Stem breakage of salt marsh vegetation under wave forcing: A field and model study

Vincent Vuik (Corresponding Author), Hannah Y. Suh Heo, Zhenchang Zhu, Bastiaan Wijnand Borsje, Sebastiaan N. Jonkman

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    Abstract

    One of the services provided by coastal ecosystems is wave attenuation by vegetation, and subsequent reduction of wave loads on flood defense structures. Therefore, stability of vegetation under wave forcing is an important factor to consider. This paper presents a model which determines the wave load that plant stems can withstand before they break or fold. This occurs when wave-induced bending stresses exceed the flexural strength of stems. Flexural strength was determined by means of three-point-bending tests, which were carried out for two common salt marsh species: Spartina anglica (common cord-grass) and Scirpus maritimus (sea club-rush), at different stages in the seasonal cycle. Plant stability is expressed in terms of a critical orbital velocity, which combines factors that contribute to stability: high flexural strength, large stem diameter, low vegetation height, high flexibility and a low drag coefficient. In order to include stem breakage in the computation of wave attenuation by vegetation, the stem breakage model was implemented in a wave energy balance. A model parameter was calibrated so that the predicted stem breakage corresponded with the wave-induced loss of biomass that occurred in the field. The stability of Spartina is significantly higher than that of Scirpus, because of its higher strength, shorter stems, and greater flexibility. The model is validated by applying wave flume tests of Elymus athericus (sea couch), which produced reasonable results with regards to the threshold of folding and overall stem breakage percentage, despite the high flexibility of this species. Application of the stem breakage model will lead to a more realistic assessment of the role of vegetation for coastal protection.
    Original languageEnglish
    Pages (from-to)41-58
    Number of pages18
    JournalEstuarine, coastal and shelf science
    Volume200
    DOIs
    Publication statusPublished - 5 Jan 2018

    Fingerprint

    breakage
    salt marshes
    saltmarsh
    stem
    vegetation
    stems
    strength (mechanics)
    wave attenuation
    Bolboschoenus maritimus
    Spartina anglica
    drag coefficient
    Scirpus
    Elymus
    Spartina
    coastal protection
    wave energy
    sodium chloride
    energy balance
    folding
    testing

    Keywords

    • Coastal protection
    • Salt marsh
    • Stem breakage model
    • Three-point-bending test
    • Vegetation
    • Wave attenuation

    Cite this

    Vuik, Vincent ; Suh Heo, Hannah Y. ; Zhu, Zhenchang ; Borsje, Bastiaan Wijnand ; Jonkman, Sebastiaan N. / Stem breakage of salt marsh vegetation under wave forcing : A field and model study. In: Estuarine, coastal and shelf science. 2018 ; Vol. 200. pp. 41-58.
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    abstract = "One of the services provided by coastal ecosystems is wave attenuation by vegetation, and subsequent reduction of wave loads on flood defense structures. Therefore, stability of vegetation under wave forcing is an important factor to consider. This paper presents a model which determines the wave load that plant stems can withstand before they break or fold. This occurs when wave-induced bending stresses exceed the flexural strength of stems. Flexural strength was determined by means of three-point-bending tests, which were carried out for two common salt marsh species: Spartina anglica (common cord-grass) and Scirpus maritimus (sea club-rush), at different stages in the seasonal cycle. Plant stability is expressed in terms of a critical orbital velocity, which combines factors that contribute to stability: high flexural strength, large stem diameter, low vegetation height, high flexibility and a low drag coefficient. In order to include stem breakage in the computation of wave attenuation by vegetation, the stem breakage model was implemented in a wave energy balance. A model parameter was calibrated so that the predicted stem breakage corresponded with the wave-induced loss of biomass that occurred in the field. The stability of Spartina is significantly higher than that of Scirpus, because of its higher strength, shorter stems, and greater flexibility. The model is validated by applying wave flume tests of Elymus athericus (sea couch), which produced reasonable results with regards to the threshold of folding and overall stem breakage percentage, despite the high flexibility of this species. Application of the stem breakage model will lead to a more realistic assessment of the role of vegetation for coastal protection.",
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    Stem breakage of salt marsh vegetation under wave forcing : A field and model study. / Vuik, Vincent (Corresponding Author); Suh Heo, Hannah Y.; Zhu, Zhenchang; Borsje, Bastiaan Wijnand; Jonkman, Sebastiaan N.

    In: Estuarine, coastal and shelf science, Vol. 200, 05.01.2018, p. 41-58.

    Research output: Contribution to journalArticleAcademicpeer-review

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    AU - Vuik, Vincent

    AU - Suh Heo, Hannah Y.

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