Measurements of shear and pressure distribution on smooth and sand coated two-dimensional triangular elements, simulating ripples and dunes, have been reported. Relations have been derived for the local and average skin shear coefficients in terms of the geometry of the elements and the flow Reynolds number. The local pressure coefficient and the form drag coefficient have been related to the relative roughness and the geometry of the elements. Analysis of the data has shown that the grain resistance of undulated beds calculated by the existing methods is generally greater than the measured average grain resistance of the bad. A large amount of alluvial channel data show agreement with the relation for form drag of the two-dimensional triangular roughness.