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The Heffernan Lab at Duke University

Urban Lawns and Urban Hydroscapes

Our current work in urban landscapes aims to test the Urban Convergence hypothesis, which states that urbanization creates similar landscapes regardless of the native biome in which cities are built.  This work is supported by a large, collaborative NSF grant (http://urbanhomogenization.org/) and involves researchers from about 10 universities, working in 6 cities (Miami, Baltimore, Boston, Minneapolis, Phoenix, and Los Angeles).  We have surveyed a large number of homeowners in each city about how they use and manage their lawns, and what social factors (neighbors, HOAs, city ordinances) constrain those choices.  We are using aerial imagery to link these survey results to land cover at the parcel scale (keeping all personal information confidential, which is very important for this kind of work).  We are also visiting a subset of these homes to obtain soil samples, measure microclimate, and survey vegetation.  This broad suite of response variables helps guard against cherry-picking to find data the support the Urban Convergence hypothesis - it is quite likely that some data will show convergent patterns, while other variables will not.  One of our lab's primary responsibilities is to make sure all of these measurements happen in the Miami site.

Our lab's other main responsibility is to evaluate how urbanization influences hydrography (the abundance and distribution of surface water).  We have expanded this analysis beyond the 6 core cities to assess how the number, area, and size distribution of lakes and ponds differs between urban areas and the surrounding native landscape.  Our preliminary analyses support the urban convergence 

We are also conducting more intensive analysis of these patterns within the Miami metropolitan area, where conversion of large areas of wetland into suburban development requires construction of lakes to provide fill soil and improve drainage.  The shapes of these man made lakes and their distribution within the city are quite striking, even if the reason for their presence is the loss of Everglades wetlands.

These ideas have their origins in a side collaboration Dr. Heffernan began as a graduate student at Arizona State.  This work focused on the historic geomorphology and construction Indian Bend Wash, a multi-use greenway in Scottsdale, AZ.  The project documented the dramatic changes in the IBW channel and catchment that resulted from rapid urbanization of this catchment.
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