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Morphosedimentary multiyear changes on a barred coast (Gulf of Lions, Mediterranean Sea, France)
Barusseau, J.-P.; Radulescu, M.; Descamps, C.; Akouango, E.; Gerbe, A. (1994). Morphosedimentary multiyear changes on a barred coast (Gulf of Lions, Mediterranean Sea, France). Mar. Geol. 122(1-2): 47-62. hdl.handle.net/10.1016/0025-3227(94)90204-6
In: Marine Geology. Elsevier: Amsterdam. ISSN 0025-3227, more
Peer reviewed article  

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Keyword
    Marine

Authors  Top 
  • Barusseau, J.-P.
  • Radulescu, M.
  • Descamps, C.
  • Akouango, E.
  • Gerbe, A.

Abstract
    An overall estimate of the relationship between the changes in the nearshore morphology, the evolution of the sedimentary budget, the beach morphodynamics and the variation of grain-size characteristics along the beach barrier of Thau Lagoon, Languedoc, France, was attempted by synthesizing the data from different surveys: a basic survey of two separate grids of 11 closely-spaced (50 m) transverse profiles during 1989–1991, a long-baseline (11 km) survey of 11 beach profiles during 1988–1991 and an earlier, long-run (1984–1990) survey of 6 widely-spaced bathymetric profiles covering discretely the whole stretch of the nearshore zone. Time intervals between profile monitorings within each type of survey differed, but many measurements during the recent 1989–1991 period were coincident.The stable two-bar system that was generally developed all over this nearshore zone has been gradually changing at the northeastern end, south of the town of Sète, since 1989, under the effect of a series of new defense structures upstream in the dominant NE-SW wave-induced longshore current, with a tendency toward a single-bar profile. The average nearshore slope was steeper (0.91%) in the Sète close-survey area than in the southwestern area (0.83%). During the same period, acceleration in beach erosion has been observed at the northeast, in contrast with a stable dynamic equilibrium over the southwestern beach and nearshore profiles.Over a longer period (1984–1990), scouring of the nearshore sand-prism down to the 10-m isobath at the northeastern end between the extreme bathymetric profiles, could be estimated at about 37,000 m3, while the overall sedimentary budget was positive.Bar migration and morphologic changes in the study areas were not related to any seasonal cycle in the wave climate, but were more significant when this was more energetic, as during 1989. An overall attenuation in nearshore morphodynamics was observed during the following two years, although some rapid local changes between consecutive measurements could be detected.Temporal variation of grain-size characteristics were therefore small and/or not significant. Conversely, on the subaerial beach, alongshore differentiation in mean diameter and in sorting and skewness parameters is consistent with the evolution of the erosion-accumulation processes following a long-period wave-like sand-transfer from northeast to southwest.

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