Laboratory hydraulic calibration of the Helley-Smith bedload sediment sampler

Druffel, Leroy; Emmett, William W.; Schneider, Verne R.; Skinner, J.V.

doi:10.3133/ofr76752

Cited by 23 publications

(16 citation statements)

References 1 publication

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“…At low flows, by contrast, when small gravel particles were just beginning to move, the Helley-Smith collected larger particles than the bedload traps. The larger particle sizes in the Helley-Smith samples at low transport rates were likely due to an inadvertent occasional dislodging of a mobile surface particle when setting the Helley-Smith sampler onto the bed and the subsequent entrainment of the dislodged particle into the sampler opening due to the sampler's high hydraulic efficiency of 154 % [46]. The authors observed this process on several occasions when the area around the sampler opening was viewed through a piece of plexi glass.…”

Section: Gravel Transport Rate (G/s)mentioning

confidence: 98%

“…Larger Helley-Smith type samplers such as the 152 by 152 mm opening size Helley-Smith and the Toutle River 1 sampler, the Elwha sampler (102 by 203 mm), and the Toutle River 2 sampler (305 by 152 mm) were developed to overcome the size limitation posed by the smaller sampler [39,40,41,[46][47][48][49][50][51]. While large gravels and small cobbles do fit into the sampler entrance, the utility of handheld versions of these larger Helley-Smith samplers is much reduced by the difficulty experienced when holding them in fast flow, the poorer control of their placement on the bed surface, and their higher potential for involuntary particle pick-up [52,53].…”

Section: Introductionmentioning

confidence: 99%

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A Comparison of Coarse Bedload Transport Measured with Bedload Traps and Helley-Smith Samplers

et al. 2008

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Gravel bedload transport rates were measured at eight study sites in coarse-bedded Rocky Mountain streams using 4-6 bedload traps deployed across the stream width and a 76 by 76 mm opening Helley Smith sampler. Transport rates obtained from bedload traps increased steeply with flow which resulted in steep and well-defined transport rating curves with exponents of 8 to 16. Gravel transport rates measured by the HelleySmith sampler started with much higher transport rates during low flows and increased less steeply, thus fitted bedload rating curves were less steep with exponents of 2 to 4. Transport rates measured with both samplers approached similar results near or above bankfull flow, but at 50 % of bankfull, transport rates from the bedload traps were 2-4 orders of magnitude lower than those obtained from the Helley-Smith sampler. The maximum bedload particle sizes also differed between the two samplers. They were smaller in the bedload traps than the Helley-Smith sampler at low flows, while at higher flows bedload traps collected larger particles than the Helley-Smith sampler. Differences in sampler opening size and sampling time contribute to the measured differences, but the biggest effect is likely attributable to the bedload traps being mounted on ground plates thus avoiding direct contact between the sampler and the bed and preventing involuntary particle pick up.

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Section: Gravel Transport Rate (G/s)mentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

A Comparison of Coarse Bedload Transport Measured with Bedload Traps and Helley-Smith Samplers

et al. 2008

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“…One sampler, here referred to as the "thick-wall" sampler, is made of cast aluminum, has a nozzle wall thickness of 6.3 mm and weighs 1.86 kg. This sampler is constructed to the specifications of Helley and Smith [1971] and is the same type of sampler used in laboratory and field calibrations [Druffel et al, 1976;Erainert, 1980]. The other sampler, here referred to as the "thin-wall" sampler, is commercially available and is constructed with sheet metal with a nozzle wall thickness of 1.5 mm and weighs 1.18 kg.…”

Section: Sampler Efficiency Evaluationmentioning

confidence: 99%

Variability of bed load measurement

Pitlick¹

1988

Water Resources Research

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The sampling efficiencies of two slightly different Helley-Smith-type bed load samplers were compared under carefully controlled field conditions. The samplers were identical in all respects except for the thickness of the metal used in their construction. The test results indicate that for coarse-grained sand bed load, the sampler with a wall thickness of 1.5 mm has a sediment trap efficiency that can be as much as two times that of the sampler with walls that are 6.3 mm thick. In a separate test, bed load transport was monitored at a single channel cross section during a 10-hour period of steady discharge. At individual sampling stations, measurement values ranged from nearly 0 to 3 times the mean. Composite bed load transport rates for full traverses of the channel width varied by a factor of 2.

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“…Laboratory testing of the Helley-Smith sampler (Druffel et al, 1976) has indicated that the exitkmtrance area ratio of the nozzle and the amount of sediment in the sample bag are the major factors affecting the hydraulic efficiency of the sampler. The sediment trapping characteristics of the sampler have been determined by field calibration (Emmett, 1979).…”

Section: Bedloadmentioning

confidence: 99%

Temporal variations in bedload transport rates: The effect of progressive bed armouring

Gómez

1983

Earth Surf Processes Landf

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The quantitative bedload transport data that are presently available confirm that the generalized bedload transport rate-stream power relationship is applicable to natural streams. However, the bedload transport rate is not solely dependent upon hydraulic parameters, but also upon the inter-relationship between bed material characteristics and flow properties. Segregation of the surficial bed material, as expressed through the development of an armour coat, limits the availability of transportable material. Under such circumstances observed bedload transport rates are less than the predicted values.The effect which the development of an armoured surface has upon the bedload transport rate is described with reference to bedload and bed material sampling in the Borgne d'Arolla, Valais, Switzerland. The data refer to two periods when the resumption of baseflow conditions following flood events which were of a sufficient magnitude to transport all but the coarsest (0.343 m) particles on the streambed, provided the opportunity for the bed to adjust to a comparatively stable flow regime. Observed and predicted bedload transport rate-stream power relationships are compared. The theoretical relationship does not adequately describe conditions in some gravel-bed channels, since it fails to take into account the effect which armouring may have upon the supply of transportable material.

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Laboratory hydraulic calibration of the Helley-Smith bedload sediment sampler

Cited by 23 publications

References 1 publication

A Comparison of Coarse Bedload Transport Measured with Bedload Traps and Helley-Smith Samplers

A Comparison of Coarse Bedload Transport Measured with Bedload Traps and Helley-Smith Samplers

Variability of bed load measurement

Temporal variations in bedload transport rates: The effect of progressive bed armouring

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