Comparison of Different Grid Cell Ordering Approaches in a Simplified Inundation Model

This study proposes a simplified model for non-riverine flood routing using a digital elevation model. The model has the advantage of running with only a few types of input, such as topographic data and cumulative rainfall. Given its ease of use, the model is stable and reliable for developing a real-time inundation forecasting system. This model uses two approaches to determine the collection of cells from which flooding is assumed to originate: (1) A traditional “lowest-elevation approach” that assumes flooding originates from the lowest elevations and that is only based on topographic data; and (2) a novel “D-infinity contributing area approach” that assumes flooding originates at the cells toward which the flow moves and that considers in situ topography and upslope information. The flood water is transferred based on the flat-water assumption that the water levels of adjacent cells are equalized. The performance was evaluated by comparing the simulated results with those from a complex inundation model. The simplified model with the lowest elevation assumption has limited applicability in flat areas and did not provide reasonable locations of the source of the flood. The D-infinity approach can improve the simplified inundation model and extend its application in various topographical areas.