Spatial patterns of urban development from optimization of flood peaks and imperviousness-based measures

Urban development within a watershed can take on a wide and diverse range of spatial patterns. The terms "sprawl" and "clustered" development, for example, are frequent in the literature, spanning the spectrum of possible spatial patterns of urban development. The relationship between flood conditions and the spatial distribution of the urban development has been poorly studied, often because of limitations in streamflow data availability or the common use of lumped watershed models in urban hydrologic modeling. We study this relationship with an optimization-based approach that accounts directly for the spatial distribution of imperviousness to investigate how the urban spatial pattern will affect flood peaks and how it can be used to reduce or minimize undesirable impacts to water resources. We employ several water resources-based objective functions to perform optimizations that result in distinct spatial patterns of urbanization showing characteristics of both sprawl and clustered development, depending on the objective function used. We conclude that the approach followed here and the resulting optimized landscapes provide a helpful understanding of the important role played by the spatial form of the urban pattern when trying to minimize impacts to water resources. One objective function, crafted to approximate ecologically based imperviousness threshold policies, resulted in an optimized urbanization pattern suggesting that unintended consequences of low density sprawl may follow from such policies. This specific finding underscores the general value of our optimization-based approach for planning and managing new urban development around water resources.