scholarly journals Self-Adjustment Process of Flow Pathway in a Narrow Curved Channel

2018 ◽  
Vol 40 ◽  
pp. 02011
Author(s):  
Hiroshi Hayakawa ◽  
Tomonori Kitao ◽  
Nobuo Sato

This study focuses on river bed fluctuation of the curved channel with channel width narrowing, where is located in the inlet of the old meandering river with 30 (m) width from straightened one with 80 (m) in the Kushiro Wetland. From field survey, in response to change in water and sediment discharges, significant streamwise variation in water flow width in the curved channel adjusts in order to establish the dynamic equilibrium. Along the outer bank of curved channel, the secular bed deposit beside the outer bank is increasing, and as a result, the main streamline flows into the old river along the inner bank as left bank. Moreover, this narrowing curved channel easily leads to overspill some flood water including rich suspended sediment and to deposit some fine sand near channel side flood plain. We intend to explain above significant bed variations by using movable bed experiments with the distorted model. As a result, we suggest, though qualitatively, that the existence of the sandbar upstream of the curved channel causes the autonomous specification of the flow path width in the curved channel with a narrowing width, and that this flow path is formed.

Author(s):  
Muhammad Irham

Dynamic interactions of hydrological and geomorphological processes in the fluvial system result in accumulated deposit on the bed because the capacity to carry sediment has been exceeded. The bed load of the Aceh fluvial system is primarily generated by mechanical weathering resulting in boulders, pebbles, and sand, which roll or bounce along the river bed forming temporary deposits as bars on the insides of meander bends, as a result of a loss of transport energy in the system. This dynamic controls the style and range of deposits in the Aceh River. This study focuses on the spatial distribution of bed-load transport of the Aceh River. Understanding the spatial distribution of deposits facilitates the reconstruction of the changes in controlling factors during accumulation of deposits. One of the methods can be done by sieve analysis of sediment, where the method illuminates the distribution of sediment changes associated with channel morphology under different flow regimes. Hence, the purpose of this mini review is to investigate how the sediment along the river meander spatially dispersed. The results demonstrate that channel deposits in the Aceh River are formed from four different type of materials: pebble deposited along upstream left bank; sand located on the upstream, downstream, and along meander belts; and silt and clay located along the cut bank of meander bends. Because of different depositional pattern, the distribution of the sediment along the river can be used as a surrogate to identify bank stability, as well as to predict critical geometry for meander bend initiation


2019 ◽  
Vol 30 (11) ◽  
pp. 1950083 ◽  
Author(s):  
Hossien Montaseri ◽  
Hossein Asiaei ◽  
Abdolhossein Baghlani ◽  
Pourya Omidvar

This paper deals with numerical study of flow field in a channel bend in presence of a lateral intake using three-dimensional numerical model SSIIM2. The effects of bend on the structure of the flow around the intake are investigated and compared with the experimental data. The tests are carried out in a U-shaped channel bend with a lateral intake. The intake is located at the outer bank of an 180∘ bend at position 115∘ with 45∘ diversion angle and the experimental data can be used to calibrate and validate numerical models. The results show that both the center-region and outer-bank cross-stream circulations are observed in the experiments while only the former is captured by the numerical model due to the limitations of the turbulence model. In the curved channel after the intake, both experimental and numerical results show another type of bi-cellular circulations in which clockwise center-region circulations and counterclockwise circulations near the inner bank and the free surface (inner-bank circulations) are captured. The study shows that the numerical model very satisfactorily predicts streamlines, velocity field and flow pattern in the channel and in vicinity of the intake. Investigation of flow pattern around lateral intake in channel bends shows that contrary to the case of flow diversion in straight channels, the width of the dividing stream surface near water surface level is greater than that of near bed level. Finally, the effects of position and diversion angle of the lateral intake, discharge ratio and upstream Froude number on the flow pattern are investigated.


2021 ◽  
Author(s):  
Volodymyr Osadchyi ◽  
Oleksii Shevchenko ◽  
Anastasiya Krasovs’ka

<p>According to the results of processing long-term data series of hydrological and hydrogeological monitoring in the upper part of the Southern Bug river basin, it has been found that meteorological or climatic changes affect both terrestrial hydrosphere and shallow groundwater aquifer (level = 0.5…7.0 m). There are two stages of different effects of temperature changes on the groundwater regime: the first stage (1974-1998) had a positive impact, with an increased infiltration recharge and large-scale flooding, while the second stage (1999-2020) is characterized by increasing drought. The average annual infiltration recharge of groundwater on the first terrace above the flood-plain at the first stage has reached 191.6 mm that is quite high for this climatic zone, while at the second stage – 115.0 mm. The highest groundwater runoff to the river was recorded in 1987-1989 (the first terrace above the flood-plain), 1996-1998, 2005, and 2014 (from the left-bank catchment). By seasonal distribution, the spring runoff mostly prevailed in 1981-1986; starting from 1996-1999 (in different areas) – summer runoff, especially in years with maximum underground runoff; the winter runoff to the river slightly prevailed in certain years (1994, 1998, 2000, 2008, 2015).</p><p>With the transition from a low-water cycle of years to a water-rich cycle (and vice versa), the dominant cyclicity in the regime of groundwater and surface water changes from 5-6 years to 7-8 years.</p><p>1974-1975 and 1987-1989 had certain temperature limits that caused significant changes in the groundwater level regime: firstly, at long-term annual average depths of 1.5-1.8 m under the surface, and later at depths of 3.0-4.4 m having led to the transition and consolidation of levels at higher grades. At the second stage, the trends of precipitation, groundwater and surface runoff change significantly (surface runoff decreases most rapidly, while the intensity of groundwater runoff has slowed down), but the temperature rises with almost the same intensity. The dependence of the total river runoff on the underground increases.</p><p>In the long-term plan (40 years), groundwater and river runoffs change in opposite directions, as the regime-forming factors (temperature and precipitation) have different effects on them: rising temperatures at the first stage have led to increased groundwater runoff; at the same time, the intensity of the decrease in river runoff under the influence of temperature as well as the decrease in precipitation at the second stage increase. The difference in the rate of reactions of groundwater and surface water levels to precipitation still provides an increase in groundwater runoff by increasing the flow gradient to the river. With decreasing rainfall, this scenario will certainly lead to the depletion of groundwater reserves.</p>


2005 ◽  
Vol 176 (3) ◽  
pp. 301-315 ◽  
Author(s):  
Alain Izart ◽  
Christian Palain ◽  
Fabrice Malartre ◽  
Stéphanie Fleck ◽  
Raymond Michels

Abstract Facies and sequences of the Westphalian C are identified in cores and well logs of three boreholes and three seismic lines supplied by Conoco-Phillips from the Lorraine coal Basin. The lithofacies associations suggest various paleoenvironments and sequences during the Westphalian C. Decameter-thick sedimentary bodies display alluvial fan deposits in the northwestern border of the basin (Chaumont borehole). Decametric sedimentary bodies constituted either of conglomeratic and sandy facies with cylindrical shape in well logs represent braided river deposits, or alternations of fining and coarsening upward sequences with sandy, silty and clayey facies with bell and funnel shapes in well log correspond to meander river and lacustrine deltaic deposits in the Saulcy and Lorettes boreholes. Three fining upward third order sequences in the center of the basin in the Lorettes and Saulcy boreholes represent a period 1 with braided river deposits, a period 2 with flood plain, lake and meandering river deposits and a period 3 with anastomosed or meandering river deposits. Period 1 is correlated with a subsidence period in the basin and uplift of the borders, period 2 with the maximum fresh water flooding period with flood plain or lake deposits and period 3 with the filling period. The seismic profiles of Conoco-Phillips confirm the tectonic structures described by previous authors in Lorraine Basin. We agree that this basin was a strike-slip basin as demonstrated by previous authors with depocenters near the South Hunsrück and Metz faults from the Westphalian to the Permian. Biomarkers show that paleoclimate changes (wet/dry) of weak amplitude in the equatorial climate could also modify the sedimentation of this basin and act on sequences of second order.


1992 ◽  
Vol 36 ◽  
pp. 55-60
Author(s):  
Shoji FUKUOKA ◽  
Takeshi SANNOMIYA ◽  
Tatsuya NISHIMURA

2014 ◽  
Vol 3 (3) ◽  
pp. 161-171
Author(s):  
Roman Victorovich Smolyaninov ◽  
Aleksey Vladimirovich Surkov

Traditionally the Early Neolithic of the Upper Don was associated the Middle Don culture (Sinyuk, 1986), but recent researches of the following sites - Karamyshevo 5, 9; Vasilyevsky Kordon 5, 7; Ivnitsa etc. have afforded ground for attributing the Early Neolithic of the Upper Don to Karamyshevo culture. This article analyzes the finds of Karamyshevo culture from 26 sites located in the basin of the Voronezh river. Those collections have all the grounds to be included into Early Neolithic antiquities as they have gone through radiocarbon dating and their chronological position correlates with the data of Elshan, Upper Volga and other Early Neolithic Cultures. In terms of location some Karamyshevo sites can be singled out: - in the Upper Voronezh region near the settlements of Preobrazhenovka and Dobroye in Lipetsk region in the right-bank flood plain of the river on the buttes of terraces above the flood-plain and leveed banks (Vasilyevsky Kordon 3, 5, 7, 25, Ratchino 22, Dobroye 1, Studenovka 3); - in the Middle Voronezh region round Lipetsk and near the settlement of Karamyshevo in Lipetsk region in the flood plain of the river on the buttes of terraces above the flood-plain (Lipetskoye Ozero, Shlyuz, Gudovsky Kordon, Krasny Bugor, Karamyshevo 1, 5, 9, 19 etc.) - in the Lower river region on the border of Lipetsk and Voronezh regions in the left-bank flood plain of the Voronezh river on the buttes of terraces above the flood-plain (Savitskoye 1, Kurino 1, Ivnitsa, Stupino) The sites of Karamyshevo culture show some typical features which are characteristic of the Upper Don region - few stone implements, so the main distinguishing feature of those antiquities is pottery according to its finish and decoration. This pottery has lumpy paste which visually consists of natural inclusions or chamotte in rare cases. More recent pottery finds have sanded paste without visible inclusions which is similar to that of the Middle Don culture. According to the method of finishing the pottery is divided into two groups: thouroughly smoothed and burnished on the outer surface pottery and smoothed one with scratches which seems to be a definite chronological marker. According to their shape the vessels are divided into straight-walled and biconical with a straight or shaped rim and mainly with a pointed bottom. The larger part of Karamyshevo pottery is plain. So among 500 pottery finds from Ivnitsa site 62% of those materials is plain, about 20% is decorated with oval, triangle and paired strokes, 11% is decorated with a short-pitch stamp, 21 finds have thin and shallow lines on the surface and 10 finds are decorated with pits. Here we can speak about a relatively early stage of the site as later sites (Karamyshevo 9, Vasilyevsky Kordon 7) have more decorated pottery. The appearance of pit-like and comb decorations is connected with the final stage of this culture. For dating of Karamyshevo culture we have the dates of the beginning of the Vth century B.C. - the first half of the IVth century B.C. (ВР). On the basis of the above-stated data we can come to a conclusion that at the end of the IVth century B.C. the first pottery complexes appeared in the forest-steppe and forest zones of Eastern Europe and they had a number of common features which specifically formed the basis of local cultures that we single out today and which existed in the Vth century B.C. Such cultures include Karamyshevo culture which sites might have dated back to the first half of the IVth century B.C.


Author(s):  
Yuniarti Yuskar ◽  
Dewandra Bagus Eka Putra ◽  
Muhammad Revanda

The study area is located in some floodplains of meandering river environment along the Kampar River, Rumbio. Typical morphology of meandering river that found in this area can be classified as stream channel, floodplain, abandoned channel, and sand bars deposit. Meandering river system carries sediment supply by suspended and bed - load (mixed load) in conjunction with low energy into a particular characteristic on sediment deposition. This study aims to determine the characteristics of the sediments, changes in vertical and lateral spread of sediment deposition on the floodplain environment. This study conducted by field survey using a hand auger of 1.5m - 4m depth and trenching which is a layer that has been exposed of 1-2 meters depth. Further analysis had been carried out using granulometri method and core data analysis to determine the characteristics and depositional facies. Sediment deposit that formed along the Kampar River is the result of the main channel migration of Kampar River. The characteristic of quaternary sediment facies is coarse to gravelly sand on the bottom followed by fine to very fine sand with pattern fining upwards and silt to clay and abundant terrestrial organic matter at the uppermost layer. Depositional facies are determined based on the characteristics of sediment facies which can be grouped into a stream channel, oblique accretion deposits, sand bars and overbank deposits.


Author(s):  
Jan Vít ◽  
Eva Břízová ◽  
Tomáš Kolář ◽  
Michal Rybníček

Organic matter, like pollen, plant detritus or subfossil woods can be found in sequences of fluvial sediments. Detail study of these remains help to assess age of accumulation processes, especially during the Holocene erosion/accumulation cycle. Two localities with exposed infill of the Bečva River valley were found near Osek nad Bečvou. The first outcrop is a gravel pit 1 km south of Osek nad Bečvou village. The second one is a river-cliff on the left bank of the Bečva River, 1 km westward of Oldřichov village, formed mostly during the extreme flood in 1997. Fluvial sediments, 4–5 m thick, of the the so called “lower flood-plain level” were exposed on both localities. At the base of the Oldřichov river-cliff was encountered a horizon of boggy soil with subfossil trunk at the base. In the gravel pit near Osek nad Bečvou was exposed layer of clay/silt with plant detritus. Up to 2 m thick middle/coarse grained gravel, situated beneath underground water level, underlie the organic-rich sediments in both localities. Badenian clay represents the bedrock of the river valley. Organic-rich layers are overlaid by middle/coarse grained gravel sediments passing gradually to sandy silt of the flood plain. Pollen analyses were made from the organic-rich layers and dendrological analysis, dendrochronology and radiometric dating from subfossil trunk.Organic-rich layer from Osek (sample LS001) was assigned to the early Holocene based on pollen analysis and represents the oldest age found. The Oldřichov samples come from oxbow sediment. The sample LV030V was poor in pollen grains and inconclusive. The sample LV030Z indicates Holocene climate optimum (Atlantic). This supposed age is compatible with radiometric dating of the subfossil trunk from the base of the layer. Radiocarbon dating using wiggle matching method gave age of 7 070–6 775 BC.Based on these data, repeated erosion/accumulation events during Late Pleistocene and Holocene are evident in Bečva River valley fill. Late Pleistocene accumulation was replaced with erosion during Late Pleistocene-Holocene transition. Erosion on the break of the Pleistocene and Holocene partly removed upper Pleistocene gravels so in places left reached level 2 m above the bedrock. The first third of Holocene (time of all interpreted data) seems to be very stable from erosion/accumulation evolution point of view. More dynamic evolution started with accumulation of “higher flood-plain level” (from cca 214 m a. s. l. up to 221 m a. s. l.). Subsequent erosion formed relatively deep cut in the northwest part of the flood plain which was filled relatively quickly by sediments as consequence of deforestation connected with a colonization of upper parts of Bečva River drainage area. This is supported by finds of much younger subfossil trunks dated from 1 century BC up to top of Middle-Age period in this accumulation (Vít et al. 2009). The surface of this accumulation is the so called “lower flood plain level” where periodicity of the inundation during floods is more regular then on the upper one.


2013 ◽  
Vol 753-755 ◽  
pp. 66-69
Author(s):  
Sheng Yun Yu ◽  
Qing Yun Meng ◽  
Hai Ying Xu

In this paper, 6 kinds of reservoir sedimentary microfacies distribution model-conceptual model have been established by the use of reservoir sedimentology theory and methods, namely, large sandy braided river sand body sedimentary model, large meandering river sand body sedimentary model, low bending-straight distributary channel sedimentary model, crevasse splay (crevasse river) sedimentary model, heart beach sedimentary model, flood plain and distributary plain sheet sand body sedimentary model. On this basis, the sedimentary facies figures of four sedimentary units have been painted, putting forward the evolution law of sedimentary environment in the research zone, thus providing basic data for the facies control modeling.


2017 ◽  
Vol 7 (1) ◽  
pp. 17-24
Author(s):  
Сериков ◽  
Mikhail Serikov ◽  
Сивцов ◽  
Sergey Sivcov

Recreational activity is the indicator, which reflects the cumulative impact of recreation on landscape complex and represents an integral indicator of recreational use of natural objects depending on the number of tourists on the item available for recreational use of space, time and prevailing forms of recreation, measured in person-days. The most important objective in addressing the problem of sustainable recreational use of forest resources today is the determination of maximum allowable recreational loads, their rules. As a result of researches on the territory of the meander part of the floodplain forests of the river Don, area of the protected natural landscape State M.A. Sholokhov Museum-Reserve, we identified the active recreational use of riparian plantings on the area of 431 hectares or 30.4 % of the total area of the studied territory. Prevailing forms of recreation are determined: roadless, obtaining and picnic one. Roadless form of recreation impact covers the largest part of areas suitable for recreational use (18 % of the total area) and it makes 256.3 ha. This form of recreation is common in largely undeveloped forest areas of the left bank and right bank of flood plain of the river Don near the villages of stanitsa Vyoshenskaya, Bazkovskaya and nearby hamlets. Picnic form of recreation is dominated on 5.5 % of the territory, but the impact caused by the consequences is the most aggressive ones. Estimated of unit values of recreational load in the prevailing forest type groups revealed that at most sites the actual load does not exceed the indicators of maximum permissible values and varies from 0.2 to 5.4 person-days./ha, given the landscape accessibility and the prevailing forms of recreation. The dependence of the distribution of resting people on the distance to the village is defined.


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