Dune Erosion on the Falsterbo Peninsula

Abstract

The Falsterbo Peninsula is a low-lying area that provides a home to 7,000 residents, as well as various bird and vegetation species. To protect this densely populated area, the municipality was granted a permit to build flood protections. As part of the strategy, the dune system in the study area will be used as natural barriers against storm surges. Despite being part of the protection strategy, the strength of the dune system in safeguarding the hinterland has not been assessed. This had led to the objective of this thesis, which aims to evaluate the strength of the current dune system. To achieve this objective, the following research question were formulated:

To what extent does the dune system on the Falsterbo Peninsula contribute to safeguarding the hinterland against the impact of historical storm conditions?

To seek answers to this question, the research was didvided into three parts. The first part of the methodology involves collecting the environmental data such as the wind, water level and wave data. Additionally, the data on the dune's morphology was collected during the field work. The second step of the methodology involves identification of extreme conditions within the time series spanning from 1959 to 2022. Considering the complex interaction between the waves and water levels, the extreme conditions were identified based on the combined effect of the two variables, which was represented in the total water level (TWL). The sampling method was based on the peak over threshold method applied to the time series of TWL. The choice of the threshold value was based on the scenarios of potential coastal flooding in the study area. The largest storm surge, the 1872 storm, was included in the analysis to evaluate its impact on the present dune system.

The dune erosion due to the selected extreme conditions was determined in the last part of the methodology. Two morphological models, the XBeach model and the storm impact model were employed to estimate the dune erosion in four transects withing the dune system.

The obtained dune erosion was expressed as a fraction of the available dune volume. The maximum dune erosion was found in the transect situated at the far-right end of the dune system when facing north. The maximum dune erosion under extreme conditions in the period 1959 to 2022, estimated by the XBeach and the storm impact model are 7.67% and 32.89%, respectively. Based on these results, it can be concluded that the present dune system is strong enough to provide protection to the hinterland against the impact of extreme condtions.

For the 1872 storm, the XBeach model estimated erosion percentage of 67.89%, whereas the storm impact model estimated more than 100%. This indicates that in the event of recurrence of the 1872 storm, a dune breach could be expected. While the 1872 storm may not be the design storm condition for the dune system, the storm impact model result highlights the need of reevaluation of the formulation of potential plans to reinforce the dune system.

For future studies, it is strongly recommended to establish a long-term monitoring program for the dune system on the Falsterbo Peninsula. The obtained dune erosion data can be used to calibrate the morphological models to enhance its accuracy in the predictions. Additionally, dune recovery data can aid in the understanding of the dune system as a whole.