The RESIST Project
Salt marshes form through deposition of fine (silt/clay/sand) particles and the colonisation by salt-tolerant (halophytic) vegetation. Together, the biological and physical sedimentation processes build the marsh surface up in a way that can allow it to maintain its height relative to sea level, even when sea level is rising. Sediments on adjacent surfaces, where there is no vegetation to bind the sediment together, however, may be more mobile. The transition from the unvegetated tidal flat or creek margin to the vegetated salt marsh surface can be exposed to strong tidal and wave forces. Prior to the RESIST project, we knew little about how these forces work to erode marsh margins, although erosion of marsh fringes has been reported from around the world. In this project, our challenge was to:
1: Understand how soil type and biology affect the resistance of exposed salt marsh to extreme wave forcing, and
2: Develop methods for mapping such resistance across space and time for any given set of sea level, wave and tide conditions.
To address this challenge, we used state-of-the art UAV (drone) technology, CT-scanning methods, and geotechnical testing apparatus.
The project was funded by the Natural Environment Research Council, UK
Hydralab IV and Hydralab+: Large-Scale Flume Salt Marsh Experiments
Measuring what happens out on the salt marsh during an extreme event is (almost) impossible, as any measuring devices are unlikely to persist and processes cannot be understood in a controlled manner. Over the period 2013-2018, Prof Möller led two large-scale flume experiments with a team of researchers, many of them early career researchers. Both experiments were run in one of the largest indoor wave flumes in the world, the Large Wave Flume Facility (Grosser Wellen-Kanal, GWK) at the University of Hannover, Germany. These experiments provided ground-breaking insights into how efficient salt marshes really are at dissipating wave energy during extreme storm events (very high water levels and waves) and how salt-tolerant vegetation seedlings and mature plants can survive under such conditions. The second (2018) experiment also exposed salt marsh cores to extreme wave impact forces to provide insights into their erosion response under such conditions (see also the RESIST project). Together, these two experiments have allowed us to appreciate both (a) the need to better represent vegetation roughness/friction effects and plant resilience in wave dissipation models and (b) the influence of salt marsh sedimentology and vegetation on the susceptibility of exposed marsh soils and fringes to erosion.
The projects were funded by the European Union’s Horizon 2020 Hydralab IV and Hydralab+ funding schemes.