Rivers : the ripple factor in sediment transport equations : report on recent investigations

Many sediment transport formulae for bed load can be expressed as a relationship between the sediment transport and the shear stress acting upon the river bed. A part of the total shear stress is transferred to the river bed via the form drag of the bed forms. It is commonly assumed that only the remaining part of the shear stress is responsible for the sediment transport. This leads to the introduction of, what is referred to as, the ripple factor, which can be interpreted as a reduction of the total shear stress. By using the ripple factor many sedimet transport formulae for bed load can be written in a dimensionless form. Although the introduction of a ripple factor is an over-simplification of the complex interaction between bed forms and shear stress, it is tempting to try to refine the expression for the factor in order to be able to make more reliable sediment transport predictions.