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Natural and Artificially Influenced Swash-Groundwater Interactions Experiments

Final Report Summary - NATARISE (Natural and Artificially Influenced Swash-Groundwater Interactions Experiments)

Effective management of European coastal erosion is one of the major stakes of the 21st century. The EU EUROSION report (2004) underlines that all European coastal states are to some extent affected by coastal erosion. Erosion of sandy beaches is exemplified by the displacement of the shoreline, which is located on a relatively steep section of the beach profile, extending shoreward from the low tide level to the berm, called the beachface. Since the 1990s, methods to fight coastal erosion have largely shifted from “hard engineering” to “soft engineering”. One potential soft-engineering measure to promote beachface sedimentation is known as the Beach Dewatering System (BDS), based on the artificial regression of the beach groundwater. The applied-research question underlying the NATARISE project is why a BDS leads to sedimentation. It was envisaged that an improved understanding of the interaction between swash motion and groundwater was crucial to answer this question. As the groundwater in a beach is actively drained, this will alter infiltration/exfiltration speeds of water into/out of the beach. This, in turn, will affect sediment transport processes, possibly leading to beach sedimentation.

Within this context, the NATARISE project was based on two major objectives:
1. To investigate swash/groundwater interactions between contrasting European beaches; and
2. To understand how BDS promotes beachface sedimentation, while investigating the instantaneous effects of the drainage influence over swash in/exfiltration speeds and volumes.
To reach these objectives, NATARISE was separated into 4 work-packages:
1. Influence of tide over beachface morphodynamics of meso-macrotidal beaches.
2. Influence of short waves / long waves over beachface morphodynamic of microtidal beaches.
3. Impact of beach dewatering systems over instantaneous beachface morphodynamics of a microtidal reflective beach.
4. Modelling of natural and artificially influenced beachface morphodynamics of contrasting beaches.

During the actual project, the researcher placed considerable effort on work-packages 1 and 2 (i.e. objective 1). The field measurements belonging to work-package 2 required far more preparation time than originally anticipated. Also, the data was more noisy that envisaged and thus more work had to be spent on data validation. As a result, work on packages 3 and 4 (i.e. objective 2) was not carried out.