Flooding is the 'overflowing of the normal confines of a stream or other body of water, or the accumulation of water over areas that are not normally submerged' (IPCC, 2012: Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation. A Special Report of Working Groups I and II of the Intergovernmental Panel on Climate Change).
Unfortunately, a severe flooding has affected Pakistan recently, inundating more than one thousand villages as reported in this article by NASA. Flood monitoring is fundamental in these emergency situations, and for planning actions of prevention and adaptation to flooding.
This tutorial illustrates how to monitor floods performing the supervised classification of Landsat images (however the same methodology could be applied to other sensors such as MODIS images). In particular, we are going to classify two images acquired in 2013 in Cambodia; in October, the heavy seasonal rains were followed by the Typhoon Nari causing the flood along the Mekong and Tonlé Sap rivers, affecting more than a half-million people (for more information about this and other flooding events, read the article by NASA here). You can see the study area before and after the flood in this image by NASA.