Development of channel organization and roughness following sediment pulses in single‐thread, gravel bed rivers

Madej, Mary Ann

doi:10.1029/2001wr000229

Cited by 90 publications

(93 citation statements)

References 39 publications

(41 reference statements)

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“…Pool filling smoothed the bed and reduced the hydraulic roughness of the channel, increasing both the flow velocity and bed load transport rate, thereby providing a mechanism for equilibrating rates of sediment supply and bed load transport and creating a stable channel morphology. Similar changes in bed topography and channel roughness have been observed in natural gravel-bed rivers in response to episodic inputs of coarse sediment (Madej, 2001).…”

Section: Sediment Loadsupporting

confidence: 50%

Controls on the size and occurrence of pools in coarse‐grained forest rivers

Buffington

Lisle

Woodsmith

et al. 2002

River Research & Apps

179

191

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Controls on pool formation are examined in gravel-and cobble-bed rivers in forest mountain drainage basins of northern California, southern Oregon, and southeastern Alaska. We demonstrate that the majority of pools at our study sites are formed by flow obstructions and that pool geometry and frequency largely depend on obstruction characteristics (size, type, and frequency). However, the effectiveness of obstructions to induce scour also depends on channel characteristics, such as channel gradient, width:depth ratio, relative submergence (ratio of flow depth to grain size), and the calibre and rate of bed material supply. Moreover, different reach-scale channel types impose different characteristic physical processes and boundary conditions that further control the occurrence of pools within a catchment. Our findings indicate that effective management of pools and associated aquatic habitat requires consideration of a variety of factors, each of which may be more or less important depending on channel type and location within a catchment. Consequently, strategies for managing pools that are based solely on single-factor, regional target values (e.g. a certain number of wood pieces or pools per stream length) are likely to be ineffective because they do not account for the variety of local and catchment controls on pool scour and, therefore, may be of limited value for proactive management of complex ecosystems.

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Section: Sediment Loadsupporting

confidence: 50%

Controls on the size and occurrence of pools in coarse‐grained forest rivers

Buffington

Lisle

Woodsmith

et al. 2002

River Research & Apps

179

191

View full text Add to dashboard Cite

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“…Indeed, configuration A, with the larger covered surface, also leaded to a wider smoothing than configuration B. In general the present observation of bed fining is in agreement with the reaction of steep mountain gravel streams to sediment pulse input observed by Madej (2001) and with recent morphodynamic modelling, where a fining of the bed surface due to increased sediment supply is predicted (Ferguson et al 2015).…”

Section: Discussionsupporting

confidence: 79%

Influence of consecutive sediment replenishment on channel bed morphology

Bösch¹,

Battisacco²,

Franca³

et al. 2016

River Flow 2016

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Dams interrupt the longitudinal connectivity of a river as they store water and trap sediment. When transport capacity downstream of dams exceeds sediment supply, water becomes hungry and channel incision, bed armouring and reduction of morphological diversity are the consequences. Sediment replenishment is an increasingly common measure to restore the sediment regime of such disturbed river reaches. In the present study the influence on channel bed morphology of different geometrical configuration of replenishments and of consecutive gravel augmentation is assessed by means of systematically laboratory experiments. The typical features of a straight armoured alpine gravel channel are reproduced on the model in terms of slope, cross section and bed grain size. The total amount of replenished sediment is deposited in four identical volumes following two different geometrical configurations (parallel and alternating). The reaction of the channel bed is analysed on image and laser data. Persistency of the first replenishment is high and it covers a large portion of the channel bed, which consequently decreases channel bed roughness remarkably. The persistency of the second replenishment is low and the effect on the depositional pattern established after the first replenishment only minor. This is explained by the smoothing of the channel bed during the first replenishment, resulting in higher transport capacities. For the alternating configuration an increase in the deposition heights in the very downstream channel reach can be observed due to the second replenishment. Thus it is assumed that consecutive replenishment can increase the impact length of restoration projects. The parallel configuration results in very spread depositions, while for the alternating configuration a clear bed form pattern could be observed with a wavelength of depositions corresponding to the length of the replenished volumes. These depositions are understood as mounds, forming the initial condition of alternating bars. Thus in order to enhance channel bed topography of an armoured layer downstream a dam, sediment replenishment added by the alternating configuration is most favourable and effective.

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“…For example, the model of Schumm (1969) indicates that decreasing stream flow while increasing sediment supply will produce a decrease in channel depth and sinuosity but either an increase or decrease in channel width. The difficulty in predicting channel response arises because many degrees of freedom exist for channel adjustment, including changes in channel slope (Lane, 1955), channel geometry and planform (Schumm, 1969), bed texture (Lisle et al, 1993), and bed organization (Madej, 2001). The nature of the adjustments to a given perturbation in a given stream reach is contingent upon prior conditions (Brewer and Lewin, 1998), such that similar changes in inputs can produce different channel adjustments in different reaches (Carling, 1988).…”

Section: Introductionmentioning

confidence: 99%