Identifying Drivers of Interannual Variability in Seasonal Sedimentation Patterns in the Corsica River (MD)

The Corsica River, located on Maryland's eastern shore, has been the site of restoration efforts targeted to sediment and nutrient load reduction. While a long-term (~100-y) sediment budget has recently been established, processes that operate over shorter time scales more relevant to management may be more useful. In addition, a shorter-term sediment budget is needed to assess the potential impact of restoration efforts. To address these needs, bottom sediments have been collected to determine end-of-summer conditions for the last 6 years (2006-2011) and analyzed for their chemical and textural properties. Short-term (annual) deposition rates and biological mixing coefficients are calculated via the naturally occurring radioisotopes ⁷Be and ²³⁴Th (half-lives 53.3 and 24.1 d, respectively). Deposition rates are then used to determine the total mass deposit on an annual time scale for comparison across years to assess sedimentation patterns, as well as the interannual variability of observations. For example, deposition is greatest immediately upstream of a sill present near the mouth in one year but is located much farther upstream in the following year. Deposition patterns are compared to relatively simple indicators of physical forcing, such as rainfall and wind direction and magnitude, to identify potential drivers of interannual variability with the ultimate goal of deriving a predictive climatology of sedimentation.