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1.
In the present study, the mean annual sediment inflow into Vistonis Lake (Thrace, northeastern Greece) was calculated. The sediment quantity originates mainly from the basins of Kossynthos, Kompsatos and Travos (Aspropotamos) Rivers. The whole basin area (mountainous part) contributing to the lake amounts to about 845 km2. The above mean annual sediment quantity was compared with the mean annual sediment accumulation in the lake. The latter quantity was estimated from the mean annual decrease of the lake water volume for a period of 22 years, which was determined by means of older and newer topographic maps (isobath contours). For the calculation of the mean annual sediment yield at the outlets of the three above mentioned basins, a mathematical model consisting of three submodels was used: a rainfall-runoff submodel, a soil erosion submodel and a sediment transport submodel for streams. The comparison of the computational results by means of the mathematical model with the estimation results by means of the topographic maps is satisfactory and encouraging.  相似文献   

2.
Knowledge of sediment exports from continental areas is essential for estimating denudation rates and biogeochemical cycles. However, the estimation of current sediment fluxes to the sea is often limited by the availability and quality of sediment discharge data. This study aims to quantify the relative contributions of French rivers to the sediment discharge to the ocean. Sediment fluxes were assessed using the French river quality database, which is characterized by a low temporal resolution but long‐term measurement periods. An improved rating curve approach (IRCA) using daily discharge data, which allows the estimation of mean annual sediment loads from infrequent sediment concentration data, was used to calculate sediment fluxes. The resulting mean annual sediment loads show that French rivers export c. 16.21 Mt yr‐1 of sediments to the sea. Among the 88 defined French rivers flowing to the sea, the four largest basins (Loire, Rhone, Garonne and Seine) export 13.2 Mt yr‐1, which corresponds to 81.3% of total exports. No relationship was found between the mass of exported sediment and the size of the drainage basins. This is due to the variety of river basin typologies among these rivers, including lowland rivers in temperate climates, such as the Seine on the one hand and rivers draining mountainous areas in Alpine/Mediterranean areas on the other hand, such as the Rhone. The latter contributes 60% to the total sediment export for France while its drainage area is only 19% of the total area considered. Differences between the river basins considered are also shown by temporal indicators describing the duration of the exports, which may be linked with sediment production processes over drained areas. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

3.
The transport of sediment from six small (0.2 to 17.6 km2) headwater catchments is described. The catchments under investigation were located in relation to predominant lithological deposits within the Cretaceous rock succession; two of the areas were underlain by (Weald) clay, two by sandstone (Ashdown Sand and Tunbridge Wells Sand) and two by chalk. The climate of the region under investigation is temperate, with an average annual precipitation (850 mm) in excess of potential evapotranspiration (450 mm). The transport of suspended material from within the catchments was examined by collecting samples of the water-sediment mixture draining the areas, using hand held depth-integrating and permanently installed stage sampling systems. The results of the regularly maintained sampling programme, over a two-year period, are described. Attempts were made to both measure and compute bed load transport. Suspended sediment concentrations are compared between catchments and related to hydrological characteristics. The nature of the material in transit is examined. Sediment rating curves are derived for each of the headwater catchments, defining the relationship in the form y = Axb (where y = suspended sediment concentration (mg/1) and x = water discharge (m3/s)). Annual rating curves are used to derive annual suspended sediment loads by combination with water discharge data, using a log-incremental computerized approach. Multiple regression techniques have been used to examine annual loads in terms of hydrological and morphological characteristics of the headwater catchments. Based on the field information available, a generalized model for the relationship between suspended sediment concentration and water discharge is described. Finally, the derived annual loads from the headwater catchments are combined with both limited observations from the larger Sussex rivers and data available for other catchment investigations in the British Isles, to produce a series of prediction equations for catchment yield under temperate climatic conditions.  相似文献   

4.
Flow diversion terraces (FDT) are commonly used beneficial management practice (BMP) for soil conservation on sloped terrain susceptible to water erosion. A simple GIS‐based soil erosion model was designed to assess the effectiveness of the FDT system under different climatic, topographic, and soil conditions at a sub‐basin level. The model was used to estimate the soil conservation support practice factor (P‐factor), which inherently considered two major outcomes with its implementation, namely (1) reduced slope length, and (2) sediment deposition in terraced channels. A benchmark site, the agriculture‐dominated watershed in northwestern New Brunswick (NB), was selected to test the performance of the model and estimated P‐factors. The estimated P‐factors ranged from 0·38–1·0 for soil conservation planning objectives and ranged from 0·001 to 0·45 in sediment yield calculations for water‐quality assessment. The model estimated that the average annual sediment yield was 773 kg ha?1 yr ?1 compared with a measured value of 641 kg ha?1 yr?1. The P‐factors estimated in this study were comparable with predicted values obtained with the revised universal soil loss equation (RUSLE2). The P‐factors from this study have the potential to be directly used as input in hydrological models, such as the soil and water assessment tool (SWAT), or in soil conservation planning where only conventional digital elevation models (DEMs) are available. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

5.
High-resolution topographic models have revolutionized monitoring of river changes by comparing sequential river topographic surveys (i.e. change detection). Nevertheless, much more may be obtained from this innovative quantification of changes. In this paper, we enhance the interpretation of geomorphic processes by presenting a new method for understanding of sources and sinks of sediment, river sediment transfers and functional sediment connectivity. Repeat digital elevation models (DEMs) obtained by photogrammetry were used to quantify topographic change after two floods by creating a DEM of difference (DoD) of a 6.5 km-long reach of Rambla de la Viuda stream, an ephemeral gravel-bed river in eastern Spain. The proposed method involved dividing the channel into 10 m-long longitudinal strips that were used to systematically draw boundaries between the erosional and depositional areas of the DoD. The analysis objectively: (i) drew a series of erosional and depositional segments, from 120 to 1360 m in length; (ii) estimated ranges of source-to-storage sediment transport distances, 320–670 m in the upstream and middle reaches and up to 2030 m in the lower reach; and (iii) obtained values of functional connectivity (i.e. the ratio between the sediment exported (erosion) and retained (deposition), ranging from 103 to 10−3). The variability in these three parameters along the river was found to be related to the level of channel disturbance by in-stream mining during the 1990s and 2000s. Additionally, this method indicates that the main process responsible for self-adjustment of the present morphosedimentary conditions is intra-reach erosion of banks and channel beds. Thus, this study proposes a new methodology to characterize morphological change, sediment transfer and connectivity that may serve as environmental indicators of the hydromorphological integrity of rivers with potential application to the European Water Framework Directive. © 2019 John Wiley & Sons, Ltd.  相似文献   

6.
Sediment load reduction in Chinese rivers   总被引：18，自引：9，他引：9  
In this paper, the changes in the annual runoff and sediment transport have been assessed by using the long term observation data from 10 gauging stations on 10 large rivers across China from far north to far south. It is found that the annual sediment yield has generally had a decreasing trend in the past half century. According to the changes in annual runoff and the sediment yield per area, rivers in China can be classified into the following three groups： 1） rivers with decreasing annual sediment transport and stable runoff; 2） rivers with both decreasing annual sediment transport and runoff and 3） rivers with greatly reduced annual sediment transport and decreasing annual runoff. The results indicate that, in all southern rivers （to the south of the Huaihe River including the Huaihe River）, there has been little change in average annual runoff but a dramatic decrease in annual sediment transport. In the northern rivers, however, both the annual sediment yield and the runoff show significant evidence of reduction. To further investigate the recent changes in annual runoff and sediment transport, the short-term observation data from these 10 gauging stations in the recent 10 years have been assessed. Results show that both the annual sediment transport and the runoff have decreased＂ significantly in the northern rivers in the past 10 years. Using the Yellow River at the Lijin Station as an example, the average annual runoff for the last 10 years is only 1/3 of the long term average value and the average annual sediment yield of the last 10 years is only 1/4 of the long term average value. More unusually, in the Yongding River the annual sediment yield has approached zero and the runoff has decreased significantly. In addition, the impacts of human activities on the changes in both runoff and sediment transport have been discussed.  相似文献   

7.
Changes in runoff and sediment loads to the Pacific Ocean from 10 major Chinese rivers are presented in this paper To quantitatively assess trends in runoff and sediment loads, a parameter called the ＂Trend Ratio T＂ has been defined in this paper. To summarize total runoff and sediment load from these rivers, data from 17 gauging stations for the duration 1955 to 2010 has been standardized, and the missing data have been interpolated by different approaches according to specific conditions. Over the observed 56-year study period, there is a quite stable change in total runoff. Results show that the mean annual runoff flux entering the Pacific Ocean from these rivers is approximately 1,425 billion cubic meters. It is found that all northern rivers within semi-arid and transitional zones including the Songhua, Liaohe, Haihe, Yellow and Huaihe rivers present declining trends in water discharge. Annual runoff in all southern rivers within humid zones including the Yangtze, Qiantang, Minjiang, Pearl and Lancang rivers does not change much, except for the Qiantang River whose annual runoff slightly increases. The annual sediment loads of all rivers show significant declining trends; the exceptions are the Songhua and Lancang rivers whose annual sediment loads have increasing trends. However, the mean annual sediment flux carried into the Pacific Ocean decreased from 2,026 million tonnes to 499 million tonnes over the 56-year period. During this time there were 4 distinct decreasing phases. The decrease in annual sediment flux is due to the integrated effects of human activity and climate change. The reduction in sediment flux makes it easy for reservoir operation; however, the decrease in sediment flux also creates problems, such as channel erosion, river bank collapse and the retreat of the delta area.  相似文献   

8.
Abstract

Placer mines are located in river valleys, along river benches, or along the pathways of ancient channels. Open-pit mining alters the stream hydrology and enhances sediment transport. The present study focuses on sediment transport in the area of the platinum placer mining located at the north of Russia’s Kamchatka Peninsula (Seynav-Galmoenan placer deposits). Based on hydrological field investigations, a conceptual model was derived to assess anthropogenic effects on the total sediment budget of rivers. The model illustrates key processes controlling sediment dynamics in the Vyvenka River basin. Field work included water-discharge and sediment-load measurements, assessment of annual channel change in rivers in mining site areas, and evaluation of the relative importance of sediment sources and transport processes. In this study, we estimated total sediment delivery from opencast placer mining of 60 t year-1; the annual mass wasting rate ranges from 2 to 5.5 kg m-2 year-1, which is three orders of magnitude higher than from non-mined streams. Mass wasting dominates surface erosion on the hillslopes and produces significant wastewater effluents; however, erosion of the artificially stratified channel reaches is the primary contributor to the annual sediment yield of the mined rivers (21.4%).
Editor D. Koutsoyiannis

Citation Chalov, S.R., 2014. Effects of placer mining on suspended sediment budget: case study of north of Russia’s Kamchatka Peninsula. Hydrological Sciences Journal, 59 (5), 1081–1094.  相似文献   

9.
Previously undocumented deposits are described that store suspended sediment in gravel‐bedded rivers, termed ‘fine‐grained channel margin’ (FGCM) deposits. FGCM deposits consist of sand, silt, clay, and organic matter that accumulate behind large woody debris (LWD) along the margins of the wetted perimeter of the single‐thread, gravel‐bed South River in Virginia. These deposits store a total mass equivalent to 17% to 43% of the annual suspended sediment load. Radiocarbon, 210Pb and 137C dating indicate that sediment in FGCM deposits ranges in age from 1 to more than 60 years. Reservoir theory suggests an average turnover time of 1·75 years and an annual exchange with the water column of a mass of sediment equivalent to 10% to 25% of the annual sediment load. The distribution of ages in the deposits can be fitted by a power function, suggesting that sediment stored in the deposits has a wide variety of transit times. Most sediment in storage is reworked quickly, but a small portion may remain in place for many decades. The presence of FGCM deposits indicates that suspended sediment is not simply transported downstream in gravel‐bed rivers in agricultural watersheds: significant storage can occur over decadal timescales. South River has a history of mercury contamination and identifying sediment sources and sinks is critical for documenting the extent of contamination and for developing remediation plans. FGCM deposits should be considered in future sediment budget and sediment transport modeling studies of gravel‐bed rivers in agricultural watersheds. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

10.
The basic peculiarities of the hydrological regime of one of the largest mouth areas of the world, i.e., the common mouth of the rivers of Ganges and Brahmaputra, are discussed. The main features of natural conditions (including climatic) of the mouth of these rivers and the delta drainage system are characterized. The hydrological regime of the Ganges and Brahmaputra rivers, the largest rivers of South Asia, is studied in greater detail; the quantitative assessments of the water and sediment runoff of these rivers are specified. Provision is made for revealing the basic peculiarities of river flow distribution among numerous delta branches, annual floods during southwest monsoons, tidal phenomena in the maritime zone of the delta, and disastrous storm surges and inundations in the period of tropical cyclones. Flood control measures taken in Bangladesh to protect the population and lands are described.  相似文献   

11.
Abstract

Using daily suspended sediment and water discharge data, we calculated the current mean annual runoff and Specific Suspended Sediment Yield (SSY) for 66 mountainous and piedmont catchments in Chile. These catchments are located from the extreme north of Chile to Southern Patagonia and cover an exceptionally wide range of climates, slopes, and vegetation. The SSY ranges mainly between 0 and 700 t km-2 year-1 with some exceptions as high as 1780 t km-2 year-1. The SSY increases between the extreme north and 33°S and then decreases toward the south. Sediment and water discharge north of 33°S occur mainly during summer. Farther south the contribution of winter precipitation increases and predominates. When the SSY database is correlated with topographic, climatic and vegetation indices, it is found to correlate significantly with runoff and mean slope only. In order to concentrate on erosion processes in the mountain range, 32 mountainous catchments were selected along a strong north–south SSY gradient between 27°S and 40°S. From north to south, SSY increases strongly with runoff and then decreases, even while runoff keeps increasing. In catchments where SSY is low, although runoff is high, the mean slope is less than 40% and the vegetation cover is greater than 8%. For the other catchments, runoff variations explain 67% of the variance in sediment yields. Thus, SSY seems to be controlled by vegetation cover and slope thresholds. In addition, SSY also correlates with glacier cover. However, a correlation between SSY and seismicity, although possible, is ambiguous.

Citation Pepin, E., Carretier, S., Guyot, J. L. & Escobar, F. (2010) Specific suspended sediment yields of the Andean rivers of Chile and their relationship to climate, slope and vegetation. Hydrol. Sci. J. 55(7), 1190–1205.  相似文献   

12.
Abstract

Abstract Since the end of the 1950s, suspended matter measurements have been carried out in the streams and rivers of Cameroon. Despite the fact that these are often point measurements, they provide a framework for a global approach towards studying the regimes of suspended sediment transport in these rivers. The objective here is to assess the intensity of sediment transport and to determine the principal factors which influence it, according to the main climatic units. The influence of human activities is pointed out. It appears that steep slopes, population density, soil cultivation and cattle grazing are the essential factors. The sediment load in these rivers is increasing with latitude with 20–40 g m-3 at the Equator, 80–100 g m-3 in the transition zones and 150–160 g m-3 in the dry tropical zones. The choice of drainage basin size for the characterisation of the rate of effective erosion is indispensable. In fact, in large drainage basins (5 × 104 km2), there is an integration of heterogeneous geomorphological, phytogeographical, pedological and anthropogenic characteristics into average characteristics which do not show the influence of local conditions on sediment transport.  相似文献   

13.
中国的水库泥沙淤积问题   总被引：18，自引：2，他引：16  
由于我国有许多河流是含沙最高、输沙量大的多泥沙河流,水库泥沙淤积问题异常严重．主要表现在：淤积数量大,淤积速率快．据统计,截止到1981年底全国水库总淤积量达115×10~8m~3．占统计水库总库容的14．2％．年平均库容损失率达2．3％,高于世界各国．水库的严重淤积,不仅影响水库兴利效益的发挥,严重威胁水库的使用寿命,而且还造成一系列在进行水库规划时未曾充分估计到的环境问题．本文重点从河流水文泥沙特性、我国水库淤积问题的严重性、水库淤积引起的问题及水库防淤减淤措施等4个方面作一较全面的分析和探讨．  相似文献   

14.
Rivers of South and Southeast Asia disgorge large suspended sediment loads, reflecting exceptionally high rates of erosion promoted by natural processes (tectonic and climatic) and anthropogenic (land‐use change) activities that are characteristic of the region. While particulate carbon and nitrogen fluxes have been characterized in some large Asian rivers, less is known about the headwater systems where much sediment and organic material are initially mobilized. This study, conducted in the 74‐km2 Mae Sa Experimental Catchment in northern Thailand, shows that the Sa River is an important source for particulate organic carbon (POC) and particulate organic nitrogen (PON) transported to larger river systems and downstream reservoirs. However, the yields during three years of investigation varied greatly: 5.0–22.3 Mg POC km?2 y?1 and 0.48–2.02 Mg PON km?2 y?1. The 22.3 Mg POC km?2 y?1 yield is the highest reported for any river on the Asian continent. Stream samples collected during 12 storms showed that almost 3% of the total suspended solid load is POC 0.7 µm to 2.0 mm in size. This percentage is higher than other values for most large rivers on the continent. Further, we documented a strong pulse hysteretic behaviour in the stream, whereby peak fluxes of POC and PON are often delayed (anticlockwise hysteresis) or accelerated (clockwise hysteresis) relative to stream flow peaks (or are complex), complicating the prediction of storm‐based or annual particulate carbon and nitrogen fluxes. Stream turbidity and total suspended sediment are reasonable proxies for POC and PON concentrations, while stream discharge is not a good predictor variable. Observed C:N ratios for measured particulate samples range from 3 to 83, with the high‐end values likely associated with fresh (non‐decomposed) vegetative material greater than 2 mm in diameter. The C:N ratio (weighted based on three sediment sizes) for 12 events ranges from 7.5 to 15.3. These modest values reflect the relatively low C:N ratios for small size fractions (0.7–0.63 µm) that comprise 50–90% of the TSS load in the events. Overall, organic material <0.63 µm contribute about 75% of the total POC load and 80% of the PON load. The annual C:N ratio for the river is approximately 10–11. Collectively, our findings indicate the occasionally high yields make the Sa River—and potentially other similar headwater rivers—a hot spot for POC and PON transported to downstream water bodies. Complex hysteresis patterns and high year‐to‐year variability hinders our ability to calculate and predict these yields without continuous, automated monitoring of discharge and turbidity. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

15.
Glacier retreat leads to changes in channel pattern during deglaciation, in response to changing water, sediment and base level controls. Recent ongoing retreat at Skaftafellsjökull, Iceland (c. 50 m per year since 1998) has resulted in the formation of a sequence of river terraces, and several changes in river channel pattern. This paper compares widely used models of river channel pattern against the changes observed at Skaftafellsjökull. Doing this reveals the role of topographic forcing in determining proglacial channel pattern, whilst examining the predictive power and limitations of the various approaches to classifying river channels. Topography was found to play a large role in determining channel pattern in proglacial environments for two reasons: firstly, glacier retreat forces rivers to flow through confined moraine reaches. In these reaches, channels which theory predicts should be braided are forced to adopt a single channel. Secondly, proximal incision of proglacial rivers, accompanied by downstream aggradation, leads to changes in slope which force the river to cross channel pattern thresholds. The findings of this work indicate that in the short term, the majority of channel pattern change in proglacial rivers is due to topographic forcing, and that changes due to changing hydrology and sediment supply are initially relatively minor, although likely to increase in significance as deglaciation progresses. These findings have implications for palaeohydraulic studies, where changes in proglacial channel pattern are frequently interpreted as being due to changes in water or sediment supply. This paper shows that channel pattern can change at timescales faster than hydrological or sediment budget changes usually occur, in association with relatively minor changes in glacier mass balance. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

16.
Among the different controls of erosion budget at basin level, the relative impact of dams and land management is yet to be investigated. In this paper, the impact of dams on sediment yield has been assessed by using a conceptual modelling framework which considers the gross erosion and the cascade of dams constructed on a river network. The sediment budget has been estimated based on the gross erosion, deposition of sediment in reservoirs, and sediment yields of 23 mainland river basins of India. The gross erosion of the country is estimated as 5.11 ± 0.4 Gt yr?1 or 1559 t km?2 yr?1, out of which 34.1 ± 12% of the total eroded soil is deposited in the reservoirs, 22.9 ± 29% is discharged outside the country (mainly to oceans), and the remaining 43.0 ± 41% is displaced within the river basins. The river basins of northern India contribute about 81% of the total sediment yield from landmass while the share of southern river basins is 19%. The components of revised sediment budget for India are prominently influenced by the sediment trapped in reservoirs and the treatment of catchment areas by soil and water conservation measures. Analysis of sediment deposition in 4937 reservoirs indicated the average annual percentage capacity loss as 1.04% though it varies from 0.8% to >2% per year in smaller dams (1–50 Mm3 capacity) and from <0.5% to 0.8% per year in larger dams (51 to >1000 Mm3 capacity). Siltation of smaller dams poses a serious threat to their ecosystem services as they cater to a wider population for domestic, agricultural, and industrial purposes. Amongst the environment controls, land use significantly impacts the gross erosion rate and specific sediment yield as compared to climatic and topographic parameters. However, to analyse their integrated effect on the complex processes of sediment fluxes in a basin, further research efforts are needed. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

17.
The variation of mechanical and chemical denudation is investigated using discharge and sediment yield data from the Upper Colorado River System. Annual precipitation ranges from approximately 150 mm to 1500 mm. Mean specific yield ranges from 0-2 1/s km2 ( = 6 mm p a) to 151/s km2 ( = 475 mm p a). The hydrological-geomorphological system adjusts itself to these varying climatic conditions; in some areas, however, the effects of lithology or land use seem to override the climatic controls. It is demonstrated that the increase in the absolute and particularly the relative amount of suspended sediment is closely related to a decrease in annual runoff and to an increase in the importance of high magnitude/low frequency events. This indicates that in areas of low annual runoff and high runoff variability, soluble rocks are more resistant than in more humid areas. During high magnitude/low frequency events, suspended sediment concentrations and loads are very high in semiarid areas due to sparse vegetation cover and dominance of direct runoff. Events of moderate magnitude and frequency, which in more humid areas transport most of the dissolved load, seldom occur. The trend towards increasing mechanical denudation is even observed in areas of very low runoff (0-221/s km2 = 7 mm p a). The peak of sediment yield in dry areas seems to approximate the point of no runoff very closely. Mechanical and chemical denudation are of equal importance at a runoff of about 300 mm per year.  相似文献   

18.
This paper presents a field investigation on river channel storage of fine sediments in an unglaciated braided river, the Bès River, located in a mountainous region in the southern French Prealps. Braided rivers transport a very large quantity of bedload and suspended sediment load because they are generally located in the vicinity of highly erosive hillslopes. Consequently, these rivers play an important role because they supply and control the sediment load of the entire downstream fluvial network. Field measurements and aerial photograph analyses were considered together to evaluate the variability of fine sediment quantity stored in a 2·5‐km‐long river reach. This study found very large quantities of fine sediment stored in this reach: 1100 t per unit depth (1 dm). Given that this reach accounts for 17% of the braided channel surface area of the river basin, the quantities of fine sediment stored in the river network were found to be approximately 80% of the mean annual suspended sediment yields (SSYs) (66 200 t year?1), comparable to the SSYs at the flood event scale: from 1000 t to 12 000 t depending on the flood event magnitude. These results could explain the clockwise hysteretic relationships between suspended sediment concentrations and discharges for 80% of floods. This pattern is associated with the rapid availability of the fine sediments stored in the river channel. This study shows the need to focus on not only the mechanisms of fine sediment production from hillslope erosion but also the spatiotemporal dynamics of fine sediment transfer in braided rivers. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

19.
A 7-year sediment transport monitoring on the Upper Niger rivers was used to study the relationship between suspended sediment concentration and river discharge. During annual floods, these relationships show positive hysteresis. This paper presents the results of two models that estimate the time evolution of suspended sediment concentration using water discharge data only. The first model is based on a statistical approach using two relationships, one for the rising stage period of the flood and one for the recession period of the annual flood; the second model is a lumped conceptual one; it supposes that the sediment flux observed in the river comes from two different sources of sediment and that these two sources may be regarded as two different reservoirs. The erosion of the first reservoir represents hillslope erosion observed during the runoff season. Sediment supply from this ‘reservoir’ is limited in time because depletion occurs during the runoff season. The second reservoir is unlimited in time and quantity and its erosion represents contributions coming from bank erosion and mobilisation of deposits in the channel network.

Both of the models are compared with a simple rating curve based model. The model results show that the conceptual model has the highest efficiency to reproduce from weekly discharge only the time evolution of weekly suspended sediment concentrations, the time evolution of weekly sediment fluxes, and the global annual sediment yields.  相似文献   


20.
This paper describes meandering alluvial rivers with mean annual suspended-sediment concentrations of more than 100 kgm?3 on the Loess Plateau, China, and explains their formation as caused by the effect of hyperconcentrated water flow. When the river is dominated by hyperconcentrated flow, the rate of energy expenditure required for sediment transport declines significantly. Accordingly, the river channel adjusts itself to a lower channel gradient by increasing the river length, resulting in a meandering channel. Since the stable transportation of sediment by hyperconcentrated flow is dependent on river channel boundary conditions, the latter play an important role in the formation of meanders of this kind. The paper also discusses the conditions for the discrimination of meandering and braided rivers in this area.  相似文献   

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