2D Modelling of the Rhone River Between Arles and the Sea in the Frame of the Flood Prevention Plan

Following the December 2003 floods on the Rhône, the public authorities embarked on a far-ranging flood prevention plan called the “Rhône Plan”, The reinforcement works for the embankments foreseen by Symadrem, the management authority overseeing the embankments of the Rhône; aim to move the banks back along certain sections and develop overflow zones in order to ensure overflows without breaches in the event of water levels higher than the reference water levels. The hydraulic study was carried out using two-dimensional modelling with Telemac-2D software and Infoworks RS 2D software. Four two-dimensional models were built: three models, each featuring approximately 300,000 elements, were built for the channel of the petit Rhône with its embankments, and the protected beds on the right bank and the left bank (the insular part of the Camargue), one model covers the left bank of the Rhône, with about 150,000 elements. The linear distances modelled cover a length of approximately 60 km of the Rhône and the Petit Rhône between Arles and the sea. The surface area modelled is approximately 1800 km². The objective of the modelling is to determine the initial and intermediate state without breaches in the riverbed within the embankments, adjust the works, determine the final state in the riverbed within its embankments, determine the hydrographs of the overflowing high water levels for propagation in the floodplain, and determine several scenarios of embankment breaches for the purpose of the hazard study.