Morphodynamics and sand transport on perched beaches

Cyprien Bosserelle

    Research output: ThesisDoctoral Thesis

    1277 Downloads (Pure)

    Abstract

    [Truncated abstract] Beach morphology results from the complex interactions between sediments and nearshore hydrodynamics. In many locations these interactions are influenced by reef and rock outcrops along the beach profile. These hard landforms form structural constraints in the nearshore that result in perched beaches, defined as beaches that are underlain and/or fronted seaward by hard landforms. Beaches along the Yanchep coastline in south-western Australia are perched on Quaternary limestone reefs. Sand transport at Yanchep Lagoon varies over a range of temporal scales and is strongly a ected by interactions with the topographically complex reefs. To better understand how perched beaches are a ected by waves, water level and the topography of reefs, this study investigated processes that in uence hydrodynamics and sand transport on perched beaches at a range of scales extending from the ocean basin; the continental shelf; the beach and at the reef scale. A suite of numerical models, complemented by eld data, were con gured and applied to cover a range of spatial and temporal scales. To include these scales, four different models were used: (1) Wave Watch III was used to hindcast waves from 1970 to 2009 in the southern Indian Ocean basin; (2) SWAN was used to evaluate the dissipation of waves on the continental shelf; (3) XBeach GPU was developed to simulate the wave dissipation, the hydrodynamics and the transport of sand at the beach scale; and, (4) Smooth Particle Hydrodynamics (SPH) model was used at ne scale to simulate the wave breaking on a steep reef and the transport of individual sand grains. The mean signi cant wave heights, at the basin scale, indicated that between 1970 and 2009, the number of large wave events incident along the Western Australian coastline did not change signi cantly despite the increasing number of large wave events in the Southern Indian Ocean. The mean latitude of large wave events was negatively correlated to the Southern Annular Mode. Therefore, the Southern Annular Mode modulates the inter annual variability of the wave heights but the swell generated from the increasing number of storms in the Southern Ocean contributed to increasing the mean annual wave height o shore of Western Australia.
    Original languageEnglish
    QualificationDoctor of Philosophy
    Publication statusUnpublished - 2014

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