Bed form characteristics in a live bed alluvial channel

Bed forms are generated in alluvial streams due to mutual interaction betweenow and erodible bed material. among the variety of possible bed forms, dunes are themost important feature and much attention has been paid to them in the literature. inthe present study, an experimental approach was carried out to investigate the geometryof dunes and their celerity in an erodible sand bed. the tests were conducted underlive bed conditions in an experimental ume capable of re-circulating both water andsediment. present experiments showed that the shields number had a considerable eecton dune height and celerity, while the eect of this parameter on the dune length wasnot signicant. furthermore, dimensional analysis is used to present the relationshipsbetween dune height and length, as well as celerity. these relationships were also comparedwith previous empirical equations and experimental data, which showed their acceptableaccuracy. bed roughness related to bed forms was also analyzed based on all availableexperimental and eld data. results demonstrated that by increasing the shields number,the ratio of manning coecient, related to bed forms, to total manning coecient increasedwith a logarithmic trend.