Processes controlling cohesive sediment transport in complex coastal environments
My current research focuses on cohesive sediment transport in tidal rivers in the form of distinct clouds of sediment. These structures are observed (e.g. in the Elbe Estuary) for a short period (up to 1 hour) after slack water during accelerating tidal currents until there is a homogenous sediment mixture occupying the water column.
The intermittent nature of suspended transport is commonly associated with the occurrence of coherent flow structures generated in the bottom boundary layer. Coherent Flow Structures are irregular, but repetitive turbulent events believed to be caused by the deformation and evolution of vortices in the seabed region. They are characterised by rapid in- and outrush of fluid from the near-bed region, interspersed with quiescent inter-event periods.
In a field campaign, high frequency hydro-acoustic and optical sensors have been deployed to derive time series of velocity fluctuations and suspended sediment concentration throughout the water column over several tidal cycles. This will enable the determination of inter-event period of the flow structures and suspension events close to the seabed and possibly scaling to dune or flow variables. Furthermore, it is aimed at a better understanding of the processes causing the confined upward transport of material and sustainment of the clouds at the water surface.
|10.2010 - present||PhD Student at Marum, Bremen|
preliminary title of dissertation: "Drivers of bed instability and their significant time and length scales".
|10.2008 - 09.2010||MSc Marine Geosciences, University of Bremen|
MSc Earth Sciences, University of Waikato, New Zealand
Title of Masterthesis: "Evaluation of the Tauranga Harbour numerical model".
|10.2005 - 09.2008||BSc Geowissenschaften, University of Bremen|
Title of Bachelorthesis: "Modern tropical carbonate sediments of a knoll structure ('Pee Shoal') in the Vulcan Graben, Timor Sea, NW Australian Shelf - A first insight to facies composition".
- Kwoll, E, Winter, C. and M. Becker (in press). Intermittent suspension and transport of fine sediment over natural tidal bedforms. In: Coherent Structures in Flows at the Earth's Surface. Venditti, J. G., Best, J., Church, M. and R. J. Hardy (eds.). Wiley-Blackwell, London.
- Badesab, F., von Dobeneck, T., Bryan, K.R, Müller, H., Briggs, R.M., Frederichs, T. and E. Kwoll (2012). Formation of
magnetite-enriched zones in and offshore of a mesotidal estuarine lagoon: An environmental magnetic study of Tauranga Harbour and Bay of Plenty, New Zealand. Geochem. Geophys. Geosyst., 13, Q06012, doi:10.1029/2012GC004125.
- Kwoll, E. and C. Winter (2011). Determination of the initial grain size distribution in a tidal inlet by means of numerical modelling. Journal of Coastal Research, SI 64, 1081-1085.
- Wienberg, C., Westphal, H., Kwoll, E. and D. Hebbeln (2010). An isolated carbonate knoll in the Timor Sea (Sahul Shelf, NW Australia): facies zonation and sediment composition: Facies 56(2): 179-193.
- Kwoll, E. and C. Winter (2011). Turbidity clouds in the Elbe Estuary. 2nd Young Scientist Excellence Cluster Conference on Marine and Climate Research, Bremen, Germany.
- Kwoll, E. and C. Winter (2011). Determination of the initial grain size distribution by means of numerical modelling. International Coastal Symposium (ICS), Stettin, Poland.
- Kwoll, E, Becker, M., Winter, C. and V. B. Ernstsen (2012). Tide-driven variations of sediment suspension over large bedforms in a tidal inlet channel. American Geophysical Union Conference, San Francisco, USA.
- Kwoll, E., Becker, M., Maushake, C. and C. Winter (2011). Formation of turbidity clouds in tidal currents - Elbe River, Germany. Conference on Coherent Flow Structures in geophysical flows at the Earth's surface, Burnaby, Canada.