Partial entrainment of gravel bars during floods

Konrad, Christopher P.; Booth, Derek B.; Burges, Stephen J.; Montgomery, David R.

doi:10.1029/2001wr000828

Cited by 48 publications

(46 citation statements)

References 44 publications

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“…According to Konrad et al (2002), the probability of bed material transport is approximately uniform over a gravel bar during a flood, provided the bar has uniform sedimentologic and hydraulic conditions. Within our SHR sites, shallow berms, LWD, and boulders are used to attract spawning Chinook salmon.…”

Section: Discussionmentioning

confidence: 99%

Sediment budget for salmonid spawning habitat rehabilitation in a regulated river

2006

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Section: Discussionmentioning

confidence: 99%

Sediment budget for salmonid spawning habitat rehabilitation in a regulated river

2006

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“…In addition, the values of less than τ * c = 0·03 for nine velocity profiles measured over the mobile bed shows that the experiments were conducted for weakly mobile bed condition, as mentioned by Nikora & Goring (2000). For example in profiles 16 and 19 of table 1, the Shields parameters are less than minimum value of incipient motion that is 0·02 (Konrad et al 2002) for gravel-bed streams. However, in the both velocity profiles (16 and 19), movement of particles was observed.…”

Section: Shields Parametermentioning

confidence: 96%

Influence of decelerating flow on incipient motion of a gravel-bed stream

Afzalimhr

Dey

Rasoulianfar

2007

Sadhana

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An experimental study on incipient motion of gravel-bed streams under steady-decelerating flow is presented. Experiments were carried out in a flume with two median grain sizes, d 50 = 16·7 mm for a fixed-bed case and d 50 = 8 mm for a mobile bed case. In addition, an effort is made to determine a simplified method for the estimation of bed shear stress in decelerating flow over fixed and mobile beds for use in field situations. From the observation of eleven fixed-bed and nine mobile-bed velocity profiles, it is revealed that the parabolic law method (PLM) and the Reynolds stress method are comparable for estimation of shear velocity in general. Also, the results show that the shear stress distribution adopts a convex form over fixed and mobile beds. Due to this form the critical Shields parameter value for decelerating flow is less than the reported values in literature.This paper supports Buffington & Montgomery (1997) statement that less emphasis should be given on choosing a universal shields parameter, and more emphasis should be given on choosing defendable values based on flow structure.

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“…Dimensionless shear stress provides an approximate index of the spatial extent of gravel entrainment from the bar surface with limited gravel entrainment beginning around 0.02-0.04 and extensive entrainment (more than about 50 per cent of the bar area) at values greater than 0.08 (Konrad et al, 2002).…”

Section: Aquatic and Riparian Habitat Field Surveymentioning

confidence: 99%

Integrating remotely acquired and field data to assess effects of setback levees on riparian and aquatic habitats in glacial‐melt water rivers

Konrad

Black

Voß

et al. 2008

River Research & Apps

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Setback levees, in which levees are reconstructed at a greater distance from a river channel, are a promising restoration technique particularly for alluvial rivers with broad floodplains where river-floodplain connectivity is essential to ecological processes. Documenting the ecological outcomes of restoration activities is essential for assessing the comparative benefits of different restoration approaches and for justifying new restoration projects. Remote sensing of aquatic habitats offers one approach for comprehensive, objective documentation of river and floodplain habitats, but is difficult in glacial rivers because of high suspended-sediment concentrations, braiding and a lack of large, well-differentiated channel forms such as riffles and pools. Remote imagery and field surveys were used to assess the effects of recent and planned setback levees along the Puyallup River and, more generally, the application of multispectral imagery for classifying aquatic and riparian habitats in glacial-melt water rivers. Airborne images were acquired with a horizontal ground resolution of 0.5 m in three spectral bands (0.545-0.555, 0.665-0.675 and 0.790-0.810 mm) spanning from green to near infrared (NIR) wavelengths. Field surveys identified river and floodplain habitat features and provided the basis for a comparative hydraulic analysis. Broad categories of aquatic habitat (smooth and rough water surface), exposed sediment (sand and boulder) and vegetated surfaces (herbaceous and deciduous shrub/forest) were classified accurately using the airborne images. Other categories [e.g. conifers, boulder, large woody debris (LWD)] and subdivisions of broad categories (e.g. riffles and runs) were not successfully classified either because these features did not form large patches that could be identified on the imagery or their spectral reflectances were not distinct from those of other habitat types. Airborne imagery was critical for assessing fine-scale aquatic habitat heterogeneity including shallow, low-velocity regions that were not feasible or practical to map in the field in many cases due to their widespread distribution, small size and poorly defined boundaries with other habitat types. At the reach-scale, the setback levee affected the amount and distribution of riparian and aquatic habitats: (1) the area of all habitats was greater where levees had been set back and with relatively more vegetated floodplain habitat and relatively less exposed sediment and aquatic habitat, (2) where levees confine the river, less low-velocity aquatic habitat is present over a range of flows with a higher degree of bed instability during high flows. As river restoration proceeds in the Pacific Northwest and elsewhere, remotely acquired imagery will be important for documenting its effects on the amount and distribution of aquatic and floodplain habitats, complimenting field data as a quantitative basis for evaluating project efficacy.

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Partial entrainment of gravel bars during floods

Cited by 48 publications

References 44 publications

Sediment budget for salmonid spawning habitat rehabilitation in a regulated river

Sediment budget for salmonid spawning habitat rehabilitation in a regulated river

Influence of decelerating flow on incipient motion of a gravel-bed stream

Integrating remotely acquired and field data to assess effects of setback levees on riparian and aquatic habitats in glacial‐melt water rivers

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