Satellite imagery has been used in many studies that seek to relate river flow to floodplain inundation. However, on rivers with moderately to highly variable daily flows it is difficult to establish a reliable relationship between river stage and area of floodplain inundation. This is because the rapid downstream movement of the flood peak results in the area of maximum inundation at any time being spatially restricted. This study presents a method that accounts for rapid variation in daily discharge using before-flood and after-flood sequences of Landsat Thematic Mapper (TM) imagery in reference to a predefined wetland vector coverage. This procedure establishes a relationship between wetland inundation and river discharge. It also reduces errors of commission arising from: the retention of water on the floodplain from previous floods; the filling of wetlands from rainfall and other non-channel sources; and pixel mis-classification.