EP045-04
Discharge dependent bifurcation asymmetry alters flow and sediment pathways through deltas
Monday, 14 December 2020: 04:12
Virtual
Christopher R Hackney, Newcastle University, Tyne and Wear, United Kingdom, Joshua Johnson, University of Hull, Energy and Environment Institute, Hull, United Kingdom, Douglas A Edmonds, Indiana University, Department of Earth & Atmospheric Sciences, Bloomington, IN, United States, Daniel R Parsons, University of Hull, Energy and Environment Institute, Hull, HU6, United Kingdom, Elizabeth Ann Olliver, Indiana University Bloomington, Geological Sciences, Bloomington, IN, United States and Connor Broaddus, Indiana University Bloomington, Department of Earth and Atmospheric Sciences, Bloomington, IN, United States
Abstract:
The preferential routes along which suspended sediment is transported through deltaic systems are key to maintaining sediment supply to delta surfaces. However, the distributive nature of deltaic systems means sediment and water are split unevenly between the multiple bifurcating channels. This results in a spatially variable ability to respond to, and counteract, delta sinking. In order to better predict and sustain delta land growth under future climate change, it is important to understand how sediment transport pathways vary spatially with changing fluvial input. Yet, it is unknown if these sediment transport pathways vary in intensity or location through time across a flood hydrograph.
Delta-wide suspended sediment and discharge budgets are developed for Wax Lake Delta for flows of 3,600 m3/s and 5,100 m3/s in November 2018 and March 2020, respectively. Discharge partitioning through the entire delta was captured with an ADCP and suspended sediment fluxes were estimated through acoustic calibration of the ADCP backscatter with observed suspended sediment concentrations obtained from a LISST-200x. We calibrate a Delft-3D morphodynamic model of Wax Lake Delta with our observed discharge and sediment observations and run a range of flows (500 – 6,000 m3/s stepped every 500 m3/s) through the model to look at temporal variation in bifurcation asymmetry, sediment and flow partitioning through the detla, highlighting how water and sediment pathways vary across the flood wave.
