Discussion on the state of the art and developing the science and engineering in order to increase fundamental understanding and modelling of strength, deformation and erosion behaviour of soils and failure processes of water retaining structures like dikes, dunes, (underwater) dams. The gained fundamental understanding is essential for designing and building dikes that can easily be adapted to new insights on design loads and strength. Especially or urban areas, with limited space and large number of lives and economic value to protect, the design of water retaining structures faces serious challenges. For these conditions hard elements, like sheet pile walls or semi hard elements, like soil mixing techniques are required to construct water retaining structures that fulfil the design criteria. This opens a new discussion on soil – structure interaction at extreme loading conditions.