ABSTRACT
In 1997, calculations showed that the design discharge of 180 m3/s (corresponding to a 100-year peak flood) could not flow without overtopping of the banks at the second bridge site. In 2001, some works were performed, in particular, the construction of a concrete bed in a 100 m reach (Fig. 1). Sediment transport was not taken into account and the huge amount of boulders deposited in the bed after the first flood (November 2004) clearly showed that a risk of flooding still exists (Fig. 2). To illustrate the effect of these works on the peak water levels during a 100-year flood, it was decided to perform calculations with a model simulating the sediment transport and the change of riverbed during the flood (Paquier, 2005).
