| Abstract: | Soil erosion and sediment movement are serious problems of upland areas of a watershed. In these areas,most of the eroded sediment is transported in overland flows; either in shallow or in concentrated flowsituations. These flows are usually associated with nonlinear waves, generally known as "roll waves" inthe hydraulic engineering literature. Under suitable hydraulic conditions, these waves contain a significantfraction of the total kinetic energy of the flow regime. Hence, the waves act as the primary energy sourcein transporting eroded sediment in shallow flows on steep slopes. Our laborat0ry experiments undercontrolled condition suggest that modulation of the roll waves is effected by the addition of increasingamouflts of sediment in the flow. The optimal condition in the sediment transport rate is reached whenmost of the available wave energy is consumed in carrying the sediment. A related set of experiments ongravitational flows of dry granular material show that the evolving scales of sediment waves are intrinsicto the transport mechanism of the solid phase. |
