Mean Annual Suspended Sediment Yield Research Articles

A multiple regression model to estimate the suspended sediment yield in Italian Apennine rivers by means of geomorphometric parameters

A new statistical prediction model, aimed to assess the mean annual suspended sediment yield (SY) in ungauged rivers of Italian Apennines, is here presented. A multiple linear regression equation was obtained by the stepwise technique investigating the relationships between a series of hydro-geomorphometric variables and sediment yield data from 41 river basins located along peninsular Italy and Sicily. The model variables were computed from hydrological data records and from vector river network lines and drainage divides derived from official maps and DEM. The analysis revealed a large variance in the observed sediment yield data. Nonetheless, an optimal result in terms of model significance and efficiency (r2adj = 0.91 at p < 0.05 significance level; Nash–Sutcliffe model efficiency NSE = 0.855; Willmott’s indexes of performance: d = 0.965; d1 = 0.862; dr = 0.862) was finally achieved. According to stepwise regression, the catchment relief and perimeter, together with the topological organization of stream network, the bedrock erodibility and the stream gradient, expressed by specific parameters, appeared as determinant features for SY prediction in the catchments here investigated. The developed model could be helpful to practitioners and scholars for rapid assessments of SY at any point of the river network in the geographic area here concerned. However, the same technique can be utilized wherever in the world since the statistical method itself allows to recognize the number and type of parameters to be used in a given geographic area, on the basis of their local significance.

A Regression-Based Prediction Model of Suspended Sediment Yield in the Cuyahoga River in Ohio Using Historical Satellite Images and Precipitation Data

Urbanization typically results in increased imperviousness which alters suspended sediment yield and impacts geomorphic and ecological processes within urban streams. Therefore, there is an increasing interest in the ability to predict suspended sediment yield. This study assesses the combined impact of urban development and increased precipitation on suspended sediment yield in the Cuyahoga River using statistical modeling. Historical satellite-based land-cover data was combined with precipitation and suspended sediment yield data to create a Multiple Linear Regression (MLR) model for the Cuyahoga watershed. An R2 value of 0.71 was obtained for the comparison between the observed and predicted results based on limited land-use and land-cover data. The model also shows that every 1 mm increase in the mean annual precipitation has the potential to increase the mean annual suspended sediment yield by 860 tons/day. Further, a 1 km2 increase in developed land area has the potential to increase mean annual suspended sediment yield by 0.9 tons/day. The framework proposed in this study provides decision makers with a measure for assessing the potential impacts of future development and climate alteration on water quality in the watershed and implications for stream stability, dam and flood management, and in-stream and near-stream infrastructure life.

Long-Term Suspended Sediment Concentrations and Loads from a Relatively Undisturbed Agroforested Catchment in the Northwest of the Iberian Peninsula

The suspended sediment dynamics in small catchments are difficult to estimate accurately because they result from the coupling of complex processes occurring at different scales. In this study, the dynamics of suspended sediment concentrations (SSC) and loads were assessed in an agroforested humid catchment in NW Spain, based on a long-term rainfall, discharge and suspended sediment dataset (12 hydrological years) from high-frequency monitoring. The results highlight the episodic nature of sediment transport in the study area, given that about 78% of SS was exported over 10% of the study period. The SS transport was related to runoff generation and flooding, although sediment availability also played an important role in SS transport. The SS load was mainly driven by high-magnitude rainfall events, while intense rainfall episodes generated high SSC peaks. The mean annual suspended sediment yield was relatively low from a quantitative stand point (10 Mg km−2 y−1); however, during 11% of the monitoring, SS concentrations exceeding the threshold threatened surface water quality (Freshwater Fish Directive 78/659/EEC and Directive 75/440/EEC), mainly during runoff events, indicating the need to adopt management practices in order to reduce or mitigate sediment loss during such episodes.

Contemporary suspended sediment dynamics within two partly glacierized mountain drainage basins in western Norway (Erdalen and Bødalen, inner Nordfjord)

This paper focuses on environmental controls, spatiotemporal variability and rates of contemporary fluvial suspended sediment transport in the neighboring, partly glacierized and steep Erdalen (79.5km2) and Bødalen (60.1km2) drainage basins in the fjord landscape of the inner Nordfjord in western Norway. Field work, including extended samplings and measurements, was conducted since 2004 in Erdalen and since 2008 in Bødalen. The distinct intra- and inter-annual temporal variability of suspended sediment transport found is mostly controlled by meteorological events, with most suspended sediment transport occurring during pluvial events in autumn (September–November), followed by mostly thermally determined glacier melt in summer (July–August), and by mostly thermally determined snowmelt in spring (April–June). Extreme rainfall events (>70mmd−1) in autumn can trigger significant debris-flow activity that can cause significant transfers of suspended sediments from ice-free surface areas with sedimentary covers into main stream channels and is particularly important for fluvial suspended sediment transport. In years with occurring relevant debris-flow activity the total annual drainage-basin wide suspended sediment yields are strongly determined by these single extreme events. The proportion of glacier coverage, followed by steepness of slopes, and degree of vegetation cover in ice-free surface areas with sedimentary covers are the main controls for the detected spatial variability of suspended sediment yields. The contemporary sediment supply from glacierized surface areas and the Jostedalsbreen ice cap through different defined outlet glaciers shows a high spatial variability. The fact that the mean annual suspended sediment yield of Bødalen is with 31.3tkm−2yr−1 almost twice as high as the mean annual suspended sediment yield of Erdalen (16.4tkm−2yr−1) is to a large extent explained by the higher proportion of glacier coverage in Bødalen (38% of the drainage basin surface area) as compared to Erdalen (18% of the drainage basin surface area) and by a significantly higher sediment yield from the glacierized area of the Bødalen drainage basin compared to the glacierized surface area in Erdalen. When looking at the total annual mass of suspended sediments being fluvially exported from both entire drainage basin systems, the total amount of suspended sediments coming from the ice-free drainage basin surface areas altogether dominates over the total amount of suspended sediments coming from the glacierized surface area of both drainage basins. Drainage-basin wide annual suspended sediment yields are rather low when compared with yields of other partly glacierized drainage basin systems in Norway and in other cold climate environments worldwide, which is mainly due to the high resistance of the predominant gneisses towards glacial erosion and weathering, the altogether only small amounts of sediments being available within the entire drainage basin systems, the stable and nearly closed vegetation cover in the ice-free surface areas with sedimentary covers, and the efficiency of proglacial lakes in trapping sediments supplied by defined outlet glaciers. Both contemporary and long-term suspended sediment yields are altogether supply-limited. Contemporary suspended sediment transport accounts for nearly two-thirds of the total fluvial transport and, accordingly, plays an important role within the sedimentary budgets of the entire Erdalen and Bødalen drainage basins.

Recent changes of suspended sediment yields in the Upper Yangtze River and its headwater tributaries

Abstract. Suspended sediment yields in the Upper Yangtze River and its four headwater tributaries (i.e. Jinsha, Min, Jialing and Wu) have declined significantly during recent decades. Compared with 1956–1970, mean annual suspended sediment yield during 2001–2011 was reduced by 84% in the Upper Yangtze River at Yichang, by 34% in the Jinsha at Pingshan, by 84% in the Jialing at Beibei, by 75% in the Wu at Wulong, and by 48% in the Min at Gaochang. Linking these observed decadal changes of runoff discharge and suspended sediment load to dam construction and multiple environmental rehabilitation projects (e.g. soil-water conservation, reforestation) during the past decades, it can be concluded that the construction of large dams on the main stem and major tributaries of the Upper Yangtze River has played a principal role in the reduction of fluvial suspended sediment yields, while the environment rehabilitation projects may make limited contributions to the changes in suspended sediment yields, except for the Jialing River.

Attribution of climate change, vegetation restoration, and engineering measures to the reduction of suspended sediment in the Kejie catchment, southwest China

Abstract. Suspended sediment transport in rivers is controlled by terrain, climate, and human activities. These variables affect hillslope and riverbank erosion at the source, transport velocities and sedimentation opportunities in the river channel, and trapping in reservoirs. The relative importance of those factors varies by context, but the specific attribution to sediment transfer is important for policymaking, and has wide implications on watershed management. In our research, we analyzed data from the Kejie watershed in the upper Salween River (Yunnan Province, China), where a combination of land cover change (reforestation, as well as soil and water conservation measures) and river channel engineering (sand mining and check dam construction) interact with a changing climate. Records (1971–2010) of river flow and suspended sediment loads were combined with five land-use maps from 1974, 1991, 2001, 2006 and 2009. Average annual sediment yield decreased from 13.7 t ha−1 yr−1 to 8.3 t ha−1 yr−1 between the period 1971–1985 and the period 1986–2010. A distributed hydrological model (Soil and Water Assessment Tools, SWAT) was set up to simulate the sediment sourcing and transport process. By recombining land-use and climate data for the two periods in model scenarios, the contribution of these two factors could be assessed with engineering effects derived from residual measured minus modeled transport. Overall, we found that 47.8% of the decrease was due to land-use and land cover change, 19.8% to climate change, resulting in a milder rainfall regime, 26.1% to watershed engineering measures, and the remaining 6.3% was due to the simulation percent bias. Moreover, mean annual suspended sediment yield decreased drastically with the increase of forest cover, making diverse forest cover one of the most effective ecosystems to control erosion. For consideration of stakeholders and policymakers, we also discuss at length the modeling uncertainty and implications for future soil and water conservation initiatives in China.

AN APPROACH TO THE MODEL USE FOR MEASURING SUSPENDED SEDIMENT YIELD IN UNGAUGED CATCHMENTS

Different types of water resources studies require the information of Suspended Sediment Yield (SSY) in different time resolutions. In ungauged watersheds where hydrometeorogical time series are not available, the mean annual SSY (SSYa) is solely predictable and catchment area is traditionally used as the predictor because it is the most important variable and generally determined during project planning. Firstly, this research tried to advance the traditional SSYa model by additionally associating global topographic data. Based on the jack-knife procedure, the modified method considering catchment area with slope greater than 15% was evaluated in 17 gauged catchments in the Lower Mekong Basin and the overall predictive accuracy was improved about 66% in term of mean absolute percentage error. Secondly, the predicted SSYa in each modeled catchment was monthly distributed using Unit mean annual Sedimentograph (USGa). The double-average USGa superior to the single-average one provides overall better quality results than the regionalized USGa dependent upon the spatial proximity approach. The model performance measured by Nash-Sutcliffe Efficiency (NSE) is about 0.66 in median value and satisfactory results (NSE >0.50) are obtained in 11 catchments. Lastly, the validated regional model was regarded as a potential and feasible tool in solving sediment-ungauged issues in the basin.

A suspended sediment budget for the agricultural Can Revull catchment (Mallorca, Spain)

Extensive rainfed herbaceous crops are one of the most representative agricultural elements of Mediterranean region, which should be one of the major factors affecting erosion processes. Although land use is commonly seen as resulting in increased sediment yields, the implementation of soil and water conservation practices can have the reverse effect. A sediment budget has been established in Can Revull, a small agricultural catchment (1.03 km2) on the island of Mallorca, by using 137Cs measurements, sediment source fi ngerprinting and more traditional monitoring techniques to quantify the individual components of the budget. A large proportion of the material mobilized from cultivated fi elds without conservation practices (gross erosion of 775 t yr 1, 1,270 t km 2 yr 1) was subsequently deposited either within the fi eld of origin (112 t yr 1, 180 t km 2 yr 1) or at intermediate locations between the source fi eld and the channel network (fi eld-to-channel conveyance loss was 454 t yr 1, 744 t km 2 yr 1). The estimates of sediment accumulation rates on the fl oodplain in the lower reaches of the catchment indicate that the mean sedimentation rate was 0.14 g cm-2 yr-1. This value was extrapolated to the total area of the fl oodplain to estimate a total annual conveyance loss or storage of 445 t yr 1. Monitoring at the catchment outlet over the study period (2004–2008) indicated a mean annual suspended sediment yield of 7 t km-2 yr-1. The sum of the estimates of sediment yield and fl oodplain storage (452 t yr-1) was taken to represent the total annual input of suspended sediment to the channel system. This value was subsequently apportioned using the information provided by the fi ngerprinting investigation, to estimate the mass of sediment reaching the channel network from cultivated fi elds and from eroding channel banks. Thus the annual contribution from channel banks was estimated to be 242 t yr-1. In the case of the contributions from cultivated fi elds, the estimates obtained were, as expected, signifi cantly less than the values of net soil loss from these zones provided by the 137Cs measurements due to conveyance losses associated to fi eld-to-channel conveyance loss. The overall sediment delivery ratios (< 1 %) indicate that approximately 99 % of the sediment mobilized by erosion within the Can Revull catchment is subsequently deposited before reaching the monitoring station. As such, the low sediment outputs from the study catchment should be seen as refl ecting the importance of conveyance losses and storage rather than a lack of sediment mobilization from the catchment surface, although part of the catchment headwaters was modifi ed historically by means of terraces and transverse walls to prevent erosion.

Estimation of suspended sediment transport in the Kebir drainage basin, Algeria

Sediment load and sediment concentration are highly important variables that may play a key role in environment quality assessment and help to evaluate the extent of potential adverse impacts. This paper introduces a methodology to predict sediment loads in the Kebir drainage basin (681 km2). The methodology is developed by a conventional sediment rating curve and a multiple regression model. The former method is investigated with the mean discharge classes derived from the recorded instantaneous suspended sediment concentrations and water discharges for the Kebir basin, prior to the Mexa reservoir construction. The latter is based on rock type erodibility, mean annual runoff and basin area variables, and which is applied for the ungauged Mexa reservoir basin located upstream of the Kebir gauging station (651 km2). The mean annual suspended sediment yield of both Kebir drainage basin and Mexa reservoir basin conducted during the 24 years (1975/1976–1998/1999) and the 9 years (1999/2000–2007/2008) are respectively 895 T km2 year-1 and 572 T km2 year-1. Despite the decline in sediment load during the reservoir period due mainly to disturbance in climatic regime, the basin is suffering severe soil loss, and currently 0.42% y-1 in loss of storage in the reservoir due to sedimentation has been evaluated. The high amount of sediment produced from the study drainage basin is a function of climatic and several physical factors including the high proportion of argillaceous materials and the amount of bare soil exposed.

Sediment rating curves developed on stage and seasonal means in discharge classes for the mellah wadi, algeria

.The focus of the present study was to estimate suspended sediment load from the Mellah catchment (550 km2) during storms. Suspended sediment rating curves were developed on data from a 23‐year period. The regression technique of this paper involves a division of data into discharge‐based classes, the mean concentrations and discharges of which are used to develop power regressions through log‐transformation. Sediment rating curves were also developed on means of data grouped into seasons and stages. Sediment loads estimated by rating curves uncorrected for bias involved underestimations of down to 9% compared with loads from measured concentrations. Correction for bias reduced underestimations to a range from 0.79 to 3%. Rating curves divided into rising and falling stages had the lowest underestimation and were used to estimate load during periods without concentration measurements. During the 23‐year study period, the mean annual suspended sediment yield was 373 TI km2.Sediment transport is dominated by winter storms accounting for 61% of the annual load. A high exponent ‘b’ of the power regression equations during the winter season confirms the intense geomorphic work by winter season storms caused by high intensity rainfall, low vegetation cover, and heavy machine activity in the fields.

Geo(Im)pulse | River Meuse suspended sediment yield: a new estimate and past estimates revisited

AbstractDespite increasing research into changes in the discharge of the River Meuse, estimates of the river’s sediment yield are less forthcoming. Three published studies (in 1883, 1982, and 1987) have estimated suspended sediment yield at the Belgian-Dutch border; the latter two studies surmise that this increased substantially between the late 19th and 20th Centuries. In this paper a more recent and longer time-series of observed discharge and suspended sediment data (1995 – 2005) is used to estimate mean annual suspended sediment yield (ca. 386,000 Mg.a−1), and the results of the previous studies are revisited. New insights suggest that those studies do not in themselves provide evidence of increased sediment yield: the higher estimates in the late 20th Century could equally be due to interannual variability or methodological differences. Furthermore, there has been no significant increase in rainfall erosivity between the late 19th and 20th Centuries, and the effect of land use change over that time would have been to cause a decrease in suspended sediment yield, rather than an increase.

Glacial Sediment Production and Development of Hydro-Electric Power in Glacierized Areas

This paper discusses the results of a sediment-monitoring programme carried out in connection with hydro-electric power development plans in the river basins surrounding the Jostedalsbreen ice cap in Norway. Whereas the highest suspended-sediment transport rates occur during years with several flash-flood events, the bed load is more dependent upon the duration of large magnitude flood events. Bed-load transport has been obtained from annual measurements of deltaic growth in small lakes at the front of glaciers. During the years 1968–86, the mean ratio of bed load to total load amounted to 0.30–0.50% of the total load, but in years with large magnitude floods this ratio decreased. The mean annual suspended sediment yield of Norwegian glaciers ranges from 100 tonnes km2 a−1 to 1300 tonnes km2 a−1. Valley glaciers cause the highest erosion rates, with the exception of the small cirque glacier, Trollbergdalsbreen, which is thought to be a soft bed glacier. The investigation programme undertaken involved monitoring the volume of suspended sediments, together with the size distribution, mineralogy and shape of grains. In general, the valley glaciers supply more sand than the smaller cirque glaciers, whereas particles in the fine sand and silt-size ranges in almost all of the glaciers are angular in shape. Methods of comparing the abrasive capacity of the sediment load at various intakes in a power plant are discussed. Long-term sediment supply from the glaciers was investigated by studies of varves and rythmites in sediment cores from glacier-fed lakes.

Glacial Sediment Production and Development of Hydro-Electric Power in Glacierized Areas

This paper discusses the results of a sediment-monitoring programme carried out in connection with hydro-electric power development plans in the river basins surrounding the Jostedalsbreen ice cap in Norway. Whereas the highest suspended-sediment transport rates occur during years with several flash-flood events, the bed load is more dependent upon the duration of large magnitude flood events. Bed-load transport has been obtained from annual measurements of deltaic growth in small lakes at the front of glaciers. During the years 1968–86, the mean ratio of bed load to total load amounted to 0.30–0.50% of the total load, but in years with large magnitude floods this ratio decreased. The mean annual suspended sediment yield of Norwegian glaciers ranges from 100 tonnes km2 a−1 to 1300 tonnes km2 a−1. Valley glaciers cause the highest erosion rates, with the exception of the small cirque glacier, Trollbergdalsbreen, which is thought to be a soft bed glacier. The investigation programme undertaken involved monitoring the volume of suspended sediments, together with the size distribution, mineralogy and shape of grains. In general, the valley glaciers supply more sand than the smaller cirque glaciers, whereas particles in the fine sand and silt-size ranges in almost all of the glaciers are angular in shape. Methods of comparing the abrasive capacity of the sediment load at various intakes in a power plant are discussed. Long-term sediment supply from the glaciers was investigated by studies of varves and rythmites in sediment cores from glacier-fed lakes.