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Titel |
Morphosedimentary evolution of carbonate sandy beaches at decadal scale : case study in Reunion Island , Indian Ocean |
VerfasserIn |
Marie-Myriam Mahabot, Gwenaelle Pennober, Serge Suanez, Roland Troadec, Christophe Delacourt |
Konferenz |
EGU General Assembly 2017
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Medientyp |
Artikel
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Sprache |
en
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Digitales Dokument |
PDF |
Erschienen |
In: GRA - Volume 19 (2017) |
Datensatznummer |
250153518
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Publikation (Nr.) |
EGU/EGU2017-18511.pdf |
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Zusammenfassung |
Global change introduce a lot of uncertainties concerning future trajectory of beaches by
directly or indirectly modifying major driving factors. An improved understanding of the past
shoreline evolution may help for anticipate future coastline response. However, in tropical
environment, studies concerning carbonate beaches dynamics are scarce compared to open
sandy beaches. Consequently, coral reef protected beaches morphological adjustment is still
poorly understood and long-term evolution rate are poorly quantified in these specific
environment.
In this context, La Reunion Island, insular department of France located in Indian
Ocean, constitute a favoured laboratory. This high volcanic island possesses 25 km of
carbonate beaches which experience hydrodynamic forcing specific from tropical
environment: cyclonic swell during summer and long period swell during winter.
Because of degraded coral reef health and high anthropogenic pressure, 50% of the
beaches are in erosion since 1970s. Beach survey has been conducted since 1990s by
scientist and are now encompassed as pilot site within a French observatory network
which guarantee long-term survey with high resolution observational techniques.
Thus, La Reunion Island is one of the rare carbonate beach to be surveyed since 20
years.
This study aims to examined and quantify beach response at decadal scale on carbonate
sandy beaches of Reunion Island. The study focus on 12 km of beaches from Cap
Champagne to the Passe de Trois-Bassins. The analyze of 15 beach profile data originated
from historical and DGPS beach topographic data confirm long term trend to erosion.
Sediment lost varies between 0.5 and 2 m3.yr−1 since 1998. However longshore current have
led to accretion of some part of beach compartment with rate of 0.7 to 1.6 m3.yr−1. Wave
climate was examined from in-situ measurement over 15 years and show that extreme waves
associated with tropical cyclones and long period swell play a major role in beach
dynamics. Swell frequency and intensity are both determinant for beach evolution. |
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