Eva Kwoll

Ongoing research projects:

Flow and sediment dynamics in Bedrock Canyons

Collaborators: J. Venditti, C. Rennie, M. Church, B. Hunt (MSc Student), E. Cao (MSc Student), S. Ansari

In this project, we examine turbulent flow in bedrock canyons, where little mobile sediment is available and the flow is severely constricted by the presence of steep canyon walls. These canyons are sites of ongoing river incision into the bedrock material. We combine hydro-acoustic, ship-based measurement of the flow field and topography in natural canyons with high-resolution laboratory investigations. Aim of this project is to understand the flow structure associated with constricted canyon entrances, the identification of associated erosional hotspots and implications for sediment transport through the canyons (Hunt et al. (sub.)).

The sub-aqueous signature of sub-aerial landslides and assessment of associated tsunami hazards

Collaborators: M. Geertsma, N. Roberts, J. Clague, J. Venditti

In this project we map landslides in some of BC lakes (so far: Lakelse, Harrison) to identify volumes of debris of previous landslides and to identify slopes that are potentially prone to repeated failure. The multibeam and lidar data are combined with evidence of past landslide-generated tsunami, including vegetation trimlines and anomalous sand and gravel layers in marshes (Geertsma et al. (sub.)).

Turbulent Suspension of Sediments in Coastal Environments

Collaborators: S. M. Amirshahi (PhD Student), C. Winter

Investigation into the coupling between near-bed suspended sediment and small-scale turbulence in the German Bight (Amirshahi et al. (2016); Amirshahi et al. (sub.)).

A list of past projects include:

Development of a long-term monitoring concept of fluid mud dynamics in the Ems Estuary (2014-2015)
Collaborators: M. Becker, C. Winter, A. Wurpts (NLWKN, Norderney)
In the frame of this project a long-term monitoring concept for fluid mud dynamics was tested, evaluated and presented to regional authorities in the network of the WIMO- Scientific Monitoring of the North Sea.

Effect of the bedform lee-slope on flow resistance and the formation of CFS (2012)
Collaborators: J. Venditti, R. Bradley, A. Lefebvre, C. Winter
This study comprised a laboratory investigation into the effect of the bedform lee-side slope on flow separation, turbulence production and flow resistance. Detailed laboratory investigations were conducted in the River Dynamics Research Laboratory at SFU, Burnaby to investigate a set of fixed bedforms with varying lee-slopes (Kwoll et al., 2016; Kwoll et al. (sub. to JGR)).

Macroturbulence and suspended sediment dynamics above tidally-influenced compound bedforms (2012-2013)
Collaborators: C. Winter and M. Becker 
In the coastal environment, morphological adaptations often lag behind changes in fluid forcing. In a Danish Wadden Sea inlet, very large compound bedforms are ebb-oriented and superimposed by smaller secondary bedforms that reverse direction with each tidal phase. This project examined differences in scale of macroturbulence production and coupling to suspended sediment transport during the flood and ebb phase (Kwoll et al., 2014).

Intermittent transport of cohesive sediment in the Elbe Estuary (2011-2012)
Collaborators: C. Winter and M. Becker
Using ship-based measurements in the Elbe Estuary, I demonstrated that the entrainment and transport in suspension of fine sediment above very large compound bedforms is coupled to distinct flow structures. These macroturbulent structures originate in the bedform field due to flow separation at the bedform crests. In the Elbe, they govern suspended sediment transport shortly after slack water and cause the appearance of large sediment clouds (10-30 m) at the river surface. The material within the clouds is part of the fine, cohesive sediment fraction that makes up the turbidity maximum zone in the Elbe Estuary. The compound bedforms on the river bed therefore play a critical role in the vertical mixing and transport of this sedimentary component (Kwoll et al. 2013; Winter et al. 2016).

Morphodynamic modelling of a coastal lagoon (2009-2010)
Collaborators: C. Winter and F. Badesab
For my M.Sc. research, I set up a numerical model of a New Zealand coastal lagoon using the morphodynamic modelling suite Delft3D. Using the calibrated model output, I proposed a technique to determine the initial grain size distribution of the seabed from modelled hydrodynamics, when no field data is available (Kwoll and Winter, 2010). I also examined the model’s capability to reproduce the morphological features of the ebb and flood tidal delta from an initial flat bed. Badesab et al. (2012) used the model to explain the formation of mangnetite-enriched depositional zones offshore the lagoon.

I am currently teaching the following courses:

Fall 2017 - GEOG 376

Spring 2018 – GEOG 476, GEOG 424

Publications in peer-reviewed journals and books

• Kwoll, E., J. G. Venditti, R. Bradley, and C. Winter (2016). Flow structure and resistance of sub-aqueous high- and low-angle dunes. Journal of Geophysical Research – Earth Surface. doi: 10.1002/2015JF003637.
• Amirshahi, S. M., C. Winter and E. Kwoll (2016). Characteristics of instantaneous turbulent events in southern German Bight. River Flow 2016. G. Constantinescu, M. Garcia and D. Hanses (Eds), Taylor & Francis Group, London, p. 175-182.
• Winter, C., Lefebvre, A, Becker, M., Ferret, Y., Ernstsen, V., Bartholdy, J., Kwoll, E., Flemming (2016) Properties of active tidal bedforms. Marine River Dune Dynamics, Bangor University and SHOM Van Landeghem, K., Garlan, T., Baas, J. (eds).p. 205-208, ISBN 978-2-11-128417-3.
• Kwoll, E., Becker, M. and Winter, C. (2014). With or against the tide: the influence of bedform asymmetry on the formation of macroturbulence and suspended sediment patterns. Water Resources Research, 50, doi:10.1002/2013WR014292.
• Kwoll, E., Winter, C. and M. Becker (2013). Intermittent suspension and transport of fine sediment over natural dunes. In: Coherent Flow Structures at the Earth’s Surface (Ed. by J. G. Venditti, J. Best, M. Church and R. Hardy). John Wiley and Sons, Chichester.
• 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. Geochemistry Geophysics Geosystems, 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., J. G. Venditti, R. Bradley, and C. Winter (Journal of Geophysical Research- Earth Surface). Observations of coherent flow structures over sub-aqueous high- and low-angle dunes.
• Amirshahi, S.M., E. Kwoll, and C. Winter (Continental Shelf Research). Suspended Sediment Flux by Single Turbulent Events
• Hunt, B., J.G. Venditti, and E. Kwoll (Earth Surface Processes and Landforms). Experiments on the morphological controls of velocity inversions in bedrock canyons.
• Geertsma, M., A. Blais-Stevens, E. Kwoll, J. Venditti, B. Menousounos, A. Grenier, and K. Wiebe (Sedimentary Geology).