Stream power

About: Stream power is a research topic. Over the lifetime, 1135 publications have been published within this topic receiving 51324 citations.

Stream Morphology and Hydraulics of the Isaac River Diversion

Abstract: A 7.8km diversion channel was constructed in 1987 to replace 9.5km of the Isaac River so that coal could be extracted from below the stream course by open cut methods. In 1988 a flood event associated with Cyclone Charlie initiated major instabilities of the diversion. This paper presents the results of an investigation to determine the cause of these instabilities and to develop strategies for future management of the diversion. In some reaches the bed of the diversion channel has widened from 40 m to 80 m, and bends have migrated laterally by up to 40 metres. Such adjustments are continuing. By comparison, the natural river upstream and downstream of the diversion is stable. Comparison of key characteristics between the diversion channel and the natural river channel forms the basis of this investigation. Deepening of the diversion channel has not occurred, so this can not explain instabilities. Bed and bank materials in the diversion are similar to those in the Isaac River so materials do not cause the instabilities. The diversion channel is lacking in fringing vegetation. Bench and bank vegetation are important stabilisers of the Isaac River and will be an important component in achieving a more stable diversion channel, but the most important factor in Isaac River instabilities is channel width. The Isaac River diversion channel was constructed to a bed width of 40 metres. This is similar to the natural channel except that the natural channel also exhibits marginal instream benches. These are low depositional features flanking the active channel and colonised by vegetation. During large flood events the vegetation is stripped and the benches are mobilised thus increasing the effective stream bed width to between 65 and 80 metres. Regime equation and stream power analyses both indicate a stable channel width of approximately 80 m.

Base-level fall, knickpoint retreat and transient channel morphology : the case of small bedrock rivers on resistant quartzites (Isle of Jura, western Scotland)

Abstract: Understanding the link between tectonics and climate and their consequences in landscape evolution is a major current issue in Earth sciences. Bedrock rivers are an important component of the landscape because they transmit changes in tectonic and/or climatic conditions by setting bedrock incision rates to which the landscape must be adjusted. Nevertheless, there remain unresolved issues in relation to bedrock river processes and response to perturbation. The effects caused by propagation of a knickpoint triggered by a sudden drop in base-level remain to be fully clarified. Questions about rates of knickpoint recession, the control exerted by structure and lithology, the morphological response of rivers after knickpoint recession and whether bedrock incision rates are re-established after the passage of a knickpoint, as theory predicts, are all issues that need to be clarified. Moreover, the estimation of bedrock incision, which is key to understand transience in landscapes, has relied on the stream power model, mainly tested on large fluvial settings. Whether the stream power model is valid for small bedrock rivers is not well understood. Some of these questions are tackled in this research, by studying small bedrock river catchments. The case of a knickpoint propagation on a homogeneous resistant lithology (quartzite), triggered by an instantaneous base-level lowering ( 18 m in 13.6 ka), is evaluated here, as well as the effect of structure and the morphological response of rivers to base-level fall. Two approaches were followed: (1) stream profile analysis using slope-area and distance-slope plots and (2) the analysis of terrestrial cosmogenic nuclides to obtain erosion rates. The Isle of Jura, located in the west coast of Scotland, was selected as natural laboratory because bedrock rivers incise the landscape and rapid rock uplift resulting from glacio-isostatic rebound after the Last Glacial Maximum has left the Jura landscape in transience. The present research is organised in seven chapters. In chapter 1, the motivation for this research is presented. In chapter 2, a review of theory underpinning research on bedrock rivers, landscape evolution and knickpoint generation, is detailed. The relevant studies in the field are also reviewed. The physical setting of Jura is characterised in chapter 3, as well as the morphometry of catchments, stressing the effect of Quaternary glaciation on the landscape of Jura. Unpublished exposure ages and analysis of the resultant raised beaches (~35 m OD) of Jura’s west coast are used to demonstrate a sudden drop in base-level in Jura ~13.6 ka. Chapter 4 details how stream long profiles were extracted and how the slope-area (SA) and distance-slope (DS) analyses were undertaken. This chapter 4 shows that the Jura rivers have strong imprints related to glacial processes and base-level fall, making it difficult to use SA and DS models to estimate channel incision as has been done for large fluvial settings. Chapter 5 is explains how the base-level fall knickpoints were identified and it is shown that stream discharge is a first-order control on knickpoint propagation. Structure and lithology, on the other hand, are not first-order controls on knickpoint recession. Chapter 5 also evaluates the vertical distribution of knickpoints and morphological response of rivers after knickpoint migration, with the results indicating that stream power controls the vertical distribution of knickpoints and the morphological response of rivers to base-level fall. A threshold of ~5 km2, where rivers’ ability to modify their channel, resulting in a channel convex profile, is also identified. In chapter 6 the problem of bedrock incision and the role of sediment is tackled. Based on the sampling of sediment in fieldwork, it is demonstrated that the median fraction in the rivers of Jura is ≈45 mm and grain-size neither fines nor increases with stream discharge and channel slope, strongly indicating that detachment-limited conditions are likely to control bedrock incision. In the second part of chapter 6, the incision rates upstream and downstream of the base-level fall knickpoint are obtained to test whether incision rates are re-established after knickpoint propagation. Incision rates were obtained from the concentrations of cosmogenic 10Be in samples extracted from the river bed. The results indicate that incision rates are not re-established at an expected value of ≈ 0.1 m/k yr after knickpoint migration. Rather, incision rates below the knickpoint remain somewhat elevated (≈ 0.5 m/k yr) reflecting: (1) ongoing base-level fall, and/or (2) the propagation of younger knickpoints (< 13.6 ka) in those transient reaches. The cosmogenic-derived incision rates were tested with different bedrock incision rules. The results indicate that the stream power model is a good predictor for channel incision, even for the case of small catchments. In chapter 7 the conclusions of this research are provided.

Critical unit stream power for sediment transport

Abstract: Yang's (1996) sediment transport theory based on unit stream power is one of the most accurate theories, but in his equations the use of product of slope and critical velocity instead for critical unit stream power is not suitable. Dimensionless critical unit stream power required at incipient motion can be derived from the principle of conservation of power as a function of dimensionless particle diameter and relative roughness. Based on a lot of data sets, this new criterion was developed. By use of this new criteria, Yang's (1973) sand transport formula and his 1984 gravel transport formula could be improved when sediment concentration is less than about 100 ppm by weight.

Freshwater Mussel Bed Habitat in an Alluvial Sand-Bed-Material-Dominated Large River: A Core Flow Sediment Refugium?

Abstract: Habitat degradation, organismal needs, and other effects influencing freshwater mussel declines have been subject to intense focus by conservationists for the last thirty plus years. While researchers have studied the physical habitat requirements and needs of mussels in small- to medium-sized rivers with variable levels of success, less research has been conducted on mussel habitat in larger non-wadeable rivers, especially at the reach scale, where core flow environmental conditions provide and maintain habitat for freshwater mussels. We designed a quasi-experimental observational field study to examine seven hydrologic energy and material variables laterally and longitudinally at Current and Extirpated mussel bed habitat reaches in lower White River, Arkansas, a large non-wadeable, sand-bed-material-dominated river. As expected, lateral and longitudinal hydrologic variable differences were identified within a reach. Mean velocity, bed velocity, the Froude number, and stream power were all significantly lower at Current mussel bed habitat stations within a sampling reach. Energy regime differences in shear stress and, marginally, stream power were higher at Extirpated mussel bed habitat reaches. Several factors emerged as important to mussel habitat in the White River. First, bed velocity warrants further exploration in terms of both flow strength and flow direction. Second, bedload appears to be the primary contributor to mussel habitat but requires additional exploration within the context of core and secondary flow pathway interactions. The combined empirical evidence from our study supports the flow refugium concept identified for mussel habitats in smaller systems but expands the concept to large non-wadeable streams and includes reach-scale refuge from sediment transport conditions.

Architectures,Relationships between Discharges and Width/depth Ratios of Stream Cross Profiles, and Stream Powers of Anastomosing Rrivers

Abstract: As a new type of rivers, anastomosing river has been concerned by researchers although some questions about it was not clear for understanding it This paper discusses the river architectures, relationships between width/depth ratios of stream cross sections and discharges, and stream powers of anastomosing rivers according to references and obtained data recently It is helpful to researchers who is interested in this river pattern to develop the theory for it Many aspects of anastomosing river appear particular characteristics compared with other river patterns In the planform architectures, the multiple channels joining each other enclose flood basins on which vegetation, swamps and lakes develop basically Longitudinal gradients of the channels are very low while the channel width/depth ratios are smaller than 40 In the depositional architectures of cross profiles, some isolated sand bodies of channel deposits are "floating" in the mud bodies of flood basins In the half logarithm diagram of width/depth ratios of stream cross profiles vs discharges, the scatters of anastomosing rivers are below compared with that of other river patterns The stream powers of anastomosing rivers are very low compared with the old trunk channel from which it diverted because the channel gradients and discharges of every anastomosing channel are smaller than that of the old trunk channel The specific stream power of the anastomosing channels: eastern Songzi River, western Songzi River, Hudu River, Ouchi River, northern Ouchi River and Songliheliu River are 30 W/m 2, 55 W/m 2, 28 W/m 2, 64 W/m 2, 37 W/m 2 and 27 W/m 2, respectively Obviously, all of them are smaller than 10 W/m 2 But the specific stream power of anabranched Changjiang trunk channel is 140 W/m 2 All of the characteristics of anastomosing rivers indicate that this river pattern is different from the anabranched rivers represented by the lower Changjiang River, especially from other river patterns