In order to determine the fate of the fine particles and adsorbed contaminants in a short macrotidal estuary, a mathematical modelling system for cohesive suspended mater transport and bottom evolution, including a new consolidation algorithm, is developed. An analysis of successive erosion, transport and deposition processes due to tidal forcing is given and comparisons with field data are provided. A description of mean-terrn bottom variations has been attempted and is partially validated by differential sounding.