The Stability of Vegetated Tidal Flats in a Coastal Lagoon Through Quasi In-Situ Measurements of Sediment Erodibility

Ganthy, F., Sottolichio A. and Verney, R., 2011. The Stability of Vegetated Tidal Flats in a Coastal Lagoon Through Quasi In-Situ Measurements of Sediment Erodibility. Journal of Coastal Research, SI 64 (Proceedings of the 11th International Coastal Symposium), 1500 - 1504. Szczecin, Poland, ISSN 0749-0208 Erosion tests performed from sediment cores collected in the Arcachon lagoon (French Atlantic coast) were used to describe and quantify the sediment erodibility and the stability of tidal flats, in relation to the growth cycle of seagrass beds of Zostera noltii. This study highlights a seasonal trend in the erosion resistance of surficial vegetated sediments, related to the modification of sediment characteristics by meadows. The bed stabilization effect induced by the root system and its seasonality has been also evidenced, with a strong stability in winter, when roots are more developed. A satisfactory parameterization of the Partheniades erosion law has also be found for different cases (vegetated/unvegetated, surface/sub-surface or root system, and the growth stage). This parameterization is based on the mud fraction for all the cases excepted for sediments located in the root system of meadows, where the parameterization is based on the ratio between the mud fraction and the root biomass.