During late morning, a dike guard noted several incipient breaks in a dike along the left bank of the PETIT RHÔNE river. The erosion phenomenon was rapid, so the operator decided to perform emergency riprap work in the bank caving to prevent the structure from rupturing. They began operations that afternoon and finished the following day. The simultaneous occurrence of 3 phenomena is at the origin of the damage caused to the structure:
- annual flooding of the Rhône river (4500 m³/s)
- a strong marine storm (5 m waves in Sète, France)
- a high sea level (0.75 m on the Sète sea gauge).
Prior to this incident, the dike had already been weakened by floods and marine storms over the preceding months. As part of the RHÔNE plan, and more particularly the operation to reinforce and pull back the embankments of the dikes along the PETIT RHÔNE, it was planned to dismantle and build the structure set back from the river. As the structure’s safety could no longer be guaranteed, the operator proposed to undertake works immediately to reinforce the dike over a length of 180 m.