Showing papers on "Stream power published in 1976"

Minimum Unit Stream Power and Fluvial Hydraulics

Abstract: Fluvial hydraulics is complex because the velocity, slope, depth, and channel roughness are all subject to change. The unit stream power, defined as the rate of potential energy expenditure per unit weight of water, required to transport a given sediment load is sensitive to water depth when the sediment concentration is low. The interdependence between unit stream power and water depth decreases as sediment concentration increases. A computer program is used to generate different combinations of velocity, slope, depth, and unit stream power for a given sediment load. The generated unit stream power in the lower flow regime either has a clear minimum value at a particular depth or approaches a minimum value for a given sediment load. These agreements suggest that an alluvial channel in the lower flow regime adjusts its velocity, slope, depth, and roughness in such a manner that a given sediment load can be transported with the minimum amount of unit stream power.

Applicability of Unit Stream Power Equation

Abstract: The usefulness of a sediment transport equation to engineering depends on its applicability to natural rivers. Data collected from six river stations are used to compare the applicability of different equations. These comparisons indicate that the dimensionless unit stream power equation is the one which can provide accurate predictions of total sediment discharge in natural rivers under diversified flow and sediment conditions. The limitations to which this dimensionless unit stream power equation can be applied are explained.

Hydraulics and Morphology of Glacial Outwash Distributaries, Skeidararsandur, Iceland

Abstract: Seasonal and short-term changes in the hydraulics and morphology of outwash distributaries on the southeast coast of Iceland were studied in April and July, 1973. In summer, when the meltwater discharge is normally at a maximum, high current velocities occur in the distributary mouths, prohibiting saltwater intrusions. Hourly variations in flow are caused by tidal-induced changes in the water surface slope. At low tide, the surface slope is the greatest, and the current, suspended sediment load and discharge are at a maximum. A current of 3.3 m/s and a suspended sediment concentration of 5.1 g/l were measured at low tide in July, 1973. As the tide rises, the surface slope is lowered and the discharge is reduced, causing meltwater to become dammed behind a barrier spit system that form the seaward boundary of the sandur. The distributaries migrate frequently due to fluctuations in the meltwater discharge. During periods of low discharge, wave power dominates over stream power and the distributaries are deflected in the direction of net longshore transport. Stream power increases with higher meltwater discharge, causing the distributaries to erode a more direct course through the barriers.