Beach restoration and erosion protection on the inner Danish coasts - a case study

Introducing hard structures to a sandy coast will inevitably disturb the equilibrium condition and cause erosion. Any initiative involving hard coastal protection should therefore, if it cannot be avoided altogether, come with a sand nourishment scheme. The Danish coastal protection schemes have for many years been governed by a national strategy encouraging integrated coastal zone management, with the general aim to find alternatives to hard coastal protection, preserve the natural beauty of the coast and provide more attractive coasts for the benefit of everyone. Typical challenges arise when there is a clash of interests, such as economic and recreational. The beach along the community of Faxe Ladeplads is an excellent example for such a conflict. This case study illustrates how successive construction of harbours, groynes and revetments during the past two centuries has resulted in a disappearing beach, and what measures a humble coastal municipality can take today to compensate for the sins of the past. Ramboll has presented different solutions with and without hard coastal protection structures. The solutions were modelled in the Mike 21 modelling program, studying both wave and hydrodynamic effects on the sediment transport over an average year. True to the beaches' history, a solution with several groynes was expected to be the most sensible and give most value for money. However, it was found that the soft solution, being a plain but intelligent beach nourishment scheme, would be relatively stable while having the benefit of avoiding the problems with downstream erosion typically seen with groynes. Ramboll therefore chose to recommend the beach nourishment scheme as the preferred solution, with the possibility of combining it with a new harbour breakwater that would improve the flow patterns in the area significantly. Hence, this would be an elegant solution when a harbour extension comes on the political agenda. It could furthermore be shown that by establishing a beach and hence decreasing the water depth, wave overtopping reduced significantly under a storm situation as wave breaking prevents the larger waves to arrive at the revetment and adjacent road.