Wave attenuation by artificial reefs

Abstract

This paper intends to demonstrate the applications of artificial reefs to a broader readership concentrating on examples in coastal protection. In Germany, artificial reefs are not widely used as a coastal protection measure probably due to limited knowledge of the potential of this kind of structures. Reefs are not intended to ensure total protection against wave forces, but to reduce the wave energy to a certain given level. In this context a desired reduction of wave agitation can be reached which depends on the demands of coastal protection, ecology and economy. In addition to this lack of information on application possibilities, the often quite complex and inconsistent design formulae for the hydraulic performance of artificial reefs are a handicap for the use of reefs as a coastal defense structure. Therefore, following the presentation of several application concepts, a newly developed analytical model describing the wave climate around a reef is introduced. This model is based on linear wave theory and the results of physical model tests focusing on the local effects at the reef, which were investigated by means of qualitative and quantitative flow visualization. Finally, the application of this analytical model is demonstrated in an example.