Geomorphic Signature of Urbanization: An Analysis of Four Streams in Southeastern Pennsylvania, USA

ABSTRACT The effects of urbanization on streams, including higher discharges and changes in the sediment budget, have been well‐documented. However, the distinct geomorphic response of streams under varying degrees of development has not been studied sufficiently. Based on Lane's stream equilibrium model, this research projected stream bed elevation changes over the next 50 years in four streams with different degrees of watershed development in Southeastern Pennsylvania using the 1D aggradation–degradation model. This study also explored the role of geomorphic drivers on stream response by performing a sensitivity analysis. The input parameters to run this numerical model were determined: stream bankfull discharge ( Q f ), intermittency ( I f ), bankfull width ( B ), as well as stream channel slope ( S ), median grain size ( D s50 ), and total annual average sediment input from upstream ( G tf ). Results suggest that the stream geomorphic signature of urbanization is influenced by the magnitude and spatial arrangement of land cover types within the watershed. Chrome Run‐upstream, the most developed site of this study, has the potential of 4.21 m of total stream bed incision, with no armoring of the bed. The least developed site, Dismal Run, will remain in equilibrium over the next 50 years. This study also found D s50 , S , Q f , and B are the parameters most sensitive to stream bed changes regardless of the degree of watershed development. However, the negative or positive response depends on the current condition of the stream channel.