Coastal Geology

at Bryn Mawr

 

What and Why?

Most coastal geologic research aims to make progress on either or both of the following questions:

      1. How and why has sea level varied in the past, and how will sea level change in the future?
      2. What factors control shoreline erosion rates and the stability of coastal landforms?

These two related questions are scientifically broad and complex, but the answers clearly are of interest to society. For this reason much coastal research focuses on facets of these questions applied to specific parts of the coastline.


Previous Projects


At Bryn Mawr, recent coastal research projects have considered 1) modern beach processes, and 2) relationships among landscape ecology, sedimentology and present-day geomorphology.

Influence of groins on short-term beach variability, southern New Jersey

Kristen Bollman Slijepcevic (MA Geology '02) carried out thesis research on the southern New Jersey shore that pertains to coastal management questions regarding methods of shoreline stabilization. The project employed repeated, high-resolution, topographic surveys at several beach sites in Stone Harbor and Avalon, NJ.  The sites were re-surveyed as many as six times during the 10 month study period. By quantifying the short-term dynamics (sand gain/loss) of the beach sites, Kristen evaluated the degree to which groins influence local sand budgets. The particular management question addressed by this work is whether groin fields should remain in place after beach nourishment has been adopted as a response to erosion. A number of state management agencies have mandated that coastal municipalities change from so-called hard stabilization (groins, seawalls, breakwaters) to soft stabilization (beach nourishment), but usually the pre-existing hard structures remain in place. Although limited in scope, the results of Slijepcevic's study show that groins offer no benefit once the shoreline has adjusted to the groin's presence. Further, her results suggest that groins may accelerate offshore sand loss compared with ungroined beaches.

The series of beach profiles collected for this study form a baseline the characterized the envelope of variability at these sites. Students in GEOL 205 (Sedimentology) have re-surveyed some of the beach profiles using the same local survey benchmarks. These follow-up surveys allow informative comparisons of how the beach profiles responds to short-term changes in the wind and wave climate (click to view an example).



Impact of grazing on barrier island geomorphology, central North Carolina coast

An undergraduate summer research project by Kira Diaz Tushman (AB Geology '04) measured topography, vegetation and sedimentology along the North Bay barrier, near the Cedar Island ferry terminal in Pamlico Sound, North Carolina. Ms. Diaz Tushman's project built on an earlier study by Barber and Pilkey (2001 abstract) and examined how animal grazing influences dune height and barrier island geomorphology. Diaz Tushman presented her results at the 2002 GSA meeting in Denver (see abstract). 

Future and Ongoing Projects

Continuing work in coastal North Carolina focuses on the Holocene history of barrier islands and shorelines in Carteret County, NC. In May, 2004, Barber and student Stephanie Nebel (BMC Geology ’05) traveled to Morehead City, NC, and conducted a joint marine geophysical survey with Dr. Walter Barnhardt (USGS-Woods Hole) and Pres Viator (Univ. of North Carolina-Chapel Hill). Seismic reflection profiles and side-scan sonar surveys were completed offshore Bogue and Shackleford Banks. Some of the data gathered were used during Nebel’s summer 2004 science research project (supervised by Barber). Nebel is incorporating these and other geophysical data into her Fall 2004 senior thesis project.

During offshore coring operations in Fall 2004, Charles Hoffman and Jessica Pierson (NC Geological Survey) and Rob Thieler (USGS-Woods Hole) obtained at least one vibracore from a Holocene channel offshore Shackleford Banks that had been mapped and interpreted by Nebel.

Ground-penetrating radar surveys during summer 2004 were carried out near Pine Knoll Shores on Bogue Banks, and along the SE limb of the North Bay barrier, where Cedar Island fronts Pamlico Sound.

A planned GPR project (pending approval by managers of the Cape Lookout National Seashore) aims to evaluate the internal stratigraphy of large dunes on Shackleford Banks, NC. The dunes targeted for study formed from a mass of sand that came ashore in the early part of the 20th century.


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Geomorphology at Bryn Mawr