Damping characteristics of wave propagation across the muddy Louisiana shelf

Abstract

To improve the understanding of the effect of a muddy seafloor on wave dynamics, a new data set, collected on the muddy Louisiana coast in the spring of 2008, is analyzed. Waves were observed for two months at 32 locations along a 25 km transect between 13- and 2-m water depth. To investigate the effects of mud on the nearshore wave energy balance, the SWAN wave model was used to hindcast the observational period, using a standard JONSWAP bottom friction term for wave-bottom interaction to represent wave propagation across a sandy shelf. The findings show that the interaction between mud and waves is episodic. We identify two types of wave-mud damping events, where either 1) the damping occurs in the energetic ranges of the spectrum, generally stronger at lower frequencies, or 2) wave growth is suppressed during times of heightened sediment concentrations throughout the water column. Our observations suggest that currents play an important role in the resuspension of sediments.