Type
PhD research
Duration
2022-2026
Persons involved
ir. J.R.M. (Jos) Muller (PhD candidate)
dr. Ir. B.W. Borsje (Daily supervisor)
dr. ir. J.J. van der Werf (Co-supervisor)
Prof. Dr. Ir. S.J.M.H. Hulscher (Promotor)
Funding of the project
This research is a part of the Living Dikes programme and is funded by NWO
Summary of the research
Large part of the world population live near coastal regions, often being classified as open coast, estuarine or lagoons. Global rising of sea levels put a pressure on coastal protection against flooding. Construction and maintenance of coastal protection schemes are often large scale and expensive. Traditionally, they are designed to fully mitigate storm surge water levels and waves. Examples are breakwaters with rock or armor layers, groins or dikes with rock revetment, often called ‘hard’ or ‘grey’. Furthermore, natural processes that keep the coastal zone in balance are disturbed, leading to exaggerated water levels, currents, undesired erosion and making the coast eventually more unstable.
Over the last decades, a more coexisting approach has developed in which natural processes are used together with the coastal protection design. This leads to a more flexible and ‘easier to adapt’ kind of coastal protection scheme. These solutions are called nature based solutions (NBS) and come in many forms, depending on local conditions of a coastal zone. An example in muddy coastal systems is the use of vegetated foreshores or salt marshes/wetlands in combination with a protecting dike behind it, also coined ‘Living Dike’. It has been shown that these vegetated foreshores help in attenuating incoming waves as they travel over the salt water vegetation. The height of the dike protecting the hinterland can be lower and more cost-effective. Additionally, these salt-marsh systems fulfil a vital ecosystem service, supporting many species. Also, with favorable conditions, these types of ecosystems can grow with rising sea levels and would require less maintenance compared to heightening a dike.
In order to incorporate man-made salt-marshes in the ‘Living Dike’ concept, the effectiveness and stability of the salt-marsh needs to be well understood. Current research shows the transition between mudflat and saltmarsh (e.g. saltmarsh edge) is critical in determining if a saltmarsh is retraining or stable. However, the dynamics in erodibility of the saltmarsh edge are still not well understood, nor are there many observations on salt marsh stability under extreme conditions. The goal of this PhD research is gaining a better understanding of salt marsh edge failure mechanisms through extensive scaled and real-life flume experiments and numerical modelling (e.g. XBeach), both under normal and extreme wave conditions.
Keywords
Salt marsh, salt marsh edge, erosion, waves, flume experiments, XBeach
More information
Jos Muller
Room Horst-Ring W203
Tel. +31 6 21610332
E-mail j.r.m.muller@utwente.nl