Showing papers on "Stream power published in 1993"
TL;DR: A simple facies model for terminal fans and their deposits is presented in this article, which includes a tripartite zonation of terminal fans into feeder, distributary and basinal zones.
172 citations
TL;DR: In this article, the authors reconstructed the Early Miocene landscape of Australia and found that the major topographic features of the highest part of the Australian continent had taken on essentially their present form by the mid-Tertiary, and that some of these features were formed during the Mesozoic.
Abstract: Basaltic lavas that flowed into river valleys draining westward from the uplands of southern New South Wales have preserved the Early Miocene landscape to a remarkable degree. The reconstruction of this landscape shows that the major topographic features of the highest part of the Australian continent had taken on essentially their present form by the Mid-Tertiary, and that some of these features were formed during the Mesozoic. Plateau surfaces have been lowered by only about 2 to 5 m/Ma, and most major streams have incised by only about 5 to 18 m/Ma, with a maximum incision of 30 m/Ma, since the Early Miocene. Despite the passage of 20 Ma, stream gradients have not waned, nor have major breaks in profiles been eliminated. On the contrary the modern stream profiles are strikingly similar to their Early Miocene counterparts, suggesting that the evolution of the profiles has been determined mainly by variations in stream power, rather than by the headward retreat of nickpoints through the drainage system. ...
102 citations
TL;DR: In this article, the depths of pools relative to the dephts of runs and riffles were correlated with reach-scale channel gradient along three rivers in coastal northern California, and the authors hypothesized that these trends reflect changes in energy expenditure with decreasing gradient, as a result of the flow's ability to erode its channel boundaries.
100 citations
TL;DR: In this paper, the authors examined the response of a gravel-bed stream following narrowing and straightening of its channel and found that the change from a slow and relatively steady degradation in the lower reaches to separate degradation events in the higher reaches is attributed to the differential rate of headcut retreat and to the control exerted by mid-channel bars upon the rate of river-energy dissipation.
Abstract: Processes induced by the channelization of the Raba River in the present century are examined to illustrate the response of a gravel-bed stream following narrowing and straightening of its channel. Up to 3 m of incision has occurred. The change from a slow and relatively steady degradation in the lower reaches to separate degradation events in the higher reaches is attributed to the differential rate of headcut retreat and to the control exerted by mid-channel bars upon the rate of river-energy dissipation. Progressive outwashing of finer grains from bed material has followed the diminishing sediment yield of the basin and the increase in stream power. The ensuing growth in mean grain size and changes in sediment fabric have increased boundary resistance to flow and reduced particle susceptibility to entrainment. Downstream magnification of peak discharges has become increasingly pronounced with the advancing incision. The decrease in flood-plain storage and self-acceleration of flows passing the relatively deep and straight channel has caused flood waves to become progressively more flashy in nature.
An increase in channel depth and reduction in gradient caused by downward and backward erosion, as well as bed material coarsening has promoted the re-establishment of an equilibrium. Conversely, flow velocity increases due to flow concentration in the deepened channel. Reduction in grain mobility allows the river to attain a new equilibrium at flow-velocity and stream-power levels higher than before the channelization.
Numerous disadvantages of the applied regulation scheme and its failure to reduce flood hazard raise the question of its maintenance. To be successful, any regulation design must take into account changes in sediment supply and flood hydrographs resulting from the simultaneous alterations in basin management.
88 citations
TL;DR: Sediment-deposition rates estimated from tree rings were used in conjunction with multi-element analyses of sediments and of selected growth rings from oak trees to estimate amounts of trapped sediment and trace elements as discussed by the authors.
Abstract: The Chickahominy River, arising near Richmond, Virginia, flows southeast toward Newport News, which impounds the river for much of its water supply. Much of the bottomland between the two cities is flooded for extended periods annually. Sediment-deposition rates estimated from tree rings were used in conjunction with multi-element analyses of sediments and of selected growth rings from oak trees to estimate amounts of trapped sediment and trace elements. Mean rates of deposition at eight study sites range from 0.7 to 5.7 mm/yr and are related to stream gradient, stream power, percent wetland, hydroperiod, and land use. Deposition rates are highest downstream from the confluence of upper basin tributaries near Richmond, where stream power is low and there is a high percentage of emergent/shrub-scrub wetlands; rates decrease, along downstream reaches toward the Chickahominy reservoir. Tree-ring data suggest that mean sedimentation rates were greater during the last 50 years than during the previous 3-year period, possibly because of urban expansion in the upper basin. Sites nearest the urban area have the highest rates of sedimentation and the highest concentrations of most trace elements in sediments. Trace elements concentrated in sediment include zinc, lead, chromium, copper, nickel, tin, and cadmium. Concentrations in tree rings of zinc, copper, nickel, and lead were generally proportional to those in sediment at a site, and some inter-site correlations were also observed. Unusually high concentrations of zinc were detected in some tree rings, including some that formed before 1950. Concentrations of zinc and lead in the most recently formed rings of those trees suggest that sediment concentrations of those elements may have declined relative to earlier periods. The trapping of substantial amounts of sediment and trace elements by these forested wetlands demonstrates their importance in the maintenance of water-quality.
81 citations
TL;DR: In this paper, the authors found that rill initiation is a function of local flow hydraulic conditions and independent of total plot discharge, which complicates prediction of this process for effective modeling as some index which links soil microtopography and flow concentration must also be incorporated in addition to runoff volume.
46 citations
TL;DR: The relationship between cataclysmic flood-generated landforms and flood hydraulics was investigated along Box Canyon, an 11 km long bedrock gorge of the lower Big Lost River as discussed by the authors.
37 citations
TL;DR: In this paper, an index of total sinuosity (∑ P ) was defined for gravel-bed river patterns, which varies continuously with both stream power per unit channel-belt length (represented as the product of mean annual flood and valley gradient) and median bed material diameter.
Abstract: Channel patterns are commonly represented as discrete types (e.g. straight, meandering, braided) separated by threshold values of slope and discharge. However, for gravel-bed river patterns, an index of total sinuosity (∑ P ) can be defined which varies continuously with both stream power per unit channel-belt length (represented as the product of mean annual flood and valley gradient) and median bed material diameter. An empirical relationship between ∑ P and these controlling variables can be used to provide palaeo-hydrological reconstructions for braided stream traces on terrace fragments, as an alternative to methods based on bed material sizes and criteria for the threshold of grain motion.
36 citations
TL;DR: In this article, the assumption that the morphology and grain-size distribution of river sediments are largely controlled by water flow variables is questioned, and it is shown that the sediment supply will depend on episodes or "sediment moves" that may involve hillslopes, banks, tributaries, or the sediment bed, in addition to transfer from the immediately upstream channel reach.
23 citations
TL;DR: In this article, the empirical relationship between sediment size and unit stream power provides an accurate and simple methodology for determining the minimum erosion threshold discharge for steep gradient streams common in western Washington and other similar mountain terrains.
Abstract: Discharges were measured in steep gradient (> 5 percent) gravel-paved streams from 1988 to 1991 in order to empirically determine erosional thresholds based on sediment size, related to critical velocity, tractive force, and unit stream power. Results suggest that the empirical relationship between sediment size and unit stream power provides an accurate and simple methodology for determining the minimum erosion threshold discharge for steep gradient streams common in western Washington and other similar mountain terrains.
13 citations
Journal Article•
TL;DR: The bridge stream tube model for alluvial river simulation (BRI-STARS) as mentioned in this paper is a semi-two-dimensional model capable of computing scour/deposition through subcritical, supercritical, and a combination of both flow conditions involving hydraulic jumps.
Abstract: The Bridge StreamTube Model for Alluvial River Simulation (BRI-STARS) is a semi-two-dimensional model capable of computing alluvial scour/deposition through subcritical, supercritical, and a combination of both flow conditions involving hydraulic jumps. The use of streamtubes allow the modeling of scour/deposition of applications involving bridges not only along a study reach but also across alluvial channels. In this paper, the basic formulations used in the BRI-STARS model are presented and various hydraulic, sediment transport, local scour, and stream power minimization computations are described. The BRI-STARS model runs on IBM PC-AT or compatibles.