Models designed to simulate physical or mechanical phenomena associated with the seafloor often require a knowledge of or at least an ability to estimate, the physical property structure of the upper portion of the sediment column. High-frequency sound propagation in the uppermost decimeters of the seafloor, for example, is controlled primarily by the spatial density structure of the sediments and the geometry and geotechnical characteristics of volume inhomogeneities, such as shells, rocks, and gas bubbles. Macrostructures (sedimentary features at spatial scales a few centimeters or less) become extremely important at acoustic frequencies approaching 100 kHz and must be considered for realistic scattering models. Biological and hydrodynamic processes are believed to be largely responsible for creating macrostructures, yet the nature and magnitude of variations in sediment physical properties induced by these mechanisms are not well known. A major obstacle to understanding these interactions better is the inability of most traditional analytical techniques to resolve these structures or provide the type of information necessary to develop models in sufficient quantitative detail. Working under Dr. Aubrey L. Anderson on the Naval Research Laboratory-sponsored Coastal Benthic Boundary Layer Special Research Project (CBBL SRP; Richardson, 1994), I addressed these problems in my dissertation by examining spatial relationships between sediment macrostructure and variations in sediment physical properties (Orsi, 1994). Defining the significance of environmental processes in the development of these relationships was particularly important.