ABSTRACT

The effects of cohesive sedimentary environments on nearshore wave evolution are studied comparing parallel in situ observations at two locations along the west Louisiana coast. The sites are similar (near the 5 m isobath, nearly identical atmospheric conditions) but are characterized by different sedimentary environments, one dominated by sand, the other by mud.

Over the muddy seabed, wave dissipation is observed across the spectrum. Strong damping of the high-frequency sea band (which interacts weakly with the bottom) suggests that a different dissipation mechanism than bottom friction becomes active during a storm, possibly increased viscosity due to resuspended sediment.

Existing wave models have been developed largely for sandy environments and do not distinguish between the different sedimentary fabrics. Preliminary numerical simulations reproduce wave evolution in the sandy environment fairly well, but they grossly overestimate wave energy in the case of the muddy environment.