Quantifying the Relative Contributions of the Physical Mechanisms Responsible for the Atlanta 2009 Flood

The September 2009 flood event that occurred in the Atlanta, Georgia metropolitan area was catastrophic, as it resulted in 11 fatalities and damage claims approaching $220 million. Previous research has qualitatively identified the physical mechanisms that likely produced the flooding: 1) moist antecedent conditions, 2) a quasi-stationary convective system, and 3) potential precipitation enhancement due to interactions with the topography and urban environment. However, due to the multifaceted nature of the event, it is challenging to determine the relative importance of each mechanism from observational records alone. This project aims to disentangle the factors that contributed to the flooding by using the Weather Research and Forecasting (WRF) meteorological model. More specifically, the study evaluates the influence of urbanization, topography, and antecedent moisture conditions on the flood response by performing modeling experiments that replace urban development with forested land cover, remove the natural topography, and alter soil moisture characteristics. Modeling results will be presented for discussion and evaluation. Collectively, the experiments will provide a quantitative understanding of the degree to which urbanization and other physical mechanisms influenced the hydro-meteorological characteristics of the 2009 Atlanta flood, which can inform policies aimed at achieving more sustainable urban development practices. Such progress appears imperative given that the urban footprint of Atlanta continues to expand and extreme rainfall events will likely become more frequent in the future due to climate change.