With the new tool, municipalities which must plan protection for exposed stretches of coast or people living in attractive areas near a beach can find out what the impact on a certain area may be, both today and in the future.
When both waves and water levels are high, flooding can be very severe and damaging.
This type of flooding is called overwash. In Sweden, coasts in the south and south-west are in the risk zone for overwash, especially the sandy beaches in Skåne, Halland, Öland and Gotland.
When overwash occurs during a storm, large quantities of water and also sand and gravel are carried on to land. This phenomenon can cause extensive damage, says Chantal Donnelly, who has a doctorate in water resources engineering. Her recent thesis describes how overwash occurs and how it affects the landscape.
In her thesis, she and her supervisor Magnus Larson developed three models which, in different ways, calculate the consequences of overwash transport. By studying and making a comprehensive assessment of the topography of the coast, for example differences in level between sand dunes and the slope of the coast, it is possible to arrive at a good estimate of how vulnerable the area is and what the consequences may be.
Previously, researchers at LTH made analyses of measurements extending over 60 years at the exposed Falsterbonäset in southern Skåne. Their results show that high water levels, which last from a few hours to perhaps a day, have risen eight times faster than the mean water level during the same period. According to Hans Hansson, Professor at Water Resources Engineering, it is important to include the rapidly rising high water levels in long term municipal planning since they will probably give rise to flooding problems much sooner than the rising mean water level.