Reza Arefi - Ph.D. Candidate, K.N. Toosi University of Technology, Tehran, Iran
Kourosh Hejazi - Civil Eng. Dept., K.N. Toosi University of Tech., Tehran, Iran
Mohsen Soltanpour - K.N. Toosi University of Technology, Tehran, Iran
Faraz Jomehri - Ph.D. Candidate, K.N. Toosi University of Technology, Tehran, Iran,

Typical muddy coasts can be found in many coastal areas of the world. In the presence of cohesive sediments, wave damping is enhanced; surface waves can beattenuated appreciably in a finite number of wave periods or wave lengths [1]. The damping of the surface waves can be considerable; in fact, Gade (1985) [2] noted that therewas a location in the Gulf of Mexico, known as the Mud Hole, where the attenuation of waves due to the mud bottom was so great that fishing boats used it as anemergency harbor during storms. The pressure gradient of water waves and the shear stress at the interface between the water layer and the mud layer are two main parameters in the wave-mud interaction. However, due to the interaction of wave and muddy bed, a zone with high suspende dloads of cohesive sediments is formed. To investigate wave-mud interaction in laboratory, the suspended cohesive sediments will cause problems in the normal procedure of the experiments.Therefore, using a thin plastic cover which separates the mud from water body and facilitates the laboratory experiments, is also included in the investigations.Although the plastic layer with very low bending strength over the muddy bed will transfer the pressure gradient from water body to mud, transmission of the shearstress will be negligible. However, the impact of the normal stress is much more than the shear stress at the water-mud interface for the wave attenuation and for theinitiation of the movement of mud [3]. To investigate the impact of a thin plastic cover on wave attenuation on a muddy bed, a series of wave flume experiments for wave-mud system has been performed in this study on both flat and inclined muddy beds.