New Ebb-Tidal Delta at an Old Inlet, Shark River Inlet, New Jersey.

摘要

Shark River Inlet, located on the north New Jersey coast, is served by a federal navigation channel that has until recently required little maintenance dredging. Although possessing a small estuary, the inlet is hydraulically efficient because of the small width to depth ratio of its entrance that is stabilized by parallel jetties. After placement of approximately 4.8 million m3 of beach nourishment to the north and south of the inlet as part of an erosion-control project conducted in the late 1990s, inlet maintenance increased beyond that anticipated. Analysis of channel and nearshore surveys indicates that an ebb-tidal delta is forming where none had existed previously, attributed to the recent availability of sand from the beach nourishment and a lack of sand prior to that construction. Jetty tip shoals also encroach on the channel, dependent on season, with longshore transport directed primarily to the north during summer (the predominant direction of transport) and to the south during winter. Formation of the ebb delta must be accounted for in the sand budget of the adjacent beaches. After conducting a GIS analysis of ebb delta growth to understand geomorphic trends, the Coastal Modeling System (CMS) was established to numerically simulate waves current, sand transport, and morphology change. The CMS reproduced observed trends in ebb-delta growth, and multi-year simulations indicate the time scale of approach to dynamic equilibrium of the ebb delta and establishment of natural sand bypassing at the inlet.