Camille Traini (PhD)

The Vilaine estuary : natural evolution and anthropisation

Abstract

The Vilaine estuary is located on the Atlantic coast in Southern Brittany. Since 1970, the Arzal dam has been protecting the Redon marshes from flooding. It constitutes an important reserve of fresh water and a main road. The presence of this structure has disrupted the hydro-sedimentary dynamics of the estuary ; this is mainly reflected in a pronounced silting of the estuary portion downstream of the dam. It took about twenty years for this structure to be integrated into the estuarine landscape and for the natural hydrodynamic parameters to take effect. Anthropic impacts must therefore be taken into account in the morpho-sedimentary functioning in order to predict their evolution and test curative and preventive solutions. The geomorphological heritage through hydrodynamic parameters (wind swell and tidal dynamics) has governed the sedimentary deposits and the estuary valley flooded about 10,000 to 9,000 years ago BP. The power of these deposits is important : locally it reaches about 40 meters. The five sequences of transgressive marine deposits recognized in the Vilaine Bay are also present within the estuary valley and up to about 40 km inland. The morphological control as well as the architecture of the deposits are indicating a ria-type sedimentary environment. The estuarine space of the Vilaine has therefore recorded the combination of natural and anthropic factors and will undergo further modifications in connection with the sea level rise over the next few years.

Supervisors
David Menier

Keywords
X-Ray fluorescence
HR sparker seismic system
Arzal dam
Bathymetric evolution
Estuarian sediments
Longshore drift
Transgression (Geology)
Holocene
France
Vilaine estuary