Role of inlet dynamics in scour and burial of marine artifacts in energetic coastal settings

摘要

Tidal inlets are among nature's most dynamic coastal environments, opening and closing in response to storms and, in some cases, migrating long distances back and forth across barrier island shorelines. Most inlets are fronted by a composite shoal system that forms a significant hazard to navigation and, indeed, many shipwrecks (e.g. mid-Atlantic Bight of U.S.) are associated with tidal inlets. For example, over 20 wrecks from a brief 5-year period in the mid-19th Century have been documented at or near tidal inlets along the North Carolina coast alone. Research on tidal inlet dynamics indicates that many of these wrecks are now threatened by a combination of inlet migration, wave scour, and subsequent settling and burial. Fine-scale, subtle changes on the seabed surrounding an exposed wreck can have potentially devastating effects on individual artifacts and their interrelationships which form the archaeological record. Preservation of important maritime wrecks will depend on our ability to not only map the artifacts, but to understand the physical processes in shallow water that can cause damage. Acquisition of scientific data over the past 2 decades reveals that many tidal inlets function in predictable ways and that this knowledge can be used to help manage and preserve wreck sites, and to establish a timetable for artifact recovery. We have developed a model for scour and burial that provides insight as to why many shallow-water wrecks are now at significantly greater depths than their initial groundings and why some are buried by sand. Ultimately, artifacts will achieve a depth equal to the maximum level of scour unless they reach an erosion-resistant substrate and the settling process is interrupted.