Wave Attenuation due to Bottom Vegetation

Abstract

It is generally acknowlegded that bottom vegetation has a wave damping effect in shallow waters. Yet the nature of the frictional processes is not fully known and quantification of the forces involved are lacking. Research on the topic is however in progress. A textbook dealing with waves and biology in a broad context is due to Denny (1988). Many of the theoretical approaches to the problem are based on investigations of flow in porous media and percolation. For reference see Liu and Dalrymple (1983) and Gu and Wang (1990). However the difference is that the bottom plants interact with the flow. Some pioneering works dealing with the interaction are due to Price, Tomlinson and Hunt (1968), Kobayashi, Raichle and Asano (1993) and Asano, Deguchi and Kobayashi (1992). Dalrymple, Kirby and Hwang (1984) have investigated the wave diffraction caused by energy dissipation in zones with bottom vegetation.Wang and T0rum (1994) and Duby and T0rum (1994) have dealt with the mutual interaction of waves and kelp plants and consequences for transport of bottom sediments. A common result of many of the works is that the amplitude of the horizontal velocity of long waves is reduced down in the kelp layer. That is not what we have observed and therefore an alternative mechanism of wave damping has been proposed. The bottom vegetation of greatest interest in our waters is the kelp called