Regime Theory for Self-Formed Sediment-Bearing Channels

Blench, T.

doi:10.1061/taceat.0006641

Cited by 25 publications

(2 citation statements)

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“…The channel-forming or dominant discharge theory stipulates that if there is a unique flow maintained in an alluvial river over a long period of time, it would produce the same bankfull morphology that is shaped by the natural sequence of flows. Even this concept is not an universally accepted method, most practitioners agree that this is applicable in perennial and ephemeral rivers (Blench, 1952;Ackers and Charlton, 1970;Bray, 1975;Biedenharn et al, 2000;USDA, 2001;Soar and Thorne, 2001).…”

Section: Channel-forming Dischargementioning

confidence: 99%

Environmental Restoration Of Concrete Flood-Control Channels

Fan¹

2021

Preprint

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Many rivers and streams throughout the world in the past century were severely affected by human activities including water extraction, watershed land use changes, power generation, dam and levee construction. In highly urbanized cities, engineering practices advocate straightening, enlarging, and converting the natural rivers and streams into concrete channels to minimize flooding and erosion problems. These engineering design approaches destroy the natural equilibrium of the fluvial systems and eliminate the aquatic and riparian species in the watercourse. The objective of this research is to develop a general stream restoration design approach for flood control concrete channels in highly urbanized areas. The restoration goals are: 1) to create a natural and self-sustainable river system in order to re-establish the aquatic species on the flood control channel; 2) to provide appropriate in-stream covers, pools and riffles features for fish spawning and rearing; and 3) to maintain the flood control function after stream restoration. There are four phrases involved in the design methodology of flood channels restoration: 1) identification of restoration goals, 2) stream assessment on the existing condition; 3) modification and verification of the low-flow channel design based on stream assessment findings; and 4) confirmation of the original flood control function. Yuen Long Nullah in Hong Kong will be used as a pilot site study to demonstrate the design framework. Meanders and deflectors will be applied to the low-flow channel modification design. A physical model representing an actual 2-metre wide meander channel section of the low-flow channel was constructed and experimented at The Hong Kong Polytechnic University’s Hydraulics Laboratory. A numerical sediment transport model using the CCHE2D program was used to adjust the modification design and verify the flood control function. The pilot site has been tentatively demonstrated the restoration design approach developed in this research where deflectors are a major factor on pools creation. Moreover, a single deflector located along the inner curvature of the meander section with 1/3 contraction ratio is proved to be the best design using the physical model. The numerical model using the CCHE2D program showed that the 7-block system can be used to model a deflector with porosity of 40%. Numerical results also demonstrated that the bed material will not be totally flushed out after a severe thunder storm.

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Section: Channel-forming Dischargementioning

confidence: 99%

Environmental Restoration Of Concrete Flood-Control Channels

Fan¹

2021

Preprint

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“…These approaches can be broadly classified into three methods, each using the same basic assumption of steady and uniform flow to achieve channel equilibrium. First, empirical equations of the regime have been obtained from the statistical rule/regression analysis of channel geometry data from different rivers (Thomas Blench 1952;Bray 1982;Hey and Thorne 1986a;Leopold and Wolman 1957;Wolman 1954). In these equations, flow discharge, bed shear stress and bedgrain diameters have been considered as the most effective parameters to predict the geometry of stable rivers (Deshpande and Kumar 2012;Parker et al 2007).…”

Section: Introductionmentioning

confidence: 99%

Predicting stable gravel-bed river hydraulic geometry: A test of novel, advanced, hybrid data mining algorithms

Khosravi

Khozani

Cooper

2021

Environmental Modelling & Software

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Accurate prediction of stable alluvial hydraulic geometry, in which erosion and sedimentation are in equilibrium, is one of the most difficult but critical topics in the field of river engineering. Data mining algorithms have been gaining more attention in this field due to their high performance and flexibility.However, an understanding of the potential for these algorithms to provide fast, cheap, and accurate predictions of hydraulic geometry is lacking. This study provides the first quantification of this potential. Using at-a-station field data, predictions of flow depth, water-surface width and longitudinal water surface slope are made using three standalone data mining techniques -, Instance-based Learning (IBK), KStar, Locally Weighted Learning (LWL) -along with four types of novel hybrid algorithms in which the standalone models are trained with Vote, Attribute Selected Classifier (ASC), Regression by Discretization (RBD), and Cross-validation Parameter Selection (CVPS) algorithms (Vote-IBK, Vote-

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