PhD position: Modelling the biogeomorphological evolution of marine sand extraction pits

University of Twente (UT), Netherlands

Updated: over 1 year ago
Job Type: Temporary
Deadline: 31 Oct 2022

You will be one of the researchers in the OR ELSE project: Operational Recommendations for Ecosystem-based Large-scale Sand Extraction. Recently funded by the Dutch Research Council within the National Science Agenda (NWA-ORC), OR ELSE aims to design solutions that minimize the adverse ecological and societal impacts of large-scale marine sand extraction in the Dutch North Sea and elsewhere. As a whole, OR ELSE consists of ten interlinked work packages involving a total of six PhD students and four postdocs working at various universities and research institutes in the Netherlands. The work package of this vacancy aims to determine the short-term sedimentological adjustment (several years) as well as the long-term (decadal) biogeomorphological evolution in response to large-scale extraction. It is divided into four stages:

  • Investigate the influence of sand-silt mixtures on the instability behind the formation of tidal sand waves. Adopting an idealized process-based modelling approach, we will set-up of a new 2DV sand wave model in which cohesive sediment transport processes (such as flocculation) are parametrically included. A linear stability analysis then reveals (i) possible shifts in the border between stability and instability, (ii) changes in the preferred sand wave mode (wavelength, migration rate, formation time scale of the fastest growing mode), and (iii) the underlying physical mechanisms.
  • Extend from sand wave patterns to large-scale sand extraction pits (on the spatial scale of an individual sand wave or longer). Here we aim to make the step from infinitesimally small yet spatially unconfined sand wave patterns (see step 1 above) to spatially confined sand extraction pits. This will be done in two ways: (i) analyzing the superposition of various modes in step 1 (still using an idealized model) and (ii) setting up a Delft3D model that accounts for cohesive transport processes in and around sand pits. Specific focus on the way silt dynamics affects the morphological evolution of the pit.
  • Include benthos in the above analysis. We will extend the Delft3D model from step 2 in order to include ecosystem engineering species. Therefore we will link their activity to physical properties of the seabed and study the biogeomorphological evolution of the pit. We will select a maximum of three ecosystem engineering species on the basis of (i) their abundance in and around sandpits, (ii) their strong modification of the environment, and (iii) their contrasting type of feeding and burrowing, and thereby contrasting influence on the sediment dynamics and hydrodynamics.
  • As a final step, we aim to actually apply the above models to aid the spatiotemporal design of large-scale sand extraction activities, i.e. on the spatial scale of tidal sand waves. Specific focus on the interaction with benthos.

    • Being part of our OR ELSE consortium implies close interaction with your direct supervisors at UT and your fellow researchers of the other work packages. The link to practice is warranted by recurring user group meetings with professionals from the Netherlands, as well as a group of international experts. Furthermore, you will present your work at national and international conferences and write your findings in journal papers and a PhD thesis to be defended at the end of your project.


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