Short-term Beach Variability at Stone Harbor, southern New Jersey coast, USA

The photos below show the beach and rock groin at 114th Street, Stone Harbor, looking to the SE. The first photo (5 Oct. 2002) followed a period of hard northeasterly wind. The narrower beach to right of groin indicates net southward littoral drift. Two weeks later (20 Oct.), an interval of hard southwesterly wind had reversed the offset in beach width, indicating at least a short interval of net northward sand transport (to the left in the photo). As longshore currents interact with the groin, some of the sand that otherwise would move downdrift may move into deeper water offshore, thereby creating a local deficit near the groin. The study by Kristen Bollman Slijepcevic evaluated this hypothesis (see description on BMC Coastal Geology page).

North  <---      5 October 2002
20 October 2002     --->  South


Stone Harbor beach profiles from three separate dates (plots below). The two sets of profiles from October 2001 are from Kristen Bollman Slijepcevic's MA project, whereas the 5 October 2002 profile (yellow triangles) was measured by students on a GEOL 205 class field trip. The 5 Oct. '02 profile is from the same date as the photo on the left, above. Compare the 5 Oct '02 beach shape on the north (upper plot) and south (lower plot) sides of the groin. In the 5 Oct. '02 profiles, the north side of the groin shows concave-downward topography and there is a prominent berm, both typical of accretion. On the south side of the groin, most of the beach profile is concave up, indicative of short-term erosion.

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