Floods are capable of happening almost anywhere given the right circumstances, but timely prediction and response still proves to be challenging. The Great Johnstown Flood of 1889 is notorious as causing the greatest single-day civilian loss of life prior to September 11, 2001. Despite the cause of this flood having been studied and debated thoroughly for decades, the precise unfolding of events leading to the flood are still being modeled in search of definitive answers; answers that could help change the flood prone nature of Johnstown and similar areas. Decision support systems (DSS) that warn of flooding are based on hydrologic models to predict flood prone areas. The level of accuracy represented in the model depends on both the accuracy of the measuring instruments and the proper analysis of variables. Geographic information systems (GIS) can assist in both the development of these models and with geostatistical analysis to determine potential sources and effects of bias. The modeling capabilities and potential of GIS have significantly increased over the decades, serving as a useful tool in hydrological analysis and modeling. Creating accurate watershed models can both inform a DSS to more effectively assist civil authorities in protecting at risk regions of flooding, in the hopes of preventing any instances resembling that of the Johnstown flood, and potentially aid in constructing practical runoff retention systems. This paper will review the flood history of the Johnstown area as well as hydrologic literature modeling flooding of this area. The results of each flood will be analyzed, and the method behind each analysis examined and compared to modern techniques. Conclusions about the integrity of modern flood modeling will be made based on their capabilities and the past methods of analysis.
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