CONCEPTUAL FRAMEWORK AND STUDY AREA Sample Clauses

CONCEPTUAL FRAMEWORK AND STUDY AREA. Introduction The inner shelf is the region adjacent to the coast where the entire water column is dominated by friction with the overlying air and the underlying seabed. In spatial terms, it lies between the shoreline and the mid-continental shelf, with the surf zone as its most landward portion. The dominant hydrodynamic variables that operate in this environment are infragravity and wind waves, as well as currents generated by winds and tides. These hydrodynamic influences jointly exert stress on the water column and seabed, causing sediment to be mobilized and transported along the bed or in suspension (Xxx et al., 1997). Given the importance of wind as a forcing mechanism, it follows that the passage of atmospheric storms often results in hydrodynamic responses, bottom boundary layer modification, and sediment transport on inner shelves. Not surprisingly, therefore, field research has often demonstrated that storm events can be responsible for transporting very large quantities of sediment in comparison with fair weather conditions. The general model for inner shelf sediment transport that has emerged is one in which fair weather wave asymmetry gradually moves sediment onshore, while during storms, high wave orbital currents suspend sediment that is then transported offshore by downwelling mean flows (Xxxxxx et al, 1991; Xxxxxxxxx and Xxxxxx, 1994). Furthermore, it is commonly assumed that alongshelf transport of suspended sediment during both fair weather and storm conditions is much higher than across-shelf transport, owing to stronger mean flows in the alongshore direction. Considerable deviation from these general models results, however, from variability in meteorological conditions, local geology, bathymetry, and physical oceanography. Additionally, a variety of complex and poorly-understood interactions and feedback mechanisms operate in the bottom boundary layer. For example, while it is sometimes assumed that waves provide the shear stress (or “stirring mechanism”) that entrains sediment that is then transported by mean currents, recent research has demonstrated that waves and currents interact in a highly non-linear fashion, complicating sediment transport predictions (Xxxxx and Xxxxxx, 1979, 1986). The Louisiana inner shelf is an example of a low-energy environment where significant hydrodynamic activity is generated almost exclusively by local storms, including both tropical (summer) and extratropical (winter) storms. Furthermore, the Louis...