Barrier Breaching Versus Overwash Deposition: Predicting the Morphologic Impact of Storms on Coastal Barriers

Jaap H. Nienhuis, Leoni G.H. Heijkers, Gerben Ruessink

Research output: Contribution to journalArticleAcademicpeer-review

Abstract

Waves and water level setup during storms can create overwashing flows across barrier islands. Overwashing flows can cause erosion, barrier breaching, and inlet formation, but their sediments can also be deposited and form washover fans. These widely different outcomes remain difficult to predict. Here we suggest that a breach develops when the sediment volume transported by overwashing flows exceeds the barrier subaerial volume. We form a simple analytical theory that estimates overwashing flows from storm characteristics, barrier morphology, and dune vegetation, and which can be used to assess washover deposition and breaching likelihood. Our theory suggests that barrier width and storm surge height are two important controls on barrier breaching. We test our theory with the hydrodynamic and morphodynamic model Delft3D as well as with field observations of 21 washover fans and 6 breaches that formed during Hurricane Sandy. There is reasonable correspondence for natural but not for developed barrier coasts, where traditional sediment transport equations do not readily apply. Our analytical formulations for breach formation and overwash deposition can be used to improve long-term barrier island models.
Original languageEnglish
Article numbere2021JF006066
Pages (from-to)1-17
Number of pages17
JournalJournal of Geophysical Research: Earth Surface
Volume126
Issue number6
DOIs
Publication statusPublished - Jun 2021

Bibliographical note

Funding Information:
This study was supported by the Netherlands Organisation for Scientific Research Grant VI.Veni.192.123 to JHN. The authors thank Joe Long for pointing us to useful data on Hurricane Sandy. The authors greatly appreciate the constructive reviewing from an anonymous reviewer, Laura Moore, and Arye Janoff, and editorial work from John Shaw and Amy East.

Publisher Copyright:
© 2021. The Authors.

Funding

This study was supported by the Netherlands Organisation for Scientific Research Grant VI.Veni.192.123 to JHN. The authors thank Joe Long for pointing us to useful data on Hurricane Sandy. The authors greatly appreciate the constructive reviewing from an anonymous reviewer, Laura Moore, and Arye Janoff, and editorial work from John Shaw and Amy East.

Keywords

  • storm
  • barrier island
  • Delft3D
  • overwash
  • inlet
  • breaching

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