Sediment Transport/Deposition Potential along Source-to-Sink Watershed Pathways: A Sediment Connectivity Framework

Sediment erosion, transport, and deposition can occur at many points throughout a watershed. Once eroded, for instance, sediment may deposit in a riparian buffer, enter a stream, transport downstream, deposit temporarily in the stream, or deposit on the floodplain. Sediment may also erode from stream banks and follow similar pathways. In this work, we assessed sediment transport/deposition potential along source to sink watershed pathways within a sediment connectivity framework. Topographic data from a 10 m digital elevation model was used to determine flow pathways for every pixel in a watershed. This provided a set of pathways through which sediment generated from anywhere in the landscape would travel on its way to the watershed outlet. We then estimated gross upland sediment erosion and discounted that erosion by considering whether that sediment would pass through a riparian buffer and/or deposit in the channel (temporarily) and/or floodplain (long-term) before reaching a downstream location. With this collection of pathways, two perspectives are considered: (1) from a single source pixel looking downstream at deposition potential along its pathway and (2) from a downstream location looking upstream at all source pixels whose pathways intersects that location. These two perspectives allow for (1) assessment of where sediment generated from a specific location will most affect downstream locations and (2) determination of which upstream areas most affect a specific downstream location. We apply our sediment connectivity framework to the Dan and Roanoke River Basins upstream of the John H. Kerr Reservoir in south-central Virginia and north-central North Carolina and discuss how different watershed configurations may deliver more or less sediment downstream.