The interaction between soil, water and structure is discussed for a bed and slope protection. It is shown that for various types of structures, and various boundary conditions, this interaction can be approached in a uniform way . The hydraulic conditions at the boundaries of the structure and along the non-protected parts of the bed result in groundwater flow. Hydraulic conditions and groundwater flow determine the loading on the protection . The structure itself influences the groundwater flow by its flow resistance and may sometimes also influence the load by deformation. Phenomena that may be relevant depending on the situation are summarized and methods are described for determining which of these phenomena should be taken into account in a specific situation when modelling soil , water and structure in order to determine the stability.