Problems in Characterizing Dynamics of Mud Shore Profiles

The relationship between profile shape and wave forcing at shores composed of soft mud is examined. At a given still water level, the modality of change in profile shape under wave action depends on the fluidization potential of mud, which in turn is contingent on the wave characteristics and the dissipative properties of mud. An important determinant of profile shape in areas where mud can be fluidized is the wave attenuation coefficient. Comparatively large values of this coefficient tend to correlate with erosional, concave-upward profiles, and low values with accretionary, convex-upward shapes. Assuming that the rate of energy dissipation per unit area of nonbreaking, normally incident waves is constant in the nearshore shallow zone, an equation to simulate soft-mud shore profiles has been developed. This equation is shown to be applicable to profile data obtained from a variety of mud shore environments. However, it is noted that realistic simulations of the accretionary and erosional characteristics of mud profiles under changing hydrodynamic conditions will require considerations of cross-shore as well as alongshore sediment sources and sinks.