Uncertainty Analysis for a GIS-based Urban Flood Inundation Model

The assumptions, structure and parameters of a model as well as the data modeled can introduce uncertainties into model output, uncertainties that are not always transferred to the consumers of the model output. The objective of this study is to identify and quantify sources of uncertainty in a model; ultimately the goal is to provide uncertainty information in a form that supports decision-making based on model output. The focus of uncertainty analysis presented here was a GIS-based urban flood inundation model. The model consists of two modules: a simple storm-runoff model and a flat-water based inundation model. Sensitivity analyses were conducted for each uncertainty source. Sources considered include: DEM, rainfall data, status of storm water drainage system, antecedent soil moisture conditions, land cover estimation, and limitations inherent in the model. Based on the sensitivity studies an uncertainty index was derived and relative weights established for each component of the overall uncertainty.