimpur district, Assam using geospatial tools and techniques.

Flood is a perennial problem plaguing large parts of the country. Assam is one of the worst affected states that is suffering from flood and Lakhimpur is one of the districts in Assam which experiences frequent floods because of the river Subansiri and its tributaries, which emerged from Arunachal Pradesh, create flood havocs during monsoon period. Remote Sensing is a very reliable and expeditious technique for assessment and mapping of flooded areas. This study introduces to generate flood inundation maps using combination of Synthetic Aperture Radar (SAR) imagery and Geographic Information Systems (GIS) for flood event of Lakhimpur District, Assam, India. Damage assessment of the study area due to the flood was also performed. The flood inundation areas were extracted from SAR images (Sentinal-1A, ALOS PALSAR-1) by several image processing techniques. Histogram or radiometric thresholding techniques was used in this study to extract the flood extent from SAR images. Band ratio based Normalized Difference Water Index (NDWI) was used to extract the water bodies from Lansat-8 imageries. Thresholding of NDWI for optical image and SAR images was done using respective histograms to distinguish water and terrestrial features. To extract the actual flooded area, the water body maps generated from Landsat-8 was multiplied with their respective water maps generated from the SAR imagery. Assessment of damage due to flood was performed using flood inundation and land use land cover changes. The result shows that crop land (203.25 km²) and around 85 villages are under the flood affected area. This study shows that integration of SAR data and GIS environment can be exploited in an efficient way to predict and map the flood areas.