8 Beaches, Barriers, and Marshes of the Southeast Coast: Dynamic Systems in a Changing Climate

Thursday, 30 March 2017
1:00 PM - 5:00 PM
Potomac G

INVESTIGATING THE MORPHOLOGICAL EVOLUTION AND CLOSURE DYNAMICS OF THE RELICT CABBAGE INLET, MASONBORO ISLAND, N.C

Paper number: 8-11
Program: Theme Sessions
Time: 4:20 PM – 4:40 PM

Authors

  • Stephen Fabian Presenting Author
    University of North Carolina Wilmington, Wilmington, NC
  • Lynn Leonard
    University of North Carolina Wilmington, Wilmington, NC
  • Andrea Hawkes
    University of North Carolina Wilmington, Wilmington, NC
  • Scott Nooner
    University of North Carolina Wilmington, Wilmington, NC

Abstract

Analysis of surface geomorphology and subsurface stratigraphy at former inlet sites can be used to improve understanding of inlet dynamics and to develop qualitative models that may predict the future behavior of active or future inlets. This study examined Cabbage Inlet, a closed inlet, located on an undeveloped, wave-dominated barrier island in southeast North Carolina. The purpose was to establish a chronology of key stages in the inlet’s evolution and determine if the behavior is consistent with the general, inlet life-cycle models (i.e. counter-clockwise rotation, clockwise rotation, or no rotation) as recently described by Seminack (2016). According to historical charts and anecdotal reports, Cabbage Inlet was active from 1737 to 1783 and closed following a large storm. Relict inlet features, including an extensive flood-tidal delta and recurved ridges are visible in aerial photographs and were used to constrain the location of ground-penetrating radar (GPR) surveys and compressed high-intensity radar pulse (CHIRP) tracklines. GPR indicated three separate breaches within the former inlet complex which included one main ebb channel with a width of 84 m. Stratigraphic analysis of channel-fill suggests that the main ebb channel prograded roughly 21 m to the north before infilling conformably. CHIRP surveys, conducted in the adjacent nearshore, detected an ebb channel at 100 m offshore. At this location, the ebb channel was 160 m wide and filled conformably. Based on the preliminary results, given the multiple breaches and northerly migration of the ebb channels, the clockwise rotation model appears to most closely relate to Cabbage Inlet’s behavior prior to closure. Given current sea level rise projections and the potential for increased storm frequency, inlets and breaches are likely to become increasingly common on barrier island shorelines. Because these shorelines are often highly developed, tidal inlet evolution models are needed to predict the behavior of these features. This study demonstrates that examination of surface and subsurface features of a closed inlet can be used to verify existing tidal inlet evolution models thus supporting a generalized model of inlet behavior that may have broad geographic applicability.

Geological Society of America Abstracts with Programs. Vol. 49, No. 3

doi: 10.1130/abs/2017SE-291414

© Copyright 2017 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.