Design of Stable Channels

Lane, E. W.

doi:10.1061/taceat.0007188

Cited by 256 publications

(36 citation statements)

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“…Future projections of the spatial expansion of gully area were made by forward-trending the slope of the outlet channel, common to all tributaries, through the scarp zone and into the uneroded alluvial plain. This assumes that the sand-bed gully-outlet channels are at an equilibrium slope or grade (sensu Mackin, 1948;Lane, 1955) due to abundant sand bed-material supplied from gully scarp failure during monsoon rains (Brooks et al, 2009;Shellberg et al, 2013a,b;Rose et al, 2015). It also assumes that over-steepened scarp fronts will flatten over time toward a graded slope, due to the unconfined nature of the high-floodplain.…”

Section: Past Gully Erosion Chronologies From Osl Datingmentioning

confidence: 99%

Degradation of the Mitchell River fluvial megafan by alluvial gully erosion increased by post-European land use change, Queensland, Australia

et al. 2016

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Along low gradient rivers in northern Australia, there is widespread gully erosion into unconfined alluvial deposits of active and inactive floodplains. On the Mitchell River fluvial megafan in northern Queensland, river incision and fan-head trenching into Pleistocene and Holocene megafan units with sodic soils created the potential energy for a secondary cycle of erosion. In this study, rates of alluvial gully erosion into incipiently-unstable channel banks and/or pre-existing floodplain features were quantified to assess the influence of land use change following European settlement. Alluvial gully scarp retreat rates were quantified at 18 sites across the megafan using recent GPS surveys and historic air photos, demonstrating rapid increases in gully area of 1.2 to 10 times their 1949 values. Extrapolation of gully area growth trends backward in time suggested that the current widespread phase of gullying initiated between 1880 and 1950, which is post-European settlement. This is supported by young optically stimulated luminescence (OSL) dates of gully inset-floodplain deposits, LiDAR terrain analysis, historic explorer accounts of earlier gully types, and archival records of cattle numbers and land management. It is deduced that intense cattle grazing and associated disturbance concentrated in the riparian zones during the dry season promoted gully erosion in the wet season along steep banks, adjacent floodplain hollows and precursor gullies. This is a result of reduced native grass cover, increased physical disturbance of soils, and the concentration of water runoff along cattle tracks, in addition to fire regime modifications, episodic drought, and 29 the establishment of exotic weed and grass species. Geomorphic processes operating over 30 geologic time across the fluvial megafan predisposed the landscape to being pushed by land 31 used change across an intrinsically close geomorphic threshold towards instability. The 32 evolution of these alluvial gullies is discussed in terms of their initiation, development, future 33 growth, and stabilisation, and the numerous natural and anthropogenic factors influencing their 34 erosion.

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Section: Past Gully Erosion Chronologies From Osl Datingmentioning

confidence: 99%

Degradation of the Mitchell River fluvial megafan by alluvial gully erosion increased by post-European land use change, Queensland, Australia

et al. 2016

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“…The weaknesses of empirical methods encouraged the formulation of new physics-based approaches. A rational method was first developed following the assumption that a stable channel forms when a threshold condition for sediment motion establishes along the whole cross-section boundary (Glover & Florey, 1951;Lane, 1955). This methodology was later revised and improved by Colombini and Tubino (1991) and Diplas and Vigilar (1992), who reformulated the problem by considering the unknown bank shape as part of the solution, and Cao and Knight (1998), who included the effect of secondary flow.…”

Section: Introductionmentioning

confidence: 99%

“…Predicting the equilibrium cross section of natural rivers has attracted the attention of many researchers for a long time. Field and laboratory observations were initially used to derive empirical methods, known as regime equations , to be used as simple predictive tools (Blench, ; Inglis, ; Lacey, ; Lane, ; Lindley, ; Simons & Albertson, ). In particular, Leopold and Maddock () expressed the channel width, the average flow depth, and the average flow velocity as functions of the annually averaged flow discharge.…”

Section: Introductionmentioning

confidence: 99%

Equilibrium Cross Section of River Channels With Cohesive Erodible Banks

et al. 2020

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Predicting the equilibrium cross section of natural rivers has been widely investigated in Q1 Q2 Q3 fluvial morphology. Several approaches have been developed to meet this aim, starting from regime equations to the empirical formulations of Parker et al. (2007) and Wilkerson and Parker (2011), who Q4 proposed quasi-universal relations for describing bankfull conditions in sand and gravel bed rivers. Nevertheless, a general physics-based framework is still missing, and it remains an open issue to better clarify the basic mechanisms whereby a river selects its width. In this contribution we focus our attention on lowland rivers with cohesive banks, whose resistance to erosion is crucial to control the river width. In particular, we formulate a theoretical model that evaluates the equilibrium width of river cross sections modeling the interaction between the core flow in the central part of the section and the boundary layer that forms in the correspondence of the cohesive banks. The model computes the cross-section equilibrium configuration by which the shear stresses on the banks equal a critical threshold value. These stresses are computed by partitioning the total shear stress into an effective grain roughness component and a form component (Kean and Smith, 2006a). The model is applied to a large data set, concerning both sand and gravel bed rivers, and it is used to determine the relations expressing the channel width and the bankfull flow depth to the bankfull discharge, which appear to provide a unitary description of bankfull hydraulic geometry.

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“…The DS is silted up over the entire length of the studied section, with a high level of substrate homogenization and with sediment bars, whose system energy during the rainy season was unable to remove [ 45 , 46 ]. These characteristics are probably a reflection of the transport of a large load of sediments from the degraded area upstream [ 7 , 47 ]. In DA, runoff is markedly affected both by the absence of vegetation and by the characteristics of high rainfall intensity, which occur mainly between October and March.…”

Section: Discussionmentioning

confidence: 99%

Changes in the hydro-sedimentary balance: Impacts of the use of a borrow pit in a low-order stream

et al. 2021

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Construction of dams for hydroelectric power requires significant quantities of soil and rock, which are often extracted in borrow pits from adjacent regions. Although the effects of dams on stream processes has received significant attention, the effects of borrow pits has not. The main objective of this study was to analyze the geomorphological and sedimentological aspects of two second-order streams, one of which was directly affected by the borrow pit located upstream of its source (Pedra Branca stream). Flow rates were measured and cross-sections of 600m stretches in both streams were monitored over a hydrological year. At the same time, sediments from the bed of the channels and soils on their banks had their physical and chemical characteristics evaluated. Streams sediments differed in their chemical and organic matter composition. The mean particle size of the sediment particles was different between the reference and degraded streams. The water flow was very similar to both streams, only varying along the seasonal seasons. However, the fluvial channels presented great geomorphological differentiation, mainly downstream, due to the location of the Pedra Branca stream and its proximity to the borrow pit. Despite the great importance for the production of clean electric energy, the construction of hydroelectric plants promotes persistent impacts that affect structural and functional aspects of the adjacent aquatic habitats. Borrow pits used for the construction of projects become large sources of sediment for aquatic environments, affecting the drainage network of the hydrographic basin and the balance of river erosion, transport and deposition processes. The results show the need to review the intervention protocols in borrow pits and the environmental legislation that regulates their rehabilitation.

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Design of Stable Channels

Cited by 256 publications

References 0 publications

Degradation of the Mitchell River fluvial megafan by alluvial gully erosion increased by post-European land use change, Queensland, Australia

Degradation of the Mitchell River fluvial megafan by alluvial gully erosion increased by post-European land use change, Queensland, Australia

Equilibrium Cross Section of River Channels With Cohesive Erodible Banks

Changes in the hydro-sedimentary balance: Impacts of the use of a borrow pit in a low-order stream

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