Journal articles: 'Gravel-bed river'

1

Hauer, F. Richard, Harvey Locke, Victoria J. Dreitz, Mark Hebblewhite, Winsor H. Lowe, Clint C. Muhlfeld, Cara R. Nelson, Michael F. Proctor, and Stewart B. Rood. "Gravel-bed river floodplains are the ecological nexus of glaciated mountain landscapes." Science Advances 2, no. 6 (June 2016): e1600026. http://dx.doi.org/10.1126/sciadv.1600026.

Full text

Abstract:

Gravel-bed river floodplains in mountain landscapes disproportionately concentrate diverse habitats, nutrient cycling, productivity of biota, and species interactions. Although stream ecologists know that river channel and floodplain habitats used by aquatic organisms are maintained by hydrologic regimes that mobilize gravel-bed sediments, terrestrial ecologists have largely been unaware of the importance of floodplain structures and processes to the life requirements of a wide variety of species. We provide insight into gravel-bed rivers as the ecological nexus of glaciated mountain landscapes. We show why gravel-bed river floodplains are the primary arena where interactions take place among aquatic, avian, and terrestrial species from microbes to grizzly bears and provide essential connectivity as corridors for movement for both aquatic and terrestrial species. Paradoxically, gravel-bed river floodplains are also disproportionately unprotected where human developments are concentrated. Structural modifications to floodplains such as roads, railways, and housing and hydrologic-altering hydroelectric or water storage dams have severe impacts to floodplain habitat diversity and productivity, restrict local and regional connectivity, and reduce the resilience of both aquatic and terrestrial species, including adaptation to climate change. To be effective, conservation efforts in glaciated mountain landscapes intended to benefit the widest variety of organisms need a paradigm shift that has gravel-bed rivers and their floodplains as the central focus and that prioritizes the maintenance or restoration of the intact structure and processes of these critically important systems throughout their length and breadth.

APA, Harvard, Vancouver, ISO, and other styles

2

Duizendstra, H. D., and M. E. Nieuwenhuijzen. "Ecological rehabilitation and morphological impact of gravel extraction in the river meuse." Water Science and Technology 31, no. 8 (April 1, 1995): 357–61. http://dx.doi.org/10.2166/wst.1995.0329.

Full text

Abstract:

For the gravel bed river, the Grensmaas, plans have been made by which extraction of gravel and ecological rehabilitation of the river will be combined. One way to study the morphological changes, the time scale of these changes and the expected ecological rehabilitation is to study gravel bed rivers with approximately the same morphological characteristics as the future Grensmaas. Since scale models in nature of the future Grensmaas do not exist, selection criteria of reference rivers have to be modified. The results of the reference investigation will be different and the interpretation will be much more complicated. An important morphological parameter is the (yearly) sediment transport. A method to measure sediment transport during high discharges is described and tested.

APA, Harvard, Vancouver, ISO, and other styles

3

Zhu, Ling Ling, and Hua Ge. "Balance Adjustment of the Gravel-Sand River Downstream Reservoir." Applied Mechanics and Materials 444-445 (October 2013): 1218–21. http://dx.doi.org/10.4028/www.scientific.net/amm.444-445.1218.

Full text

Abstract:

In this article, the typical phenomenon of bed armoring was firstly summarized based on both the field and experiment data, and then followed by the analysis on its internal influence on the reformation process to the balance status for the gravel-sand rivers. It was pointed out that this phenomenon is caused by the chosen of the flow, that the finer sediment particles are washed away and the coarser ones are left on the river bed surface. This phenomenon firstly restricts the start of the sediment particles on the bed surface, secondly increases the river bed surface resistance and reduces the flow velocity. The comprehensive effect of these two aspects leads to the final balance status for the gravel-sand river.

APA, Harvard, Vancouver, ISO, and other styles

4

Guerit, L., L. Barrier, C. Narteau, F. Métivier, Y. Liu, E. Lajeunesse, E. Gayer, P. Meunier, L. Malverti, and B. Ye. "The Grain-size Patchiness of Braided Gravel-Bed Streams – example of the Urumqi River (northeast Tian Shan, China)." Advances in Geosciences 37 (February 11, 2014): 27–39. http://dx.doi.org/10.5194/adgeo-37-27-2014.

Full text

Abstract:

Abstract. In gravel-bed rivers, sediments are often sorted into patches of different grain-sizes, but in braided streams, the link between this sorting and the channel morpho-sedimentary elements is still unclear. In this study, the size of the bed sediment in the shallow braided gravel-bed Urumqi River is characterized by surface-count and volumetric sampling methods. Three morpho-sedimentary elements are identified in the active threads of the river: chutes at flow constrictions, which pass downstream to anabranches and bars at flow expansions. The surface and surface-layer grain-size distributions of these three elements show that they correspond to only two kinds of grain-size patches: (1) coarse-grained chutes, coarser than the bulk river bed, and (2) finer-grained anabranches and bars, consistent with the bulk river bed. In cross-section, the chute patches are composed of one coarse-grained top layer, which can be interpreted as a local armour layer overlying finer deposits. In contrast, the grain size of the bar-anabranch patches is finer and much more homogeneous in depth than the chute patches. Those patches, which are features of lateral and vertical sorting associated to the transport dynamics that build braided patterns, may be typical of active threads in shallow gravel-bed rivers and should be considered in future works on sorting processes and their geomorphologic and stratigraphic results.

APA, Harvard, Vancouver, ISO, and other styles

5

Gorczyca, Elżbieta, Kazimierz Krzemień, and Krzysztof Jarzyna. "The Evolution of Gravel-Bed Rivers during the Post-Regulation Period in the Polish Carpathians." Water 12, no. 1 (January 16, 2020): 254. http://dx.doi.org/10.3390/w12010254.

Full text

Abstract:

This study provides a conceptual model of the functioning of gravel-bed rivers during the post-regulation period in Poland and forecasts their subsequent evolution. The main difference between fluvial processes during the pre-regulation and post-regulation period is that they are limited to a zone that is currently several times narrower and trapped in a deep-cut channel. During the river post-regulation period, the construction of additional river training works was significantly limited in river channels. Moreover, all forms of economic activity were significantly reduced in the channel free migration zone, particularly bed gravel extraction operations. As a result of these changes, a limited recovery of the functioning and hydromorphology of the river channel occurred via a return to conditions in effect prior to river regulation. In recovering sections of river, the channel gradually broadens, and its sinuosity and number of threads increase. The overall process can be called spontaneous renaturalization, which yields a characteristic post-regulation river channel. The conceptual model was developed on the basis of the evolution of the gravel-bed river, the Raba River, during the post-regulation period in the Polish Carpathian Mountains.

APA, Harvard, Vancouver, ISO, and other styles

6

Afzalimehr, Hossein, Mohammad Reza Maddahi, and Jueyi Sui. "Bedform characteristics in a gravel-bed river." Journal of Hydrology and Hydromechanics 65, no. 4 (December 20, 2017): 366–77. http://dx.doi.org/10.1515/johh-2017-0023.

Full text

Abstract:

AbstractEstimation of hydraulic and geometric parameters of a gravel-bed river such as dimensions of bedforms is very difficult task, although they play a fundamental role in river engineering projects. One of the methods to get essential information regarding the bedform characteristics is to find the relations between the flow parameters and bedform dimensions. We conducted this field study in the Babolroud River in northern Iran to investigate the application of double averaged method in unspecific gravel bedforms to evaluate friction factor. Using data collected from several river reaches with total length of 356 m of a gravel-bed river, the relationship between bedform geometry (height and the length of bedforms) and flow parameters including shear velocity, transport stage parameter with friction factor is investigated. Different methods for estimating bedforms dimensions are examined to assess the ability of predicting bedform parameters (length and height) in a gravel-bed river. Using bedform parameters, the contribution of particle and form friction is estimated. Results confirm the application of the double averaged method and existing bedform parameters for unspecific bedforms. There exists a similar trend between aspect ratio and friction factor in gravel bedforms.

APA, Harvard, Vancouver, ISO, and other styles

7

Glasbergen, K., M. Stone, B. Krishnappan, J. Dixon, and U. Silins. "The effect of coarse gravel on cohesive sediment entrapment in an annular flume." Proceedings of the International Association of Hydrological Sciences 367 (March 3, 2015): 157–62. http://dx.doi.org/10.5194/piahs-367-157-2015.

Full text

Abstract:

Abstract. While cohesive sediment generally represents a small fraction (<0.5%) of the total sediment mass stored in gravel-bed rivers, it can strongly influence physical and biogeochemical processes in the hyporheic zone and alter aquatic habitat. This research was conducted to examine mechanisms governing the interaction of cohesive sediments with gravel beds in the Elbow River, Alberta, Canada. A series of erosion and deposition experiments with and without a gravel bed were conducted in a 5-m diameter annular flume. The critical shear stress for deposition and erosion of cohesive sediment without gravel was 0.115 Pa and 0.212 Pa, respectively. In experiments with a gravel bed, cohesive sediment moved from the water column into the gravel bed via the coupling of surface and pore water flow. Once in the gravel bed, cohesive sediments were not mobilized under the maximum applied shear stresses (1.11 Pa) used in the experiment. The gravel bed had an entrapment coefficient (ratio between the entrapment flux and the settling flux) of 0.2. Accordingly, when flow conditions are sufficient to produce a shear stress that will mobilize the armour layer of the gravel bed (>16 Pa), cohesive materials trapped within the gravel bed will be entrained and transported into the Glenmore Reservoir, where sediment-associated nutrients may pose treatment challenges to the drinking water supply.

APA, Harvard, Vancouver, ISO, and other styles

8

Adams, David Lawson. "Toward bed state morphodynamics in gravel-bed rivers." Progress in Physical Geography: Earth and Environment 44, no. 5 (January 30, 2020): 700–726. http://dx.doi.org/10.1177/0309133320900924.

Full text

Abstract:

In fluvial geomorphology, one of the most pervasive paradigms is that the size of the grains present in a river exercises an important effect on its character. In gravel-bed rivers, there is considerable scatter in the relations between so-called “representative grain sizes” and basic channel processes and morphologies. Under a grain size paradigm, our ability to rationalize the characteristics of a given channel and predict how it will respond to a change in conditions is limited. In this paper, I deconstruct this paradigm by exploring its historical origins in geomorphology and fluid dynamics, and identify three of its underlying premises: (1) the association between grain diameter and fluid drag derived from Nikuradse’s experiments with sand-coated surfaces; (2) the use of grain size by early process geomorphologists to describe general trends across large samples of sand-bed rivers; and (3) a classificatory approach to discerning bed structures originally developed for bed configurations found in sand-bed rivers. The conflation of sand- and gravel-bed rivers limits our ability to understand gravel-bed morphodynamics. Longstanding critique of the grain size paradigm has generated alternative ideas but, due to technological and conceptual limitations, they have remained unrealized. One such unrealized idea is the morphology-based definition of bed state – an important degree of freedom within fluvial systems, particularly in reaches where adjustments to planform are not easily achieved. By embracing recent advancements in fluid dynamics and remote sensing, I present an alternative or complementary concept of bed state based on the notion that fluvial systems act to maximize flow resistance. The proposed quantitative index represents the relative contribution of morphologic adjustments occurring at different spatial scales (discriminated using a wavelet transform) to a stable channel configuration. By explicitly acknowledging the complexity of bed adjustments we can move toward a more complete understanding of channel stability in gravel-bed rivers.

APA, Harvard, Vancouver, ISO, and other styles

9

Bui, Van, Minh Bui, and Peter Rutschmann. "Advanced Numerical Modeling of Sediment Transport in Gravel-Bed Rivers." Water 11, no. 3 (March 17, 2019): 550. http://dx.doi.org/10.3390/w11030550.

Full text

Abstract:

Understanding the alterations of gravel bed structures, sediment transport, and the effects on aquatic habitat play an essential role in eco-hydraulic and sediment transport management. In recent years, the evaluation of changes of void in bed materials has attracted more concern. However, analyzing the morphological changes and grain size distribution that are associated with the porosity variations in gravel-bed rivers are still challenging. This study develops a new model using a multi-layer’s concept to simulate morphological changes and grain size distribution, taking into account the porosity variabilities in a gravel-bed river based on the mass conservation for each size fraction and the exchange of fine sediments between the surface and subsurface layers. The Discrete Element Method (DEM) is applied to model infiltration processes and to confirm the effects of the relative size of fine sediment to gravel on the infiltration depth. Further, the exchange rate and the bed porosity are estimated while using empirical formulae. The new model was tested on three straight channels. Analyzing the calculated results and comparing with the observed data show that the new model can successfully simulate sediment transport, grain sorting processes, and bed change in gravel-bed rivers.

APA, Harvard, Vancouver, ISO, and other styles

10

Dingle, Elizabeth H., Hugh D. Sinclair, Jeremy G. Venditti, Mikaël Attal, Tim C. Kinnaird, Maggie Creed, Laura Quick, Jeffrey A. Nittrouer, and Dilip Gautam. "Sediment dynamics across gravel-sand transitions: Implications for river stability and floodplain recycling." Geology 48, no. 5 (February 14, 2020): 468–72. http://dx.doi.org/10.1130/g46909.1.

Full text

Abstract:

Abstract The gravel-sand transition (GST) is commonly observed along rivers. It is characterized by an abrupt reduction in median grain size, from gravel- to sand-size sediment, and by a shift in sand transport mode from wash load–dominated to suspended bed material load. We documented changes in channel stability, suspended sediment concentration, flux, and grain size across the GST of the Karnali River, Nepal. Upstream of the GST, gravel-bed channels are stable over hundred- to thousand-year time scales. Downstream, floodplain sediment is reworked by lateral bank erosion, particularly during monsoon discharges. Suspended sediment concentration, grain size, and flux reveal counterintuitive increases downstream of the GST. The results demonstrate a dramatic change in channel dynamics across the GST, from relatively fixed, steep gravel-bed rivers with infrequent avulsion to lower-gradient, relatively mobile sand-bed channels. The increase in sediment concentration and near-bed suspended grain size may be caused by enhanced channel mobility, which facilitates exchange between bed and bank material. These results bring new constraints on channel stability at mountain fronts and indicate that temporally and spatially limited sediment flux measurements downstream of GSTs are more indicative of flow stage and floodplain recycling than of continental-scale sediment flux and denudation rate estimates.

APA, Harvard, Vancouver, ISO, and other styles

11

Habersack, Helmut M., and Jonathan B. Laronne. "Bed load texture in an Alpine gravel bed river." Water Resources Research 37, no. 12 (December 2001): 3359–70. http://dx.doi.org/10.1029/2001wr000260.

Full text

APA, Harvard, Vancouver, ISO, and other styles

12

MATSUOKA, Yasumasa. "Turbulent Flow over a Gravel River Bed." PROCEEDINGS OF THE JAPANESE CONFERENCE ON HYDRAULICS 33 (1989): 481–86. http://dx.doi.org/10.2208/prohe1975.33.481.

Full text

APA, Harvard, Vancouver, ISO, and other styles

13

Afzalimehr, Hossein, and François Anctil. "Estimation of Gravel-Bed River Flow Resistance." Journal of Hydraulic Engineering 124, no. 10 (October 1998): 1054–58. http://dx.doi.org/10.1061/(asce)0733-9429(1998)124:10(1054).

Full text

APA, Harvard, Vancouver, ISO, and other styles

14

Aberle, Jochen, Andreas Dittrich, Franz Nestmann, Pavel Novak, Colin D. Rennie, and Robert G. Millar. "Estimation of Gravel-Bed River Flow Resistance." Journal of Hydraulic Engineering 125, no. 12 (December 1999): 1315–19. http://dx.doi.org/10.1061/(asce)0733-9429(1999)125:12(1315).

Full text

APA, Harvard, Vancouver, ISO, and other styles

15

Legleiter, C. J., and B. T. Overstreet. "Mapping gravel bed river bathymetry from space." Journal of Geophysical Research: Earth Surface 117, F4 (November 21, 2012): n/a. http://dx.doi.org/10.1029/2012jf002539.

Full text

APA, Harvard, Vancouver, ISO, and other styles

16

Pfeiffer, Allison M., Noah J. Finnegan, and Jane K. Willenbring. "Sediment supply controls equilibrium channel geometry in gravel rivers." Proceedings of the National Academy of Sciences 114, no. 13 (March 13, 2017): 3346–51. http://dx.doi.org/10.1073/pnas.1612907114.

Full text

Abstract:

In many gravel-bedded rivers, floods that fill the channel banks create just enough shear stress to move the median-sized gravel particles on the bed surface (D50). Because this observation is common and is supported by theory, the coincidence of bankfull flow and the incipient motion of D50 has become a commonly used assumption. However, not all natural gravel channels actually conform to this simple relationship; some channels maintain bankfull stresses far in excess of the critical stress required to initiate sediment transport. We use a database of >300 gravel-bedded rivers and >600 10Be-derived erosion rates from across North America to explore the hypothesis that sediment supply drives the magnitude of bankfull shear stress relative to the critical stress required to mobilize the median bed surface grain size (τbf*/τc*). We find that τbf*/τc* is significantly higher in West Coast river reaches (2.35, n = 96) than in river reaches elsewhere on the continent (1.03, n = 245). This pattern parallels patterns in erosion rates (and hence sediment supplies). Supporting our hypothesis, we find a significant correlation between upstream erosion rate and local τbf*/τc* at sites where this comparison is possible. Our analysis reveals a decrease in bed surface armoring with increasing τbf*/τc*, suggesting channels accommodate changes in sediment supply through adjustments in bed surface grain size, as also shown through numerical modeling. Our findings demonstrate that sediment supply is encoded in the bankfull hydraulic geometry of gravel bedded channels through its control on bed surface grain size.

APA, Harvard, Vancouver, ISO, and other styles

17

Othman, Khaleel I., and Ayman T. Hameed. "Properties of Tigris River Bed Material at Mosul City." Tikrit Journal of Engineering Sciences 21, no. 1 (July 18, 2013): 30–44. http://dx.doi.org/10.25130/tjes.21.1.09.

Full text

Abstract:

In this research the characteristics of bed material of 35km of Tigris river from Badoosh tothe end of Mosul City was studied ,nine locations were selected for sampling surface and subsurfacematerial, at each location samples are collected from left and right bank of the river. Analysis ofthese samples show that the gravel surface bed material of Tigris river had D50 equal to 33mm witha dominant size very coarse and coarse gravel with a percentage 42%, 36% , respectively, sand isalmost mislaid in this layer. The particles of surface layer had a disc shape with a percentage 51%and blade 19%, spherical 17%, and cylindrical 13%. The results show that the right bank particlesare coarser than left bank. The subsurface bed material consist of gravel and sand, the D50 of thislayer was equal to 17mm, the domain size was coarse gravel with a percentage 29% , sandpercentage in this layer was about 17%. The subsurface layer is unaffecting on any changes in flowregime because it is completely protected by gravel surface layer. Comparison of obtained resultswith previous results shows that there is no significant changes occurred in properties of the riverbed material except little changes in composition of surface layer especially in the fine material.The river under the current flow conditions with flow rate in around of 500m3/s will reserve to thesame bed material properties in the future.

APA, Harvard, Vancouver, ISO, and other styles

18

Li, S. Samuel, and Robert G. Millar. "Simulating Bed-Load Transport in a Complex Gravel-Bed River." Journal of Hydraulic Engineering 133, no. 3 (March 2007): 323–28. http://dx.doi.org/10.1061/(asce)0733-9429(2007)133:3(323).

Full text

APA, Harvard, Vancouver, ISO, and other styles

19

Oviatt, Charles G., David B. Madsen, and Dave N. Schmitt. "Late Pleistocene and early Holocene rivers and wetlands in the Bonneville basin of western North America." Quaternary Research 60, no. 2 (September 2003): 200–210. http://dx.doi.org/10.1016/s0033-5894(03)00084-x.

Full text

Abstract:

AbstractField investigations at Dugway Proving Ground in western Utah have produced new data on the chronology and human occupation of late Pleistocene and early Holocene lakes, rivers, and wetlands in the Lake Bonneville basin. We have classified paleo-river channels of these ages as “gravel channels” and “sand channels.” Gravel channels are straight to curved, digitate, and have abrupt bulbous ends. They are composed of fine gravel and coarse sand, and are topographically inverted (i.e., they stand higher than the surrounding mudflats). Sand channels are younger and sand filled, with well-developed meander-scroll morphology that is truncated by deflated mudflat surfaces. Gravel channels were formed by a river that originated as overflow from the Sevier basin along the Old River Bed during the late regressive phases of Lake Bonneville (after 12,500 and prior to 11,000 14C yr B.P.). Dated samples from sand channels and associated fluvial overbank and wetland deposits range in age from 11,000 to 8800 14C yr B.P., and are probably related to continued Sevier-basin overflow and to groundwater discharge. Paleoarchaic foragers occupied numerous sites on gravel-channel landforms and adjacent to sand channels in the extensive early Holocene wetland habitats. Reworking of tools and limited toolstone diversity is consistent with theoretical models suggesting Paleoarchaic foragers in the Old River Bed delta were less mobile than elsewhere in the Great Basin.

APA, Harvard, Vancouver, ISO, and other styles

20

Wickert, Andrew D., and Taylor F. Schildgen. "Long-profile evolution of transport-limited gravel-bed rivers." Earth Surface Dynamics 7, no. 1 (January 10, 2019): 17–43. http://dx.doi.org/10.5194/esurf-7-17-2019.

Full text

Abstract:

Abstract. Alluvial and transport-limited bedrock rivers constitute the majority of fluvial systems on Earth. Their long profiles hold clues to their present state and past evolution. We currently possess first-principles-based governing equations for flow, sediment transport, and channel morphodynamics in these systems, which we lack for detachment-limited bedrock rivers. Here we formally couple these equations for transport-limited gravel-bed river long-profile evolution. The result is a new predictive relationship whose functional form and parameters are grounded in theory and defined through experimental data. From this, we produce a power-law analytical solution and a finite-difference numerical solution to long-profile evolution. Steady-state channel concavity and steepness are diagnostic of external drivers: concavity decreases with increasing uplift rate, and steepness increases with an increasing sediment-to-water supply ratio. Constraining free parameters explains common observations of river form: to match observed channel concavities, gravel-sized sediments must weather and fine – typically rapidly – and valleys typically should widen gradually. To match the empirical square-root width–discharge scaling in equilibrium-width gravel-bed rivers, downstream fining must occur. The ability to assign a cause to such observations is the direct result of a deductive approach to developing equations for landscape evolution.

APA, Harvard, Vancouver, ISO, and other styles

21

Doyle, P. F. "Performance of alternative methods of bank protection." Canadian Journal of Civil Engineering 19, no. 6 (December 1, 1992): 1049–61. http://dx.doi.org/10.1139/l92-125.

Full text

Abstract:

The durability of several common bank protection methods used as less expensive or environmentally acceptable alternatives to toe-trenched angular rock riprap has been documented during the 1980s at seven typical bank erosion sites in British Columbia. Since the sites were uncontrolled examples of actual river training works in operation, natural events hindered a precise comparison of each scheme with toe-trenched angular rock riprap protection. However, of the four alternatives investigated – gravel dykes, tree revetments, riprap with toe apron, and semi-round riprap – all but semi-round riprap performed less than satisfactorily over the years of observation. Documentation of performance is sufficient to conclude that on steep gravel-bed rivers, gravel dykes do not endure; tree revetments require constant maintenance and will not endure large floods, unless extremely well-constructed; toe aprons are not as reliable as toe trenches for the same volume of rock; and well-placed, large semi-round rock performs well under moderately severe attack. Key words: erosion, bank protection, channel stability, river training structures, gravel-bed.

APA, Harvard, Vancouver, ISO, and other styles

22

Liro, Maciej, and Kazimierz Krzemień. "Wpływ cofki zbiornika zaporowego na koryto rzeki górskiej – perspektywy badań = The impact of dam-reservoir backwater on mountain river channel – research perspectives." Przegląd Geograficzny 92, no. 1 (2020): 55–68. http://dx.doi.org/10.7163/przg.2020.1.4.

Full text

Abstract:

Dam reservoir construction is one of the most important factors shaping river-valley morphology in the Anthropocene. While a large number (>58,000) of these constructions are in operation all over the world, we remain quite ignorant of what happens upstream of them (in so called backwater zone), especially for the case of gravel-bed rivers. Existing studies have shown that adjustments of the gravel-bed river in the backwater zone differ between the initial and long-term adjustments. The initial adjustments (occurring ≈ <20 years following dam construction) are controlled by large floods and in-channel deposition which trigger bi-directional bar↔bank interactions (bank erosion causing bar growth and vice versa) resulting in channel-widening. The long-term adjustments (≈ >20 years following dam construction) are characterized by river sinuosity increa sing and channel planform stabilization resulted from deposition of fine sediment and associated vegetation expansion. The long-term adjustments are controlled by the initial river morphology, which creates accommodation space for the deposition of fine sediment and for the associated expansion of vegetation on channel bars. The multi-thread river in backwater zone is significantly narrowed, its sinuosity increase (phase 1) and the planform is stabilized (phase 2). Whereas, in the case of initially single-thread river only planform stabilization occur (phase 2). This article summarizes recent findings on the backwater effects on gravel-bed channel morphodynamics, suggesting that backwater zones may be treated as hot-spots of human-induced changes in river geomorphology and biogeomorphology.

APA, Harvard, Vancouver, ISO, and other styles

23

Dinehart, Randal L. "Correlative velocity fluctuations over a gravel river bed." Water Resources Research 35, no. 2 (February 1999): 569–82. http://dx.doi.org/10.1029/1998wr900038.

Full text

APA, Harvard, Vancouver, ISO, and other styles

24

Shvidchenko, A. B., and Z. D. Kopaliani. "Hydraulic Modeling of Bed Load Transport in Gravel-Bed Laba River." Journal of Hydraulic Engineering 124, no. 8 (August 1998): 778–85. http://dx.doi.org/10.1061/(asce)0733-9429(1998)124:8(778).

Full text

APA, Harvard, Vancouver, ISO, and other styles

25

Radecki-Pawlik, Artur, Piotr Kuboń, Bartosz Radecki-Pawlik, and Karol Plesiński. "Bed-Load Transport in Two Different-Sized Mountain Catchments: Mlynne and Lososina Streams, Polish Carpathians." Water 11, no. 2 (February 4, 2019): 272. http://dx.doi.org/10.3390/w11020272.

Full text

Abstract:

The prediction and calculation of the volume of gravel and/or sand transported down streams and rivers—called bed-load transport is one of the most difficult things for river engineers and designers because, in addition to field measurements, personnel involved in such activities need to be highly experienced. Bed-load transport treated by many engineers marginally or omitted and often receives only minor consideration from engineers or may be entirely disregarded simply because they do not know how to address the issue—in many cases, this is a fundamental problem in river management tasks such as: flood protection works; river bank protection works against erosion; building bridges and culverts; building water reservoirs and dams; checking dams and any other hydraulic structures. Thus, to share our experience in our paper, bed-load transport was calculated in two river/stream mountain catchments, which are different in terms of the characteristics of the catchment area and the level of river engineering works performed along the stream channel—both are tributaries of the Dunajec River and have similar Carpathian flysh geology. The studies were performed in the Mlyne stream and in the Lososina River in Polish Carpathians. Mlynne is one of the streams in the Gorce Mountains—it is prone to flash flooding events and has caused many problems with floods in the past. It flows partially in the natural river channel and partially in a trained river channel lined with concrete revetments. The stream bed load is accumulated in the reservoir upstream of the check dam. The Lososina River is one of the Polish Carpathian mountainous streams which crosses the south of the Beskid Wyspowy Mountains. It mostly has a gravel bed and it is flashy and experiences frequent flooding spring. At the mouth of the Lososina River, there is one of the largest Polish Carpathian artificial lakes—the Czchow lake. The Lososina mostly transports gravel as the bed load to the Czchow water reservoir where the sediment is deposited. In the early seventies, the Lososina was partly canalised, especially in places where passes inhabited areas. The paper compares the situation of bed-load transport in the Lososina River before and after engineering training works showing how much sediment is transported downstream along the river channel to the Czchow artificial lake. Also compared is the Mlynne bed load transport upstream and downstream from the check dam showing how much sediment might be transported and deposited in the reservoir upstream from the check dam and when one could expect this reservoir to be clogged.

APA, Harvard, Vancouver, ISO, and other styles

26

Brown, Rocko A., and Gregory B. Pasternack. "Bed and width oscillations form coherent patterns in a partially confined, regulated gravel–cobble-bedded river adjusting to anthropogenic disturbances." Earth Surface Dynamics 5, no. 1 (January 11, 2017): 1–20. http://dx.doi.org/10.5194/esurf-5-1-2017.

Full text

Abstract:

Abstract. Understanding the spatial organization of river systems in light of natural and anthropogenic change is extremely important because it can provide information to assess, manage, and restore them to ameliorate worldwide freshwater fauna declines. For gravel- and cobble-bedded alluvial rivers studies spanning analytical, empirical and numerical domains suggest that at channel-forming flows there is a tendency towards covarying bankfull bed and width undulations amongst morphologic units such as pools and riffles, whereby relatively wide areas have relatively higher minimum bed elevations and relatively narrow areas have relatively lower minimum bed elevations. The goal of this study was to determine whether minimum bed elevation and flow-dependent channel top width are organized in a partially confined, incising gravel–cobbled bed river with multiple spatial scales of anthropogenic and natural landform heterogeneity across a range of discharges. A key result is that the test river exhibited covarying oscillations of minimum bed elevation and channel top width across all flows analyzed. These covarying oscillations were found to be quasiperiodic at channel-forming flows, scaling with the length scales of bars, pools and riffles. Thus, it appears that alluvial rivers organize their topography to have quasiperiodic, shallow and wide or narrow and deep cross section geometry, even despite ongoing, centennial-scale incision. Presumably these covarying oscillations are linked to hydrogeomorphic mechanisms associated with alluvial river channel maintenance. The biggest conclusion from this study is that alluvial rivers are defined more so by variability in topography and flow than mean conditions. Broader impacts of this study are that the methods provide a framework for characterizing longitudinal and flow-dependent variability in rivers for assessing geomorphic structure and aquatic habitat in space, and if repeated, through time.

APA, Harvard, Vancouver, ISO, and other styles

27

Wishart, Duncan, Jeff Warburton, and Louise Bracken. "Gravel extraction and planform change in a wandering gravel-bed river: The River Wear, Northern England." Geomorphology 94, no. 1-2 (February 2008): 131–52. http://dx.doi.org/10.1016/j.geomorph.2007.05.003.

Full text

APA, Harvard, Vancouver, ISO, and other styles

28

Bray, Dale I., and Kersi S. Davar. "Resistance to flow in gravel-bed rivers." Canadian Journal of Civil Engineering 14, no. 1 (February 1, 1987): 77–86. http://dx.doi.org/10.1139/l87-010.

Full text

Abstract:

An emphasis is placed on the importance of understanding the processes responsible for resistance to flow and on the necessity of critically reviewing the assumptions and limitations associated with the methods that are commonly adopted to evaluate resistance to flow in gravel-bed rivers.A commonly applied technique is first presented for estimating the local effective boundary roughness, ks, by the use of data from a vertical velocity profile. Then methods of estimating bulk measures of resistance to flow in a river reach are outlined. Resistance equations in terms of the friction-factor parameter, [Formula: see text],are classified into three main types: dimensional power equations, nondimensional power equations, and nondimensional semilogarithmic equations. The results of seven independent studies are considered when recommending tentative equations for each of the three defined classes of resistance equations. The bulk flow equations are considered to be applicable for the case where d/D50 is greater than 10, there is no bed-load transport, and the flows are in-bank flows. Finally, a brief summary of the problems of estimating resistance to flow for an ice-covered channel is presented. Key words: resistance, flow, hydraulics, rivers, gravel-bed, velocity, friction factor, equations, Manning, Keulegan, classification.

APA, Harvard, Vancouver, ISO, and other styles

29

Rachelly, Cristina, Volker Weitbrecht, David F. Vetsch, and Robert M. Boes. "Morphological development of river widenings with variable sediment supply." E3S Web of Conferences 40 (2018): 02007. http://dx.doi.org/10.1051/e3sconf/20184002007.

Full text

Abstract:

River widening is a common restoration approach to mitigate the adverse effects of past stream alterations on infrastructure and the riparian ecosystem by stabilizing the river bed and enhancing habitat heterogeneity. In this study, two river widening approaches, excavated and dynamic, are described for the case of moderately steep gravel-bed rivers in the Alpine foothills, with a focus on dynamic river widening. As most channelized rivers exhibit ongoing degradation due to the lack of sediment supply and efforts to restore sediment transport are increasing, the consideration of the response of river widenings to variable sediment supply is important. For this purpose, insights from regime theory are applied to river widening and several experimental flume and field studies on channel response to variable sediment supply are reviewed. Dynamic river widenings are expected to be morphologically active in weakly degraded rivers with sufficient sediment supply, while they may not be an appropriate restoration approach for highly degraded rivers due to persistent impairment of morphological activity.

APA, Harvard, Vancouver, ISO, and other styles

30

Dunne, Kieran B. J., and Douglas J. Jerolmack. "Evidence of, and a proposed explanation for, bimodal transport states in alluvial rivers." Earth Surface Dynamics 6, no. 3 (July 25, 2018): 583–94. http://dx.doi.org/10.5194/esurf-6-583-2018.

Full text

Abstract:

Abstract. Gravel-bedded rivers organize their bank-full channel geometry and grain size such that shear stress is close to the threshold of motion. Sand-bedded rivers, on the other hand, typically maintain bank-full fluid stresses far in excess of threshold, a condition for which there is no satisfactory understanding. A fundamental question arises: are bed-load (gravel-bedded) and suspension (sand-bedded) rivers two distinct equilibrium states, or do alluvial rivers exhibit a continuum of transport regimes as some have recently suggested? We address this question in two ways: (1) reanalysis of global channel geometry datasets, with consideration of the dependence of critical shear stress upon site-specific characteristics (e.g., slope and grain size); and (2) examination of a longitudinal river profile as it transits from gravel to sand bedded. Data reveal that the transport state of alluvial riverbed sediments is bimodal, showing either near-threshold or suspension conditions, and that these regimes correspond to the respective bimodal peaks of gravel and sand that comprise natural riverbed sediments. Sand readily forms near-threshold channels in the laboratory and some field settings, however, indicating that another factor, such as bank cohesion, must be responsible for maintaining suspension channels. We hypothesize that alluvial rivers adjust their geometry to the threshold-limiting bed and bank material, which for gravel-bedded rivers is gravel but for sand-bedded rivers is mud (if present), and present tentative evidence for this idea.

APA, Harvard, Vancouver, ISO, and other styles

31

HARADA, Morihiro, Atsuki YOSHIKAWA, and Hiroshi MIWA. "THE FLOW RESISTANCE AND RIVER-BED CONDITION IN THE SHALLOW RIFFLE ON GRAVEL-BED RIVERS." Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering) 77, no. 2 (2021): I_637—I_642. http://dx.doi.org/10.2208/jscejhe.77.2_i_637.

Full text

APA, Harvard, Vancouver, ISO, and other styles

32

Lakshmanan, Susithra, Gareth Pender, Heather Haynes, and William Holmes. "Characterization of flow transport within pore spaces of an open-work gravel bed." International Journal of Engineering & Technology 3, no. 4 (September 27, 2014): 457. http://dx.doi.org/10.14419/ijet.v3i4.3430.

Full text

Abstract:

Analysis of the flow dynamics within the near-bed and sub-surface regions of river bed sediment is critical in understanding fluid exchange and related chemical transfer/reactions. The knowledge in above is limited as these regions are difficult to measure using traditional instrumentation methods. In this paper, we tried the use of Magnetic Resonance Imaging (MRI) technique to non-invasively image flow dynamics of simulated river bed. We developed a bespoke MRI-compatible open-channel flume in order to acquire real-time flow images from within the MRI bore and used contrast agent (Gd-DTPA) as a tracer through an immobile, porous gravel bed. Single MR Image slices along the flume length were obtained for analysis. The flow tracer images from within the sediment bed are calibrated from the output data in order to provide fully quantitative maps of tracer concentration at regular time intervals. These white-box (i.e. data from within the porous bed) tracer profiles were evaluated with the CXTFIT computer package to estimate the transport parameters. The intention was both, to illustrate the appropriateness of MRI for flow-sediment research and to analyse the relationship between tracer dispersion and gravel framework structure. Keywords: Porous Gravel Bed, Magnetic Resonance Imaging, Tracer Transport, CXTFIT.

APA, Harvard, Vancouver, ISO, and other styles

33

Vázquez-Tarrío, Daniel, and Ramon J. Batalla. "Assessing Controls on the Displacement of Tracers in Gravel-Bed Rivers." Water 11, no. 8 (July 31, 2019): 1598. http://dx.doi.org/10.3390/w11081598.

Full text

Abstract:

Particle travel length is one of the main dimensions of bedload and strongly influences river morpho-dynamics, particularly when exploring the interactions between sediment transport and channel morphology. This process has been traditionally studied by using tagged stones that allow tracking the movement experienced by individual grains during transport episodes. In this paper, we relate measured particle travel lengths to flow metrics and river channel parameters. First, we link the event-based bedload volumes to the active-layer dimensions, and the product between the average bedload rates and the duration of competent flows. We then hypothesize that travel length depends on channel width, surface grain-size, particle size, bed structure, flow strength, and duration of competent flow. The results from this approach are, subsequently, tested with a set of tracer observations from eight rivers that were available in the literature. The relationship between travel length and flow metrics was found to be statistically strong and has the potential to allow us to quantitatively assess the one-day dynamics of particles moving along streambeds. We also analyzed the influence of channel morphology and bed structure and identified morphological signatures for particle transport in gravel-bed rivers.

APA, Harvard, Vancouver, ISO, and other styles

34

Gomez, Basil, Brenda J. Rosser, David H. Peacock, D. Murray Hicks, and Julie A. Palmer. "Downstream fining in a rapidly aggrading gravel bed river." Water Resources Research 37, no. 6 (June 2001): 1813–23. http://dx.doi.org/10.1029/2001wr900007.

Full text

APA, Harvard, Vancouver, ISO, and other styles

35

Sloff, Kees, and Erik Mosselman. "Bifurcation modelling in a meandering gravel-sand bed river." Earth Surface Processes and Landforms 37, no. 14 (August 27, 2012): 1556–66. http://dx.doi.org/10.1002/esp.3305.

Full text

APA, Harvard, Vancouver, ISO, and other styles

36

Török, Gergely T., János Józsa, and Sándor Baranya. "Validation of a Novel, Shear Reynolds Number Based Bed Load Transport Calculation Method for Mixed Sediments against Field Measurements." Water 11, no. 10 (September 30, 2019): 2051. http://dx.doi.org/10.3390/w11102051.

Full text

Abstract:

In this study, the field measurement-based validation of a novel sediment transport calculation method is presented. River sections with complex bed topography and inhomogeneous bed material composition highlight the need for an improved sediment transport calculation method. The complexity of the morphodynamic features (spatially and temporally varied bed material) can result in the simultaneous appearance of the gravel and finer sand dominated sediment transport (e.g., parallel bed armoring and siltation) at different regions within a shorter river reach. For the improvement purpose of sediment transport calculation in such complex river beds, a novel sediment transport method was elaborated. The base concept of it was the combined use of two already existing empirical sediment transport models. The method was already validated against laboratory measurements. The major goal of this study was the verification of the novel method with a real river case study. The combining of the two sediment transport models was based on the implementation of a recently presented classification method of the locally dominant sediment transport nature (gravel or sand transport dominates). The results were compared with measured bed change maps. The verification clearly referred to the meaningful improvement in the sediment transport calculation by the novel manner in the case of spatially varying bed content.

APA, Harvard, Vancouver, ISO, and other styles

37

NAGATA, Tomonori, Yasuharu WATANABE, Yasuyuki SHIMIZU, Takuya INOUE, and Jungo FUNAKI. "STUDY ON DYNAMICS OF RIVER CHANNEL AND VEGETATION IN GRAVEL BED RIVER." Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering) 72, no. 4 (2016): I_1081—I_1086. http://dx.doi.org/10.2208/jscejhe.72.i_1081.

Full text

APA, Harvard, Vancouver, ISO, and other styles

38

Smith, Simon A. "Sedimentation in a meandering gravel-bed river: The River Tywi, South Wales." Geological Journal 24, no. 3 (April 30, 2007): 193–204. http://dx.doi.org/10.1002/gj.3350240304.

Full text

APA, Harvard, Vancouver, ISO, and other styles

39

Bui, Van Hieu, Minh Duc Bui, and Peter Rutschmann. "Combination of Discrete Element Method and Artificial Neural Network for Predicting Porosity of Gravel-Bed River." Water 11, no. 7 (July 14, 2019): 1461. http://dx.doi.org/10.3390/w11071461.

Full text

Abstract:

In gravel-bed rivers, monitoring porosity is vital for fluvial geomorphology assessment as well as in r ecosystem management. Conventional porosity prediction methods are restricting in terms of the number of considered factors and are also time-consuming. We present a framework, the combination of the Discrete Element Method (DEM) and Artificial Neural Network (ANN), to study the relationship between porosity and the grain size distribution. DEM was applied to simulate the 3D structure of the packing gravel-bed and fine sediment infiltration processes under various forces. The results of the DEM simulations were verified with the experimental data of porosity and fine sediment distribution. Further, an algorithm was developed for calculating high-resolution results of porosity and grain size distribution in vertical and horizontal directions from the DEM results, which were applied to develop a Feed Forward Neural Network (FNN) to predict bed porosity based on grain size distribution. The reliable results of DEM simulation and FNN prediction confirm that our framework is successful in predicting porosity change of gravel-bed.

APA, Harvard, Vancouver, ISO, and other styles

40

Ferguson, R. I., K. L. Prestegaard, and P. J. Ashworth. "Influence of sand on hydraulics and gravel transport in a braided gravel bed river." Water Resources Research 25, no. 4 (April 1989): 635–43. http://dx.doi.org/10.1029/wr025i004p00635.

Full text

APA, Harvard, Vancouver, ISO, and other styles

41

Vázquez-Tarrío, Daniel, Elena Fernández-Iglesias, María Fernández García, and Jorge Marquínez. "Quantifying the Variability in Flow Competence and Streambed Mobility with Water Discharge in a Gravel-Bed Channel: River Esva, NW Spain." Water 11, no. 12 (December 17, 2019): 2662. http://dx.doi.org/10.3390/w11122662.

Full text

Abstract:

Streambed mobility in gravel-bed rivers is largely controlled by the rate at which particles with different grain sizes are recruited from the riverbed into the bed load. In this paper, we present a study case in which we explored this question, based on combining field observations using painted plots and the grain size analysis of a large flood sediment deposit in the River Esva, northwest Spain, and the generalized threshold model (GTM) competence model developed by Recking. The main aim was to accomplish a complete characterization of streambed mobility in this river. The obtained results suggest the large potential of the GTM model compared to previous competence models when searching for the quantitative description of particle entrainment and streambed mobility in the River Esva. We observed how the grain size of the bed load in the River Esva tended to be closer to that of the sub-armour bed material during large floods, while moderate magnitude flows tended to carry a relatively fine bed load. Additionally, we compared our results with previously published field observations on flow competence. This comparison outlined the large degree of site specificity in the links between grain size of the bed load and that of the bed material.

APA, Harvard, Vancouver, ISO, and other styles

42

Vericat, Damià, Fanny Ville, Antonio Palau-Ibars, and Ramon J. Batalla. "Effects of Hydropeaking on Bed Mobility: Evidence from a Pyrenean River." Water 12, no. 1 (January 8, 2020): 178. http://dx.doi.org/10.3390/w12010178.

Full text

Abstract:

Hydropower production involves significant impacts on the dynamics and continuity of river systems. In this paper we analyse the effects of hydropeaks on river-bed particle mobility along a 2-km river channel. For this, a total of four study reaches were stablished: one considered a control reach (no impact by hydropeaking) and three impacted (upstream and downstream from the confluence of tributaries). Mobility related to three hydrological scenarios considered representative of the entire flow conditions in the control and impacted reaches was investigated. Results indicate that sediment availability and dynamics proved different in the control reach to those observed downstream in reaches daily affected by hydropeaks. In the absence of large floods capable of resetting the system from a sedimentary point-of-view, only the role of tributaries during small flow events reduces the effects of hydropeaks on river-bed particles’ availability and mobility. The effects of a hydropeaked regime are not observed for the whole spectrum of grain-sizes present in the river-bed. While the structural large elements (i.e., boulders) in the channel do not move, sand and fine gravel stored in patches of the bed are constantly entrained, transported and depleted whereas, in between, medium and large gravel are progressively winnowed. Our results point out that hydropeaked flows, which are generally not considered as disturbances in geomorphic terms, initiate frequent episodes of (selected) bed mobility and, consequently, the river-bed becomes depleted of fine sediments from patches and progressively lacks other fractions such as medium gravels, all of which are highly relevant from the ecological point of view.

APA, Harvard, Vancouver, ISO, and other styles

43

Kurashige, Y., T. Nakano, E. Kasubuchi, M. Maruo, and H. Domitsu. "Annual layers in river-bed sediment of a stagnant river-mouth area of the Kitagawa Brook, Central Japan." Proceedings of the International Association of Hydrological Sciences 367 (March 3, 2015): 251–57. http://dx.doi.org/10.5194/piahs-367-251-2015.

Full text

Abstract:

Abstract. The river mouth of Kitagawa Brook is normally stagnant because it is easily closed by sand and gravel transported by littoral currents of Biwa Lake, Japan. A new urban area exists in the basin and sewerage works were constructed in the early 1990s, so contaminated water with a bad odour had flowed into the brook before the sewerage works. To reduce the smell, the river mouth was excavated to narrow the channel in the early 1980s. Thus, river-bed sediment after this excavation only occurs at the river mouth. From the upper 24 cm of a sediment core, we found 19 strata of leaves which were supplied from deciduous trees in autumn. We also found several gravel layers which were supplied from the lake during severe storms. The combination of veins and gravel layers were reconstructed for about 20 years of sediment records with an error of two to three years.

APA, Harvard, Vancouver, ISO, and other styles

44

Haddadchi, Arman, Omid Mohammad H, and Dehghani Amir A. "Assessment of Bed-Load Predictors Based on Sampling in a Gravel Bed River." Journal of Hydrodynamics 24, no. 1 (February 2012): 145–51. http://dx.doi.org/10.1016/s1001-6058(11)60229-1.

Full text

APA, Harvard, Vancouver, ISO, and other styles

45

Núñez-González, Francisco, Albert Rovira, and Carles Ibàñez. "Bed load transport and incipient motion below a large gravel bed river bend." Advances in Water Resources 120 (October 2018): 83–97. http://dx.doi.org/10.1016/j.advwatres.2017.07.026.

Full text

APA, Harvard, Vancouver, ISO, and other styles

46

Geay, T., P. Belleudy, C. Gervaise, H. Habersack, J. Aigner, A. Kreisler, H. Seitz, and J. B. Laronne. "Passive acoustic monitoring of bed load discharge in a large gravel bed river." Journal of Geophysical Research: Earth Surface 122, no. 2 (February 2017): 528–45. http://dx.doi.org/10.1002/2016jf004112.

Full text

APA, Harvard, Vancouver, ISO, and other styles

47

Haddadchi, Arman, Mohammad H. Omid, and Amir A. Dehghani. "Bedload Equation Analysis Using Bed Load-Material Grain Size." Journal of Hydrology and Hydromechanics 61, no. 3 (September 1, 2013): 241–49. http://dx.doi.org/10.2478/johh-2013-0031.

Full text

Abstract:

Abstract Twelve predictive bedload sediment transport equations are rated against 14 sets of gravel-bed river field data collected by handheld bedload sampler in Narmab River, northeastern Iran. To evaluate these formulas two types of grain size namely bedload and bed material were used. The results show that the equations of Engelund and Hansen, Van Rijn and Einstein perform well with bed material grain size, while Shocklitsch, Meyer-Peter and Mueller, and Frijlink yield the best results using the bedload grain size.

APA, Harvard, Vancouver, ISO, and other styles

48

Cilli, Silvia, Paolo Billi, Leonardo Schippa, Edoardo Grottoli, and Paolo Ciavola. "Field data and regional modeling of sediment supply to Emilia-Romagna’s river mouths." E3S Web of Conferences 40 (2018): 04002. http://dx.doi.org/10.1051/e3sconf/20184004002.

Full text

Abstract:

The Fiumi Uniti and Savio rivers are two small sandy-bed river systems which sediment yield contributes feeds part of the Emilia-Romagna beaches (Italy). Since the twentieth century the northern Adriatic coast has been affected by well-known beach retreat phenomena. As the sediment supply of these local rivers is not well known, an analysis of bed-load transport rates for the last 10 kilometres of the river has been done. Multiple analysis, supported by direct field measurements of the 2005-06 and 2017 years (still ongoing) have been realized. Complementary hydraulic investigation and modelling have been performed. Repeated bed-material samplings have been carried out during different flood conditions, obtaining a significant number of observations. Aiming at defining the behaviour of sediment-transport in these two rivers, this paper focuses on the analysis of threshold sediment transport condition. Several formulae available in literature were used to test the field measurements. All these criteria seem inappropriate to predict the threshold conditions for bed particle entrainment in terms of the value of bed shear stress. The inaccurate estimation given by these formulae is due to the fact that they do not consider natural grain-shape factors or are mainly suitable for gravel-bed rivers.

APA, Harvard, Vancouver, ISO, and other styles

49

Allemand, Pascal, Eric Lajeunesse, Olivier Devauchelle, and Vincent J. Langlois. "Entrainment and deposition of boulders in a gravel bed river." Earth Surface Dynamics 11, no. 1 (January 19, 2023): 21–32. http://dx.doi.org/10.5194/esurf-11-21-2023.

Full text

Abstract:

Abstract. Bedload transport, entrainment of coarse sediment by a river, is inherently a stochastic and intermittent process whose monitoring remains challenging. Here, we propose a new method to characterize bedload transport in the field. Using an uncrewed aerial vehicle (UAV) equipped with a high-resolution camera, we recorded yearly images of a bar of the Grande Rivière des Vieux-Habitants, a gravel bed river located on Basse-Terre Island (Guadeloupe, French West Indies). These images, combined with high-frequency measurements of the river discharge, allow us to monitor the evolution of the population of sediments of a diameter between 0.5 and 0.75 m on the riverbed. Based on this dataset, we estimate the smallest discharge that can move these boulders and calculate the duration of effective transport. We find that the transport of boulders occurs for approximately 10 h yr−1. When plotted as a function of the effective transport time, a given population of boulders decreases exponentially with an effective residence time of approximately 17 h. This exponential decay suggests that the probability of dislodging a grain from the bed is proportional to the number of grains at repose on the bed, an observation consistent with laboratory experiments. Finally, the residence time of bedload particles on a riverbed can be used to evaluate bedload discharge.

APA, Harvard, Vancouver, ISO, and other styles

50

Roushangar, Kiyoumars, Yousef Hassanzadeh, Mohammad Ali Keynejad, Mohammad Tagi Alami, Vahid Nourani, and Dominique Mouaze. "Studying of flow model and bed load transport in a coarse bed river: case study – Aland River, Iran." Journal of Hydroinformatics 13, no. 4 (December 17, 2010): 850–66. http://dx.doi.org/10.2166/hydro.2010.010.

Full text

Abstract:

This paper describes a mathematical model which solves the 1D unsteady flow over a mobile bed. The model is based on the Richtmyer second-order explicit scheme. Comparison of the model results with the experimental flume data for alluvial steady flow (aggradation due to overloading) and unsteady flow shows that, by using the two-step method of Richtmyer, one can solve the equations, governing the phenomenon, in a coupled method with the desired accuracy. Firstly, the Badalan reach located at the Aland River is considered. Variations of flow rate, water level and bed level profiles due to flood hydrographs are assessed. Secondly, bed load discharge data were collected from the Aland River and a variety of bed load discharge formulae were compared with measured data. Results show that, by using the grain size of the bed surface layer to predict the bed load discharge, a larger relative error will occur compared to the other two cases and a proper choice of grain size has the main role in reduction of the relative error of bed load discharge estimation in gravel bed rivers. The applicability of formulae varies depending on flow rate, and should be split into low and high flow transport formulae.

APA, Harvard, Vancouver, ISO, and other styles

Journal articles on the topic 'Gravel-bed river'

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles