Third correction of the Rhône River in Switzerland: physical and numerical modelling of the “Martigny bend” priority measure

The Rhône River, second largest in Switzerland, has already been corrected twice (1863-1893; 1930-1960) to ensure safety and economic development in the Rhône valley. However, in October 2000, the highest flood of the century occurred showing the limitations of the two first corrections and the need for a third one. The Rhône bend, located near the city of Martigny, is a priority project because of the high damage potential. Given the complexity of the hydraulic and morphological phenomena, physical and numerical modelling are used to validate and optimize the project design. To obtain the best results, the two models must be used together and the results cross-compared. Hence, they are checked and adjusted in parallel. The first tests, which were purely hydraulic, showed a good agreement between them. The extreme flood succeeded to pass through the enlarged cross-section with an acceptable water level. After these encouraging results, the morphodynamic tests are ongoing.