The map corresponds to the 'mean' flood risk intensity shown in the graph. This plots the amount of land inundated as a function of the flood stage (height of the flood above the base river level). The errors shown are derived from the error on the digital terrain model used in FloodNET, and also include variation due to user specification of the initial river position. See the technical page for more details.
Also shown on the graph is the stage-area relationship previously published by Al-Taiee and Rasheed (2009) using the Simplified Dam Break model, illustrating the good agreement between that model and FloodNET.