In model test,due to the model scale effect and the difference of model sand and natural sand,the time scale for flow and riverbed scouring and silting are inconsistent.Therefore,it is necessary to select different scouring and silting time scales for different tidal flow-sediment models.Researches show that the time scale for the erosion model is different from the one for the deposition model,so does for the tidal reach and runoff reach；when the riverbed evolution is controlled by both tide and runoff,the time scale is determined according to the bed-forming role of the flow；when selecting the scouring and silting time scale of the storm surge,the characteristics of flow and sediment transportation are always considered,and the equal time scale for scouring and silting and flow are generally used,while the sediment volume scale needs to be adjusted accordingly.