Showing papers on "Stream power published in 1986"
TL;DR: In this article, the volume of sediment eroded from the outer bank of a meander bend is shown to be largely a function of river size and grain size of sediment at the base of the inner bank.
Abstract: Mean lateral-migration rates for 18 meandering river channels in western Canada are explained statistically in terms of hydraulic and sedimentological variables. The volume of sediment eroded from the outer bank of a meander bend is shown to be largely a function of river size and grain size of sediment at the base of the outer bank. These variables explain almost 70% of the volumetric migration rate for these relatively large, sand- and gravel-bed streams. It would appear that bank erosion and channel migration are essentially problems of sediment entrainment which is dependent on total stream power and sediment size. Vegetation on the outer bank is seen to have little significant effect in controlling channel migration. Further refinements of the type of data used here should permit the development of an accurate predictive model of regional channel migration. To this effect, it is most important to develop a precise relationship between bank resistance and the size of sediment at the base of the outer bank.
290 citations
TL;DR: Theoretical equations for calculating the unit stream power of both sheet and rill flow were developed and used to predict the sediment transport capacity of such flows in this paper, and the results were very good and demonstrated the simplicity and robustness of the method.
Abstract: Theoretical equations for calculating the unit stream power of both sheet and rill flow were developed and used to predict the sediment transport capacity of such flows. Independent data sets from three sources representing both finely aggregated clay soils and coarse textured nonaggregated soils, sheet, rill, and composite sheet rill flow systems, and a range of slopes were used to test the utility of the method. The results were very good and demonstrated the simplicity and robustness of the method. For shallow overland flow the best results were obtained when the critical unit stream power at incipient sediment motion was treated as a constant value that was independent of slope. The results also suggest that a unique value of critical unit stream power for rill initiation exists that is independent of soil type. For noncohesive loams or fine sands and finely aggregated clay soils the sediment transport capacity can be accurately predicted from a knowledge of the physical characteristics of the soil or bed material alone. For aggregated clay soils this requires information on the aggregate size distribution and the effects of soil particle size differentiation as flow rates and unit stream powers increase with the transition from sheet to rill flow.
279 citations
TL;DR: In this article, the authors discuss the importance of small streams for a wide range of resource benefits, such as spawning habitat, stream power, and energy dissipation, where channel morphology is modified or structural features such as woody root systems, logs, boulders or bedrock.
Abstract: Throughout the United States, land managers are becoming increasingly aware of the importance of small streams for a wide range of resource benefits. Where channel morphology is modified or structural features are added, stream dynamics and energy dissipation need to be considered. Unit stream power, defined here as the time-rate loss of potential energy per unit mass of water, can be reduced by adding stream obstructions, increasing channel sinuosity, or increasing flow resistance with large roughness elements such as woody root systems, logs, boulders, or bedrock. Notable morphological features of small streams are pools, riffles, bed material, and channel banks. Pools, which vary in size, shape, and causative factors, are important rearing habitat for fish. Riffles represent storage locations for bed material and are generally utilized for spawning. The particle sizes and distributions of bed material influence channel characteristics, bedload transport, food supplies for fish, spawning conditions, cover, and rearing habitat. Riparian vegetation helps stabilize channel banks and contributes in various ways to fish productivity. Understanding each stream feature individually and in relation to all others is essential for proper stream management. Although engineered structures for modifying habitat may alter stream characteristics, channel morphology must ultimately be matched to the hydraulic, geologic, and (especially) vegetative constraints of a particular location.
246 citations
TL;DR: In this article, the authors studied the transporting capacity of thin flows, in the laminar and transitional flow regime, and found that sediment concentration was clearly related to grain shear velocity and unit stream power, expressed as the product of mean velocity and slope.
Abstract: In this paper the transporting capacity of thin flows, in the laminar and transitional flow regime, is studied. Experiments were carried out on irregular as well as on plane beds, using two totally different set-ups. The results of these two types of experiment were convergent. In both cases, sediment concentration was clearly related to grain shear velocity and unit stream power, expressed as the product of mean velocity and slope (Yang, 1973). The data agreed with those of Kramer and Meyer (1969). For a sandy bed, the unit stream power relationship was able to predict reasonably well the sediment concentrations measured on a mulched surface. For laminar and transitional flows, both the unit stream power and the shear velocity are related in the same way to slope and unit discharge. The unit stream power is a parameter which in particular can be very easily measured and might therefore become useful in obtaining a quick estimate of the transporting capacity of a thin flow. However, before a sediment transport equation for thin flows can be developed, more information is needed about the influence of the flow regime and grain size and density.
149 citations
TL;DR: The low-flow channel morphology of Boulder Creek is characterized by a well-developed pool-and-riffle pattern, which consists of accumulations of basaltic boulders deposited from upstream source areas during extremely large flows.
Abstract: The low-flow channel morphology of Boulder Creek is characterized by a well-developed pool-and-riffle pattern. The riffles consist of accumulations of basaltic boulders deposited from upstream source areas during extremely large flows. Paleoflood water-surface profiles defined by high-water indicators such as slack-water sediments and silt lines indicate that discharges of up to 400±50 m 3 /s have affected the lower reaches of this bedrock stream system. Stratigraphic relationships and archaeologic and radiometric age constraints indicate that at least four large-magnitude, low-frequency flow events have occurred within the past 500 to 1,000 radiocarbon years B.P. Step-backwater hydraulic reconstructions of these large flows suggest that the positions of the boulder-comprised riffles are controlled by spatial variations in large-flow stream power. Boulder deposition occurs where channel stream power drops below critical-power thresholds necessary for boulder transport. High-discharge stream-power minima occur in reaches immediately upstream of canyon bends and constrictions and downstream of canyon expansions. The low-flow riffles occur at these sites. Comparison of calculated stream-power values and measured boulder sizes with established coarse-particle transport relationships indicates that a 400-m 3 /s flow is approximately the minimum discharge competent to affect this pool-and-riffle pattern.
109 citations
TL;DR: In this article, an automatic and continuously recording samplers are deployed in a Hertfordshire gravel-bed stream to show that bedload transport is related to stream power, which is similar to that established for North American channels but, because the record is so detailed, it is possible to identify the cause of the considerable scatter that is normal in such relationships.
Abstract: Automatic and continuously recording samplers are deployed in a Hertfordshire gravel-bed stream to show that bedload transport is related to stream power. The pattern is similar to that already established for North American channels but, because the record is so detailed, it is possible to identify the cause of the considerable scatter that is normal in such relationships. A major factor is the occurrence of rhythmic pulses in bedload discharge that are not matched by similar fluctuations in hydraulic variables. It is suggested that these pulses reflect downstream differences in the concentration of mobile particles in a slow-moving traction carpet, and that they may be likened to kinematic waves. The record also reveals that the threshold of sediment transport—always presumed hithero to be associated with incipient motion—is related to the cessation of bedload transport in a river flood. Indeed, the mean value of stream power at the finish of bedload transport is only 20 percent of that prevailing at the moment of incipient sediment motion. Because of this, there is an inevitably poor correlation between actual bedload transport rates and those predicted by bedload equations which rely upon a single traction threshold. These new data show that the general inverse relationship between bedload discharge and water-depth : grain-size ratio proposed by Bagnold (1977, 1980) is not universal. Transport efficiency for this gravel-bed stream is typically 0.05 per cent of available stream power, which compares with 1.6 per cent for a river moving both gravel and sand, and 5 per cent for another channel where bedload is composed predominantly of sand-sized particles. It is argued that coarse and fine-grained alluvial channels may need to be considered separately. By allowing for differences in traction threshold at the beginning and end of bedload events, and by averaging bedload discharge flood by flood in order to smooth out the effect of pulses, it is possible to achieve a reasonably good prediction of average bedload transport rate in terms of stream power.
93 citations
TL;DR: In this paper, the authors show that at the same applied stream power, defined as bed shear stress multiplied by mean flow velocity, the unit mass transport rate of sand, as bedload, varies as (stream depth) −2/3 and as (grain size) −½.
Abstract: The limited scope of laboratory experiments had suggested that at the same applied stream power, defined as bed shear stress multiplied by mean flow velocity, the unit mass transport rate of sand, as bedload, varies as (stream depth) –2/3 and as (grain size) –½ . Further, at constant flow depth the rate varies as (stream power) 3/2 . To test the generality of these empirical relations they were used in reverse to convert measured transport rates in both natural rivers and small laboratory flumes to notional values corresponding to a common arbitrary flow depth and grain size. Plotting stream power against the converted transport rates, all the results fall along a single narrow belt extending over virtually the whole range of magnitude and grain size conditions found on Earth, irrespective of geology, climate, channel magnitude, irregularity and boundary roughness. No quantitative explanation of this correlation is apparent, but some qualitative ideas are suggested.
51 citations
01 Jan 1986
TL;DR: In this article, the authors derived analytical equations for predicting erosion and deposition on complex slope geometries found in real three-dimensional terrain and used unit stream power theory to derive the relationships between these relationships.
Abstract: Physically based, computationally simple, analytical equations are derived for predicting erosion and deposition on complex slope geometries found in real three-dimensional terrain. Unit stream power theory provides the basis from which these relationships are developed. An example is given of predicted erosion and deposition on an experimental catchment at Wagga Wagga, Australia. Predicted zones of high erosion show good agreement with the observed locations of gullies and zones of severe sheet erosion.
4 citations