Monitoring of Brahmaputra Flood Using Passive Microwave Remote Sensing in Morigaon District of Assam, India

Abstract

Brahmaputra is the largest river in India, and it flows through the state of Assam over a length of 916 km. The river causes flood in many places in the valley along its length during monsoon season. Among many flood prone areas in Assam, the district of Morigaon is one of the frequently flood affected districts in the state, where flood is primarily caused by the overflow of river water in the Brahmaputra. Monitoring of these flooding events using conventional optical remote sensing methods is often not feasible due to cloud cover over these regions, throughout the entire monsoon season. Hence, passive microwave remote sensing is used in the present work for monitoring the changes in the expanse of river water over the Brahmaputra near Morigaon district. As discussed in the paper, polarization index (PI) derived from passive microwave brightness temperature in X-band acts as an indicative parameter for monitoring the river water expanse and flooding in the region. A threshold value of the average PI measured over an optimum number of pixels bordering the river can indicate flood occurrences accurately and hence can be used to monitor flood in the region as explained in the paper.