Defining perennial, intermittent, and ephemeral channels in Eastern Kentucky: Application to forestry best management practices

Abstract

Typically, Forestry Best Management Practices (BMPs) that are applied to riparian areas are dependent upon stream flow duration. Definitions vary but most often perennial, intermittent and ephemeral channels are classified and used to determine the specific BMP prescription for a site. The most common technique to determine stream class is to use USGS Quadrangle “blue line” maps where blue lines are considered perennial, dashed blue lines are considered intermittent, and ephemeral channels occur where there is convergent topography but no lines are present. This research and others indicate that the “blue line” method is highly inaccurate at the site scale, especially for lower flow systems. In this study we use the channel geometry method and watershed characteristics to develop multiple regression models to predict flow duration across the range of channels in the Eastern Coalfield Region of Eastern Kentucky, USA. Based on our set of predictive models, we can explain 78–91% of the observed variability in flow duration. Parameters that were most common in the models included the natural log of watershed area, bankfull width, width:depth ratio, stream slope and entrenchment ratio. By utilizing our most encompassing model (all sites for their longest time period), we were able to develop a table of general guidelines that classified >95% of study channels correctly. Given the high predictive capability of our models and the geographic range of sites, we believe that our table of guidelines is robust for the Eastern Coalfield Physiographic Region of Eastern Kentucky.