Effect of Wind Waves on Distribution of Muddy Bottom Sediments in Baltimore Harbor, USA

Abstract

Muddy bottom sediments in industrialized coastal areas are often quite enriched in contaminants and organic matter. It is important to study the processes that control fine sediment accumulation in these areas. In order to examine the relationship between hydrodynamic forcing and sediment characteristics in Baltimore Harbor, MD, USA, estimated wave-induced bottom shear stresses were compared with sediment mud content distributions. Wave fields in the harbor were simulated with a numerical wave hindcasting model, HISWA. Spatial distributions of expected wave-induced bottom shear stresses in four wind speed ranges were obtained by directionally averaging wave-induced bottom shear stress predictions, weighting each direction by its probability of occurrence based on wind statistics from a long term data set collected near the harbor. A negative relationship between mud content and wave-induced shear stress was clear only for the stronger wind cases that occurred less than 5% of the time. The results suggest that the distribution of muddy bottom sediments in the mainstem of Baltimore Harbor is controlled largely by high wind wave events that occur infrequently. INTRODUCTION Contaminated bottom sediments in coastal areas present one of the most serious problems to be solved for restoration of healthy coastal and estuarinc environments. It is quite important to study processes that control fine sediment accumulation patterns in the coastal zone because contaminant concentrations are highly correlated with mud content in the sediments. Thus, the movement of contaminants can be understood only by understanding the movement of fine particles (Dyer, 1989). Spatial patterns of fine particle accumulation in coastal areas may depend on several factors including proximity to sources of fine sediment as well as hydrodynamic conditions such as tidal currents, wave forcing, and so on. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Port and Harbor Research Institute, Ministry of Transport, 3-1-1 Nagase, Yokosuka 239-0826, Japan, ; y_nakagawa@ipc.phd.go.jp e University of Maryland Center for Environmental Science, Horn Point Laboratory 3 Maryland Department of Natural Resources, Maryland Geological Survey