2018 CSDMS meeting-059
Coupling fine particle transport, storage, and remobilization with sediment bed morphodynamics
During storms nutrients and contaminants are washed from landscapes into rivers in the form of fine particulate matter. Once in a river, fine particles are typically treated as if they pass through the environment as wash load without interacting with the stream bed. However, laboratory and field experiments have demonstrated that fine particles can be advected towards the bed where they participate in hyporheic exchange and eventual filtration within the river bed. Irreversibly filtered particles can only be remobilized through scour and bed erosion. Therefore, understanding fine particle transport, storage, and remobilization in rivers requires coupling fine particle dynamics and sediment morphodynamics. Here we analyze the dynamics of solute tracers, fine suspended particles, and bed morphodynamics within a coastal stream during baseflow and an experimental flood. These field data represent a unique set of coupled surface and subsurface observations of solute and fine particle dynamics and simultaneous time-lapse photography of sandy bedform motion. From the time-lapse photography, we use novel image analysis techniques to extract time series of bedform wavelength and celerity. In tandem, we utilize existing databases of bedform topography from laboratory experiments to determine relations between the statistical distributions of bedform wavelength, height, and the maximum scour depths. The understanding gained from the high-resolution experimental dataset allows us to create time series of bedform height and scour depth to explore how changing bedform dynamics affects solute and fine particle residence times within the stream bed.