Mean Annual Suspended Sediment Load Research Articles

Catchment properties controlling suspended sediment transport in wind-water erosion crisscross region

Study regionWuding River catchment, the wind-water erosion crisscross region on the Chinese Loess Plateau. Study focusThe wind-water erosion crisscross region suffers severe soil erosion in the world, and various catchment properties control fluvial processes. This study investigated suspended sediment (SS) transport characteristics in a typical catchment with two geomorphological types (aeolian sand and loess hilly). Lorenz curves and partial least-squares regression were used to quantify the SS transport characteristics and attributions. New hydrological insights for the regionThere were significant differences in the SS transport characteristics between the two geomorphological regions. In the aeolian sand region, the mean annual SS loads were much lower than that in the loess hilly region (P < 0.01) under similar precipitation and runoff conditions. Rivers in this region transported SS all year round. The relatively lower concentration indicated that extreme events did not dominate total SS load. Conversely, SS transport in the loess hilly region was highly concentrated during a few events in rainy season, with the largest 10% of the events transporting exceed 80% of the total SS load. Statistical analysis showed that drainage density, catchment slope, and soil texture were the dominant factors controlling SS load, while the concentration of SS transport events was more related to the perimeter-area fractal. These findings have important implications for fluvial sediment transport in arid and semi-arid environments.

River Network and Reach‐Scale Controls on Habitat for Lamprey Larvae in the Umpqua River Basin, Oregon

AbstractThis study developed a spatially explicit framework to support the conservation of Western Brook Lamprey Lampetra richardsoni and Pacific Lamprey Entosphenus tridentatus in the Umpqua River basin, Oregon. This framework identified locations within the river network likely to support “potential burrowing habitat” for lamprey larvae based on geomorphic conditions and evaluated the overlap of potential burrowing habitat with water temperatures suitable for the nonnative, piscivorous Smallmouth Bass Micropterus dolomieu. The study also documented reach‐scale factors that create heterogeneity in potential burrowing habitat to guide on‐the‐ground habitat restoration. Based on criteria for mean annual suspended sediment loads and channel slope, 18% of the Umpqua River network was classified as potential burrowing habitat. Existing mean August water temperatures of ≥20°C were suitable for Smallmouth Bass for 32% of the potential burrowing habitat. This percentage increased to 41% of the potential burrowing habitat using projected mean August water temperatures for year 2040, suggesting that water temperatures in the future will facilitate upstream expansion of Smallmouth Bass into the potential burrowing habitat. At finer spatial scales, potential burrowing habitat was influenced by channel features, such as large wood, pools, and local channel slope and width. These results provide an initial template for identifying locations in river networks likely to have potential burrowing habitat, considering the overlap between threats and lamprey habitats, and planning conservation actions to support native lampreys.

STREAMFLOW AND SUSPENDED SEDIMENT LOAD TRENDS IN TROTUȘ DRAINAGE BASIN: GEOMORPHIC IMPLICATIONS

The research focusing on the trends of the streamflow and suspended sediment, as well as on the controls involved in these changes, are currently topics of significant interest in fluvial geomorphology. In this context, the aim of this study is to analyze the trends of the streamflow discharge and the sediment load based on a geomorphological approach of the relations between the two variables. These trends were assessed based on three testing methods frequently employed in hydro-geomorphological studies (Mann–Kendall trend test, Șen's slope estimator and the innovative trend method) applied on data from 10 gauging stations located on major tributaries of Trotuș River. Results reveal an overall downward trend of the mean annual streamflow and an increasing trend of the mean annual suspended sediment load. Whereas the decreasing streamflow trend was linked to the diminishing precipitation amounts, the upward trend of suspended sediment load was related to the changes occurring within river channels as a result of flood events.

Annual suspended sediment load of the Yenisei river

Field studies, including high-frequency sampling for suspended sediment flux estimation, were conducted in 20142016 in the city of Igarka, at the outlet of the Yenisei River. During spring freshet of each year, multiple suspended sediment concentration (SSC) peaks were observed, irrelated to water discharge fluctuations. The form of hysteresis loops evidences the importance of input from local in-channel sediment sources, i.e. banks and bedforms, and scouring of bed material, deposited during winter, in observed sharp SSC peaks. On the falling stage of the freshet, longer peaks are related to sediment waves from major tributaries, notably the Nizhnyaya Tunguska River. Annual sediment load was calculated based on the daily water discharge and observed SSC data, using sediment rating curves and LOADEST models as two reference methods. Mean annual suspended sediment load of the Yenisei River in Igarka is estimated at 8.1 0.5 mln t., which significantly exceeds previously published values for the 19702001 period, from 4.6 to 5.9 mln t. Cumulative sediment load for 20142016 totals 24.2 2.1 mln t.

Suspended sediment transport in the Magdalena River (Colombia, South America): Hydrologic regime, rating parameters and effective discharge variability

The Magdalena River has the greatest length (1612km) and drainage area (257400km2) of any river system in Colombia, and its watershed occupies 24% of the Colombian territory. The river originates in the Andean Cordillera at an elevation of 3685m and flows to its mouth in the Caribbean Sea (Bocas de Cenizas). For this study, information on daily flow discharge (Q), suspended sediment transport (Qs) and mean suspended sediment concentration (Cs) from 1990–2010 for the Magdalena River, based on measurements at the Calamar gauging station (the closest station to the mouth), was provided by the Institute of Hydrology, Meteorology and Environmental Studies of Colombia (IDEAM in Spanish). The mean annual suspended sediment load was 169±73×106tyr−1 for the period from 1990–1999 and 145±47×106tyr−1 for the period from 2000–2010, amounting to a 14% reduction in the suspended sediment transport rate between the two periods. The sediment rating curve (Qs=aQb) was also evaluated for these two periods (1990–1999 and 2000–2010). An analysis of the regression coefficients (a, b) for the two periods showed a decrease in b and an increase in a after 1999, which coincides with a decrease in suspended sediment transport. This change might be attributed to natural factors, including the accumulation of sediment in the Depresion Momposina and variation in hydro-climatological patterns in the Caribbean region. Decreases in effective transport were confirmed using three methods (Log-Normal and Normal distribution, and magnitude-frequency histogram) for the study period.

Contribution of diffuse hillslope erosion to the sediment export of French rivers

Soil erosion is one of the major drivers of landscape evolution in Western Europe. However, depending on the land use characteristics and on the geological and topographical settings, miscellaneous forms of erosion may lead to a very diverse morphological evolution. A key element is the connection between the hillslope and the river. In this context, the objective of this study is to investigate to what extent eroded soil particles contribute to river sediment exports for the major French basins. The hillslope erosion rates are deduced from a distributed pan-European assessment of hillslope, rill, and interrill erosion by water, which was quantified by interpolation of erosion plot data as a function of topographical, land use, and pedological parameters. Sediment fluxes were mainly assessed from the French river quality database using an improved rating curve approach from the daily discharge data (IRCA), which allows estimation of the mean annual suspended sediment load. A similar approach based on the same datasets was used to calculate the mean annual dissolved load over the same period. The resulting mean annual suspended sediment loads show that French rivers export approximately 50 Mt of sediments per year to the seas, including ca. 17 Mt as particulate matter, corresponding to a specific sediment yield of ca. 0.4tha−1yr−1. No relationship was found between the mass of the exported sediment and the size of the drainage basins, but large differences were observed between the different basins. For the Seine river basin and the Rhône river basin, the estimated average gross erosion rates are comparable, with ca. 1.14tha−1yr−1 for the Rhone and ca. 1.80tha−1yr−1 for the Seine. In contrast, the Rhône exports ca. 10 times more than the Seine River. The ratio of gross erosion to sediment exports calculated in this work ranges from 6.8% for the Seine to more than 100% for the Rhône. To explain these variations, we propose the use of indices that represent the landscape patchiness and connectivity.

Reach-scale suspended sediment balance downstream from dams in a large Mediterranean river

This paper presents a reach-scale sediment balance of a large impounded Mediterranean river (the lower Ebro, 1998–2008). Multi-temporal sediment storage and the influence of floods and tributaries on the sediment load were examined using continuous discharge and turbidity records. The mean annual suspended sediment load at the reach outlet (Xerta) is 0.12 × 106 t, corroborating previous results. Suspended sediment concentrations were low (SSCmean = 13 mg L-1), attaining a maximum of 274 mg L-1. Erosion processes (channel-scour, bank erosion) are dominant, and net export of sediment occurs over the long term. Unexpectedly, ephemeral tributaries were found to contribute significantly: sediment delivered during torrential events attained 5% of the Ebro annual load, and was even larger than that in flushing flows. Overall, most of the suspended sediment load is transported by floods (up to 65% in some years). The results constitute basic information to underpin current management actions aiming to achieve the sustainability of the riverine and deltaic system. Editor D. Koutsoyiannis; Associate editor D. Hughes Citation Tena, A., Batalla, R.J. and Vericat, D., 2012. Reach-scale suspended sediment balance downstream from dams in a large Mediterranean river. Hydrological Sciences Journal, 57 (5), 831–849.

Integrating farming systems and landscape processes to assess management impacts on suspended sediment loads

A catchment-scale framework was developed to assess the contribution of sediment sources from farm management actions, gully and streambank erosion on the suspended sediment loads delivered to rivers and associated wetlands and floodplains for two catchments (Avon Richardson, 2885 km 2 and Avoca, 4550 km 2) in Victoria, south-eastern Australia. After considering commonly available data sets, outputs from the point-scale model (HowLeaky2008) were coupled to a catchment scale framework (CatchMODS). Spatially constant, linear scaling factors were used to link point-scale water surplus to streamflow and gross soil loss to hillslope erosion. The model was calibrated against discharge and suspended sediment loads estimated at water quality monitoring gauging stations. Following calibration, estimates of annual and monthly streamflow and 10-year average annual sediment loads were in good agreement with observations. Catchment-scale outputs, particularly sediment loads, were sensitive to scaling factors. The high sensitivity coupled with limited data hindered tight identification of sediment scaling parameters, therefore sediment outputs were uncertain, particularly in the Avoca catchment. Propagation of uncertainty in parameter estimation to model estimates was assessed qualitatively. The boundaries of model estimations were assessed by retaining predictions of behavioural parameter sets, defined as parameter sets that resulted in efficiencies of sediment load and specific sediment yield estimations not more than 5% lower than the efficiency of the optimal parameter set. Under current management conditions, mean annual suspended sediment load at the Avon-Richardson catchment outlet was estimated to be 3350 (3300–3700) t y −1, of which hillslope erosion contributed 65% (60–80%) and gully erosion 35% (20–40%). In the Avoca catchment, annual suspended sediment load was estimated to be 4000 (3500–5100) t y −1, of which hillslope erosion contributed 17% (5–24%), gully erosion 72% (55–93%), and streambank erosion 11% (1–21%). In the Avon-Richardson catchment management scenarios showed that alternative farming systems focussed on retaining vegetation cover throughout the year would yield a 50 per cent reduction of suspended sediment load, estimated at 1700 t y −1. In contrast, fencing and revegetation of connected gullies was estimated to yield the largest reduction in suspended sediment load (1770 t y −1, 44% of current load) in the Avoca catchment. The framework provides an improved tool to make more informed decisions about how much suspended sediment loads can be reduced in response to farm management actions, gully and streambank protection. Its primary strength lies in the ability to propagate farm management impacts to the catchment scale. Other valuable features for use by natural resource management agencies include a high level of transparency, availability of user-friendly interfaces, and a modular structure that provides flexibility and adaptability to new systems.

Composite suspended sediment particles in river systems: their incidence, dynamics and physical characteristics

AbstractMost of the existing data on the effective particle size characteristics of fluvial suspended sediment derive from instantaneous sampling methods that may not be representative of the overall suspended sediment loads. This presents difficulties when there is a need to incorporate effective particle size data into numerical models of floodplain sedimentation and sediment‐associated contaminant transfer. We have used a field‐based water elutriation apparatus (WEA) to assemble a large (36 flood) database on the time‐integrated nature of the effective and absolute particle size characteristics of suspended sediment in four subcatchments of the River Exe basin of southwest England. These catchments encompass a wide range of terrains and fluvial environments that are broadly representative of much of the UK and temperate, low relief northwest Europe. The WEA provides important data on the physical characteristics of composite particles that are not attainable using other methods. This dataset has allowed, for the first time, detailed interbasin comparisons of the time‐integrated particle size characteristics of suspended sediment and reliable estimates of the contribution of five effective size classes to the mean annual suspended sediment load of the study catchments. The suspended sediment load of each river is dominated by composite rather than primary particles, with, for example, almost 60% (by mass) of the sediment load of the River Exe at Thorverton transported as composite particles &gt; 16 µm in size. All the effective size classes contain significant clay components. A key outcome of this study is the recognition that each catchment has a distinctive time‐integrated effective particle size signature. In addition, the time‐integrated effective particle size characteristics of the suspended loads in each of the catchments display much greater spatial variability than the equivalent absolute particle size distributions. This indicates that the processes producing composite particles vary significantly between these catchments, and this has important implications for our understanding of the dynamics of suspended sediment properties. Copyright © 2007 John Wiley &amp; Sons, Ltd.

The storage and provenance of fine sediment on the channel bed of two contrasting lowland permeable catchments, UK

AbstractFine sediment (&lt;63 µm) storage in river channels frequently represents a significant term in catchment sediment budgets and plays an important role in diffuse pollution problems. A combination of a sediment remobilization technique and the fingerprinting approach was used to examine the storage and provenance of fine sediment on the channel bed of two contrasting lowland permeable catchments in the UK. In the upper Tern (∼231 km2) study catchment, estimates of mean fine sediment storage on the channel bed ranged between 860–5500 g m−2, with an overall average of 2391 g m−2, compared to 470–2290 g m−2 and 1065 g m−2 in the Pang (∼166 km2) and 770–1760 g m−2 and 1255 g m−2 in the Lambourn (∼234 km2) sub‐catchments. Mean total fine sediment storage on the bed of the main channel was equivalent to 37% (upper Tern), 38% (Pang) and 21% (Lambourn) of the mean annual suspended sediment loads measured at the catchment outlets. Over the study period, the total gain (1427 t) and loss (1877 t) to fine sediment storage on the channel bed in the upper Tern catchment were equivalent to 82% and 108% of the mean annual suspended sediment load, respectively, compared to 149% (740 t) and 136% (678 t) in the Pang sub‐catchment, and 39% (422 t) and 49% (528 t) in the Lambourn sub‐catchment. The source of the fine sediment stored on the channel bed within each study area varied. In the upper Tern catchment, the weighted mean relative contributions from individual source types were estimated to be 35 ± 5% (pasture), 51 ± 5% (cultivated) and 14 ± 3% (channel banks and subsurface sources). The corresponding estimates were 49 ± 8%, 33 ± 5% and 18 ± 5% for the Pang sub‐catchment, compared to 19 ± 6%, 64 ± 5% and 17 ± 5% for the Lambourn sub‐catchment. These sediment source estimates have important implications for the design and implementation of targeted sediment control policies within the study areas. Copyright © 2007 John Wiley &amp; Sons, Ltd.

Fluvial process and morphology of the Brahmaputra River in Assam, India

The Brahmaputra River finds its origin in the Chema Yundung glacier of Tibet and flows through India and Bangladesh. The slope of the river decreases suddenly in front of the Himalayas and results in the deposition of sediment and a braided channel pattern. It flows through Assam, India, along a valley comprising its own Recent alluvium. In Assam the basin receives 300 cm mean annual rainfall, 66–85% of which occurs in the monsoon period from June through September. Mean annual discharge at Pandu for 1955–1990 is 16,682.24 m 3 s − 1. Average monthly discharge is highest in July (19%) and lowest in February (2%). Most hydrographs exhibit multiple flood peaks occurring at different times from June to September. The mean annual suspended sediment load is 402 million tons and average monthly sediment discharge is highest in June (19.05%) and lowest in January (1.02%). The bed load at Pandu was found to be 5–15% of the total load of the river. Three kinds of major geomorphic units are found in the basin. The river bed of the Brahmaputra shows four topographic levels, with increasing height and vegetation. The single first order primary channels of this braided river split into two or more smaller second order channels separated by bars and islands. The second order channels are of three kinds. The maximum length and width of the bars in the area under study are 18.43 km and 6.17 km, respectively. The Brahmaputra channel is characterised by mid-channel bars, side bars, tributary mouth bars and unit bars. The geometry of meandering tributary rivers shows that the relationship between meander wavelength and bend radius is most linear. The Brahmaputra had been undergoing overall aggradation by about 16 cm during 1971 to 1979. The channel of the Brahmaputra River has been migrating because of channel widening and avulsion. The meandering tributaries change because of neck cut-off and progressive shifting at the meander bends. The braiding index of the Brahmaputra has been increasing from 6.11 in 1912–1928 to 8.33 in 1996. During the twentieth century, the total amount of bank area lost from erosion was 868 km 2. Maximum rate of shift of the north bank to south resulting in erosion was 227.5 m/year and maximum rate of shift of the south bank to north resulting in accretion was 331.56 m/year. Shear failure of upper bank and liquefaction of clayey-silt materials are two main causes of bank erosion.

Suspended Sediment Transport in the Storglaciären Drainage Basin

The mean annual suspended sediment load in the Storglaciaren drainage basin is estimated to be 5.74×106kg yr-1. Assuming, that erosion and sedimentation in the proglacial area is in balance, the sp...

Causes and effects of siltation on the environment of Nepal

The present investigation was carried out in 1986, and is based upon about 20 years of river discharge data (1960s to 1980s). There are three important river-systems in Nepal - Sapt Kosi River system in East Nepal, Sapt Gandaki River system in mid- Nepal, and Karnali River system in West Nepal. The average annual highest rainfall is 3,685 mm yr−1, and the greatest mean annual suspended sediment load (1.434 g L−1) was recorded in Sapt Gandaki, while the water discharge from Sapt Kosi (1,747 m3 s−1) was the highest and so also was the silt discharge (0.4 million ton day−1). The correlation between water discharge and silt discharge was found to be statistically highly significant as verified by correlation and regression analyses.