Floods are the most regular vulnerabilities in mountain regions, particularly in Middle Himalayas of Nepal. It is well accepted fact that natural events cannot be prevented but if we take care and be prepared in advanced, potential disasters can be minimized to some extent. Remote sensing, the science of acquiring information about the Earth using remote instruments, such as distant camera, airplanes, satellites etc., could make substantial contribution in preparedness, prevention and relief phases of flood disaster management. It offers accurate, frequent and near real-time data over large areas anywhere in the world.  Moreover, field visit and ground observation is extremely dangerous, limited and time-consuming, remote sensing is the only practical way to monitor the relatively larger area of the earth surface at the time of disaster. In this work, we have used remote sensing images extensively to keep track the changes in the river in between 2000 to 2013 (before Mahakali flood) and the change map induced by 2013 flood in Mahakali River. The results show that in between 2000 to 2013 there is not such a significant change in the river area though there are some minor diversion, the total river area in 2000 was 40.03ha while it is in 2013 before flooding was 42.047. But the 2013 Mahakali river flood caused a substantial changes in its course and hit the town badly, the river area after the 2013 flood was found 55.98ha. We observed that several hectares of agricultural land and residential area washed away along with several sections of the Mahakali highway. In light of the limited financial resources of developing countries, remote sensing appears as the most cost-benefit implications of disaster-induced changes are very important. It can provide the expected damage (or hazard assessment) one of the necessary inputs in cost-benefit analyses within a short interval of time for the early assessment.