科研之友
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摘要
Coastal Louisiana is geologically unique in the United States because its complex shallow geologic structure is the result of fluvial deposition (Mississippi and Atchafalaya Rivers) and marine reworking over thousands of years. Other characteristics include the preponderance of fine sediment, relative youth, and shallow nearshore slope. It has been impacted by more than 150 years of project-focused designs that have modified regional sediment transport. Because of engineering and commercial activities on the upper Mississippi River and the delta, the system is now suffering from innumerable geomorphic changes, which have produced profound social and economic consequences. Sediment to this coast has been almost totally supplied by the Mississippi's distributaries, with deltaic lobes changing over the centuries. Sediment delivery has diminished by over 50% during the last 150 years because of up-river engineering activities such as dam construction, bank stabilization, dredging, and levees. The ultimate implication of reduced sediment and rapid relative sea-level rise is that the delta can no longer grow as it did before urbanization and development of the continent. A sediment budget has been developed for the Louisiana coast based on multiyear data preceding Hurricanes Katrina and Rita. The budget is based on numerous sources and dredging data from the U.S. Army Corps of Engineers, New Orleans District. Despite the typically low-wave energy climate, sediment is transported alongshore between some cells. Also, there is significant loss offshore, possibly a consequence of storm impacts, sediment consolidation, and rapid relative sea-level rise.
- 出版日期2013
