Abstract:
The current study estimates the damage occurred due to flood wave recently affected in the entire stretch of Brahmaputra river course along Assam. During 12-17th September 2018 River was reportedly flowing high, above danger level all along the course of the channel from Neamatighat, Sonitpur (Tezpur), Guwahati, Goalpara and Dhubri. Daily accumulated precipitation of GPM from IMERG V5 (late run) Satellite derived data from combined microwave & IR estimate analyzed for the above dates it shows continuous precipitation at a rate of 25-75 nun/day during 9-16, September 2018 with a lag of 2 days along the districts Lakhimpur, Dhemaji, Sibsagar, Jorhat & Sonitpur. Also intense precipitation at a rate of 76-126 mm/day during 9-11, September 2018 has been estimated in the districts of Dhubri, Bongaigoan, Goalpara, Barpeta, Nalbari&Kamrup. Flood situation reports of Assam State Disaster Management Authority and News from various source indicated that standing crops over an area of 115.32 Km2 are damaged in the Districts of Dhimaji, Lakhimpur, Sibsagar, Sonitpur, Morigaon, Kamrup, and Barpeta and 2000 Km2 cropland has been submerged in the floods. The same are compared with the estimates derived from the present study. Sentinel 1 C-Band SAR, Landsat 8 & Sentinel 2 Satellite Images have been used for assessment of flood inundation mapping. Normal river flow has been quantified using October 2017 & May 2018 Sentinel 1 Images. Flood event analyzed using Satellite images of 14th and 17th on Sentinel 1 SAR; on 17th of Landsat 8 and on
16th of Sentinel 2 during September 2018 showed an inundation area of 2101.88 Km2 in the 16 districts. Assessment of Sentinel 1 SAR Vs Landsat 8 and Sentinel 2 derived water body showed accuracy more than 88% in 7 districts, in which there is overlap, indicated that the coefficient of determination, R2 is 0.97. The junctions of tributaries (i.e., Subanshiri, Ranganathi, Danshiri, Jia Bareli, Kopili, Puthimari, Beki &Kulsi) & low lying areas of main river channel has been affected during the flood. This approach undertaken in the study is very useful to quantify the flooded/inundated zones very reliably.
