Stream power

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

Woody debris and channel morphology in first‐ and second‐order forested channels in Washington's coast ranges

Abstract: [1] While there are conceptual and theoretical reasons to believe small streams behave differently than larger streams, the lack of information on small streams has lead land managers to rely on data from larger streams to guide management decisions. In response to the need for descriptive information on habitat and channel morphology specific to small, non-fish-bearing streams in the Pacific Northwest, morphologies and wood frequencies in 42 first- and second-order forested streams 40 cm diameter) created <10% of steps. Streams in virgin and managed stands did not differ in relative importance of very large woody debris. Because of low fluvial power, pool habitat was rare. These streams featured mostly step-riffle morphology, not step-pool, indicating insufficient both flow for pool-scour. Stream power and unit stream power were dominant channel shaping factors.

Paleohydrology of pool-and-riffle pattern development: Boulder Creek, Utah

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.

Bedrock Channel Morphology in Relation to Erosional Processes

Abstract: Bedrock channel morphology reflects the interactions between erosive processes and the resistance of the channel substrate. The controls on these interactions change with spatial scale. Mineralogy, exposure age of the substrate, and local heterogeneities are particularly important in controlling substrate resistance at the micro scale (mm to cm). Substrate discontinuities created by bedding, joints, and lithologic contacts become progressively more important at the meso scale (cm to m), whereas regional structure and baselevel history may dominate substrate resistance at the macro scale (m to km). In a similar manner, turbulent fluctuations that create localized abrasion and cavitation are more important at the micro and meso scales, whereas longitudinal patterns of unit and total stream power exert a stronger influence on channel morphology at the macro scale. Most studies of bedrock channel morphology have described meso-scale erosional features. In the absence of direct measurements, investigators have inferred both the erosive processes that produced the observed features, and the controls on the location of the features. Fluvial erosion of bedrock may occur via; (1) corrosion, or chemical weathering and solution, (2) corrasion, or abrasion by sediment in transport along the channel, or (3) cavitation and other hydrodynamic forces associated with flow turbulence. Very few direct measurements of rate exist for any of these erosive processes. Bedrock channel morphologies may be divided into multiple or single flowpath channels, and subdivided on the basis of sinuosity, uniformity of bed gradient, and uniformity of erosion across a cross section. These categories may be used to infer dominant erosional processes and relative rates of erosion, but we cannot yet predict the occurrence of specific channel morphologies as a function of driving and resisting forces. In this context, the traditional assumption that substrate dominates bedrock channel morphology may be too restrictive.

The Use of Evolutionary Trajectories to Guide ‘Moving Targets’ in the Management of River Futures

Abstract: River histories provide important guidance with which to inform river management. Evolutionary trajectories and appraisals of system responses to changing flux conditions and disturbance events can be used to determine the range of potential future states and associated behavioural regimes, assessing the likelihood that that these states will be attained over a given timeframe. In these analyses, natural or historical reference reaches may not provide a realistic basis to set target conditions for management actions, as what has gone before does not necessarily provide a complete and reliable picture of prospective future conditions. This paper outlines the use of a conceptual tool, the river evolution diagram, as a geomorphic platform to assess river history and the potential range of river futures for any given system. Evolutionary adjustments of a sand bed river in southeastern Australia are used to demonstrate the application of this approach. Applying adaptive management principles, ‘moving targets’ for river management are framed in relation to the range of likely future states and trajectories of adjustment. Copyright © 2015 John Wiley & Sons, Ltd.