Hindcast of the wave climate in Öresund : modelling of wave climate over 50 years using WAM with wind measurements input

Abstract: Öresund is a very dynamic economic area with numerous projects, there is a great need of a deeper understanding of the wave climate. The wave measurements currently available are scarce and they do not cover the whole area. For this reason, a modeled wave climate would be of interest and the results could be a starting point for different in depth analysis. The objective of this study was to produce a wave climate over Öresund. The period considered was from 1961 to 2011, such a long period was chosen to be able to have reliable statistics on waves that can be expected at different locations in Öresund. In order to produce the wave climates the WAM model was used with wind measurements from meteorological stations as an input. Once produced, the results of WAM were compared to actual wave measurements from Öresund to validate the model and parameters used. The conclusion of the validation was that the model has a good global estimation but tends to overestimate smaller waves. The results showed that the significant wave height were in average around 0.5 m for coastal locations and presented a maximum of 2.5 m. The monthly averages of significant wave height were slightly lower during summer months in comparison to the winter ones. The same pattern is seen with the mean period of the waves. The study of the return period lead to the conclusion that for most coastal locations a 1 year wave had a significant wave height of 1.3 m and a 50 years wave presented a Hs of 2.3 m. Also, a 2 m Hs wave had a return period of 10 years. Monthly average run-up levels ranged from 0.15 to 0.62 m. A drop can be noticed in April and May, this due to the fairly low Hs and water levels during period. The direction of wave propagation also seem to be of importance in this process, during April south-eastern direction were stronger and lead to low run-up heights. The 10 year run-up were between 2 and 2.8 m (depending on the location), and the 1 year were between 1.4 and 1.8 m (respectively for Falsterbo and Landskrona). In this study, the potential sediment transport along the Swedish coast was calculated and lead to the identification of potential accumulation and erosion areas. The potential areas of accumulation were located south of Helsingborg, in the center of Lundåkra bay and Lomma bay, at the horn of the bay outside of Vellinge and North of Falsterbo. Erosion could occur outside of Landskrona and Barsebäck, at a location situated between Malmö and Vellinge and in the bay of Höllviken. A hypothetical scenario of climate change was tested in order to evaluate the impact of such a change on the wave climate of Öresund. The conclusion concerned more the behavior of the response than the actual values obtained. The wave climate in the region seemed to be more sensitive to a change in wind speed rather than wind direction, this could be due to the already limited fetch length in the strait. The wind direction affected the results as well but was more of an aggravating factor when coupled with a wind speed change. Hindcasting wave climate is useful for many different applications, this thesis only explored some of the coastal processes. The results from it could give an indication about how the waves in the strait behave.