Linking channel instability to urbanization in the upper Beaver Creek Watershed, Knox County, Tennessee

Within the past 15 years, the 223 km2 Beaver Creek watershed of Knox County, Tennessee has begun to undergo rapid development. Past studies of urbanizing watersheds have indicated that even small degrees of development can impact channel stability through increased runoff from impervious areas. Already, bank erosion seems to be prevalent throughout the upper reaches, and it is likely that this channel instability is contributing to the watershed's severe flooding and water quality problems. To determine whether urban development is a cause of the channel instability observed in upper Beaver Creek, I took qualitative and quantitative field measurements of channel stability at 10 sites within eight adjacent sub-basins and tested for bivariate correlation between the channel stability indicators and 10 urbanization metrics generated using a geographic information system (GIS). The selected sub-basins ranged from 3.1 km2 to 10.1 km2 in area, varied from predominately rural to urban in land use, and encompassed many of the different types of topography and underlying geology found throughout the upper Beaver Creek watershed. I found that the prevalence of bank erosion does increase as urbanization increases within the upper Beaver Creek watershed. My data suggest that a total impervious area greater than 13-20% and a wooded area of less than 38-51% may lead to channel instability within the upper Beaver Creek sub-basins. The observed channel erosion is also correlated with the proportion of human to natural uses within the catchment and the 30-meter riparian buffer zone, as well as the proportion of wooded riparian buffer upstream of the site.