Narrow and wooded dykes reinforcement : the particular situation of Isere river levees

Abstract

Protection dikes along the Isere river are unusual as they are wooded, narrow and made with loose material. They were built with a design of the kind upstream toe under water. As a result, it is observed both a recurrent risk of face sliding and a typical risk of internal erosion due to root progression within heterogeneous embankments. Moreover, this vegetation induces a real difficulty for human inspection and diagnosis. For those reasons, the local association in charge of dikes maintenance established the following strategy: along normal sections, vegetation reviving with a planting scheme in order to stabilize forest stand; along sections with strengthening necessity, site planning with external toe thickening and delayed intervention within river-bed. This graduated reinforcement design allows for one typical section the time-spreading out of expenses and a satisfactory stake to dike-aging weighing.