Review of step-pool hydrodynamics in mountain streams:

doi:10.1177/0309133319859807

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Review of step-pool hydrodynamics in mountain streams:

Journal Article•DOI•

Review of step-pool hydrodynamics in mountain streams:

Sruthi Thazhathe Kalathil¹, Venu Chandra¹•Institutions (1)

Indian Institute of Technology Madras¹

24 Jun 2019-Vol. 43, Iss: 5, pp 607-626

TL;DR: In this paper, steppools are one of the major types of bed morphology prevalent in mountain streams and they have a unique flow structure as compared to low-gradient streams, in terms of large boundary elements and...

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Abstract: Step-pools are one of the major types of bed morphology prevalent in mountain streams. They have a unique flow structure as compared to low-gradient streams, in terms of large boundary elements and...

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Journal Article•DOI•

The role of infrequently mobile boulders in modulating landscape evolution and geomorphic hazards

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Charles M. Shobe¹, Charles M. Shobe², Jens M. Turowski², Ron Nativ³, Ron Nativ², Rachel C. Glade⁴, Georgina L. Bennett⁵, Benedetta Dini⁶ - Show less +4 more•Institutions (6)

West Virginia University¹, University of Potsdam², Ben-Gurion University of the Negev³, University of Rochester⁴, University of Exeter⁵, University of East Anglia⁶

01 Sep 2021-Earth-Science Reviews

TL;DR: In this paper, the authors review progress on five key questions related to how boulders influence the evolution of unglaciated, eroding landscapes: 1) What factors control boulder production on eroding hillslopes and the subsequent downslope evolution of the boulder size distribution.

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27 citations

Journal Article•

Step-Pool Streams: An Adjustment to Maximum Flow Resistance

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Athol D. Abrahams, Gang Li, Joseph F. Atkinson

01 Jan 1994-Hydraulic Engineering

TL;DR: In this paper, an experiment was conducted to study the maximum flow resistance of step pool streams and the morphology of the steps formed from clastic materials, and the step pool formation was qualitatively simulated to analyze numerically the formation process.

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Abstract: An experiment was conducted to study the maximum flow resistance of step pool streams and the morphology of the steps formed from clastic materials. The step pool formation was qualitatively simulated to analyze numerically the formation process. A flume 4.88 mm long and .15 m wide was used and flow velocity measurements were done by electronically timing passage of salt plume down the flume. Observations showed that the natural step pool streams arranged the morphology to maximize flow resistance.

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9 citations

Journal Article•DOI•

Energy Loss in Steep Open Channels with Step-Pools

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Suresh Kumar Thappeta¹, S. Murty Bhallamudi, Venu Chandra¹, Peter Fiener, Abul Basar M. Baki - Show less +1 more•Institutions (1)

Indian Institute of Technology Madras¹

31 Dec 2020-Water

TL;DR: In this paper, three-dimensional numerical simulations were performed for different flow rates and various geometrical parameters of step-pools in steep open channels to gain insight into the occurrence of energy loss and its dependence on the flow structure.

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Abstract: Three-dimensional numerical simulations were performed for different flow rates and various geometrical parameters of step-pools in steep open channels to gain insight into the occurrence of energy loss and its dependence on the flow structure. For a given channel with step-pools, energy loss varied only marginally with increasing flow rate in the nappe and transition flow regimes, while it increased in the skimming regime. Energy loss is positively correlated with the size of the recirculation zone, velocity in the recirculation zone and the vorticity. For the same flow rate, energy loss increased by 31.6% when the horizontal face inclination increased from 2° to 10°, while it decreased by 58.6% when the vertical face inclination increased from 40° to 70°. In a channel with several step-pools, cumulative energy loss is linearly related to the number of step-pools, for nappe and transition flows. However, it is a nonlinear function for skimming flows.

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9 citations

Equilibrium geomorphological conditions for high gradient bed streams

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A N Papanicolaou, A R Maxwell

01 Jan 2000

TL;DR: In this article, the authors identify the flow conditions under which stable bedforms exist; provide the geometric characteristics of these bedforms; measure the magnitude of the streamwise velocity and energy dissipation factor; and determine the friction factor under various flow conditions and gravel sizes.

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Abstract: The goal of this study was to identify the flow conditions under which stable bedforms exist; provide the geometric characteristics of these bedforms; measure the magnitude of the streamwise velocity and energy dissipation factor; and determine the friction factor under various flow conditions and gravel sizes. Design criteria and recommendations for stable bedforms were provided upon the termination of this research. Stable bedforms are defined as those bedforms of which the spatial characteristics (height and spacing) do not change with time. The focus of this study was on streams with slopes greater than 3%, as clear design requirements for bed geomorphologic stability are lacking for these cases, and they are of particular interest in the design and retrofit of culverts for both anadromous and resident migratory fish passage.

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2 citations

Journal Article•DOI•

Flow Resistance in Very Rough Channels

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Aurora Reid¹•Institutions (1)

ETH Zurich¹

01 Oct 2022-Water Resources Research

TL;DR: In this paper , the authors used a double-averaging approach to estimate the width, reach, and doubleaveraged variables for steady, uniform flow in an open channel, using an empirical model for the coefficient of form drag, and a flow resistance model that compares well to a large data set of flow velocity in natural channels.

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Abstract: Flow resistance in open channels determines the average flow velocity in a river, with important implications for downstream and at-a-station hydraulic geometry and sediment transport in natural channels. However, flow resistance in steep mountain channels is challenging to understand and predict due to heterogeneous channel morphology and spatially variable flow. Using a double-averaging approach appropriate for very rough channels, the width, reach, and double-averaged variables for steady, uniform flow in an open channel are derived. Using an empirical model for the coefficient of form drag, a flow resistance model is derived that compares well to a large data set of flow velocity in natural channels. Several parameters that together describe bed morphology are observed to be relatively consistent in the data set used and compare well to previous estimates of their values. This implies a degree of self-organization in bed morphology that may simplify the challenging problem of predicting flow resistance in steep mountain rivers.

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1 citations

References

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Journal Article•DOI•

Flow Resistance in Gravel-Bed Rivers

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Richard D. Hey¹•Institutions (1)

University of East Anglia¹

01 Apr 1979-Journal of Hydraulic Engineering

TL;DR: In this article, a general approach for the estimation of the Darcy-Weisbach friction factor is presented and independent field data indicates that the method can be successfully applied to predict the resistance to uniform flow in gravel-bed rivers.

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Abstract: The resistance to uniform flow in straight gravel-bed rivers is basically dependent on the flow geometry, the cross-sectional variation in roughness heights, and the roughness height of the graded gravel bed sediment. The effect of these factors on the resistance to flow is evaluated and a general approach for the estimation of the Darcy-Weisbach friction factor is presented. Independent field data indicates that the method can be successfully applied to predict the resistance to uniform flow in gravel-bed rivers.

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423 citations

"Review of step-pool hydrodynamics i..." refers methods in this paper

...Such relations are prone to giving spurious results (Pagliara and Chiavaccini, 2006) as f has an inherent relationship with Fr as displayed in equation (6), where is the shear velocity of flow (Ferguson, 2007)....
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...S ¼ Sf 0 þ Sf 00 ð16Þ The grain roughness coefficient f 0 was calculated using equation (2) from Keulegan (1938), by substituting ks ¼ D50 or as a suitable multiplier of D84 to allow for the presence of form roughness (Bathurst, 1985; Bray, 1979; Comiti et al., 2007; Curran and Wohl, 2003; David et al., 2011; Ferguson, 2007; Hey, 1979; Thompson and Campbell, 1979)....
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...Rickenmann and Recking (2011) also provided an explicit form of the VPE equation by applying the logarithmic matching technique, which maintained less than 1% error with the initial VPE equation: u ¼ 1:443ðq Þ0:60 1þ q 43:78 0:8214" # 0:2435 ð13Þ Adding on to the two-component approach in flow resistance calculation used by Ferguson (2007), the authors proposed a flow resistance partitioning technique with a base-level resistance for intermediate- and large-scale roughness, given by the following equations:ffiffiffi 8 f0 s ¼ u0q 1:5ffiffiffiffiffiffiffiffi gqS p ð14aÞ ffiffiffi 8 f0 s ¼ u0dffiffiffiffiffiffiffiffi gdS p ð14bÞ where f0 is the base-level resistance factor, and u0 is its equivalent flow velocity calculated using equation (9a)....
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...The standard parameters identified for developing flow resistance equations in step-pools include a measure of discharge (unit discharge, flow depth or hydraulic radius in the case of narrow channels), characteristic grain size and average bed slope (Aberle and Smart, 2003; Comiti et al., 2007; Lee and Ferguson, 2002)....
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...It relates the non-dimensional flow velocity u ¼ u= ffiffiffiffiffiffiffiffiffi gDm p with non- dimensional unit discharge q ¼ q= ffiffiffiffiffiffiffiffiffiffiffi gDm3 p and slope as in equation (7), where C, a and b are constants: u ¼ C½ðq ÞaSbb ð7Þ Ferguson (2007) integrated the previously discussed power relation (equation (3) with d ¼ R and Dm ¼ D84) and the hydraulic geometry approach (equation (7)) in an attempt to define end-members for both shallow and deep flows....
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Journal Article•DOI•

The science and practice of river restoration

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Ellen Wohl, Stuart N. Lane¹, Andrew C. Wilcox²•Institutions (2)

University of Lausanne¹, University of Montana²

01 Aug 2015-Water Resources Research

TL;DR: A review of river restoration can be found in this article, where the authors critically examine how contemporary practitioners approach river restoration and challenges for implementing restoration, which include clearly identified objectives, holistic understanding of rivers as ecosystems, and the role of restoration as a social process.

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Abstract: River restoration is one of the most prominent areas of applied water-resources science. From an initial focus on enhancing fish habitat or river appearance, primarily through structural modification of channel form, restoration has expanded to incorporate a wide variety of management activities designed to enhance river process and form. Restoration is conducted on headwater streams, large lowland rivers, and entire river networks in urban, agricultural, and less intensively human-altered environments. We critically examine how contemporary practitioners approach river restoration and challenges for implementing restoration, which include clearly identified objectives, holistic understanding of rivers as ecosystems, and the role of restoration as a social process. We also examine challenges for scientific understanding in river restoration. These include: how physical complexity supports biogeochemical function, stream metabolism, and stream ecosystem productivity; characterizing response curves of different river components; understanding sediment dynamics; and increasing appreciation of the importance of incorporating climate change considerations and resiliency into restoration planning. Finally, we examine changes in river restoration within the past decade, such as increasing use of stream mitigation banking; development of new tools and technologies; different types of process-based restoration; growing recognition of the importance of biological-physical feedbacks in rivers; increasing expectations of water quality improvements from restoration; and more effective communication between practitioners and river scientists.

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419 citations

Journal Article•DOI•

Paleohydraulic reconstruction of flash-flood peaks from boulder deposits in the Colorado Front Range

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John E. Costa¹•Institutions (1)

University of Denver¹

01 Aug 1983-Geological Society of America Bulletin

TL;DR: In this article, the authors used a simple arithmetic average of two theoretical and two empirical relationships to estimate average flood velocity using boulder size and shape, and the appropriate flood width for the estimated average depth was found by iteration, using the valley cross sections.

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Abstract: Nine watersheds in the Colorado Front Range with steep bedrock channels were used to test the accuracy of paleohydraulic reconstruction of large flash floods using boulder deposits. The nine basins consist of eight small ungauged basins ranging in size from 1.6 to 29 km2 and the Big Thompson River at the mouth of the Big Thompson Canyon, draining 790 km2. Between 1923 and 1976, all nine basins had had one catastrophic flash flood, the magnitude of which has been estimated by the conventional slope-area method. In each basin, coarse boulder deposits of the large flash floods were identified, and three axes of the five largest boulders were measured, along with at least two profiles of the valley cross section. A simple arithmetic average of two theoretical and two empirical relationships was used to estimate average flood velocity using boulder size and shape. Average depth was estimated as the arithmetic average of four values computed from the Manning equation, a regression equation for boulder size and unit stream power, a relative smoothness equation, and a modified Shields' relationship. The appropriate flood width for the estimated average depth was found by iteration, using the valley cross sections. The paleohydraulic discharges thus computed generally underestimate conventional slope-area discharge estimates on small streams by as much as 75%, although the average amount is only 28% too low, and the reconstructed discharge in one stream was 31% too large. The Big Thompson River flood of 1976 was overestimated by 76%. Reasons for discrepancy in reconstructed peaks could include (1) the possibility that floods may have been able to move boulders larger than those available to be moved; (2) overestimation of the slope-area discharge because high-water marks were set prior to erosion of the channel; (3) underestimation of original roughness coefficients; and (4) macroturbulent effects during fast, deep flows. The paleohydraulic technique is applied to two other streams in Colorado with sedimentological evidence of large flash floods, but no conventional indirect discharge estimates. A small tributary to the Big Thompson River draining 1.8 km2 has a paleohydraulic reconstructed flood peak of about 60 m3/s from a flood in 1976. Using boulders excavated from a foundation site in Holocene alluvium along Boulder Creek in Boulder, Colorado, a paleohydraulic reconstructed flood peak of between 860 and 1,512 m3/s is calculated. This is 1.4 to 2.4 times the magnitude of the estimated 500-yr flood.

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379 citations

"Review of step-pool hydrodynamics i..." refers background in this paper

...…for different Dm such as D50, D84, D90 and s for representing the characteristic grain size, where Dm (m ¼ 50, 84, 90) is the bed material size which passes m% of the total bed material, and s is the geometric standard deviation of the bed material (Chin, 1998; Costa, 1983; Lee and Ferguson, 2002)....
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Journal Article•DOI•

Flow Resistance Estimation in Mountain Rivers

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James C. Bathurst

01 Apr 1985-Journal of Hydraulic Engineering

TL;DR: In this article, the authors examined the flow resistance of high-gradient gravel and boulder-bed rivers, using data collected in British mountain rivers with slopes of 0.4 - 4%.

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Abstract: Examination of the flow resistance of high-gradient gravel and boulder-bed rivers, using data collected in British mountain rivers with slopes of 0.4 - 4%, shows that there are differences in resistance variation between mountain and lowland rivers and that between-site variations do not necessarily reflect at-a-site variations. Comparison of data with the familiar resistance equation relating the Dracy-Weisbach friction factor to the logarithm of relative submergence shows that the equation tends to overestimate the resistance in uniform flow. The equation also tends to underestimate the rate of change of resistance at a site (as discharge varies) with high gradients. The influences of nonuniform channel profile, sediment size distribution, channel slope and sediment transport are reviewed, but the data do not allow any quantification of these effects. Instead an empirical approach based on the available data is presented, allowing the friction factor to be calculated from the relative submergence with an error of up to ±\N25% to ±\N35%. A summary of the field data is included.

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362 citations

"Review of step-pool hydrodynamics i..." refers background or methods in this paper

...S ¼ Sf 0 þ Sf 00 ð16Þ The grain roughness coefficient f 0 was calculated using equation (2) from Keulegan (1938), by substituting ks ¼ D50 or as a suitable multiplier of D84 to allow for the presence of form roughness (Bathurst, 1985; Bray, 1979; Comiti et al., 2007; Curran and Wohl, 2003; David et al., 2011; Ferguson, 2007; Hey, 1979; Thompson and Campbell, 1979)....
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...…velocity for the entire data set considered was evaluated using the resistance equations given by Strickler (1923), Keulegan (1938), Hey (1979), Bathurst (1985), Smart and Jäggi (1983) and Ferguson (2007) since these studies covered both simple and complex equations such as power law,…...
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...…based on hydraulic geometry. f ¼ 8gRSb u2 ð1Þ Semi-logarithmic relations are adopted from the boundary layer theory and pipe flow hydraulics and they relate relative submergence with f through a semi-logarithmic relation (Bathurst, 1985; Bray, 1979; Griffiths, 1981; Hey, 1979; Keulegan, 1938)....
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...The reduced shear stress for the initiation of sediment movement, yr ¼ RSr=ðs 1ÞD50, is supplied in the bedload transport equation, fb ¼ 2:5 ffiffiffiffi yr p ðyr yc;rÞFr (Rickenmann, 2001), where fb is the non-dimensional bedload transport rate, s is the specific gravity of the sediment and yc;r ¼ RcSrðRcÞ=ðs 1ÞD50 is the reduced critical shear stress corresponding to the critical hydraulic radius Rc and critical unit discharge, qc ¼ 0:065ðs 1Þ1:67 ffiffiffi g p D1:550 S 1:12....
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...Semi-logarithmic relations are adopted from the boundary layer theory and pipe flow hydraulics and they relate relative submergence with f through a semi-logarithmic relation (Bathurst, 1985; Bray, 1979; Griffiths, 1981; Hey, 1979; Keulegan, 1938)....
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Journal Article•DOI•

Flow resistance equations for gravel- and boulder-bed streams

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Robert I. Ferguson¹•Institutions (1)

Durham University¹

01 May 2007-Water Resources Research

TL;DR: In this paper, a non-dimensional hydraulic geometry equation with different parameters for deep and shallow flows, and a variable power resistance equation that is asymptotic to roughness-layer formulations for shallow flows and to the Manning-Strickler approximation of the logarithmic friction law for deep flows are proposed.

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Abstract: [1] Alternative general forms are considered for equations to predict mean velocity over the full range of relative submergence experienced in gravel- and boulder-bed streams. A partial unification is suggested for some previous semiempirical models and physical concepts. Two new equations are proposed: a nondimensional hydraulic geometry equation with different parameters for deep and shallow flows, and a variable-power resistance equation that is asymptotic to roughness-layer formulations for shallow flows and to the Manning-Strickler approximation of the logarithmic friction law for deep flows. Predictions by existing and new equations using D84 as roughness scale are compared to a compilation of measured velocities in natural streams at relative submergences from 0.1 to over 30. The variable-power equation performs as well as the best existing approach, which is a logarithmic law with roughness multiplier. For predicting how a known or assumed discharge is partitioned between depth and velocity, a nondimensional hydraulic geometry approach outperforms equations using relative submergence. Factor-of-two prediction errors occur with all approaches because of sensitivity to operational definitions of depth, velocity, and slope, the inadequacy of using a single grain-size length scale, and the complexity of flow physics in steep shallow streams.

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310 citations