A Methodology for Developing Probabilistic River Flood Inundation Maps
To determine probabilities, predicted peak discharges for the Tonawanda Creek are first collected from the Meteorological Model-based Ensemble Forecast System (MMEFS), which generates predictions of various hydrometeorological parameters in real-time, and are used to create a suite of inundation rasters, one for each individual peak discharge prediction. These inundation rasters are then overlaid and the probabilities are calculated by grid cell based on how many inundations overlap. The resulting map depicts the range of flooding extent probabilities based on the real-time forecast. An alternative probabilistic map is also devised to depict the depth of flooding given a flood event's probability. The 10th, 50th, and 90th percentiles are calculated for the forecast ensemble's peak discharge predictions. These percentiles correspond to benchmarks of flooding likelihood, such that the 10th percentile indicates a 90% likely flood event, 50th percentile a 50% event, and 90th percentile a 10% event. Once completed, the maps are qualitatively evaluated for potential applications in predicting flood events and mitigating flood-induced damages.