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Line, Dan E., Deanna L. Osmond y Wesley Childres. "Nutrient Export from Agricultural Watersheds in the Piedmont and Coastal Plain, North Carolina". Transactions of the ASABE 62, n.º 5 (2019): 1135–45. http://dx.doi.org/10.13031/trans.13052.
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Abstract. Nitrogen (N) and phosphorus (P) input and export rates were determined in six rural, predominantly agricultural watersheds located in the Piedmont and Coastal Plain regions of North Carolina. Water quality monitoring was conducted at the outlets for 2.3 to 8.0 years to determine the annual N and P export from each watershed. Total N and P input and export from five of the six watersheds were correlated, with only a no-till cropland watershed differing. The correlation showed that N and P exports increased by about 4.0% and 8.7%, respectively, of applied N and P for the range of applications rates, whereas dissolved N (NOx-N) export increased by 2.8% with increasing N application rates. Therefore, practices that reduce inputs, such as nutrient management, should result in similar percentage reductions in exports. The Small Watershed Nutrient Forecasting Tool (SWIFT) was used to forecast discharge, N, P, and sediment export from each of the six watersheds. For the no-till cropland watershed, the SWIFT-forecasted N and P export rates were more than 2.5 times those measured, while the sediment export rate was 72 times the measured value. Thus, these data showed that the SWIFT forecasts for N, P, and sediment export were poor for the no-till cropland watershed. For the pasture watershed, the SWIFT forecasts for N and sediment export agreed reasonably well with measured export; however, the forecasted P export was much less than measured. For the four mixed land use watersheds, the SWIFT forecasts for discharge, TN, and sediment were mostly greater than measured, and the forecasted TP export was less than measured for three of the four watersheds. Thus, as with many predicstion tools, SWIFT results must be used with caution. Keywords: Nutrient export, Nutrient management practice, Water quality monitoring.
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Djunarsjah, E., M. M. Julian, A. A. Baskoro y N. R. Alfandi. "Spatial Modeling of Sediment Export Rate with Rainfall Variability Scenario in Peusangan Watershed, Aceh Province". IOP Conference Series: Earth and Environmental Science 925, n.º 1 (1 de noviembre de 2021): 012026. http://dx.doi.org/10.1088/1755-1315/925/1/012026.
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Abstract The rainfall affects the environmental interaction of watersheds and coastal areas. The high intensity of rain and water runoff will lift and carry particles in the watershed environment in the erosion process. This study estimates the total exports of sediment in Peusangan Watershed in the period 1995, 2005, 2015, and 2018 with rainfall variability scenarios. Total sediment exports are calculated from the erosion rate and sediment delivery ratio (SDR). Erosion rate modeling uses the RUSLE (Revised Universal Soil Loss Equation) that takes into account erosivity of rainfall, soil erodiability, topography, land cover, and land-use practices. While SDR is calculated based on its function as watershed area so that homogeneous value that causes the value of sediment export rate is directly proportional to the erosion rate value. The correlation between rainfall variability and sediment export rates is calculated based on rainfall variability correlation to erosion rate change. There is a direct relationship between rainfall variability and sediment export rates because the correlation coefficient is close to one. The rate of erosion in Peusangan watersheds falls into the light category based on the classification of erosion hazard levels according to the Ministry of Forestry in 1998. Based on the estimated rate of erosion and SDR, the total annual number of sediment exports obtained in the Peusangan watershed in 1995, 2005, 2015, and 2018 amounted to 1,066,027,426 tons, 909,914,623 tons, 1,075,759,133 tons, and 1,085,490,841 tons, respectively. Based on the spatial distribution of sediment export, Peusangan Watershed falls into the category of normal erosion.
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Santos, Ana Isabel, Anabela Oliveira, José Paulo Pinto y M. Conceição Freitas. "Hydrodynamic and Sediment Transport Patterns in the Minho and Douro Estuaries (NW Portugal) Based on ADCP Monitoring Data: Part 1-Tidal Sediment Exchanges". Coasts 1, n.º 1 (11 de noviembre de 2021): 31–55. http://dx.doi.org/10.3390/coasts1010003.
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The tidal variability of the Minho and Douro lower estuaries (NW Portugal) water column structure was assessed at the semi-diurnal and fortnightly time scales under two contrasting seasonal river flow scenarios during the summer of 2005 and winter of 2006. Sediment fluxes inferred from calibrated ADCP acoustic backscatter revealed that, during spring tides and low runoff conditions, both estuaries act as sinks instead of sources of sediments into the inner shelf. Sediment export occurred during neaps, in both estuaries, when the river flow values were high enough to counteract the effect of the entering flood. No evidence of coarse sediment export into the inner shelf that would eventually nourish the littoral system could be inferred from these datasets.
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Kulsoontornrat, Jiraporn y Suwit Ongsomwang. "Suitable Land-Use and Land-Cover Allocation Scenarios to Minimize Sediment and Nutrient Loads into Kwan Phayao, Upper Ing Watershed, Thailand". Applied Sciences 11, n.º 21 (5 de noviembre de 2021): 10430. http://dx.doi.org/10.3390/app112110430.
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Human activity and land-use changes have affected the water quality of Kwan Phayao, Upper Ing watershed, due to the associated high sediment load and eutrophication. This study aims to identify suitable LULC allocation scenarios for minimizing sediment and nutrient export into the lake. For this purpose, the LULC status and change were first assessed, based on classified LULC data in 2009 and 2019 from Landsat images, using the SVM algorithm. Later, the land requirements of three scenarios between 2020 and 2029 were estimated, based on their characteristics, and applied to predict LULC change using the CLUE-S model. Then, actual LULC data in 2019 and predicted LULC data under three scenarios between 2020 and 2029 were used to estimate sediment and nutrient export using the SDR and NDR models. Finally, the ecosystem service change index identified a suitable LULC allocation for minimizing sediment or/and nutrient export. According to the results, LULC status and change indicated perennial trees and orchards, para rubber, and rangeland increased, while forest land and paddy fields decreased. The land requirements of the three scenarios provided reasonable results, as expected, particularly Scenario II, which adopts linear programming to calculate the land requirements for maximizing ecosystem service values. For sediment and nutrient export estimation under the predicted LULC for the three scenarios, Scenario II led to the lowest yield of sediment and nutrient exports, and provided the lowest average ESCI value among the three scenarios. Thus, the LULC allocation under Scenario II was chosen as suitable for minimizing sediment or/and nutrient export into Kwan Phayao. These results can serve as crucial information to minimize sediment and nutrient loads for land-use planners, land managers, and decision makers.
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Nugroho, N. P. "Sediment export estimation from the catchment area of Lake Rawapening using InVEST model". IOP Conference Series: Earth and Environmental Science 950, n.º 1 (1 de enero de 2022): 012072. http://dx.doi.org/10.1088/1755-1315/950/1/012072.
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Abstract Sedimentation is one of the main problems of the fifteen priority lakes in Indonesia, including Lake Rawapening. It has adverse impacts on lake, such as siltation that contribute to eutrophication and reduce the lake’s lifetime. Therefore, reducing sedimentation rate was set as one of the super-priority programs of the Lake Rescue Movement. Information on the spatial distribution of sediment export becomes important to implement the program effectively. This study aims to estimate the magnitude and the spatial distribution of sediment export from the catchment area of Lake Rawapening. The analysis was based on the Sediment Delivery Ratio sub-model. The results indicated that the total sediment export from the catchment area of Lake Rawapening is 501,628.6 tons/year. The largest export of sediment came from Galeh Sub-sub watershed, i.e., 161,091.7 tons/year (32.1% of the total sediment). However, Legi Sub-sub watershed has the highest average of sediment export per hectare, i.e., 42.9 tons/ha. High sediment export generally occurs in the upstream area with very steep slope, high rainfall, and dominated by dryland agriculture and vegetable farm land. Thus, efforts to reduce sediment export to Lake Rawapening should be focused on the hot-spot area, such as the upstream area of Legi Sub-sub watershed.
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Ariagno, Coline, Caroline Le Bouteiller, Peter van der Beek y Sébastien Klotz. "Sediment export in marly badland catchments modulated by frost-cracking intensity, Draix–Bléone Critical Zone Observatory, SE France". Earth Surface Dynamics 10, n.º 1 (21 de enero de 2022): 81–96. http://dx.doi.org/10.5194/esurf-10-81-2022.
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Abstract. At the interface between the lithosphere and the atmosphere, the critical zone records the complex interactions between erosion, climate, geologic substrate, and life and can be directly monitored. Long data records (30 consecutive years for sediment yields) collected in the sparsely vegetated, steep, and small marly badland catchments of the Draix–Bléone Critical Zone Observatory (CZO), SE France, allow analyzing potential climatic controls on regolith dynamics and sediment export. Although widely accepted as a first-order control, rainfall variability does not fully explain the observed interannual variability in sediment export. Previous studies in this area have suggested that frost-weathering processes could drive regolith production and potentially modulate the observed pattern of sediment export. Here, we define sediment export anomalies as the residuals from a predictive model with annual rainfall intensity above a threshold as the control. We then use continuous soil temperature data recorded at different locations over multiple years to highlight the role of different frost-weathering processes (i.e., ice segregation versus volumetric expansion) in regolith production. Several proxies for different frost-weathering processes have been calculated from these data and compared to the sediment export anomalies, with careful consideration of field data quality. Our results suggest that frost-cracking intensity (linked to ice segregation) can explain about half (47 %–64 %) of the sediment export anomalies. In contrast, the number of freeze–thaw cycles (linked to volumetric expansion) has only a minor impact on catchment sediment response. The time spent below 0 ∘C also correlates well with the sediment export anomalies and requires fewer field data to be calculated than the frost-cracking intensity. Thus, frost-weathering processes modulate sediment export by controlling regolith production in these catchments and should be taken into account when building predictive models of sediment export from these badlands under a changing climate.
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Teng, Tse-Yang, Jr-Chuan Huang, Tsung-Yu Lee, Yi-Chin Chen, Ming-Young Jan y Cheng-Chien Liu. "Investigating Sediment Dynamics in a Landslide-Dominated Catchment by Modeling Landslide Area and Fluvial Sediment Export". Water 12, n.º 10 (18 de octubre de 2020): 2907. http://dx.doi.org/10.3390/w12102907.
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Few models are capable of simultaneously simulating the sequences of landslide occurrence and sediment export. Quantification of the temporarily stored sediment within the watershed plays a key role to link hillslope landslides with fluvial sediment export. In this study, two coupled models were proposed to simulate time-series total landslide area and the subsequent sediment export on a daily basis with only the inputs of rainfall and runoff. The landslide model considers per-existing and models new landslide, and the sediment transport model incorporates a sediment storage variable. The landslide and sediment transport model were well evaluated with Nash-Sutcliffe efficiency (EC) of 0.89 and logarithmic Nash-Sutcliffe efficiency (EClog) of 0.90, respectively, in the Tsengwen Reservoir watershed in southern Taiwan by using long-term observed data (2005–2015). It is found that reactivated landslides were up to 72% of the pre-landslide area, which contributed sediment comparable to the new landslide. Besides, the landslide model indicates that pre-landslide area controls the total landslide area but when rainfall is large it takes control in turn. With the simulation of sediment storage, the sediment transport model can well simulate the sediment export after the catastrophic event (typhoon Morakot in 2009). During the post-Morakot period, small rainfall and runoff can lead to high sediment export owing to the storage of Morakot-triggered landslide. This model will be a useful tool to diagnose the sediment dynamics in the watershed.
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Chiang, Li-Chi, Yung-Chieh Wang y Ci-Jyun Liao. "Spatiotemporal Variation of Sediment Export from Multiple Taiwan Watersheds". International Journal of Environmental Research and Public Health 16, n.º 9 (8 de mayo de 2019): 1610. http://dx.doi.org/10.3390/ijerph16091610.
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Soil erosion and landslide triggered by heavy rainfall are serious problems that have threatened water resources in Taiwan watersheds. This study investigated the relationship among streamflow, sediment load, sediment concentration and typhoon characteristics (path and rainfall amount) during 2000–2017 for nine gauging stations in five basins (Tamshui River basin, Zhuoshui River basin, Zengwen River basin, Gaoping River basin, and Hualien River basin) representing the diverse geomorphologic conditions in Taiwan. The results showed that streamflow and sediment load were positively correlated, and the correlation was improved when the sediment load data were grouped by sediment concentration. Among these basins, the Zhuoshui River basin has the highest unit-discharge sediment load and unit-area sediment load. The soil in the upstream was more erodible than the downstream soil during the normal discharge conditions, indicating its unique geological characteristics and how typhoons magnified sediment export. The spatiotemporal variation in sediment loads from different watersheds was further categorized by typhoons of different paths. Although typhoon path types matter, the Zhuoshui and Hualien River basin were usually impacted by typhoons of any path type. The results indicated that sediment concentration, the watershed soil characteristics, and typhoons paths were the key factors for sediment loads. This study can be useful for developing strategies of soil and water conservation implementation for sustainable watershed management.
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Costa, Anna, Peter Molnar, Laura Stutenbecker, Maarten Bakker, Tiago A. Silva, Fritz Schlunegger, Stuart N. Lane, Jean-Luc Loizeau y Stéphanie Girardclos. "Temperature signal in suspended sediment export from an Alpine catchment". Hydrology and Earth System Sciences 22, n.º 1 (22 de enero de 2018): 509–28. http://dx.doi.org/10.5194/hess-22-509-2018.
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Abstract. Suspended sediment export from large Alpine catchments (> 1000 km2) over decadal timescales is sensitive to a number of factors, including long-term variations in climate, the activation–deactivation of different sediment sources (proglacial areas, hillslopes, etc.), transport through the fluvial system, and potential anthropogenic impacts on the sediment flux (e.g. through impoundments and flow regulation). Here, we report on a marked increase in suspended sediment concentrations observed near the outlet of the upper Rhône River Basin in the mid-1980s. This increase coincides with a statistically significant step-like increase in basin-wide mean air temperature. We explore the possible explanations of the suspended sediment rise in terms of changes in water discharge (transport capacity), and the activation of different potential sources of fine sediment (sediment supply) in the catchment by hydroclimatic forcing. Time series of precipitation and temperature-driven snowmelt, snow cover, and ice melt simulated with a spatially distributed degree-day model, together with erosive rainfall on snow-free surfaces, are tested to explore possible reasons for the rise in suspended sediment concentration. We show that the abrupt change in air temperature reduced snow cover and the contribution of snowmelt, and enhanced ice melt. The results of statistical tests show that the onset of increased ice melt was likely to play a dominant role in the suspended sediment concentration rise in the mid-1980s. Temperature-driven enhanced melting of glaciers, which cover about 10 % of the catchment surface, can increase suspended sediment yields through an increased contribution of sediment-rich glacial meltwater, increased sediment availability due to glacier recession, and increased runoff from sediment-rich proglacial areas. The reduced extent and duration of snow cover in the catchment are also potential contributors to the rise in suspended sediment concentration through hillslope erosion by rainfall on snow-free surfaces, and increased meltwater production on snow-free glacier surfaces. Despite the rise in air temperature, changes in mean discharge in the mid-1980s were not statistically significant, and their interpretation is complicated by hydropower reservoir management and the flushing operations at intakes. Overall, the results show that to explain changes in suspended sediment transport from large Alpine catchments it is necessary to include an understanding of the multitude of sediment sources involved together with the hydroclimatic conditioning of their activation (e.g. changes in precipitation, runoff, air temperature). In addition, this study points out that climate signals in suspended sediment dynamics may be visible even in highly regulated and human-impacted systems. This is particularly relevant for quantifying climate change and hydropower impacts on streamflow and sediment budgets in Alpine catchments.
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Tofelde, Stefanie, Sara Savi, Andrew D. Wickert, Aaron Bufe y Taylor F. Schildgen. "Alluvial channel response to environmental perturbations: fill-terrace formation and sediment-signal disruption". Earth Surface Dynamics 7, n.º 2 (1 de julio de 2019): 609–31. http://dx.doi.org/10.5194/esurf-7-609-2019.
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Abstract. The sensitivity of fluvial systems to tectonic and climatic boundary conditions allows us to use the geomorphic and stratigraphic records as quantitative archives of past climatic and tectonic conditions. Thus, fluvial terraces that form on alluvial fans and floodplains as well as the rate of sediment export to oceanic and continental basins are commonly used to reconstruct paleoenvironments. However, we currently lack a systematic and quantitative understanding of the transient evolution of fluvial systems and their associated sediment storage and release in response to changes in base level, water input, and sediment input. Such knowledge is necessary to quantify past environmental change from terrace records or sedimentary deposits and to disentangle the multiple possible causes for terrace formation and sediment deposition. Here, we use a set of seven physical experiments to explore terrace formation and sediment export from a single, braided channel that is perturbed by changes in upstream water discharge or sediment supply, or through downstream base-level fall. Each perturbation differently affects (1) the geometry of terraces and channels, (2) the timing of terrace cutting, and (3) the transient response of sediment export from the basin. In general, an increase in water discharge leads to near-instantaneous channel incision across the entire fluvial system and consequent local terrace cutting, thus preserving the initial channel slope on terrace surfaces, and it also produces a transient increase in sediment export from the system. In contrast, a decreased upstream sediment-supply rate may result in longer lag times before terrace cutting, leading to terrace slopes that differ from the initial channel slope, and also lagged responses in sediment export. Finally, downstream base-level fall triggers the upstream propagation of a diffuse knickzone, forming terraces with upstream-decreasing ages. The slope of terraces triggered by base-level fall mimics that of the newly adjusted active channel, whereas slopes of terraces triggered by a decrease in upstream sediment discharge or an increase in upstream water discharge are steeper compared to the new equilibrium channel. By combining fill-terrace records with constraints on sediment export, we can distinguish among environmental perturbations that would otherwise remain unresolved when using just one of these records.
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Schmidt, Lena Katharina, Till Francke, Peter Martin Grosse y Axel Bronstert. "Projecting sediment export from two highly glacierized alpine catchments under climate change: exploring non-parametric regression as an analysis tool". Hydrology and Earth System Sciences 28, n.º 1 (9 de enero de 2024): 139–61. http://dx.doi.org/10.5194/hess-28-139-2024.
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Abstract. Future changes in suspended sediment export from deglaciating high-alpine catchments affect downstream hydropower reservoirs, flood hazard, ecosystems and water quality. Yet, quantitative projections of future sediment export have so far been hindered by the lack of process-based models that can take into account all relevant processes within the complex systems determining sediment dynamics at the catchment scale. As a promising alternative, machine-learning (ML) approaches have recently been successfully applied to modeling suspended sediment yields (SSYs). This study is the first, to our knowledge, exploring a machine-learning approach to derive sediment export projections until the year 2100. We employ quantile regression forest (QRF), which proved to be a powerful method to model past SSYs in previous studies, for two nested glaciated high-alpine catchments in the Ötztal, Austria, above gauge Vent (98.1 km2) and gauge Vernagt (11.4 km2). As predictors, we use temperature and precipitation projections (EURO-CORDEX) and discharge projections (AMUNDSEN physically based hydroclimatological and snow model) for the two gauges. We address uncertainties associated with the known limitation of QRF that underestimates can be expected if values in the projection period exceed the range represented in the training data (out-of-observation-range days, OOOR). For this, we assess the frequency and extent of these exceedances and the sensitivity of the resulting mean annual suspended sediment concentration (SSC) estimates. We examine the resulting SSY projections for trends, the estimated timing of peak sediment and changes in the seasonal distribution. Our results show that the uncertainties associated with the OOOR data points are small before 2070 (max. 3 % change in estimated mean annual SSC). Results after 2070 have to be treated more cautiously as OOOR data points occur more frequently, and glaciers are projected to have (nearly) vanished by then in some projections, which likely substantially alters sediment dynamics in the area. The resulting projections suggest decreasing sediment export at both gauges in the coming decades, regardless of the emission scenario, which implies that peak sediment has already passed or is underway. This is linked to substantial decreases in discharge volumes, especially during the glacier melt phase in late summer, as a result of increasing temperatures and thus shrinking glaciers. Nevertheless, high(er) annual yields can occur in response to heavy summer precipitation, and both developments would need to be considered in managing sediments, as well as e.g., flood hazard. While we chose the predictors to act as proxies for sediment-relevant processes, future studies are encouraged to try and include geomorphological changes more explicitly, e.g., changes in connectivity, landsliding, rockfalls or vegetation colonization, as these could improve the reliability of the projections.
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Stacy, E. M., S. C. Hart, C. T. Hunsaker, D. W. Johnson y A. A. Berhe. "Soil carbon and nitrogen erosion in forested catchments: implications for erosion-induced terrestrial carbon sequestration". Biogeosciences 12, n.º 16 (17 de agosto de 2015): 4861–74. http://dx.doi.org/10.5194/bg-12-4861-2015.
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Abstract. Lateral movement of organic matter (OM) due to erosion is now considered an important flux term in terrestrial carbon (C) and nitrogen (N) budgets, yet most published studies on the role of erosion focus on agricultural or grassland ecosystems. To date, little information is available on the rate and nature of OM eroded from forest ecosystems. We present annual sediment composition and yield, for water years 2005–2011, from eight catchments in the southern part of the Sierra Nevada, California. Sediment was compared to soil at three different landform positions from the source slopes to determine if there is selective transport of organic matter or different mineral particle size classes. Sediment export varied from 0.4 to 177 kg ha−1, while export of C in sediment was between 0.025 and 4.2 kg C ha−1 and export of N in sediment was between 0.001 and 0.04 kg N ha−1. Sediment yield and composition showed high interannual variation. In our study catchments, erosion laterally mobilized OM-rich litter material and topsoil, some of which enters streams owing to the catchment topography where steep slopes border stream channels. Annual lateral sediment export was positively and strongly correlated with stream discharge, while C and N concentrations were both negatively correlated with stream discharge; hence, C : N ratios were not strongly correlated to sediment yield. Our results suggest that stream discharge, more than sediment source, is a primary factor controlling the magnitude of C and N export from upland forest catchments. The OM-rich nature of eroded sediment raises important questions about the fate of the eroded OM. If a large fraction of the soil organic matter (SOM) eroded from forest ecosystems is lost during transport or after deposition, the contribution of forest ecosystems to the erosion-induced C sink is likely to be small (compared to croplands and grasslands).
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Vanmaercke, M., F. Obreja y J. Poesen. "Impact of earthquake-triggered landslides on catchment sediment yield". Proceedings of the International Association of Hydrological Sciences 367 (3 de marzo de 2015): 291–96. http://dx.doi.org/10.5194/piahs-367-291-2015.
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Abstract. This study explores the role of seismic activity in explaining spatial and temporal variation in sediment export from the Siret basin in Romania. Based on long-term (>30 years) sediment export measurements for 38 subcatchments, we found that spatial variation in sediment yield (SY) is strongly correlated to the degree of seismic activity and catchment lithology. Combined, these factors explain 80% of the variation in SY. To investigate the role of earthquake-triggered landslides in explaining these correlations, we studied the temporal variability in sediment concentrations before and after the 7.4 Mw earthquake of 1977 for ten subcatchments. Despite the fact that this earthquake triggered many landslides, only one subcatchment showed a clear (3-fold) increase in sediment concentration per unit discharge after the earthquake. This shows that, although prolonged seismic activity strongly controls average SY, individual earthquakes do not necessarily affect sediment export at short timescales.
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Lee, Hyejung, Valier Galy, Xiaojuan Feng, Camilo Ponton, Albert Galy, Christian France-Lanord y Sarah J. Feakins. "Sustained wood burial in the Bengal Fan over the last 19 My". Proceedings of the National Academy of Sciences 116, n.º 45 (21 de octubre de 2019): 22518–25. http://dx.doi.org/10.1073/pnas.1913714116.
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The Ganges–Brahmaputra (G-B) River system transports over a billion tons of sediment every year from the Himalayan Mountains to the Bay of Bengal and has built the world’s largest active sedimentary deposit, the Bengal Fan. High sedimentation rates drive exceptional organic matter preservation that represents a long-term sink for atmospheric CO2. While much attention has been paid to organic-rich fine sediments, coarse sediments have generally been overlooked as a locus of organic carbon (OC) burial. However, International Ocean Discovery Program Expedition 354 recently discovered abundant woody debris (millimeter- to centimeter-sized fragments) preserved within the coarse sediment layers of turbidite beds recovered from 6 marine drill sites along a transect across the Bengal Fan (∼8°N, ∼3,700-m water depth) with recovery spanning 19 My. Analysis of bulk wood and lignin finds mostly lowland origins of wood delivered episodically. In the last 5 My, export included C4 plants, implying that coarse woody, lowland export continued after C4 grassland expansion, albeit in reduced amounts. Substantial export of coarse woody debris in the last 1 My included one wood-rich deposit (∼0.05 Ma) that encompassed coniferous wood transported from the headwaters. In coarse layers, we found on average 0.16 weight % OC, which is half the typical biospheric OC content of sediments exported by the modern G-B Rivers. Wood burial estimates are hampered by poor drilling recovery of sands. However, high-magnitude, low-frequency wood export events are shown to be a key mechanism for C burial in turbidites.
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Peng, Li-Chun, Yu-Pin Lin, Guan-Wei Chen y Wan-Yu Lien. "Climate Change Impact on Spatiotemporal Hotspots of Hydrologic Ecosystem Services: A Case Study of Chinan Catchment, Taiwan". Water 11, n.º 4 (25 de abril de 2019): 867. http://dx.doi.org/10.3390/w11040867.
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Hydrologic ecosystem services are greatly affected by the changing climate. In this study, the Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) model was used to quantify hydrologic ecosystem services. Five general circulation models (GCMs) and two representative concentration pathways (RCPs) were selected to estimate hydrologic ecosystem services. The Local Indicators of Spatial Association (LISA) index was used to identify hydrologic ecosystem hotspots. The hotspots were used to evaluate the impact of climate change on the services. Results indicate that annual water yields vary from −17% to 8%, with significant intra-year fluctuation. Compared to baseline data, the CESM1-CAM5 predicts an increase of 45% in June, but HadGEM2-AO predicts a drop to only 12% in January. Sediment export results show a similar trend to water yield, with sediment export increasing significantly under RCP 8.5, and monthly sediment export increases concentrated from June and October. Nitrogen and phosphorous exports both show less significant changes but obvious intra-year variations. The CESM1-CAM5 predicts strong seasonal and spatial variation of the hydrologic ecosystem services. Our proposed approach successfully identifies annual and monthly hotspot spatial changes of hydrologic ecosystem services under climate change.
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Simone, Michelle N., Kai G. Schulz, Joanne M. Oakes y Bradley D. Eyre. "Warming and ocean acidification may decrease estuarine dissolved organic carbon export to the ocean". Biogeosciences 18, n.º 5 (16 de marzo de 2021): 1823–38. http://dx.doi.org/10.5194/bg-18-1823-2021.
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Abstract. Relative to their surface area, estuaries make a disproportionately large contribution of dissolved organic carbon (DOC) to the global carbon cycle, but it is unknown how this will change under a future climate. As such, the response of DOC fluxes from microbially dominated unvegetated sediments to individual and combined future climate stressors of temperature change (from Δ−3 to Δ+5 ∘C compared to ambient mean temperatures) and ocean acidification (OA, ∼ 2× current CO2 partial pressure, pCO2) was investigated ex situ. Warming alone increased sediment heterotrophy, resulting in a proportional increase in sediment DOC uptake; sediments became net sinks of DOC (3.5 to 8.8 mmol C m−2 d−1) at warmer temperatures (Δ+3 and Δ+5 ∘C, respectively). This temperature response changed under OA conditions, with sediments becoming more autotrophic and a greater sink of DOC (up to 4× greater than under current pCO2 conditions). This response was attributed to the stimulation of heterotrophic bacteria with the autochthonous production of labile organic matter by microphytobenthos. Extrapolating these results to the global area of unvegetated subtidal estuarine sediments, we find that the future climate of warming (Δ+3 ∘C) and OA may decrease estuarine export of DOC by ∼ 80 % (∼ 150 Tg C yr−1) and have a disproportionately large impact on the global DOC budget.
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Douglas, G. B., P. W. Ford, M. Palmer, R. M. Noble y R. Packett. "Fitzroy River, Queensland, Australia. II. Identification of Sources of Estuary Bottom Sediments". Environmental Chemistry 3, n.º 5 (2006): 377. http://dx.doi.org/10.1071/en06010.
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Environmental Context. The Fitzroy River Basin constitutes a major source of suspended sediment and nutrient fluxes to the southern Great Barrier Reef. Improved land management practices to ameliorate these catchment loads require an understanding of the sediment sources and dynamics. This multidisciplinary geochemical and modelling study provides for the first time a quantitative estimate of sediment sources delivered to, and their degree of retention in, the Fitzroy River Estuary. Abstract. Sources of sediment deposited in the Fitzroy River Estuary (FRE) have been identified and quantified using an integrated geochemical, modelling and reconnaissance soil sampling approach. A companion paper (this volume) identifies the major sources of sediments in impoundments on the major river systems and sediment sampled from flood events in the Fitzroy River Basin (FRB). Sediment within the FRE may display distinct longitudinal variation with little basaltic material retained. Sediments derived from the Bowen Basin, which occupies the greatest portion of the FRB, and from the Surat Basin display the greatest longitudinal variation. All FRB soils have a similar total phosphorus (P) concentration. Thus, in considering P export from the catchment it is the total sediment flux which is of major importance, rather than the relative proportions of individual catchment soils. This research provides crucial new regional scale information on the sediment sources deposited within the FRE.
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Douglas, Grant B., Mio Kuhnen, Lynda C. Radke, Gary Hancock, Brendan Brooke, Mark J. Palmer, Tim Pietsch, Phillip W. Ford, Michael G. Trefry y R. (Bob) Packett. "Delineation of sediment sources to a coastal wetland in the Great Barrier Reef catchment: influence of climate variability and land clearing since European arrival". Environmental Chemistry 7, n.º 2 (2010): 190. http://dx.doi.org/10.1071/en09089.
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Environmental context. Undisturbed sediments provide a record to past events in a catchment. In this study we examine changes in sources of sediment and their variation over the past century due to changes in climate and extensive modification of the catchment after European settlement. We also highlight how multiple lines of forensic evidence acquired from the sediments can be used to reconstruct catchment history over a range of timescales. Abstract. Enhanced delivery of sediment and nutrients to the Great Barrier Reef has the potential to profoundly influence ecological processes in this natural icon. Within the Fitzroy River Basin (FRB) of north-eastern Australia, natural impoundments such as Crescent Lagoon provide an invaluable archive of accumulated sediment that can be dated using multiple techniques to reconstruct the history of sediment export. During the last century, net rates of accumulation of sediment remain similar; however, large variations in sediment sources are apparent. A major sedimentary and geochemical discontinuity is present between ~45 to 29 years before present. Within this time interval a redox front is preserved corresponding to a change in organic matter influx; C3 plant detritus derived from the onset of broadscale agriculture within the FRB provided an assimilable carbon source resulting in more reducing conditions within the sediments. Statistical correlations demonstrate a notable correspondence between some sediment fractions supporting the notion of a short-lived disturbance to the sedimentation regime in the 1960–70s.
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Hanief, Aslam y Andrew E. Laursen. "SWAT modeling of hydrology, sediment and nutrients from the Grand River, Ontario". Water Quality Research Journal 52, n.º 4 (3 de octubre de 2017): 243–57. http://dx.doi.org/10.2166/wqrj.2017.014.
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Abstract The Grand River watershed (GRW) is an important agricultural area in Southern Ontario. Land use has been modified by various human endeavors, altering hydrology and increasing export of sediment and nutrients. The objective of this study was to predict spatial and temporal patterns of hydrology, and export of sediment and nutrients from the GRW to Lake Erie using the Soil and Water Assessment Tool (SWAT) model. The Sequential Uncertainty FItting (SUFI2) program was used to calibrate and validate stream flow for years 2001–2010. Calibration and validation of the SWAT model for monthly stream flow at York indicated good model performance (R2, NSE, and PBIAS = 0.64, 0.63 and 7.1 for calibration (2001–2005); = 0.82, 0.74 and 0.2, for validation (2006–2010)). The model was applied to predict sediment and nutrient export from the GRW into Lake Erie. Predicted loading at Dunnville (near the mouth) was 2.3 × 105 tonnes y−1 total suspended sediment, 7.9 × 103 tonnes y−1 TN, and 2.3 × 102 tonnes y−1 TP. This SWAT model can now be used to investigate the relative effects of best management practices, and to forecast effects of climate change, on sustainable water management, hydrology, and sediment and nutrient export to Lake Erie.
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Masselink, R., A. J. A. M. Temme, R. Giménez, J. Casalí y S. D. Keesstra. "Assessing hillslope-channel connectivity in an agricultural catchment using rare-earth oxide tracers and random forests models". Cuadernos de Investigación Geográfica 43, n.º 1 (30 de junio de 2017): 17. http://dx.doi.org/10.18172/cig.3169.
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Soil erosion from agricultural areas is a large problem, because of off-site effects like the rapid filling of reservoirs. To mitigate the problem of sediments from agricultural areas reaching the channel, reservoirs and other surface waters, it is important to understand hillslope-channel connectivity and catchment connectivity. To determine the functioning of hillslope-channel connectivity and the continuation of transport of these sediments in the channel, it is necessary to obtain data on sediment transport from the hillslopes to the channels. Simultaneously, the factors that influence sediment export out of the catchment need to be studied. For measuring hillslope-channel sediment connectivity, Rare-Earth Oxide (REO) tracers were applied to a hillslope in an agricultural catchment in Navarre, Spain, preceding the winter of 2014-2015. The results showed that during the winter no sediment transport from the hillslope to the channel was detected.To test the implication of the REO results at the catchment scale, two contrasting conceptual models for sediment connectivity were assessed using a Random Forest (RF) machine learning method. The RF method was applied using a 15-year period of measured sediment output at the catchment scale. One model proposes that small events provide sediment for large events, while the other proposes that only large events cause sediment detachment and small events subsequently remove these sediments from near and in the channel. For sediment yield prediction of small events, variables related to large preceding events were the most important. The model for large events underperformed and, therefore, we could not draw any immediate conclusions whether small events influence the amount of sediment exported during large events. Both REO tracers and RF method showed that low intensity events do not contribute any sediments from the hillslopes to the channel in the Latxaga catchment. Sediment dynamics are dominated by sediment mobilisation during large (high intensity) events. Sediments are for a large part exported during those events, but the system shows a memory of the occurrence of these large events, suggesting that large amounts of sediments are deposited in and near the channel after these events. These sediments are gradually removed by small events. To better understand the delivery of sediments to the channel and how large and small events influence each other more field data on hillslope-channel connectivity and within-channel sediment dynamics is necessary.
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Suryanta, J., Y. Wahyudin, M. Darmawan, F. Amhar, I. P. Santikayasa y I. Nahib. "Estimated sediment exports and erosion in Central Citarum watershed". IOP Conference Series: Earth and Environmental Science 1114, n.º 1 (1 de diciembre de 2022): 012099. http://dx.doi.org/10.1088/1755-1315/1114/1/012099.
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Abstract In addition to the problem of water availability and quality, the Citratum watershed is also experiencing problems with soil erosion and sedimentation. Climate change and land use cover are the leading causes of this. Therefore, monitoring water conditions and soil erosion is prioritized in the central Citarum watershed covering an area of 227,020 hectares. The purpose of this study was to determine soil erosion and the spatial distribution of sediment exports. The InVEST SDR method was used to calculate sediment exports and soil erosion. The results showed that the total sediment export of the Central Citarum watershed was 4.61 x million tons/year or an average of 20.31 tons/ha/year. Significant distributions occur in several sub-watersheds, including Cilawang, Cihalaya, Cipada, Citarum 58, and Cimurah, each contributing 36.56%, 14.83%, 13.70%, 4.73%, and 4.53 %. Meanwhile, total soil erosion is 23.16 million tons/year or an average of 102 tons/ha/year, with the most extensive distribution in the Cilawang sub-watershed, 35.12%. High sediment discharge occurs in areas with steep slopes, high rainfall, and dry land agriculture. Furthermore, efforts to reduce sediment exports to the Cirata and Jatiluhur reservoirs should focus on these five sub-watersheds.
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Ferket, B., M. Van De Broek, T. Van Hoestenberghe, J. Degerickx, R. De Sutter, G. Govers, N. Dezillie y P. Deproost. "Erosion modelling towards, and sediment transport modelling in unnavigable watercourses in Flanders, Belgium". Proceedings of the International Association of Hydrological Sciences 367 (3 de marzo de 2015): 349–56. http://dx.doi.org/10.5194/piahs-367-349-2015.
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Abstract. Antea Group and KULeuven were awarded a project in Flanders to identify the regions exporting high sediment loads to unnavigable watercourses and the sedimentation zones within them. Two types of models are applied: hydrological sediment export models (SEM) and hydraulic sediment transport models (STM). The influence of erosion control measures on sediment export as well as river engineering measures needs to be taken into account. A concept will be developed to connect the SEM and STM, enabling the sediment to be routed from upstream to the sedimentation zones. Results of the study will be used by the Flemish government to plan erosion control measures, estimate future sedimentation volumes, steer sedimentation and optimize river engineering and dredging works. Finally, model results could also be used to obtain better insights to the re-suspension risks of contaminated sediment in watercourses.
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Dawoud, Osama, Alaeddinne Eljamassi y Ziyad Abunada. "Mapping and Quantification of Soil Erosion and Sediment Delivery in Poorly Developed Urban Areas: A Case Study". Sustainability 15, n.º 18 (13 de septiembre de 2023): 13683. http://dx.doi.org/10.3390/su151813683.
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Poorly developed regions in the Gaza Strip, Palestine, face significant risks to public safety, the environment, and stormwater infrastructure due to soil erosion and deposition. This study is the first of its kind to investigate soil erosion in this area. A revised universal soil loss equation (RUSLE) model was utilized and validated using field measurements of accumulated sediments at three major stormwater detention basins from 2014 to 2020. High-resolution maps were created to capture the urbanization effect and to further improve the future prediction of urbanization. The findings revealed that the highest potential for sediment generation in the Gaza governorate occurred over the slopes of the eastern ridge, which drain toward the city center. Sediment generation ranged from 1784 to 4281 ton/ha for the years of 2018 and 2020, respectively. The average sediment delivery ratio (SDR) was calculated to be 0.00134. The estimations for sediment export ranged from 0 to 135.3 ton/ha for the year 2020, with an average of 0.0737 ton/ha. The urban areas exhibited the least sediment export rate; however, the model revealed abnormal behavior for a dataset of the field measurements which was ascribed to the impact of destruction/reconstruction activities in the corresponded watersheds that followed the war in 2014. This conducted research stands as a pioneering effort in quantifying and cartographically representing sediment erosion potential within the Gaza Strip. Thus, it serves as an indispensable point of reference for future researchers in terms of the employed parameterization and calibration methodology. Furthermore, it holds distinct significance as an unparalleled resource for experts and stakeholders who are invested in comprehending the ramifications of erosion on urban landscapes and drainage systems.
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Mekonnen, Balew Admas, Kerry Anne Mazurek y Gordon Putz. "Sediment Export Modeling in Cold-Climate Prairie Watersheds". Journal of Hydrologic Engineering 21, n.º 5 (mayo de 2016): 05016005. http://dx.doi.org/10.1061/(asce)he.1943-5584.0001336.
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Delmas, Magalie, Olivier Cerdan, Bruno Cheviron, Jean-Marie Mouchel y Frederique Eyrolle. "Sediment export from French rivers to the sea". Earth Surface Processes and Landforms 37, n.º 7 (1 de marzo de 2012): 754–62. http://dx.doi.org/10.1002/esp.3219.
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Krafft, Douglas R., Richard Styles y Mitchell E. Brown. "Feedback between Basin Morphology and Sediment Transport at Tidal Inlets: Implications for Channel Shoaling". Journal of Marine Science and Engineering 10, n.º 3 (18 de marzo de 2022): 442. http://dx.doi.org/10.3390/jmse10030442.
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Increasing societal pressures (e.g., population growth and urbanization) are driving land use change practices in coastal areas that could potentially alter the hydrodynamics and sediment transport patterns near coastal inlets in ways that might exacerbate existing shoaling conditions. To investigate the potential impact of coastal development, a numerical model is used to predict the long-term evolution of an idealized lagoonal-type barrier island inlet under five different morphological conditions that transitioned from net sediment import to net sediment export. The simulations were designed to address the potential effect of inter-tidal placement and land reclamation on sediment transport and the resulting deposition/erosion patterns. Estuaries that were deeper and devoid of extensive tidal flats tended to promote sediment import and had a greater propensity to exacerbate channel shoaling. Simulations that were characteristic of inter-tidal placement showed net export, yet the likelihood of channel shoaling was increased because some of the material eroded from the tidal flats was deposited in the deeper channels as opposed to being carried out the inlet throat. Alternatively, it was found that regions in which the intertidal area was restricted to elevations higher in the tidal frame, which also showed a net export, produced greater sediment loss in the inter-tidal zone that tended to bypass the deeper sections, reducing the likelihood of channel shoaling.
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Yavari, Shahla, Neil McIntyre y Thomas Baumgartl. "An Empirical Analysis of Sediment Export Dynamics from a Constructed Landform in the Wet Tropics". Water 13, n.º 8 (15 de abril de 2021): 1087. http://dx.doi.org/10.3390/w13081087.
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Although plot-scale erosion experiments are numerous, there are few studies on constructed landforms. This limits the understanding of their long-term stability, which is especially important for planning mined land rehabilitation. The objective of this study was to gain insight into the erosion processes in a 30 × 30 m trial plot on a mine waste rock dump in tropical northern Australia. The relationships between rainfall, runoff and suspended and bedload sediment export were assessed at annual, seasonal, inter-event and intra-event timescales. During a five-year study period, 231 rainfall–runoff–sediment export events were examined. The measured bedload and suspended sediments (mainly represented in nephelometric turbidity units (NTU)) showed the dominance of the wet season and heavy rainfall events. The bedload dominated the total mass, although the annual bedload diminished by approximately 75% over the five years, with greater flow energy required over time to mobilise the same bedload. The suspended load was more sustained, though it also exhibited an exhaustion process, with equal rainfall and runoff volumes and intensities, leading to lower NTU values over time. Intra-event NTU dynamics, including runoff-NTU time lags and hysteretic behaviours, were somewhat random from one event to the next, indicating the influence of the antecedent distribution of mobilisable sediments. The value of the results for supporting predictive modelling is discussed.
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Sparkes, Robert B., Melissa Maher, Jerome Blewett, Ayça Doğrul Selver, Örjan Gustafsson, Igor P. Semiletov y Bart E. van Dongen. "Carbonaceous material export from Siberian permafrost tracked across the Arctic Shelf using Raman spectroscopy". Cryosphere 12, n.º 10 (11 de octubre de 2018): 3293–309. http://dx.doi.org/10.5194/tc-12-3293-2018.
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Abstract. Warming-induced erosion of permafrost from Eastern Siberia mobilises large amounts of organic carbon and delivers it to the East Siberian Arctic Shelf (ESAS). In this study Raman spectroscopy of carbonaceous material (CM) was used to characterise, identify and track the most recalcitrant fraction of the organic load: 1463 spectra were obtained from surface sediments collected across the ESAS and automatically analysed for their Raman peaks. Spectra were classified by their peak areas and widths into disordered, intermediate, mildly graphitised and highly graphitised groups and the distribution of these classes was investigated across the shelf. Disordered CM was most prevalent in a permafrost core from Kurungnakh Island and from areas known to have high rates of coastal erosion. Sediments from outflows of the Indigirka and Kolyma rivers were generally enriched in intermediate CM. These different sediment sources were identified and distinguished along an E–W transect using their Raman spectra, showing that sediment is not homogenised on the ESAS. Distal samples, from the ESAS slope, contained greater amounts of highly graphitised CM compared to the rest of the shelf, attributable to degradation or, more likely, winnowing processes offshore. The presence of all four spectral classes in distal sediments demonstrates that CM degrades much more slowly than lipid biomarkers and other traditional tracers of terrestrial organic matter and shows that alongside degradation of the more labile organic matter component there is also conservative transport of carbon across the shelf toward the deep ocean. Thus, carbon cycle calculations must consider the nature as well as the amount of carbon liberated from thawing permafrost and other erosional settings.
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Mueller, E. N., A. Güntner, T. Francke y G. Mamede. "Modelling sediment export, retention and reservoir sedimentation in drylands with the WASA-SED model". Geoscientific Model Development 3, n.º 1 (8 de abril de 2010): 275–91. http://dx.doi.org/10.5194/gmd-3-275-2010.
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Abstract. Current soil erosion and reservoir sedimentation modelling at the meso-scale is still faced with intrinsic problems with regard to open scaling questions, data demand, computational efficiency and deficient implementations of retention and re-mobilisation processes for the river and reservoir networks. To overcome some limitations of current modelling approaches, the semi-process-based, spatially semi-distributed modelling framework WASA-SED (Vers. 1) was developed for water and sediment transport in large dryland catchments. The WASA-SED model simulates the runoff and erosion processes at the hillslope scale, the transport and retention processes of suspended and bedload fluxes in the river reaches and the retention and remobilisation processes of sediments in reservoirs. The modelling tool enables the evaluation of management options both for sustainable land-use change scenarios to reduce erosion in the headwater catchments as well as adequate reservoir management options to lessen sedimentation in large reservoirs and reservoir networks. The model concept, its spatial discretisation scheme and the numerical components of the hillslope, river and reservoir processes are described and a model application for the meso-scale dryland catchment Isábena in the Spanish Pre-Pyrenees (445 km2) is presented to demonstrate the capabilities, strengths and limits of the model framework. The example application showed that the model was able to reproduce runoff and sediment transport dynamics of highly erodible headwater badlands, the transient storage of sediments in the dryland river system, the bed elevation changes of the 93 hm3 Barasona reservoir due to sedimentation as well as the life expectancy of the reservoir under different management options.
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Amatya, D. M., R. W. Skaggs, J. W. Gilliam y J. H. Hughes. "Effects of Orifice-Weir Outlet on Hydrology and Water Quality of a Drained Forested Watershed". Southern Journal of Applied Forestry 27, n.º 2 (1 de mayo de 2003): 130–42. http://dx.doi.org/10.1093/sjaf/27.2.130.
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Abstract Orifice-weir structures at ditch outlets are proposed to reduce peak drainage rates during high flows and to store water during the growing season in poorly drained managed pine plantations. Two coastal watersheds, one conventionally drained (D1) and another with an orifice-weir outlet (D3), were monitored to examine the effects of this orifice treatment on drainage outflows and nutrient exports from drained pine plantations in eastern North Carolina. Five years (1995–1999) of measured hydrologic data showed that the daily water table elevation on D3 was 7 cm higher on average, but was 13.5 cm higher during wet periods compared to conventional drainage. The peak drainage rates from D3 were substantially dampened by the orifice-weir. Accordingly, average annual outflow was reduced by 18%. The reduction in outflow was as much as 34% in 1995. Taking the characteristic differences observed in concentrations between these two watersheds during the pretreatment phase into consideration, the measured average annual TKN concentration in the watershed with the orifice appeared to be higher, and total P and sediment lower than expected for conventional drainage. Despite the reduction of flow in all 5 yr, the measured exports of NO3-N, TKN, and total N increased in the first 3 yr (except for TKN in 1995) and decreased in 1998 and 1999 with no significant effects because of the orifice-weir treatment. However, on an average annual basis, total sediment and total P export from D3 were reduced by 54% and 30%, respectively. These results showed that an orifice-weir at the drainage outlet can be used to reduce peak rates, annual drainage outflows, total P and sediment export. The orifice-weir outlet did not have an effect on the export of nitrogen components as happens when controlled drainage with a raised weir is used. South. J. Appl. For. 27(2):130–142.
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Hanebuth, Till Jens Jörg, Vera Barbara Bender y Renata Hanae Nagai. "SEDIMENT EXPORT DYNAMICS REFLECTING THE HOLOCENE HYDRODYNAMIC VARIABILITY OF A HIGH-ENERGY CONTINENTAL SHELF SYSTEM (SOUTHEASTERN SOUTH AMERICA)". Journal of Sedimentary Environments 4, n.º 3 (28 de septiembre de 2019): 312–31. http://dx.doi.org/10.12957/jse.2019.45616.
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This study reconstructs Holocene hydrodynamic changes on the outer shelf off Uruguay by examining deposits from a morphological terrace on the uppermost continental slope (250 m water depth). Seismo-acoustics, litho- and chronostratigraphy, granulometry, and Neodymium isotopy were applied to three sediment cores. The 9.5-m thick terrace sediment record, documenting the past 11.5 cal ka BP, provides exceptional insight into the transport and settling mechanisms of the sand injected from the shelf into the open ocean. The sandy outer shelf is identified as the principal sediment origin. Contouritic bottom currents do not significantly affect deposition on the terrace. Instead, the sandy sediment gets spilled over the shelf edge in the form of suspension clouds, spreading uniformly over the whole terrace. The suspended sand does not transform into high-concentration gravity-driven bottom flows but rains down onto the terrace as a quasi-permanent material supply. This observation suggests that the formation of turbidite beds, as frequently found at the deeper slope in this region, requires first a temporary storage of sediment at deposition-favoring locations on the uppermost continental slope (terraces, canyon heads), before a secondary and episodic process can mobilize the mass.An overall fining-upward trend in silty sand shelf export over Holocene times reflects the deglacial sea-level rise dynamics, leading to overall less effective material mobilization on and transfer across the shelf due to water deepening. The pronounced vertical hydrographic shelf front, as a shallow expression of the regional oceanic confluence zone, acted temporarily as main sediment exporting conveyer, before it shifted further north. The water depth of the terrace coincides with the transition zone between Central Water and Intermediate Water. The pronounced water density gradient might influence sediment distribution twofold, acting as a barrier for sand suspension cloud spreading as well as a medium for incoming internal waves bringing sediment remobilization. DINÂMICA DE EXPORTAÇÃO DE SEDIMENTOS EM FUNÇÃO DA VARIABILIDADE HIDRODINÂMICA DURANTE O HOLOCENO NUM SISTEMA DE PLATAFORMA CONTINENTAL DE ELEVADA ENERGIA (SE DA AMÉRICA DO SUL) ResumoEste estudo pretende ser uma contribuição para a reconstrução das alterações hidrodinâmicas Holocénicas, da plataforma continental externa do Uruguai, a partir de depósitos sedimentares de um terraço do talude continental superior (250 m de profundidade). Três testemunhos de sedimentos foram submetidos a análises geofísicas, lito e cronostratigráficas e granulométricas, tendo também sido obtidos resultados de isótopos de neodímio. O registro sedimentar com 9,5 m de espessura no terraço, documentando os últimos 11,5 ka cal BP, fornece importantes informações sobre os mecanismos de transporte e sedimentação da areia remobilizada da plataforma continental e transportada para o oceano profundo.Os dados obtidos na área de estudo revelaram que o substrato arenoso da plataforma continental externa foi a principal fonte de sedimento para o talude continental superior. As correntes de fundo de contorno não afetaram significativamente a deposição de sedimentos no referido terraço. Em vez disso, o sedimento arenoso remobilizado da plataforma formou nuvens de partículas em suspensão que se espalharam uniformemente por todo o terraço. A areia, uma vez em suspensão, não deu ludar a fluxos gravitacionais de fundo concentrados, mas “choveu” de modo quase continuo por todo o terraço. Esta constatação sugere que a formação de camadas turbidíticas, tais como as que freqüentemente são encontradas no talude continental inferior da região, requerem que primeiramente haja um armazenamento temporário de sedimentos em locais favoráveis à sua deposição na plataforma continental superior (terraços, cabeceiras de cânions), antes da ocorrência de um processo secundário e episódico poder mobilizar os materiais acumulados.Verifica-se, na área de estudo, uma tendência geral de redução da granulometria da areia siltosa ao longo do Holoceno devido à subida do nível do mar após a deglaciação; esta terá levado a uma menor remobilização e a uma transferência menos eficaz de sedimentos da plataforma continental para o talude devido ao aumento da profundidade da coluna de água.A pronunciada frente hidrográfica vertical da plataforma, expressão da zona de confluência oceânica regional, atuou temporariamente como principal processo de transporte e exportação de sedimentos, para norte. A profundidade da água do terraço coincide com a zona de transição entre a Água Central e a Água Intermediária. O pronunciado gradiente de densidade da água poderá ter influenciado de duas maneiras a distribuição de sedimentos, atuando como uma barreira para a propagação da nuvem de areia em suspensão e como meio de propagação de ondas internas que chegam, remobilizando e exportando sedimentos. Palavras-chave: Exportação de sedimentos de plataforma. Margem oceânica de elevada energia. Sudeste da América do Sul. Holoceno.
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Palleiro, L., M. L. Rodríguez-Blanco, M. M. Taboada-Castro y M. T. Taboada-Castro. "Hydroclimatic control of sediment and metal export from a rural catchment in northwestern Spain". Hydrology and Earth System Sciences 18, n.º 9 (18 de septiembre de 2014): 3663–73. http://dx.doi.org/10.5194/hess-18-3663-2014.
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Abstract. This paper examines sediment and metal (Al, Fe, Mn, Cu, and Zn) exportation at different timescales (annual, seasonal and event) during a 3-year period (2005–2008) in the Mero River headwater, a rural catchment under humid temperate climate. Interannual differences were found both in annual loads and their distributions throughout the year. At annual scale, sediment and particulate metal loads followed the same trend as streamflow, while dissolved metals showed different patterns. Runoff events contributed to 63% of the total sediment load, whereas particulate and dissolved loads in events accounted for between 38–61 and 27–49%, respectively. Runoff events were characterized by high variability in sediment and metal loads, a few events representing a high percentage of the metal exported. Sediment loads were related to maximum and initial discharge. Particulate metal loads were highly correlated with sediment loads, runoff being the hydrological variable that best explains the load of these metals. Dissolved metal loads displayed different patterns. Dissolved Al, showed a great correlation with runoff, while dissolved Mn with maximum discharge.
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Palleiro, L., M. L. Rodríguez-Blanco, M. M. Taboada-Castro y M. T. Taboada-Castro. "Hydroclimatic control of sediment and metal export from a rural catchment in Northwest Spain". Hydrology and Earth System Sciences Discussions 11, n.º 4 (1 de abril de 2014): 3757–86. http://dx.doi.org/10.5194/hessd-11-3757-2014.
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Abstract. This paper examines sediment and metal (Al, Fe, Mn, Cu, and Zn) exportation at different time scales (annual, seasonal and event) during a three-year period (2005–2008) in the Mero River headwater, a rural catchment under humid temperate climate. Inter-annual differences were found both in annual loads and their distributions throughout the year. At annual scale, sediment and particulate metal loads followed the same trend as streamflow, while dissolved metals showed different patterns. Runoff events contributed to 63% of the total sediment load, whereas particulate and dissolved metal loads accounted for between 38–61 and 27–49% of the total load, respectively. Runoff events were characterized by high variability in sediment and metal loads, a few events representing a high percentage of the metal exported. Sediment loads were related to maximum and initial discharge. Particulate metal loads were highly correlated with sediment loads, runoff being the hydrological variable that best explains the load of these metals. Dissolved metal loads displayed different patterns. Dissolved Al, showed a great correlation with runoff, while dissolved Mn with maximum discharge.
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Sharpe, Hannah, Michel Gosselin, Catherine Lalande, Alexandre Normandeau, Jean-Carlos Montero-Serrano, Khouloud Baccara, Daniel Bourgault, Owen Sherwood y Audrey Limoges. "Influence of a small submarine canyon on biogenic matter export flux in the lower St. Lawrence Estuary, eastern Canada". Biogeosciences 20, n.º 24 (18 de diciembre de 2023): 4981–5001. http://dx.doi.org/10.5194/bg-20-4981-2023.
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Abstract. Submarine canyons enhance shelf–slope sediment exchange and influence hydrodynamic processes, with consequences for biogeochemical cycles. This work documents variations in the vertical export of biogenic matter on the northern shore of the lower St. Lawrence Estuary (LSLE, Quebec, eastern Canada), which is characterized by the presence of an active submarine canyon system. A total of three moorings were deployed from November 2020 to September 2021. One nearshore mooring (PDMc) was deployed in the main axis of the Pointe-des-Monts (PDM) canyon system and was equipped with an acoustic Doppler current profiler (ADCP), and two moorings equipped with sediment traps were deployed in the distal PDM canyon system (PDM-154, PDM-224) and offshore Baie-Comeau (BC-133). The ADCP data revealed the occurrence of a minor sediment remobilization event (December 2020) and a small turbidity current (February 2021) in the canyon. Concurrent elevated fluxes of total particulate matter, particulate organic carbon, particulate nitrogen, and chloropigments showed that these events left a signature in sediment traps PDM-154 and PDM-224 located > 2.6 km further offshore by enhancing lateral dispersion of resuspended sediments. The composition of diatom and dinoflagellate assemblages was similar in the canyon system and offshore BC, but the diatom bloom occurred 2 weeks earlier (in mid-April) at the PDM site. A bloom of the potentially toxic diatom Pseudo-nitzschia seriata was also observed during the second half of September 2021 at the BC site. Annual diatom and dinoflagellate fluxes were almost 2 times lower at the PDM site than at the BC site, possibly due to differences in riverine input and the structure of the water column, as well as increased sediment input and resuspension at the PDM site, leading to limited light availability. This study notably helps identify the relationship between near-bed canyon processes and biogenic matter export in the water column, thereby directly influencing the ecosystem offshore PDM. The study period further covered an anomalously nearly ice-free winter, and thus, in the context of climate change, it provides valuable insight into future trends of biogenic matter export in the LSLE.
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Kraushaar, Sabine, Gregor Ollesch, Christian Siebert, Hans-Joerg Vogel y Markus Fuchs. "Long-Term Sediment Export Estimates from Northern Jordan using Roman Cisterns as Sediment Traps". Geoarchaeology 30, n.º 4 (22 de junio de 2015): 369–78. http://dx.doi.org/10.1002/gea.21517.
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Lu, Shenglan, Brian Kronvang, Joachim Audet, Dennis Trolle, Hans Estrup Andersen, Hans Thodsen y Ann van Griensven. "Modelling sediment and total phosphorus export from a lowland catchment: comparing sediment routing methods". Hydrological Processes 29, n.º 2 (26 de febrero de 2014): 280–94. http://dx.doi.org/10.1002/hyp.10149.
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Diodato, Nazzareno, Naziano Filizola, Pasquale Borrelli, Panos Panagos y Gianni Bellocchi. "The Rise of Climate-Driven Sediment Discharge in the Amazonian River Basin". Atmosphere 11, n.º 2 (18 de febrero de 2020): 208. http://dx.doi.org/10.3390/atmos11020208.
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The occurrence of hydrological extremes in the Amazon region and the associated sediment loss during rainfall events are key features in the global climate system. Climate extremes alter the sediment and carbon balance but the ecological consequences of such changes are poorly understood in this region. With the aim of examining the interactions between precipitation and landscape-scale controls of sediment export from the Amazon basin, we developed a parsimonious hydro-climatological model on a multi-year series (1997–2014) of sediment discharge data taken at the outlet of Óbidos (Brazil) watershed (the narrowest and swiftest part of the Amazon River). The calibrated model (correlation coefficient equal to 0.84) captured the sediment load variability of an independent dataset from a different watershed (the Magdalena River basin), and performed better than three alternative approaches. Our model captured the interdecadal variability and the long-term patterns of sediment export. In our reconstruction of yearly sediment discharge over 1859–2014, we observed that landscape erosion changes are mostly induced by single storm events, and result from coupled effects of droughts and storms over long time scales. By quantifying temporal variations in the sediment produced by weathering, this analysis enables a new understanding of the linkage between climate forcing and river response, which drives sediment dynamics in the Amazon basin.
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Stenfert Kroese, Jaqueline, John N. Quinton, Suzanne R. Jacobs, Lutz Breuer y Mariana C. Rufino. "Particulate macronutrient exports from tropical African montane catchments point to the impoverishment of agricultural soils". SOIL 7, n.º 1 (15 de marzo de 2021): 53–70. http://dx.doi.org/10.5194/soil-7-53-2021.
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Abstract. Agricultural catchments in the tropics often generate high concentrations of suspended sediments following the conversion of natural ecosystems. The eroded fine particles are generally enriched with carbon (TC) and nutrients (TN and TP) originating from the topsoil of agricultural land. Sediment-associated TC, TN and TP are an important loss to the terrestrial ecosystem and tightly connected to an increase in riverine particulate TC and nutrient export. Soil nutrient depletion can limit crop growth and yields, whereas an excess of nutrients in streams can cause eutrophication in freshwater systems. Streams in East Africa, with widespread land conversion from forests to agriculture, are expected to receive high loads of sediment-associated TC, TN and TP. In this study, we assess the effect of land use on particulate TC, TN and TP concentrations. Suspended sediments (time-integrated, manual-event-based and automatic-event-based sediment samples) were analysed for TC, TN and TP concentrations collected at the outlet of a natural montane forest (35.9), a tea-tree plantation (33.3) and a smallholder agriculture (27.2 km2) catchment in western Kenya during a wet sampling period in 2018 and a drier sampling period in 2019. Particulate TC, TN and TP concentrations were up to 3-fold higher (p<0.05) in the natural forest catchment compared to fertilized agricultural catchments. However, because of higher sediment loads from the smallholder agriculture catchment, the total sediment-associated loads of TC, TN and TP were higher compared to the natural forest and tea-tree plantation catchment. The higher C:N ratios in the natural forest suggest that the particulate nutrients are of organic origin due to tighter nutrient cycles, whereas lower ratios in both agricultural catchments suggest a mixture of mineral and organic sediment sources. The findings of this study imply that with the loss of natural forest, the inherent soil fertility is progressively lost under the current low fertilization rates and soil management strategies.
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Zúñiga, Diana, Celia Santos, María Froján, Emilia Salgueiro, Marta M. Rufino, Francisco De la Granda, Francisco G. Figueiras, Carmen G. Castro y Fátima Abrantes. "Diatoms as a paleoproductivity proxy in the NW Iberian coastal upwelling system (NE Atlantic)". Biogeosciences 14, n.º 5 (13 de marzo de 2017): 1165–79. http://dx.doi.org/10.5194/bg-14-1165-2017.
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Abstract. The objective of the current work is to improve our understanding of how water column diatom's abundance and assemblage composition is seasonally transferred from the photic zone to seafloor sediments. To address this, we used a dataset derived from water column, sediment trap and surface sediment samples recovered in the NW Iberian coastal upwelling system. Diatom fluxes (2.2 (±5.6) 106 valves m−2 d−1) represented the majority of the siliceous microorganisms sinking out from the photic zone during all studied years and showed seasonal variability. Contrasting results between water column and sediment trap diatom abundances were found during downwelling periods, as shown by the unexpectedly high diatom export signals when diatom-derived primary production achieved their minimum levels. They were principally related to surface sediment remobilization and intense Minho and Douro river discharge that constitute an additional source of particulate matter to the inner continental shelf. In fact, contributions of allochthonous particles to the sinking material were confirmed by the significant increase of both benthic and freshwater diatoms in the sediment trap assemblage. In contrast, we found that most of the living diatom species blooming during highly productive upwelling periods were dissolved during sinking, and only those resistant to dissolution and the Chaetoceros and Leptocylindrus spp. resting spores were susceptible to being exported and buried. Furthermore, Chaetoceros spp. dominate during spring–early summer, when persistent northerly winds lead to the upwelling of nutrient-rich waters on the shelf, while Leptocylindrus spp. appear associated with late-summer upwelling relaxation, characterized by water column stratification and nutrient depletion. These findings evidence that the contributions of these diatom genera to the sediment's total marine diatom assemblage should allow for the reconstruction of different past upwelling regimes.
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Gehlen, M., L. Bopp, N. Emprin, O. Aumont, C. Heinze y O. Ragueneau. "Reconciling surface ocean productivity, export fluxes and sediment composition in a global biogeochemical ocean model". Biogeosciences Discussions 3, n.º 3 (28 de junio de 2006): 803–36. http://dx.doi.org/10.5194/bgd-3-803-2006.
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Abstract. This study focuses on an improved representation of the biological soft tissue pump in the global three-dimensional biogeochemical ocean model PISCES. We compare three parameterizations of particle dynamics: (1) the model standard version including two particle size classes, aggregation-disaggregation and prescribed sinking speed; (2) an aggregation-disaggregation model with a particle size spectrum and prognostic sinking speed; (3) a mineral ballast parameterization with no size classes, but prognostic sinking speed. In addition, the model includes a description of surface sediments and organic carbon early diagenesis. The integrated representation of material fluxes from the productive surface ocean down to the sediment-water interface allows taking advantage of surface ocean observations, sediment trap data and exchange fluxes at the sediment-water interface. The capability of the model to reproduce yearly averaged particulate organic carbon fluxes and benthic oxygen demand does at first order not dependent on the resolution of the particle size spectrum. Model results obtained with the standard version and with the one including a particle size spectrum and prognostic sinking speed are not significantly different. Both model versions overestimate particulate organic carbon between 1000 and 2000 m, while deep fluxes are of the correct order of magnitude. Predicted benthic oxygen fluxes correspond with respect to their large scale distribution and magnitude to data based estimates. Modeled particulate organic C fluxes across the mesopelagos are most sensitive to the intensity of zooplankton flux feeding. An increase of the intensity of flux feeding in the standard version results in lower mid- and deep-water particulate organic carbon fluxes, shifting model results to an underestimation of particulate organic carbon fluxes in the deep. The corresponding benthic oxygen fluxes are too low. The model version including the mineral ballast parameterization yields an improved fit between modeled and observed particulate organic carbon fluxes below 2000 m and down to the sediment-water interface. Our results suggest that aggregate formation alone might not be sufficient to drive an intense biological pump. The later is most likely driven by the combined effect of aggregate formation and mineral ballasting.
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Golbuu, Yimnang, Eric Wolanski, Peter Harrison, Robert H. Richmond, Steven Victor y Katharina E. Fabricius. "Effects of Land-Use Change on Characteristics and Dynamics of Watershed Discharges in Babeldaob, Palau, Micronesia". Journal of Marine Biology 2011 (2011): 1–17. http://dx.doi.org/10.1155/2011/981273.
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This study assessed the impacts of differing levels of land development in four watersheds in Palau on river sediment yield and on sedimentation and turbidity. Area corrected sediment yield was strongly related to land development (r2=0.96,P=0.02), varying from 9.7 to 216 tons km−2yr−1between the least and most developed watershed. Mean sedimentation rates on reefs ranged from 0.7 to 46 mg cm−2d−1, and mean turbidity ranged from 9 to 139 mg l−1. The higher values exceeded those known to harm corals. Because Palau's watersheds and estuaries are small, river floods were short-lived (typically lasting less than a day) and the estuaries adjusted just as quickly to a number of different estuarine circulation patterns that, in turn, generated a large variability in the export of riverine fine sediment to the reefs. The ultimate fate of the fine sediment deposited on the reefs depended on wind resuspension, local currents, and geomorphology (whether the bay was open or semi-enclosed). Palau's small estuaries were generally not as effective as bigger estuaries in trapping sediments and thus at sheltering the reefs. Therefore, greater efforts are needed to control and mitigate land activities that contribute to the increase in sediment yield.
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Kineke, G. C., K. J. Woolfe, S. A. Kuehl, J. D. Milliman, T. M. Dellapenna y R. G. Purdon. "Sediment export from the Sepik River, Papua New Guinea: evidence for a divergent sediment plume". Continental Shelf Research 20, n.º 16 (diciembre de 2000): 2239–66. http://dx.doi.org/10.1016/s0278-4343(00)00069-8.
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Santos, Ana Isabel, Anabela Oliveira, Dora Carinhas, José Paulo Pinto y M. Conceição Freitas. "Hydrodynamic and Sediment Transport Patterns in the Minho and Douro Estuaries (NW Portugal) Based on ADCP Monitoring Data: Part 2—Statistical Interpretation of Bottom Moored Datasets". Coasts 1, n.º 1 (20 de noviembre de 2021): 56–72. http://dx.doi.org/10.3390/coasts1010004.
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Exploratory statistical partitioning methods (K-means Clustering analysis) were applied to ADCP monitoring datasets collected inside the Douro and Minho estuaries. This analysis is aimed to discriminate ADCP acoustic responses according to the variations of the suspended particles within the ensonified medium. Based on the interpretation of the results, this work establishes general sediment transport patterns at both estuaries’ exits under continuously varying river flows and tidal amplitudes recorded during a summer dry seasonal scenario (September 2005) and winter high river discharge (January/February 2007) conditions. Results confirm the already known present scarcity of (sandy) sediment export from the Douro and Minho estuaries into the inner shelf and the consequent sediment depletion of the adjacent littoral, with no effective contribution of the Douro and some evidence of sand export observed at the Minho outlet during the winter of 2007.
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Turner, Kevin W., Michelle D. Pearce y Daniel D. Hughes. "Detailed Characterization and Monitoring of a Retrogressive Thaw Slump from Remotely Piloted Aircraft Systems and Identifying Associated Influence on Carbon and Nitrogen Export". Remote Sensing 13, n.º 2 (6 de enero de 2021): 171. http://dx.doi.org/10.3390/rs13020171.
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Ice-rich permafrost landscapes are sensitive to ongoing changes in climate. Permafrost retrogressive thaw slumps (RTSs) represent one of the more abrupt and prolonged disturbances, which occur along Arctic river and lake shorelines. These features impact local travel and infrastructure, and there are many questions regarding associated impacts on biogeochemical cycling. Predicting the duration and magnitude of impacts requires that we enhance our knowledge of RTS geomorphological drivers and rates of change. Here we demonstrate the utility of remotely piloted aircraft systems (RPAS) for documenting the volumetric change, associated drivers and potential impacts of the largest active RTS along the Old Crow River in Old Crow Flats, Yukon, Canada. RPAS surveys revealed that 29,174 m3 of sediment was exported during the initial evacuation in June 2016 and an additional 18,845 m3 continued to be exported until June 2019. More sediment export occurred during the warmer 2017 summer that experienced less cumulative rainfall than summer 2018. However, several rain events during 2017 were of higher intensity than during 2018. Overall mean soil organic carbon (SOC) and total nitrogen (TN) within sampled thaw slump sediment was 1.36% and 0.11%, respectively. A combination of multispectral, thermal and irradiance (derived from the RPAS digital surface model) data provided detailed classification of thaw slump floor terrain types including raised dry clay lobes, shaded and relatively stable, and low-lying evacuation-prone sediments. Notably, the path of evacuation-prone sediments extended to a series of ice wedges in the northern headwall, where total irradiance was highest. Using thaw slump floor mean SOC and TN values in conjunction with sediment bulk density and thaw slump fill volume, we estimated that 713 t SOC and 58 t TN were exported to the Old Crow River during the three-year study. Findings showcase the utility of high-resolution RPAS datasets for refining our knowledge of thaw slump geomorphology and associated impacts.
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Graf, Emma L. S., Hugh D. Sinclair, Mikaël Attal, Boris Gailleton, Basanta Raj Adhikari y Bishnu Raj Baral. "Geomorphological and hydrological controls on sediment export in earthquake-affected catchments in the Nepal Himalaya". Earth Surface Dynamics 12, n.º 1 (16 de enero de 2024): 135–61. http://dx.doi.org/10.5194/esurf-12-135-2024.
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Abstract. Large earthquakes can contribute to mountain growth by building topography but also contribute to mass removal from mountain ranges through widespread mass wasting. On annual to decadal or centennial timescales, large earthquakes also have the potential to significantly alter fluvial sediment dynamics if a significant volume of the sediment generated reaches the fluvial network. In this contribution, we focus on the Melamchi–Indrawati and Bhote Koshi rivers in central Nepal, which have both experienced widespread landsliding associated with the 2015 Gorkha (Nepal) earthquake. Using a time series of high-resolution satellite imagery, we have mapped exposed sediment along the rivers from 2012–2021 to identify zones of active channel deposition and document changes over time. Counter to expectations, we show negligible increases in coarse-sediment accumulation along both river corridors since the Gorkha earthquake. However, an extremely high-concentration flow event on 15 June 2021 caused an approximately 4-fold increase in exposed sediment along a 30 km reach of the channel with up to 12 m of channel aggradation in the Melamchi–Indrawati rivers; this event was localised and did not impact the neighbouring Bhote Koshi catchment. Based on published reports, new helicopter-based photography, and satellite data, we demonstrate that this event was sourced from a localised rainfall event between 4500 and 4800 m and that a significant fraction of the sediment was supplied from sources that were unrelated to the landslides generated by the Gorkha earthquake.
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Gourdin, E., S. Huon, O. Evrard, O. Ribolzi, T. Bariac, O. Sengtaheuanghoung y S. Ayrault. "Sources and export of particle-borne organic matter during a monsoon flood in a catchment of northern Laos". Biogeosciences 12, n.º 4 (19 de febrero de 2015): 1073–89. http://dx.doi.org/10.5194/bg-12-1073-2015.
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Abstract. The yields of the tropical rivers of Southeast Asia supply large quantities of carbon to the ocean. The origin and dynamics of particulate organic matter were studied in the Houay Xon River catchment located in northern Laos during the first erosive flood of the rainy season in May 2012. This cultivated catchment is equipped with three successive gauging stations draining areas ranging between 0.2 and 11.6 km2 on the main stem of the permanent stream, and two additional stations draining 0.6 ha hillslopes. In addition, the sequential monitoring of rainwater, overland flow and suspended organic matter compositions was conducted at the 1 m2 plot scale during a storm. The composition of particulate organic matter (total organic carbon and total nitrogen concentrations, δ13C and δ15N) was determined for suspended sediment, soil surface (top 2 cm) and soil subsurface (gullies and riverbanks) samples collected in the catchment (n = 57, 65 and 11, respectively). Hydrograph separation of event water was achieved using water electric conductivity and δ18O measurements for rainfall, overland flow and river water base flow (n = 9, 30 and 57, respectively). The composition of particulate organic matter indicates that upstream suspended sediments mainly originated from cultivated soils labelled by their C3 vegetation cover (upland rice, fallow vegetation and teak plantations). In contrast, channel banks characterized by C4 vegetation (Napier grass) supplied significant quantities of sediment to the river during the flood rising stage at the upstream station as well as in downstream river sections. The highest runoff coefficient (11.7%), sediment specific yield (433 kg ha−1), total organic carbon specific yield (8.3 kg C ha−1) and overland flow contribution (78–100%) were found downstream of reforested areas planted with teaks. Swamps located along the main stream acted as sediment filters and controlled the composition of suspended organic matter. Total organic carbon specific yields were particularly high because they occurred during the first erosive storm of the rainy season, just after the period of slash-and-burn operations in the catchment.
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Antia, A. N. "Solubilization of particles in sediment traps: revising the stoichiometry of mixed layer export". Biogeosciences 2, n.º 2 (4 de agosto de 2005): 189–204. http://dx.doi.org/10.5194/bg-2-189-2005.
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Abstract. Sinking particles, once caught in sediment trap jars, release dissolved elements into the surrounding medium through leaching from their pore fluids, chemical dissolution and the activity of free exoenzymes. This results in an increase in dissolved elements in the trap jar supernatant. Elemental fluxes as traditionally measured by sediment traps underestimate total export when this particle-associated dissolved flux is not considered. The errors introduced are variable and alter both the absolute levels of flux as well as the stoichiometry of export. These errors have been quantified and corrections applied for samples from sediment traps in the North Atlantic based on measurements of excess dissolved carbon, nitrogen, phosphorus, silica and calcium in the supernatant of the collection cups. At the base of the winter mixed layer, on average 90±6% of phosphorus fluxes are found as excess phosphate whereas for carbon and nitrogen dissolved concentrations account for 30 (±8)% and 47(±11)% of total fluxes respectively. Excess dissolved silica is on average 61 (±17)% of total biogenic silica flux. Little (<10%) of calcium is solubilized. The proportion of dissolved to total flux decreases with trap deployment depth. Calculations of the C:N:P ratios for particles only are well above the Redfield ratios of 106:16:1 (Redfield et al., 1963), although the mid-water dissolved N:P and N:Si values as well as the C:N:P ratios of remineralisation along isopycnals conform to the Redfield ratios at this site. Accounting for dissolved fluxes of all these elements brings the stoichiometry of export in agreement with the Redfield Ratio and with other geochemical estimates of winter mixed layer export. A factor of 3 to 4 higher ratios of organic: inorganic carbon export also implies that the net atmospheric CO2 sequestration by the biological pump is about 50% higher at this site when the dissolved elemental fluxes are considered. Solubilization is thus a process that should be accounted for in protocols used to measure vertical fluxes with sediment traps.
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Mueller, E. N., A. Güntner, T. Francke y G. Mamede. "Modelling water availability, sediment export and reservoir sedimentation in drylands with the WASA-SED Model". Geoscientific Model Development Discussions 1, n.º 1 (2 de octubre de 2008): 285–314. http://dx.doi.org/10.5194/gmdd-1-285-2008.
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Abstract. The process-based, spatially semi-distributed modelling framework WASA-SED for water and sediment transport in large dryland catchments is presented. The WASA-SED model simulates the runoff and erosion processes at the hillslope scale, the transport processes of suspended and bedload fluxes in the river reaches and the retention and remobilisation processes of sediments in reservoirs. The modelling tool enables the evaluation of management options both for sustainable land-use change scenarios to reduce erosion in the headwater catchments as well as adequate reservoir management options to lessen sedimentation in large reservoirs and reservoir networks. The model concept, its spatial discretisation and the numerical components of the hillslope, river and reservoir processes are summarised and current model applications are reviewed to demonstrate the capabilities, strengths and limits of the model framework.
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Welsh, Molly K., Sara K. McMillan y Philippe G. Vidon. "Impact of Riparian and Stream Restoration on Denitrification in Geomorphic Features of Agricultural Streams". Transactions of the ASABE 63, n.º 5 (2020): 1157–67. http://dx.doi.org/10.13031/trans.13777.
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HighlightsDenitrification enzyme activity (DEA) was measured in stream sediments of restored and unrestored agricultural streams.Nitrate, sediment characteristics, riparian vegetation, and geomorphology influenced DEA.Pools at restored sites had lower organic carbon, coarser sediment textures, and lower denitrification potential.Restoration strategies should increase organic carbon and residence times through complex flowpaths.Abstract. Agricultural land use, channel modifications, and riparian vegetation composition can affect instream denitrification by altering geomorphic features, such as sediment texture, organic matter, retention time, and hyporheic exchange. Stream and riparian restoration is widely implemented in agricultural watersheds to mitigate excess nutrient export to sensitive downstream waters; however, the cumulative impact of channel reconstruction and altered channel and near-stream morphology on nitrogen dynamics remains poorly understood. We measured denitrification enzyme activity (DEA) and environmental variables (e.g., water chemistry, sediment texture, and organic matter) in different geomorphic features in agriculturally influenced streams in North Carolina with varied channel and riparian zone characteristics. Our results indicate that denitrification is primarily influenced by increased transport of nitrate (NO3-) to the streams in wetter months. Secondarily, structural factors, including riparian vegetation and stream geomorphology, impact denitrification by controlling the distribution of sediment texture and organic carbon. In the newly restored stream, we observed coarser streambed sediments and low sediment organic carbon, especially in scour pools constructed downstream from cross-vanes. Lower DEA was observed in restored pools (39.1 ng N g-1 dry mass h-1) compared to naturally occurring pools (70.7 to 278.1 ng N g-1 dry mass h-1). These results highlight the need for restoration strategies to be directed at increasing organic carbon and residence times through complex flowpaths (e.g., meanders, root wads, artificial woody debris dams). Keywords: Denitrification, Freshwater, Nitrogen, Restoration, Riparian, Stream, Water quality.
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White, Michael, Daren Harmel, Haw Yen, Jeff Arnold, Marilyn Gambone y Richard Haney. "Development of Sediment and Nutrient Export Coefficients for U.S. Ecoregions". JAWRA Journal of the American Water Resources Association 51, n.º 3 (30 de enero de 2015): 758–75. http://dx.doi.org/10.1111/jawr.12270.
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