Micro-scale moveable bed physical model

The objective of this research is to document criteria for qualitative and quantitative application of small-scale loose-bed river distorted models and to evaluate relaxation of similarity requirements for use of the models.; Loose bed physical models are frequently used to investigate training structure design and navigation operational issues pertaining to river reaches with complex sedimentation phenomena. Similarity between model and prototype conditions are necessary for the successful application of loose bed models. The present investigation uses results from thirty previous large- and small-scale movable bed model studies to investigate Shields parameters, roughness distortion and sediment transport similarity relationships. Evaluation of the Shields criterion through scale ratios indicates that the small-scale models provide a high degree of similarity in the state of sediment mobility. Morphologic similarity also is assessed using thalweg position and reach-weighted cross section area, water surface width, hydraulic depth, width to depth ratio. Cumulative frequency graphs and squared error terms provide a quantitative procedure to assess the morphologic similarity. These techniques can also be used in model calibration.; Development of small-scale distorted models can provide economical benefits through timely evaluation of training structure configuration. Small-scale distorted models also provide the capability to visually demonstrate flow and sediment response in a prototype river.; Results of this study indicate that micromodels reproduce the channel bathymetry (i.e., bed configuration) that occurred in the prototype river reach to the same relative degree of similarity commensurate with the large-scale models.