Author(s): Hanwen Cui; Stefan Felder; Matthias Kramer
Keywords: Ir-water flows; Environmental-friendly spillway; Flow resistance; Time-varying flow properties
Abstract: In grass-lined spillways, erosion of the canopy layer and the underlying soil by high-velocity flows can ultimately lead to a structural failure, implying rapid and unexpected flooding with potential destruction of environment and property. From a hydrodynamic point of view, canopy loss and soil erosion dynamically change the bed roughness, which leads to an alteration of flow properties. Previous research of flow resistance of grassed spillways with natural grass has not considered the dynamic changes of the soil properties and flow parameters. Herein, novel experiments on a mildly sloped spillway model with real grass were conducted. Free-surface elevations and aeration properties were measured continuously using acoustic displacement meters and phasedetection intrusive probes, thereby observing temporal variations in flow depth, flow resistance and air concentrations. The research identified that the erosion process was characterised by gradual changes over extended periods, while abrupt bed deteriorations resulted in the strongest change in flow properties.