Heterogeniety in the urban landscape: impacts on hydrologic processes and nitrogen pollution Public Deposited

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  • March 21, 2019
  • Smith, Monica Lipscomb
    • Affiliation: College of Arts and Sciences, Department of Geography
  • The objective of this dissertation was to define the most critical features of the heterogeneous urban landscape that characterize nitrate source/sink dynamics and hydrology driving stream nutrient pollution. This volume of research evaluated the usefulness of the commonly used National Land Cover Database (NLCD) for deriving urban hydrologic parameters, defined metrics linking suburban landscape structure and nitrogen fluxes, and determined variance of hydrologic properties of residential lawns according to social and physical factors. Field research and remote sensing analysis took place within watersheds of the Baltimore Ecosystem Study (BES) Long-Term Ecological Research (LTER) site. Results suggested that the NLCD is insufficient for urban hydrologic studies due to biases and variability of these datasets. However, nitrate concentrations of suburban streams were better characterized by watershed infrastructure than land cover composition or location. Septic-managed watersheds' stream nitrate correlated with fine-scale and spatially explicit metrics, including population/septic density, septic location and presence of wetlands. However, the spatiality of sewer nitrate-N sources was not assessed because infrastructure displaced the source downstream from sampling points. Hydrologic properties of residential soils were found to vary spatially at the parcel and watershed scales. Reduced saturated infiltration rates in residential lawns caused only marginal differences in overland flow when compared to regional rain records. However, the reduction in lawn soil structural properties implies watershed-scale changes in hydrologic connectivity between nitrogen sources and streams. Controlling for geographic differences in soil properties, saturated infiltration rates correlated with housing age, and percent organic matter correlated with property value and fertilizer application rate. However, these relationships were non-monotonic, and the ability to use social and physical data to explain the range of soil properties among residential lawns was limited. This dissertation defines a range of soil parameters of residential lawn properties for spatially explicit modeling. Of the factors assessed in this dissertation, waste management infrastructure was defined as the most critical feature explaining nitrate source/sink dynamics of the heterogeneous urban landscape. This finding suggests that previous regional-scale studies linking nutrient enrichment to urban land cover variables may be substituting land cover as a surrogate measure for waste management infrastructure.
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  • In Copyright
  • Band, Lawrence
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  • University of North Carolina at Chapel Hill
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