suspended load
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2021 ◽  
Author(s):  
Guosheng Duan ◽  
Haifei Liu

Abstract. The transportation of bank-collapsed materials is a key issue among river evolution processes. In this study, a series of flume experiments were conducted to monitor riverbank collapse processes and to explore the regularity of transportation for cohesive collapsed materials. The collapsed materials, both the bed and suspended loads, that transformed from collapsed materials were intensively evaluated under experimental conditions. The results showed that the collapsed materials contributed to 12~20 % sedimentation in situ, 8~14 % suspended loads and 70~80 % bed loads. In addition, the bed load motion efficiency coefficient (eb), suspended load motion efficiency coefficient (es) and sediment carrying capacity factor (U3/gRω) were introduced to describe the transportation of collapsed materials in terms of energy dissipation. This research provides theoretical and practical benefits for predicting channel evolution processes.


2021 ◽  
Author(s):  
◽  
John Edward Adams

<p>Uplift and erosion are roughly equal in the Southern Alps of New Zealand and the following rates have been determined: tectonic uplift 620 +/- 20 Mt y^-1, river load 700 +/- 200 Mt y^-1, offshore deposition 580 +/- 110 Mt y^-1. The tectonic uplift is the result of oblique collision between the Indian and Pacific plates, with the edge of the Pacific plate being upturned and uplifted as the Southern Alps, crustal narrowing of 22 mm y^-1 being converted to uplift along a curved fault plane. Almost all rock eroded from the Southern Alps is carried as suspended load by rivers. River bedload is of minor importance, and its abrasion adds to the suspended load. The estimated suspended load amounts to 265 Mt y^-1, but with a single exception only normal load have been sampled, and the additional abnormal load from earthquake-caused landslips is estimated to double the normal load. The river load estimate is confirmed in part by spot checks from sediment accumulated in onshore traps. A model proposed for the growth of the Southern Alps from a peneplain shows that the range attained steady state about 1.5 My after uplift started. With uplift initial non steady state, flat topped mountains like those that remain in Otago, become steady state spiky mountains. The range as a whole is in steady state, though the individual mountains change. The offshore deposition rates agree with the river load and tectonic uplift estimates and thus provide substantial confirmation for the steady state model.</p>


2021 ◽  
Author(s):  
◽  
John Edward Adams

<p>Uplift and erosion are roughly equal in the Southern Alps of New Zealand and the following rates have been determined: tectonic uplift 620 +/- 20 Mt y^-1, river load 700 +/- 200 Mt y^-1, offshore deposition 580 +/- 110 Mt y^-1. The tectonic uplift is the result of oblique collision between the Indian and Pacific plates, with the edge of the Pacific plate being upturned and uplifted as the Southern Alps, crustal narrowing of 22 mm y^-1 being converted to uplift along a curved fault plane. Almost all rock eroded from the Southern Alps is carried as suspended load by rivers. River bedload is of minor importance, and its abrasion adds to the suspended load. The estimated suspended load amounts to 265 Mt y^-1, but with a single exception only normal load have been sampled, and the additional abnormal load from earthquake-caused landslips is estimated to double the normal load. The river load estimate is confirmed in part by spot checks from sediment accumulated in onshore traps. A model proposed for the growth of the Southern Alps from a peneplain shows that the range attained steady state about 1.5 My after uplift started. With uplift initial non steady state, flat topped mountains like those that remain in Otago, become steady state spiky mountains. The range as a whole is in steady state, though the individual mountains change. The offshore deposition rates agree with the river load and tectonic uplift estimates and thus provide substantial confirmation for the steady state model.</p>


2021 ◽  
Vol 3 ◽  
Author(s):  
H. You ◽  
M. Muste ◽  
D. Kim ◽  
S. Baranya

Non-intrusive technologies for the in-situ measurement of river morphological features are increasingly popular in the scientific and practice communities due to their efficient and productive data acquisition. While the measurement of suspended load with optical and acoustic technologies is currently an active area of research, the measurement of bedform dynamics has not experienced similar progress. We have successfully demonstrated through laboratory experiments that, by combining acoustic mapping with image velocimetry concepts, we can characterize the planar dynamics of the bedform migration. The technique, labeled Acoustic Mapping Velocimetry (AMV), is currently transferred to field conditions using multiple-beam echo-sounders (MBES) for producing acoustic maps. During this transfer, new questions emerged because, in field conditions, many of the morphologic features targeted by AMV measurements are not a priori known. Moreover, the image velocimetry processing can be approached with several alternatives, each of them characterized by strength and limitations. This paper assembles guidelines for establishing optimal parameters for the acquisition of the acoustic maps based on analytical considerations, and for selecting essential features of the processing for image velocimetry. We test these guidelines using MBES data acquired in the Mississippi River.


2021 ◽  
Vol 83 (11) ◽  
Author(s):  
Hiroyuki A. Shimizu ◽  
Takehiro Koyaguchi ◽  
Yujiro J. Suzuki ◽  
Ermanno Brosch ◽  
Gert Lube ◽  
...  

AbstractNumerical results of a two-layer depth-averaged model of pyroclastic density currents (PDCs) were compared with an experimental PDC generated at the international eruption simulator facility (the Pyroclastic flow Eruption Large-scale Experiment (PELE)) to establish a minimal dynamical model of PDCs with stratification of particle concentrations. In the present two-layer model, the stratification in PDCs is modeled as a voluminous suspended-load layer with low particle volume fractions ($$\lesssim {10}^{-3})$$ ≲ 10 - 3 ) and a thin basal bed-load layer with higher particle volume fractions ($$\sim {10}^{-2}$$ ∼ 10 - 2 ) on the basis of the source condition in the experiment. Numerical results for the suspended load quantitatively reproduce the time evolutions of the front position and flow thickness in the experimental PDC. The numerical results of the bed-load and deposit thicknesses depend on an assumed value of settling speed at the bottom of the bed load ($${W}_{\mathrm{sH}}$$ W sH ). We show that the thicknesses of bed load and deposit in the simulations agree well with the experimental data, when $${W}_{\mathrm{sH}}$$ W sH is set to about $$1.25\times {10}^{-2}$$ 1.25 × 10 - 2 m/s. This value of the settling speed is two orders of magnitude smaller than that predicted by a hindered-settling model. The small value of $${W}_{\mathrm{sH}}$$ W sH is considered to result from decreasing in the effective deposition speed due to the erosion process accompanied by saltating/rolling of particles at the bottom of the bed load.


2021 ◽  
Vol 83 (3) ◽  
pp. 93-108
Author(s):  
Alireza Sepahvand ◽  
Mitja Prelovsek ◽  
Ali Akbar Nazari Samani ◽  
Robert Wasson

We conducted a one-year-long study of solute load measured three times per month in three neighboring subwatersheds (Alashtar, Khorram Abad, and Biranshahr) located in the Karkheh River basin in the Zagros region of southwestern Iran. Research was focused on the chemical composition of water (solute load), karst denudation rate, spatial and temporal variability, as well as comparison of solute load with suspended load. Results show that Ca-Mg-HCO3 is the dominant water type that reflects the lithological characteristics of the catchment areas. Lack of seasonal fluctuation of solute load and absence of dilution during high water levels but evident seasonal course of discharge defines the highest solute flux during the annual maximum of discharge in spring months. The highest solute flux is related to flood events. High annual variation of Na1 concentration compared to conservative Cl2 as well as Chloro-Alkali indexes (CAI and CAI2) suggests that Na1 adsorption and desorption during ion-exchange reactions occur in the regolith. This Na+ variability, to some extent, explains weak Ca21 and Mg21 dilution effect during high water levels. During the measurement period (2014-2015), solute flux calculated per catchment area amounted to 49-69 t km-2 a-1 (tons per km per year). The chemical composition of water and discharge shows by far the highest chemical denudation of limestones and dolomites (87−89 %), while dissolution of gypsum is of minor importance (11−13 %). As a result, the carbonate karst solutional denudation rate is between 0.010 and 0.040 mm a21 , where the higher values are more probable for longer periods due to the relatively low discharge during the spring of 2015. Comparison of dissolved and suspended loads indicates that the transport of suspended load is an order of magnitude less than transport of the dissolved load; the only exception is one flash flood event when suspended load exceeded the dissolved load. Besides a small decrease in solute flux as well as carbonate karst dissolution rates from NW to SE, no large hydrochemical differences between the three subwatersheds were detected.


2021 ◽  
Vol 2 (1) ◽  
pp. 1-7
Author(s):  
Ramadhan Hidayat Putra ◽  
Amad Syarif Syukri ◽  
Catrin Sudarjat ◽  
Vickky Anggara Ilham

Research on Aepodu Weir Sediment Transport Analysis in South Konawe District, based on observations in the field, Aepodu Weir hasa sediment buildup that has now exceeded the height of the weirlight house. The purpose of the study was to analyze the magnitudeof Aepodu river flow and to analyze the amount of sedimenttransport that occurred in the Aepodu dam. The method used todetermine the amount of bed load transport uses stchoklitscht, whilefor transporting suspended load using forcheimer.The results of the analysis of the average flow of the Aepodu riverwere 3,604 m3/ second. Sediment transport that occurs in Aepoduweir is Bedload transport (Qb) of 291625.771 tons / year, andsuspended load transport (Qs) of 16972,423 tons / year, so that thetotal sediment transport (QT) is 308598,194 tons / year.


2021 ◽  
Author(s):  
Hua Zhang ◽  
Jie Wu ◽  
Mianmian Dong ◽  
Weize An ◽  
Yuhang Zhou

2021 ◽  
Author(s):  
Megasari Kurnia ◽  
Suprijanto Suprijanto ◽  
Narendra Kurnia Putra ◽  
Andar Bagus Sriwarno

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