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CSDMS all hands meeting 2013

Combined Effects of Climate Change and Urbanization on Cohesive Streambank Erosion

Siavash Hoomehr, Virginia Tech Blacksburg Virginia, United States. hoomehrs@vt.edu
Tess Wynn-Thompson, Virginia Tech Blacksburg Virginia, United States. tthompson@vt.edu
Olivia W Parks, Virginia Tech Blacksburg Virginia, United States. wparks@vt.edu
Matthew J Eick, Virginia Tech Blacksburg Virginia, United States. eick@vt.edu


[[Image:|300px|right|link=File:]]Urbanization and global climate change will severely stress our water resources. One potential unforeseen consequence of these stressors, which is neglected in channel evolution models, is accelerated stream channel erosion due to change in stream water temperature, pH and salinity which affect the surface potential and hence stability of soil colloids. Summer thunderstorms in urban watersheds can increase stream temperature >7 °C and the impact of global warming on average stream temperature is already evident in some stream systems. Initial estimates indicate a 2 °C rise in stream temperature could increase erosion by 30%. Urbanization has significant effects on the pH and salinity of stormwater runoff and as a result on the water quality of headwater streams. Channel erosion and the resulting sediment pollution threaten the sustainability of water resources and urban infrastructure. The goal of this research is to assess the impact of changes in stream water temperature, pH and salinity on stream channel erosion rates and to explore changes in the electrical surface potential of clay colloids as a potential soil stability mechanism. This exploratory research utilizes two reference clays with different permanent surface charges: montmorillonite, and vermiculite. Samples will be eroded in a recirculating sediment flume to determine soil critical shear stress and erodibility. Three water temperatures (12 °C, 20 °C, 27 °C), two pH (5 and 7), and two salinity levels (5 and 50 mg/l NaCl) will be analyzed. Three replicates of each treatment will be conducted for each clay. Additionally, the zeta potential of the clays will be determined under each condition. Research has demonstrated that variations in zeta potential affect liquid limit and shear stress of soil colloids. Results of this research could lead to a reassessment of stream channel stability modelling in urban watersheds and a paradigm shift in urban stormwater management.