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Effects of proposed sediment borrow pits on nearshore wave climate and longshore sediment transport rate along Breton Island, Louisiana

Open-File Report 2015-1055

Prepared in cooperation with the U.S. Fish and Wildlife Service
By:
https://doi.org/10.3133/ofr20151055

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Abstract

As part of a plan to preserve bird habitat on Breton Island, the southernmost extent of the Chandeleur Islands and part of the Breton National Wildlife Refuge in Louisiana, the U.S. Fish and Wildlife Service plans to increase island elevation with sand supplied from offshore resources. Proposed sand extraction sites include areas offshore where the seafloor morphology suggests suitable quantities of sediment may be found. Two proposed locations east and south of the island, between 5.5–9 kilometers from the island in 3–6 meters of water, have been identified. Borrow pits are perturbations to shallow-water bathymetry and thus can affect the wave field in a variety of ways, including alterations in sediment transport and new erosional or accretional patterns along the beach. A scenario-based numerical modeling strategy was used to assess the effects of the proposed offshore borrow pits on the nearshore wave field. Effects were assessed over a range of wave conditions and were gaged by changes in significant wave height and wave direction inshore of the borrow sites, as well as by changes in the calculated longshore sediment transport rate. The change in magnitude of the calculated sediment transport rate with the addition of the two borrow pits was an order of magnitude less than the calculated baseline transport rate.

Suggested Citation

Dalyander, P.S., Mickey, R.C., Long, J.W., and Flocks, James, 2017, Effects of proposed borrow pits on the nearshore wave climate and longshore sediment transport rate along Breton Island, Louisiana (ver. 2.0, August 2017): U.S. Geological Survey Open-File Report 2015–1055, 44 p., https://doi.org/10.3133/ofr20151055.

ISSN: 2331-1258 (online)

Study Area

Table of Contents

  • List of Figures
  • List of Tables
  • Conversion Factors
  • Abbreviations
  • Abstract 
  • Introduction
  • Methods
  • Results
  • Conclusions
  • Acknowledgments
  • Digital Data Files
  • References Cited
  • Appendix 1
  • Appendix 2
  • Appendix 3
  • Appendix 4

Additional publication details

Publication type:
Report
Publication Subtype:
USGS Numbered Series
Title:
Effects of proposed sediment borrow pits on nearshore wave climate and longshore sediment transport rate along Breton Island, Louisiana
Series title:
Open-File Report
Series number:
2015-1055
DOI:
10.3133/ofr20151055
Edition:
Version 1.0: May 2015; Version 2.0: August 2017
Year Published:
2015
Language:
English
Publisher:
U.S. Geological Survey
Publisher location:
Reston, VA
Contributing office(s):
St. Petersburg Coastal and Marine Science Center
Description:
Report: vi, 44 p.; HTML Document; Downloads Directory; Data Release; Version History
Country:
United States
State:
Louisiana
Other Geospatial:
Breton Island
Online Only (Y/N):
Y
Additional Online Files (Y/N):
Y