scholarly journals Short communication: Field data imply that the sorting (<i>D</i><sub>96</sub> / <i>D</i><sub>50</sub> ratios) of gravel bars in coarse-grained streams influences the probability of sediment transport

2020 ◽  
Author(s):  
Fritz Schlunegger ◽  
Romain Delunel ◽  
Philippos Garefalakis
Keyword(s):  
Water Discharge ◽  
Bedload Transport ◽  
Swiss Alps ◽  
Coarse Grained ◽  
Water Runoff ◽  
Shear Stresses ◽  
Sediment Discharge ◽  
Peruvian Andes ◽  
Gravel Bars ◽  
Bed Material

Abstract. Conceptual models suggest that the mobility of fluvial gravel bars is mainly controlled by sediment discharge. Here we present field observations from streams in the Swiss Alps and the Peruvian Andes to document that for a given water runoff, the probability of bedload transport also depends on the sorting of the bed material. We calculate shear stresses that are expected for a mean annual water discharge, and compare these estimates with grain-specific thresholds. We find a positive correlation between the predicted probability of transport and the sorting of the bed material, expressed by the D96 / D50 ratio. These results suggest that besides sediment discharge, the bedload sorting exerts a measurable control on the gravel bar mobility.

scholarly journals Short communication: Field data reveal that the transport probability of clasts in Peruvian and Swiss streams mainly depends on the sorting of the grains

2020 ◽  
Vol 8 (3) ◽  
pp. 717-728
Author(s):  
Fritz Schlunegger ◽  
Romain Delunel ◽  
Philippos Garefalakis
Keyword(s):  
Water Discharge ◽  
Swiss Alps ◽  
Coarse Grained ◽  
Shear Stresses ◽  
Material Transport ◽  
Peruvian Andes ◽  
Annual Water ◽  
Annual Water Discharge ◽  
Bed Material ◽  
Annual Discharge

Abstract. We present field observations from coarse-grained streams in the Swiss Alps and the Peruvian Andes to explore the controls on the probability of material entrainment. We calculate shear stress that is expected for a mean annual water discharge and compare these estimates with grain-specific critical shear stresses that we use as thresholds. We find that the probability of material transport largely depends on the sorting of the bed material, expressed by the D96∕D50 ratio, and the reach gradient but not on mean annual discharge. The results of regression analyses additionally suggest that among these variables, the sorting exerts the largest control on the transport probability of grains. Furthermore, because the sorting is significantly correlated neither to reach gradient nor to water discharge, we propose that the granulometric composition of the material represents an independent, yet important control on the motion of clasts in coarse-grained streams.

Bed configuration and microscale processes in alluvial channels

1993 ◽  
Vol 17 (2) ◽  
pp. 123-136 ◽  
Author(s):  
André Robert
Keyword(s):  
Probabilistic Approach ◽  
Field Measurements ◽  
Bedload Transport ◽  
Transport Processes ◽  
Coarse Grained ◽  
Small Scale ◽  
Alluvial Channels ◽  
Gravel Beds ◽  
Sand And Gravel ◽  
Bed Material

Numerous recent studies on fluvial processes, both in Canada and internationally, have focused on small-scale phenomena. Investigations on the characterization of surface roughness in coarse-grained channels and its links with flow resistance and sediment transport processes have been a dominant field of research. Closely related is a second major area of investigation on turbulent flow structures in boundary layers over both sand and gravel beds and their relations with the transport of bed material. Phenomena potentially related to 'bursting' have been shown to control bedload transport processes and the concentration of sediment in suspension. Detailed investigations have also been conducted on the links between flow turbulence, bed material movement, and bed morphology at channel junctions. Finally, selective entrainment and transport of individual coarse particles have been studied from field measurements and laboratory experi ments. Emphasis has been put on bed microtopography, surface structure and texture, and on a probabilistic approach to bedload transport.

scholarly journals LAJU ANGKUTAN SEDIMEN MELAYANG DI SUNGAI WIMBI SUB DAS WIMBI KABUPATEN POSO

2021 ◽  
Vol 9 (1) ◽  
pp. 43
Author(s):  
Herman Harijanto ◽  
Abdul Wahid ◽  
Arief Sudhartono ◽  
Nikteri Perori
Keyword(s):  
River Water ◽  
Cross Section ◽  
Loading Rate ◽  
Water Discharge ◽  
Survey Method ◽  
Water Runoff ◽  
Sediment Loading ◽  
Sediment Discharge ◽  
The Cross ◽  
The Relationship

The research purpose was to determine of floating sediment loading rate which transported along Wimbi river water runoff and analyzed the relationship between water discharge with floating sediment discharge in the Wimbi river. The method used in this study was a survey method, namely by conducting direct measurements in the field, including: measurement of water discharge and water sampling for analysis of floating sediment content. Parameter  measured for the purpose of analyzing the sediment loading rate, namely floating sediment concentration Cs (mg / l), river water discharge Q (m3 / sec) and floating sediment discharge Qs (kg / sec). The relationship between water discharge and sediment discharge was analyzed using a suspended sediment rating curve. The results showed the flow of river water flowing at the cross section of the Wimbi river ranged from 0.88 m3 / sec - 13.7 m3 / sec (average of 6.17 m3 / sec). Furthermore, the height of the water level (H) flowing in the cross section of the Wimbi river ranged from 0.5 to 1.84 m with  average = 1.14m. Sediment loading rates float in the Wimbi river ranged from 2.110 - 99.511kg / sec (average of 35.222 kg / sec). The analyzed results of the relationship between water discharge and floating sediment discharge obtained a positive relationship with a correlation value of 0.96.

scholarly journals Hydrological and suspended sediment regime in the Kolubara River during the extreme year of 2014

2016 ◽  
Vol 18 (1) ◽  
pp. 32-46 ◽  
Author(s):  
Slavoljub DRAGIĆEVIĆ ◽  
Nenad ŽIVKOVIĆ ◽  
Ivan NOVKOVIĆ ◽  
Ana PETROVIĆ ◽  
Radislav TOŠIĆ ◽  
...  
Keyword(s):  
Suspended Sediment ◽  
Water Discharge ◽  
Suspended Sediment Transport ◽  
Water Runoff ◽  
Sediment Discharge ◽  
Daily Discharge ◽  
Large Water ◽  
Climate Events ◽  
Large Discharge

The previous methodology of sampling and determining the suspended sediment con­cen­tration (SSC) in the rivers of Serbia is characterized by a number of disadvantages, so that any re­search of this kind has a large water management impact. In the largest number of hydrological stations in Serbia, daily SSC were obtained based on only one sampling, which raises the question of the representativeness of such sample. Previous SSC – water discharge relationship and detailed analyses of errors in calculating the suspended sediment transport on the profile of Draževac were done for the year of 2004, when the annual difference was very high, which required a very detailed ana­lysis and methodological improvements. In order to define the sediment regime in the Kolubara River, precise monitoring of SSC has been implemented since 2013. The Kolubara River has an unfavourable water regime which is reflected in the excessiveness of water runoff, with floods that are sudden, expressive and short-term, and long-term low waters, so, that are why it is cha­rac­terized by a large discharge and SSC variability. Incidentally, monitoring also covered the year of 2014, when the area of western Serbia (in particular the Kolubara River Basin) was under the influence of extreme climate events that strongly reflected on the hydrological condition with the absolute highest daily discharge. A total of 220 water samples were collected on Draževac gauging station in 2014, in order to determine SSC and sediment discharge. The total number of days covered was 206, which means that there were even more samplings per day, when the discharge was changing fast. The minimal daily measured SSC was only 0.0016 g/l and the maxi­mal recorded value of SSC was 2.6122 g/l and was measured in May at the water discharge of 1 260 m3/s. Тhe total amount of sus­pended sediment discharge at the profile of Draževac in 2014 was 1 104 435 t (the spe­ci­fic suspended sediment yield – 308 t/sqkm/yr). The main objective of this study is to improve SSC – water discharge relationship in the Kolubara River based on the extreme hydrological conditions in 2014.

scholarly journals Possible threshold controls on sediment grain properties of Peruvian coastal river basins

2017 ◽  
Vol 5 (3) ◽  
pp. 571-583 ◽  
Author(s):  
Camille Litty ◽  
Fritz Schlunegger ◽  
Willem Viveen
Keyword(s):  
Grain Size ◽  
Drainage Basin ◽  
Water Discharge ◽  
Shear Stresses ◽  
Mountain Range ◽  
Large Area ◽  
Peruvian Andes ◽  
Gravel Beds ◽  
Denudation Rates ◽  
Grain Properties

Abstract. To determine possible controls on sediment grain properties, 21 coastal rivers located along the entire western Peruvian margin were analysed. This represents one of the largest grain size dataset that has been collected over a large area. Modern gravel beds were sampled along a north–south transect on the western side of the Peruvian Andes where the rivers cross the tip of the mountain range, and at each site the long a axis and the intermediate b axis of about 500 pebbles were measured. Morphometric properties of each drainage basin, sediment and water discharge, together with flow shear stresses, were determined and compared against measured grain properties. Pebble size data show that the values for the D50 are nearly constant and range between 2 and 3 cm, while the values of the D96 range between 6 and 12 cm. The ratios between the intermediate and the long axis range from 0.67 to 0.74. Linear correlations between all grain size percentiles and water shear stresses, mean basin denudation rates, mean basin slopes and basin sizes are small to non-existent. However, exceptionally large D50 values of 4–6 cm were measured for basins situated between 11–12 and 16–17° S latitude where hillslope gradients are steeper than on average or where mean annual stream flows exceed the average values of the western Peruvian streams by a factor of 2. We suggest that the generally uniform grain size pattern has been perturbed where either mean basin slopes or water fluxes exceed threshold conditions.

Bedforms, bed material, and bedload transport in a salt-wedge estuary: Fraser River, British Columbia

1989 ◽  
Vol 26 (7) ◽  
pp. 1440-1452 ◽  
Author(s):  
R. A. Kostaschuk ◽  
M. A. Church ◽  
J. L. Luternauer
Keyword(s):  
British Columbia ◽  
River Discharge ◽  
Bedload Transport ◽  
Fraser River ◽  
Seasonal Fluctuations ◽  
Salt Wedge ◽  
Migration Rates ◽  
Material Load ◽  
Bed Material

The lower main channel of the Fraser River, British Columbia, is a sand-bed, salt-wedge estuary in which variations in velocity, discharge, and bedform characteristics are contolled by river discharge and the tides. Bed-material composition remains consistent over the discharge season and in the long term. Changes in bedform height and length follow but lag behind seasonal fluctuations in river discharge. Migration rates of bedforms respond more directly to river discharge and tidal fall than do height and length. Bedform characteristics were utilized to estimate bedload transport in the estuary, and a strong, direct, but very sensitive relationship was found between bed load and river discharge. Annual bedload transport in the estuary is estimated to be of the order of 0.35 Mt in 1986. Bedload transport in the estuary appears to be higher than in reaches upstream, possibly because of an increase in sediment movement along the bed to compensate for a reduction in suspended bed-material load produced by tidal slack water and the salt wedge.

scholarly journals Sediment dynamics on a steep, megatidal, mixed sand-gravel-cobble beach

2014 ◽  
Vol 2 (1) ◽  
pp. 117-152 ◽  
Author(s):  
A. E. Hay ◽  
L. Zedel ◽  
N. Stark
Keyword(s):  
Wide Band ◽  
Sediment Dynamics ◽  
Coarse Grained ◽  
Bay Of Fundy ◽  
Wave Forcing ◽  
Structure Of Flow ◽  
Median Diameter ◽  
Field Deployment ◽  
Bed Material ◽  
Cobble Beach

Abstract. Results are presented from a pilot study of shoreface sediment dynamics on a steep, poorly sorted, coarse-grained, mega-tidal beach at the head of the Bay of Fundy, Nova Scotia, Canada. The experiment involved the first field deployment of a prototype wide- band, pulse-coherent, bistatic acoustic Doppler profiling system. Measurements of the vertical structure of flow and turbulence above a sloping bed, as well as bed material velocity, demonstrate the capabilities of this instrument vis-a-vis studies of nearshore sediment dynamics at the field scale. The second focus of the paper is the surprising observation that the surficial sediment median diameter, across the lower two-thirds of the intertidal zone, underwent a pronounced decrease when wave forcing was more energetic, compared to values observed during calmer conditions. The explanation for this result appears to involve the formation – in wave-dominated conditions – of O(1 m)-wavelength, 20 cm high ripples on the rising tide, which are then planed flat by the swash and/or the shorebreak on the subsequent ebb.

scholarly journals Probabilistic Modeling of Slip System-Based Shear Stresses and Fatigue Behavior of Coarse-Grained Ni-Base Superalloy Considering Local Grain Anisotropy and Grain Orientation

Metals ◽  
2019 ◽  
Vol 9 (8) ◽  
pp. 813 ◽  
Author(s):  
Engel ◽  
Mäde ◽  
Lion ◽  
Moch ◽  
Gottschalk ◽  
...  
Keyword(s):  
Finite Element ◽  
Crack Initiation ◽  
Test Data ◽  
Grain Orientation ◽  
Fatigue Behavior ◽  
Coarse Grained ◽  
Shear Stresses ◽  
Grain Sizes ◽  
Crack Initiation Life ◽  
Base Superalloy

New probabilistic lifetime approaches for coarse grained Ni-base superalloys supplement current deterministic gas turbine component design philosophies; in order to reduce safety factors and push design limits. The models are based on statistical distributions of parameters, which determine the fatigue behavior under high temperature conditions. In the following paper, Low Cycle Fatigue (LCF) test data of several material batches of polycrystalline Ni-base superalloy René80 with different grain sizes and orientation distribution (random and textured) is presented and evaluated. The textured batch, i.e., with preferential grain orientation, showed higher LCF life. Three approaches to probabilistic crack initiation life modeling are presented. One is based on Weibull distributed crack initiation life while the other two approaches are based on probabilistic Schmid factors. In order to create a realistic Schmid factor distribution, polycrystalline finite element models of the specimens were generated using Voronoi tessellations and the local mechanical behavior investigated in dependence of different grain sizes and statistically distributed grain orientations. All models were first calibrated with test data of the material with random grain orientation and then used to predict the LCF life of the material with preferential grain orientation. By considering the local multiaxiality and resulting inhomogeneous shear stress distributions, as well as grain interaction through polycrystalline Finite Element Analysis (FEA) simulation, the best consistencies between predicted and observed crack initiation lives could be achieved.

scholarly journals A 2600-year history of floods in the Bernese Alps, Switzerland: frequencies, mechanisms and climate forcing

2015 ◽  
Vol 19 (7) ◽  
pp. 3047-3072 ◽  
Author(s):  
L. Schulte ◽  
J. C. Peña ◽  
F. Carvalho ◽  
T. Schmidt ◽  
R. Julià ◽  
...  
Keyword(s):  
North Atlantic ◽  
Solar Irradiance ◽  
Catchment Area ◽  
Soil Formation ◽  
Organic Soil ◽  
Flood Damage ◽  
Total Solar Irradiance ◽  
Swiss Alps ◽  
Coarse Grained ◽  
Instrumental Data

Abstract. A 2600-year long composite palaeoflood record is reconstructed from high-resolution delta plain sediments of the Hasli–Aare floodplain on the northern slope of the Swiss Alps. Natural proxies compiled from sedimentary, geochemical and geomorphological data were calibrated by textual and factual sources and instrumental data. No fewer than 12 of the 14 historically recorded extreme events between 1480 and the termination of the Hasli–Aare river channel correction in 1875 were also identified by coarse-grained flood layers, log(Zr / Ti) peaks and factor 1 anomalies. Geomorphological, historical and instrumental data provide evidence for flood damage intensities and discharge estimations of severe and catastrophic historical floods. Spectral analysis of the geochemical and documentary flood series and several climate proxies (TSI, δ18O, tree-rings, NAO, SNAO) identify similar periodicities of around 60, 80, 100, 120 and 200 years during the last millennia, indicating the influence of the North Atlantic circulation and solar forcing on alpine flood dynamics. The composite floodplain record illustrates that periods of organic soil formation and deposition of phyllosilicates (from the medium high catchment area) match those of total solar irradiance maxima, suggesting reduced flood activity during warmer climate pulses. Aggradation with multiple sets of flood layers with increased contribution of siliciclasts from the highest catchment area (plutonic bedrock) (e.g. 1300–1350, 1420–1480, 1550–1620, 1650–1720 and 1811–1851 cal yr AD) occurred predominantly during periods with reduced solar irradiance, lower δ18O anomalies, cooler summer temperatures and phases of drier spring climate in the Alps. Increased water storage by glaciers, snow cover and snow patches susceptible to melting processes associated with rainfall episodes and abrupt rises in temperature substantially increased surface runoff on slopes and discharges of alpine rivers. This interpretation is in agreement with the findings that the severe and catastrophic historical floods in the Aare since 1670 occurred mostly during positive SNAO (Summer North Atlantic Oscillation) pulses after years or even decades dominated by negative SNAO and cooler annual temperatures.

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