Sand Bypassing Restores Natural Processes to Assateague Island, Maryland

Abstract

The North End Restoration Project uses a regional sediment management approach to address jetty-induced sediment deprivation and accelerated erosion on Assateague Island, Maryland. The biannual sand bypassing project dredges sand from the ebb and flood tidal deltas and places it in the nearshore area of the project site rather than on the upper shoreface, thereby replicating natural sediment transport processes and minimizing adverse impacts to subaerial habitats. Calm weather has prevailed since sand bypassing began, and accretion occurred at all depths within the placement area and at shallow depths to the north and south. Erosion occurred at lower depths and north of the ebb tidal delta attachment bar, which may block sand transport to the northernmost shoreface and where and where wave refraction over the ebb tidal delta and unique tidal circulation patterns contribute to upper shoreface erosion.

Transient and persistent shoreline change from a storm

“…Jetties constructed on both sides of the inlet in 1935 interrupted alongshore sediment transport from the north, causing severe coastal erosion south of the inlet [Rosati and Ebersole, 1996]. An ebb tidal delta subsequently formed and developed into a 300 m attachment bar connected to the shore about 650-950 m south of the inlet [Schupp et al, 2007;Rosati and Ebersole, 1996] thus restoring a portion of the alongshore sediment transport [Kraus, 2000].…”

“…Its Atlantic side consists of coastal dunes that seldom reach elevations above 2 meters, and its landward side is a low-elevation back barrier flat, sand and tidal wetland. Dominant waves have an average height of 1 m [Schupp et al, 2007], and spring tides fluctuate between −1 and 3 m [Field, 1979]. Ocean City Inlet formed during a hurricane in 1933.…”

Dynamics of sediments disposed in the marine coastal zone near the Vistula Lagoon inlet, south-eastern part of the Baltic Sea

“…This paper verifies a proposal to use the dredged material to protect the eroded shore segment at the Vistula Spit along the Kosa village following known examples of using dredged material to replace natural sediment transport processes (Boswood, Murray 2001;Schupp et al 2007). In contrast to the conditions at the relatively deep dumping sites (25-30 m and 44-49 m) located near the Lithuanian shore, where material remains untouched even after extreme storms (Pupienis, Žilinskas 2005), the new dumping site is proposed at shallower depths of 7-9 metres, which is still safe enough for disposal operations by the dredger and allows the material to be easily redeposited shoreward by wind, waves and currents during moderate atmospheric forcing.…”