High-head storage hydropower plants operate their turbines during periods of high energy demand. The starting and stopping of turbines results in rapid fluctuations of discharge and water levels in rivers called hydropeaking, which are unfavourable from an ecological point of view. Besides retention basins, morphological measures can help to reduce the fluctuations by increasing the natural retention capacity of rivers. Systematic hydraulic model tests have been performed to evaluate the influence of macro roughness and cavities at the banks on the flow resistance and the propagation of (surge) waves. For the estimation of the flow resistance empirical formulas could be developed. The passive retention due to bank cavities influences the propagation of waves. The effect of morphological measures on hydropeaking is generally less than that of managed retention basins, especially for long operation sequences of turbines.