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The rapid expansion of laver (Porphyra yezoensis) cultivation on lower tidal flats has become integral to the local economy, yet it also raises concerns regarding its potential impact on the morphological evolution due to increasing human activities. This study utilizes integrated near-bed field measurements to assess morphological dynamics and quantify sediment erosion processes, highlighting the significant impact of laver harvest on tidal flat stability. Our results show that erosion and bed coarsening in the cultivated areas experienced a notable intensification immediately after harvest, with net erosion in cultivated areas reaching approximately −38.2 mm during the first tide post-harvest, markedly higher—more than an order of magnitude—compared to adjacent uncultivated areas. The erosion rate notably spiked with the average bed level change rate increasing to −13.8 × 10−4 mm/s, compared to a rate of +0.3 × 10−4 mm/s during the unharvest period. Subsequently, the cultivated areas entered a recovery phase with a deposition amount of +12.5 mm, while the net cumulative erosion thickness throughout the entire observation period was −25.2 mm. The cultivation method, characterized by consistent harvests every 10 days, means that even minor erosion from continuous harvests can escalate into significant degradation. This study suggests that long-term cultivation cycle practices may result in irreversible changes to the depositional environment, potentially jeopardizing the habitat viability and ecological function. Sustainable agricultural strategies, including site selection, infrastructure planning, monitoring environmental changes, ecological assessments and sustainable practices, are recommended to mitigate the negative impacts of cultivation on regional stability and preserve the coastal ecological balance. [Display omitted] • Post-harvest erosion rates illustrate dramatic sediment loss in cultivated areas. • Regular harvesting practices lead to cyclic environmental degradation. • Strategies for sustainable cultivation enhance tidal flat ecosystem resilience. [ABSTRACT FROM AUTHOR]

— The sediment transport plays a major role in every aquatic ecosystem. However, the lack of instruments to monitor this process has been an obstacle to understanding its effects. We present the design of a single sensor built to measure water velocity, suspended sediment concentration and depth in situ , and how to associate the three variables to estimate and analyse sediment transport. During the laboratory calibrations, the developed instrument presented a resolution from 0.001 g/L to 0.1 g/L in the 0–12 g/L range for the measurement of suspended sediment concentration and 0.05 m/s resolution for 0–0.5 m/s range and 0.001 m/s resolution for 0.5–1 m/s range for the measurement of water velocity. The device was deployed for 6 days in an estuarine area with high sediment dynamics to evaluate its performance. During the field experiment, the sensor successfully measured the tidal cycles and consequent change of flow directions, and the suspended sediment concentration in the area. These measurements allowed to estimate water discharge and sediment transport rates during the different phases of tides, and the daily total volume of water and total amount of sediment passing through the estuary. • Development of an instrument for in-situ continuous monitoring of sediment transport. • Methodology to calibrate the sensor for flow velocity and sediment concentration. • Field experiment in an estuarine environment to measure hydraulic dynamics. • Measurement of the stream flow inversion during high and low tides. • Estimation of water discharge and sediment transport rate. [ABSTRACT FROM AUTHOR]

Water erosion poses a significant environmental threat in the Mediterranean region, with pronounced impacts observed throughout Morocco. It impairs soil quality and disrupts both sediment transport and water availability. Contributing factors range from natural (climate, topography, and geology) to anthropogenic (land use, vegetation cover, and management). This study introduces an improved Priority Actions Program/Regional Activity Centre (PAP/RAC) model, enriched with GIS and the Caesium-137 (137Cs) technique, to investigate erosion within Morocco's Raouz basin. Enhanced with additional variables including soil types, slope length, rainfall erosion potential, slope orientation, soil moisture, and land surface temperature, the model transcends the classical approach, promoting granularity and precision in predictions. In addition to the comprehensive model, the 137Cs method, which discerns long-term soil erosion and redistribution, provides a dual-faceted validation, bolstering the robustness of this project's erosion risk evaluation. This study's outcomes underscore the gravity of the erosion hazard with significant soil depletion rates ranging from 8.1 to 20 t ha−1 yr−1, demonstrating the model's alignment with empirical data, affirming its utility. The modified PAP/RAC model concurs with the 137Cs data, demonstrating its usefulness for water erosion assessment and management in similar areas. • The modified PAP/RAC model enhances erosion prediction. •Model validated with extensive 137Cs data. •GIS integration identifies erosion hotspots. •A comparative study with global erosion data. • The model adapts to diverse Mediterranean climates. [ABSTRACT FROM AUTHOR]

Hydro-morphological threats impact the natural physical characteristics of river ecosystems, such as flow regimes, sediment transport, and channel morphology. These negative effects can occur at multiple scales, ranging from local microhabitats to geographic regions. Understanding these interactions can be useful for an integrated conservation approach and is needed for effective freshwater management. The aim of the study was to elucidate the combined effects of hydro-morphological threats on macroinvertebrates at three spatial scales: macroscale, including whole catchments, mesoscale (hydro-morphological changes in individual river sections) and the microscale, describing the microhabitat conditions of European rivers. The diversity and trophic structure of 1120 local macroinvertebrate communities in 28 catchments of various hydro-morphological disturbance levels, ranging from 0 to 2400 m asl, were analyzed. The response of macroinvertebrates to the main disturbance gradient differed between mountain and lowland communities. Random forest analysis indicated that the most important predictor of the ecological, diversity, and trophic indices was described by flow rate reduction. Generalized additive mixed models showed that decreased flow combined with river incision explained most of the variation in macroinvertebrate indices. Our results emphasize that based on multi-spatial scale analysis, hydro-morphological threats are very important factors in invertebrates biodiversity loss. Thus, to implement effective river management, we should pay more attention to the combined effects of geomorphological threats. • Hydro-morphological disturbances lead to the loss of invertebrate biodiversity. • The effects of hydro-morphological pressure were studied at various spatial scales. • Incision and flow reduction described most of the river macroinvertebrates variation. • The most favourable microhabitats for macrofauna are shallow and redeposited sites. • Efficient river management should focus on the combined effects of multiscale threats. [ABSTRACT FROM AUTHOR]

The complexity of micro-tidal inlets arises from the combined action of littoral drift and tidal range on their stability. Consequently, understanding and evaluating their stability poses a significant challenge. This study aims to shed some insight on the assessment of inlet stability by employing Delft 3D model. The stability of the inlet between the ocean and estuary relies on the balance between the longshore transport rate and the spring tidal prism. Disrupting this equilibrium results in the closure of the inlets. The movement of sediments in the surf zone is primarily driven by longshore velocity, which acts as the driving force for littoral drift, which is estimated using Delft 3D wave model. The longshore transport rate is estimated by employing empirical relationships and numerical codes based on the obtained driving force. Subsequently, the stability of the inlet is assessed based on these estimations. The spring tidal prism refers to the discharge of water flowing into the ocean from inlets and estuaries. Flow velocity is determined using Delft 3D flow model. The input data for nearshore circulation resulting from waves and currents is primarily collected through field measurements and data collected from I ndian N ational C entre for O cean I nformation S ervices (INCOIS). For the current study, Muttukadu (12°47′13″N, 80°15′01″E) inlet, Kovalam along the East Coast of the Indian Peninsula is investigated by assessing its seasonal variations. This study contributes to the management of marine biological ecology, the expansion of small-scale artisanal fishing, the promotion of water sports-related tourism, the advancement of fishing harbor development, and the execution of coastal engineering projects. • This study tackled a complex challenge in coastal and hydraulic engineering. • The study aimed to understanding nearshore wave and current dynamics and its influence on sediment accretion in tidal inlet. • The Delft 3D model was used to estimate longshore velocity, currents, and sediment transport rates. • The stability assessment of the Muttukadu estuarine inlet was performed. [ABSTRACT FROM AUTHOR]

Sediment associated carbon and nitrogen loss under rainfall, an important cause of soil quality degradation and water eutrophication, strongly depends on the intrinsic properties of original soil types. Relative to total loss, the transport behaviors of organic carbon and nitrogen among sediment size classes and response to soil types remain poorly understood. The concentrations of organic carbon (OC) and total nitrogen (TN) in different sediment size classes (>1, 0.25–1, 0.10–0.25, and <0.10 mm) and their contributions to total sediment load during rainfall erosion were determined under field plot rainfall simulation (at 90 mm h−1) on three contrasting soil types (Luvisol, Alisol and Ferralsol) with increased aggregate stability. During rainfall erosion, the concentrations of OC and TN in total and different sized sediments decreased first and then reached a steady state. The variability of OC and TN concentrations (coefficient of variations in 4.2–53.1% and 6.6–41.9%) among sediment size classes decreased from Luvisol to Ferralsol. Compared to original soils, sediments exhibited larger C/N ratios for Luvisol, and smaller values for Alisol, indicating the more selective transport of labile organic matter for weaker aggregated soils. Among sediment size classes, fine particles (<0.10 mm) accounted 69–88% of total OC and TN losses for Luvisol, and decreased to 30–39% for Ferralsol; and the main transport mechanisms of sediment associated OC and TN shifting from suspension-saltation (<0.10 mm) to rolling (>0.25 mm) with increased aggregate stability. Among original soil properties, inorganic cementing agents (including amorphous iron oxides and clay minerals) showed closer relationships with sediment OC and TN losses (|r| = 0.61–0.89, p < 0.001) than organic matter properties (|r| = 0.55–0.87, p < 0.001), further implying the important role of soil aggregate stability across soil types. This study provides an in-depth understanding on soil carbon and nitrogen losses and their divergent characteristics among soil types deserves consideration in the development of erosion model and land management in agricultural systems. • Variability of OC and TN concentrations among sediment sizes decreased from Luvisol to Ferralsol. • Suspension-saltation (<0.10 mm) dominated OC and TN losses for weak aggregated soils. • Contribution of coarse particles by rolling to OC and TN losses increased with aggregate stability. • Runoff rate, iron oxides and sediment size controlled the loss characteristics of OC and TN. [ABSTRACT FROM AUTHOR]

Rainfall plays a crucial role in influencing the loss of agricultural diffuse pollution. The middle Yangtze River region is well-know for its humid climate and numerous agricultural activities. Thus, this study quantitatively analyzed the concentration and distribution of nitrogen (N) and phosphorus (P) load and loss in a major tributary of the middle Yangtze River under different rainfall patterns by using sampling analysis and SWAT model simulation. The total nitrogen (TN) and nitrate-nitrogen (NO 3 −) concentrations were 1.604–3.574 and 0.830–2.556 mg/L, respectively. The total phosphorous (TP) and Soluble Reactive Phosphorus (SRP) were 2–148 and 2–104 μg/L, respectively. The modeling results demonstrated that higher rainfall intensity led to greater load and loss flux of diffuse pollutant at the outlet. Organic nitrogen (ORGN) is the main nitrogen form transported from the subbasin to the reach, while organic phosphorus (ORGP) and inorganic phosphorus (INORGP) were transported at similar amounts. Under the condition of conventional rainfall, the outlet reaches mainly transported NO 3 −, and ORGN gradually increased when rainstorm events occurred. The ratio of INORGP to ORGP was relatively stable. During extreme rainfall event, rainfall is the dominant element of agricultural diffuse pollution. A strong positive correlation exists between rainfall intensity and pollution loss during rainstorms. Storm rain events were the main source of TN and TP losses. Few storm rain days generated pollutants that accounted for a large proportion of the total loss, and their impact on TP loss was significantly greater than that of TN. The influence of storm rain on TN is mainly the increase in runoff, while TP is sensitive to the runoff and sediment transport promoted by rainfall. By setting different precipitation scenarios, it was confirmed that under the same rainfall amount, short-term storm rain has the most significant impact on the TN load, whereas TP load may be influenced more by the combined effects of rainfall duration and intensity. Therefore, to reduce the impact of agricultural diffuse pollution, it is important to take targeted measures for the rainstorm days. • The dynamics of diffuse pollution under different rainfall patterns were analyzed. • Storm rain is the main source of nitrogen and phosphorus pollution loss. • Compared with nitrogen, phosphorus loss is more sensitive to storm rain. • Short-term storm rain can significantly increase the annual load of nitrogen. [ABSTRACT FROM AUTHOR]

Flooding is one of the most significant environmental challenges and can easily cause fatal incidents and economic losses. Flood reduction is costly and time-consuming task; so it is necessary to accurately detect flood susceptible areas. This work presents an effective flood susceptibility mapping framework by involving an adaptive neuro-fuzzy inference system (ANFIS) with two metaheuristic methods of biogeography based optimization (BBO) and imperialistic competitive algorithm (ICA). A total of 13 flood influencing factors, including slope, altitude, aspect, curvature, topographic wetness index, stream power index, sediment transport index, distance to river, landuse, normalized difference vegetation index, lithology, rainfall and soil type, were used in the proposed framework for spatial modeling and Dingnan County in China was selected for the application of the proposed methods due to data availability. There are 115 flood occurrences in the study area which were randomly separated into training (70% of the total) and verification (30%) sets. To perform the proposed framework, the step-wise weight assessment ratio analysis algorithm is first used to evaluate the correlation between influencing factors and floods. Then, two ensemble methods of ANFIS-BBO and ANFIS-ICA are constructed for spatial prediction and producing flood susceptibility maps. Finally, these resultant maps are assessed in terms of several statistical and error measures, including receiver operating characteristic (ROC) curve and area under the ROC curve (AUC), root-mean-square error (RMSE). The experimental results demonstrated that the two ensemble methods were more effective than ANFIS in the study area. For instance, the predictive AUC values of 0.8407, 0.9045 and 0.9044 were achieved by the methods of ANFIS, ANFIS-BBO and ANFIS-ICA, respectively. Moreover, the RMSE values for ANFIS, ANFIS-BBO and ANFIS-ICA using the verification set were 0.3100, 0.2730 and 0.2700, respectively. In addition, as regards ANFIS-BBO and ANFIS-ICA, a total areas of 39.30% and 35.39% were classified as highly susceptible to flooding. Therefore, the proposed ensemble framework can be used for flood susceptibility mapping in other sites with similar geo-environmental characteristics for taking measures to manage and prevent flood damages. Image 1 • Prediction power of two novel ensemble methods for flood susceptibility mapping. • The proposed ensemble methods can improve the prediction performance of ANFIS. • The proposed methods can accurately produce flood susceptibility maps for mitigation and management. [ABSTRACT FROM AUTHOR]

Change of hydrodynamic conditions is a key factor inducing sedimentation, water eutrophication and algal blooms in the Three Gorges Reservoir (TGR). How to mitigate sedimentation and phosphorus (P) retention by improving hydrodynamic conditions in the Three Gorges Reservoir area (TGRA) is an urgent issue in the study of sediment and water environment. In this study, a Hydrodynamic-Sediment-Water quality model for the whole TGRA is proposed considering sediment and P inputs from numerous tributaries, and a new reservoir operation method namely the tide-type operation method (TTOM) is used to investigate the large-scale sediment and P transport in the TGR based on the model. Results indicate that the TTOM can reduce sedimentation and total phosphorus (TP) retention in the TGR. Compared with the actual operation method (AOM), sediment outflow and sediment export ratio (E ratio) of the TGR increased about 17.13% and 1%–3% in 2015–2017, and sedimentation decreased about 3% under the TTOM. TP retention flux and retention rate (RE) decreased about 13.77% and 2%–4%. The flow velocity (V) and sediment carrying capacity (S *) increased about 40% in the local reach. Larger daily water level fluctuation at dam site is more conducive to reducing sedimentation and TP retention in the TGR. Sediment inputs from the Yangtze River, Jialing River, Wu River and other tributaries account for 59.27%, 11.21%, 3.81% and 25.70% of the total sediment inflow during 2015–2017, and TP inputs were 65.96%, 10.01%, 17.40% and 6.63%. In the paper, an innovative method is proposed to reduce sedimentation and P retention in the TGR under the given hydrodynamic conditions and related quantitative contribution driven by the proposed method is analyzed. The work is favorable for expanding the understanding of the hydrodynamic and nutrition flux changes in the TGR, and provides a new perspective for water environment protection and reasonable operation of large reservoirs. • A Hydrodynamic-Sediment-Water quality model for the whole TGR area was proposed. • A new operation method was used to study the sediment and P transport in the TGR. • The new operation method can alleviate sedimentation and TP retention in the TGR. [ABSTRACT FROM AUTHOR]

Abstract Decreasing per capita water consumption in several OECD countries has led to a notable flow reduction into sewer systems. However, sewers still transport similar quantities of solids and pollutants, leading to increased wastewater concentration and, potentially, excess solids deposition. The shift towards decentralised water schemes in cities and widely reported changes in rainfall patterns cast additional uncertainty on future wastewater quality and flows into sewers. Excess solids deposition in sewers can cause increased environmental pollution risks at Combined Sewer Overflows from solids resuspension and reduced sewer hydraulic capacities. This review analyses the magnitude of excess solids deposition due to changing wastewater composition and evaluates current approaches to modelling sewer solids. Gaps in commonly used modelling approaches for deposited bed processes, specifically in bed consolidation and bed particle cohesion processes, and gross solids transport were identified and addressed to enable better solids risk prediction and management. Graphical abstract Image 1072 Highlights • Future water use practices will increase the risk of excess sewer solids deposition. • There is a need to enhance certain aspects of current sewer solids models. • A pathway for the development and scaling up of an enhanced model is discussed. [ABSTRACT FROM AUTHOR]

Abstract Oospores of Cryptosporidium , a waterborne pathogen of great concern, are widely distributed in surface waters in China and pose a threat to human health. This study seeks to explore the spatio-temporal patterns of Cryptosporidium concentrations. We focus on the Daning River watershed (4166 km2) of the Three Gorges Reservoir Region (TGR) during the period 2008 to 2013 and use the SWAT (Soil and Water Assessment Tool) model to test two mitigation scenarios. Based on data on animal husbandry, population, agriculture and WWTPs (wastewater treatment plants), Cryptosporidium transport in the Daning River watershed was simulated using a calibrated hydrological and sediment transport model. Our model results showed that the average annual concentration of oocysts in the whole watershed was 9.5 oocysts/10L, but high spatial variability occurred, ranging from 0.7 to 33.4 oocysts/10L. Highest monthly mean oocysts concentrations at the outlets of the sub-basins were found at high runoff and high fertilization or at the lowest flow, while minimum monthly mean oocysts concentrations were recorded at high runoff only. A model parameter sensitivity analysis showed that the Cryptosporidium soil partitioning coefficient (BACTKDQ) and the temperature adjustment factor for Cryptosporidium die-off (THBACT) were the only two sensitive parameters among the microbial parameters. The construction of multiple WWTPs throughout the watershed and composting of 50% of the feces from rural citizens and livestock up to 56 days before its application as fertilizer could significantly reduce the concentration of oocysts. Our Cryptosporidium transport model and simulation results may assist in the establishment of better pollution control countermeasures in the Daning River and other similar watersheds. Graphical abstract Conceptual representation of the Cryptosporidium transport processes in Daning River Watershed modelled by SWAT. Image Highlights • The first study to model the fate and transport of Cryptosporidium in a watershed of a developing country. • The effect of runoff on the Cryptosporidium load should be considered together with other factors such as fertilization and the sources of pollution. • Two mitigation scenarios were modelled, both predicting a significant reduction of Cryptosporidium load. [ABSTRACT FROM AUTHOR]

Soil degradation due to erosion is connected to two serious environmental impacts: (i) on-site soil loss and (ii) off-site effects of sediment transfer through the landscape. The potential impact of soil erosion processes on biogeochemical cycles has received increasing attention in the last two decades. Properly designed modelling assumptions on effective soil loss are a key pre-requisite to improve our understanding of the magnitude of nutrients that are mobilized through soil erosion and the resultant effects. The aim of this study is to quantify the potential spatial displacement and transport of soil sediments due to water erosion at European scale. We computed long-term averages of annual soil loss and deposition rates by means of the extensively tested spatially distributed WaTEM/SEDEM model. Our findings indicate that soil loss from Europe in the riverine systems is about 15% of the estimated gross on-site erosion. The estimated sediment yield totals 0.164 ± 0.013 Pg yr −1 (which corresponds to 4.62 ± 0.37 Mg ha −1 yr −1 in the erosion area). The greatest amount of gross on-site erosion as well as soil loss to rivers occurs in the agricultural land (93.5%). By contrast, forestland and other semi-natural vegetation areas experience an overall surplus of sediments which is driven by a re-deposition of sediments eroded from agricultural land. Combining the predicted soil loss rates with the European soil organic carbon (SOC) stock, we estimate a SOC displacement by water erosion of 14.5 Tg yr −1 . The SOC potentially transferred to the riverine system equals to 2.2 Tg yr −1 (~15%). Integrated sediment delivery-biogeochemical models need to answer the question on how carbon mineralization during detachment and transport might be balanced or even off-set by carbon sequestration due to dynamic replacement and sediment burial. [ABSTRACT FROM AUTHOR]

Forty nine sediment samples were collected [Upstream section: Zahuapan River (1–12) and Atoyac River (13–20); Confluence Zone (21–31); Valsequillo dam (32–49)] to investigate the geochemical sources, enrichment, contamination and ecological risks of metals in the fluvial sediments of Atoyac River basin, an area experiencing tremendous urban and industrial development in Central Mexico. The sediments were analyzed for 23 major (Al, Fe, Ca, Mg, Na, K, P, S & Ti) and trace (Ba, Mn, As, Co, Cr, Cu, Mo, Ni, Pb, Sc, Sr, V, Zn & Zr) acid leachable metals (ALMs). The grain size results revealed that the sand fraction of sediments accounts for 53.1% and silt for 46.9% respectively. The concentration pattern (avg. values) shows a spatial distribution of metals in the four zones indicating that S (0.10; 0.13; 0.34; 0.80 in %), Ca (0.96; 0.73; 4.98; 1.85 in %), P (0.05; 0.05; 0.16; 0.08 in %), Cr (122; 182; 111; 104 in µg g −1 ), Mo (5; 9; 6; 10 in µg g −1 ), Cu (13; 14; 53; 29 in µg g −1 ), Ni (19; 22; 29; 46 in µg g −1 ), Pb (9; 12; 21; 14 in µg g −1 ), Zn (92; 62; 204; 92 in µg g −1 ) & As (2.63; 2; 3.35; 4.49 in µg g −1 ) exceeded the local background values primarily attributed to the natural volcanic inputs. Geochemical indices such as enrichment factor (EF), geoaccumulation index (I geo ) and pollution load index (PLI) were used to assess the degree of metal enrichment and the results revealed significant external influences over some metals (As, Cu, Pb and Zn). The calculation of potential ecological hazards index showed that among 23 tested metals, As, Pb, Cu, Ni and Cr were the main potential risk factors that will cause harmful biological effects in the riverine environment. A new complementary approach which integrates metal contamination, enrichment and ecological risks aided in more accurate determination of metal sources and their environmental impacts. Multivariate statistical analysis revealed the groupings of elements as lithogenic (Al, Fe, Ca, Mg, Na, K, P, S, Ti, Ba, Mn, Co, Cr, Ni, Sc, Sr, V & Zr) and external (Cu, Pb, Zn, Mo & As) suggesting that the metal sources are from volcanic events, natural weathering processes and the industrial influences from the Puebla City. [ABSTRACT FROM AUTHOR]

We examined the temporal profiles of many organic micropollutants analysed in a sediment core sampled from a highly anthropized tributary of the Po River, the Lambro River. Analysed for extractable organic halogens (EOX), total petroleum hydrocarbons (C 10 –C 40 TPH), polycyclic aromatic hydrocarbons (PAHs), common legacy pollutants (DDTs, PCBs), halogenated flame retardants (PBDEs, DBDPE, TBBPA-bis, TCBPA, TBBPA, HBCDs), organotins (TBT, TPhT), antimicrobials (TCS, TCC), fragrances (AHTN, HHCB) and phthalates (DMP, DEP, DnBP, BBP, DEHP, DnOP), the dated sediment core revealed the historical record of 50 years of chemical contamination discharged into the Lambro and thereby the Po River. In this regard, the peak levels of PCBs and DDTs found in Lambro sediments were also identified in other sediment cores collected from the Po River prodelta in the Adriatic Sea, thus hundreds of kilometres downstream (Combi et al., 2020). The highest risk to aquatic organisms was associated with decades of high levels of C 10 –C 40 TPH, PBDEs, PCBs, PAHs, DDTs, EOX, TCC, AHTN and DEHP, which in different periods of the contamination history, showed exceedances of guideline/threshold values. C 10 –C 40 TPH and TCC, for example, were very high in the 1960s, whereas PCBs, DDTs, and PBDEs, peaked from the 1980s onward. The corresponding sums of PEC quotients ranged between 0.48 and 28.63, with a mean value (±SD) for the entire recording period of 10.62 ± 9.83. Environmental legislations and improved wastewater treatments were the main drivers of the recent downward trends observed for most of the chemicals investigated. Floods in turn resulted in macroscopic yet temporary improvements in the chemical quality of the tributary, conveying contaminated sediments into the Po River. [Display omitted] • Many chemicals analysed in a sediment core of a highly polluted tributary of the Po River. • The 50-year contamination record showed long exceedances of guideline/threshold values. • Polluting peaks from the Lambro River had corresponding peaks in the Adriatic Sea. • Most of the chemicals investigated have endocrine disrupting potentials. [ABSTRACT FROM AUTHOR]

Reliable quantitative information on sediment sources to rivers is critical to mitigate contamination and target conservation and restoration actions. However, for large-scale river basins, determination of the relative importance of sediment sources is complicated by spatiotemporal variability in erosional processes and sediment sources, heterogeneity in sediment transport and deposition, and a paucity of sediment monitoring data. Sediment source fingerprinting is an increasingly adopted field-based technique that identifies the nature and relative source contribution of sediment transported in waterways. Notably, sediment source fingerprinting provides information that is independent of other field, modeling, or remotely sensed techniques. However, the diversity in sampling, analytical, and interpretive methods for sediment fingerprinting has been recognized as a problem in terms of developing standardized procedures for its application at the scale of large river basins. Accordingly, this review focuses on sediment source fingerprinting studies conducted within the Mississippi River Basin (MRB), summarizes unique information provided by sediment source fingerprinting that is distinct from traditional monitoring techniques, evaluates consistency and reliability of methodological approaches among MRB studies, and provides prospects for the use of sediment source fingerprinting as an aid to large-scale landscape conservation and restoration under current management frameworks. Most MRB studies reported credible fingerprinting results and found near-channel sources to be the dominant sediment sources in most cases, and yet a lack of standardization in procedural steps makes results difficult to compare. Findings from MRB studies demonstrated that sediment source fingerprinting is a highly valuable and reliable sediment source assessment approach to assist land and water resource management under current management frameworks, but efforts are needed to make this technique applicable in large-scale landscape conservation and restoration efforts. We summarize research needs and discuss sediment fingerprinting use for basin-scale management efforts with the aim of encouraging that this technique is robust and reliable as it moves forward. • Sediment fingerprinting studies within the Mississippi River Basin were reviewed. • Most studies considered near-channel sources as the dominant sediment sources. • Comparability of studies suffers from a lack of standardization in procedural steps. • Sediment fingerprinting is a reliable technique under current management frameworks. • Efforts are needed to make this approach applicable to large-scale landscapes. [ABSTRACT FROM AUTHOR]

One of the greatest threats to maintaining sustainable agro-ecosystems is mitigating the episodic soil loss from farm operations, further exacerbated by meteorological extremes. The Revised Universal Soil Loss Equation (RUSLE) is a model that combines the effects of rain, soil erodibility, topography, land cover, and conservation practices for estimating the annual average soil losses. This study aims to quantify soil water erosion to continental South America (S.A.) through RUSLE using available datasets and characterizing the average sediment delivery rate (SDR) to the major S.A. basins. Soil erodibility was estimated from the Global Gridded Soil Information soil database. LS-factor's topographical parameter was derived from Digital Elevation Models using the "Shuttle Radar Topography Mission" dataset. The R-factor was estimated from a previous study developed for S.A. and the C-factor from the Global Land Cover (Copernicus Global Land Services) database. We used a modeling study for SDR that simulated the annual average sediment transport in 27 basins in S.A. RUSLE set up presented a satisfactory performance compared to other applications on a continental scale with an estimated averaged soil loss for S.A. of 3.8 t ha−1 year−1. Chile (>20.0 t ha−1 year−1) and Colombia (8.1 t ha−1 year−1) showed the highest soil loss. Regarding SDR, Suriname, French Guyana, and Guyana presented the lowest values (<1.0 t ha−1 year−1). The highest soil losses were found in the Andes Cordillera of Colombia and the Center-South Region of Chile. In the former, the combination of "high" K-factor, "very high" C-factor, and "very high" LS-factor were the leading causes. In the latter, agriculture, livestock, deforestation, and aggressive R-factor explained the high soil loss. Basins with the highest SDR were located in the North Argentina – South Atlantic basin (27.73%), Mar Chiquitita (2.66%), Amazon River basin (2.32%), Magdalena (2.14%) (in Andes Cordillera), and Orinoco (1.83%). • Water erosion is one of the most relevant impacts on sustainable food production. • South America (S.A.) shelters several biomes and landscapes on the earth planet. • Countries in S.A. are highly dependent on agricultural and livestock for their GPD. • RUSLE was set up for the first time in all S.A. to identify critical erosion areas. • Planning and management of the soils are fundamental for a cleaner production. [ABSTRACT FROM AUTHOR]

Sedimentation affects the normal function of reservoirs and is a decisive factor in the reservoir's service life. Flushing sediment during reservoir operation is an effective non-engineering measure to alleviate reservoir sedimentation; however, lowering water level to discharge more flow conflicts with hydropower generation. In this study, reservoir management software is developed to simultaneously optimise sediment discharge and hydropower generation with the reservoir discharge as the decision variables. The sediment transport rate is calculated by an integral of the vertical distribution of suspended load concentration and flow velocity instead of empirical formulas. The model is solved by the most widely used multi-objective optimisation algorithm NSGA-II, resulting in the optimal schedule corresponding to the maximal sediment discharge and hydropower generation, which can be displayed graphically in the software. The software was developed in MATLAB with a Graphical User Interface (GUI) and applied to a large reservoir and can be generalised to other reservoirs. The results show that within the recommended discharge variation of 5%, the sediment release can be increased by 2.07 × 106 t as a reduction of per 1010 kW h in annual power generation. Compared with the original scheme, sediment release can be increased most by 3.31% at the cost of 0.03% loss of power generation. Moreover, the dual objective in the flood season was optimised by 7.30% and 3.92%, respectively. • Novel calculation equation sediment transport rate for reservoirs based on vertical distribution of suspended load. • Multi-objective reservoir operation for sediment flushing and power generation. • Common Software Platform providing optimal reservoir schedule for decision makers. [ABSTRACT FROM AUTHOR]

Forest fires intensify sediment transport and aggravate local and off-site consequences of soil erosion. This study evaluates the influence of post-fire measures on structural and functional sediment connectivity (SC) in five fire-affected Mediterranean catchments, which include 929 sub-catchments, by using the "aggregated index of connectivity" (AIC) at two temporal scenarios: I) immediately after the fire and before implementing post-fire practices ('Pre-man'), and II) two years after the fire ('Post-man'). The latter includes all the emergency stabilization practices, that are hillslope barriers, check-dams and afforestation. The stream system was set as the target of the computation (STR), to be representative of intense rainfall-runoff events with effective sediment delivery outside the catchments. Output normalization (AIC N) allows comparing the results of the five basins between them. The sedimentological analysis is based on specific sediment yield (SSY) –measured at the check-dams installed after the fire –, and this data is used for output evaluation. Stream density and slope variables were the most influential factors on AIC N-STR results at the sub-catchment scale. Post-fire hillslope treatments (barriers when built in high densities and afforestation) significantly reduced AIC N-STR in comparison with untreated areas in both structural and functional approaches. Despite the presence of hillslope treatments, the higher erosive rainfall conditions resulted in higher AIC N-STR values in the Post-man scenario (functional approach). A positive and good correlation was found between the measured SSY and the AIC N-STR changes due to the post-fire practices and vegetation recovery, showing the good correspondence of the computation results and the real sediment dynamics of the studied catchments. Overall, AIC N demonstrated to be a useful and versatile tool for post-fire management, which needs further research to optimize its applicability. [Display omitted] • High-density hillslope barriers and afforestation boosted lower connectivity. • Under intense rainfall conditions, an increase of lateral connectivity is observed. • Check-dams produced a clear and local disconnectivity in the flow path. • Changes in connectivity correlated well with measured SSY and stabilization measures density. • AIC reflected satisfactorily the effects of the different emergency stabilization measures. [ABSTRACT FROM AUTHOR]

A healthy mangrove ecosystem includes diverse landscape structures, such as tidal flats, tidal channels, and areas with circulating waters, in addition to mangrove stands. The complex structure of mangrove forests affects the hydrodynamics and sediment transport behaviour of tidal channels. Understanding the influence of the mangrove invasion of tidal flats on the pattern and stability of tidal channels is essential. In this study, two types of remote sensing images, Google Earth images and aerial photographs, were collected to analyze the relationship between mangrove colonization and changes in tidal channel patterns. After applying binary image processing, these two kinds of images show similar abilities to discriminate the locations, extents, and boundaries of mangroves and tidal channels. We found that the mangrove area was inversely proportional to the tidal channel sinuosity and width. The tidal channels exhibited a meandering pattern with a wider width before the mangroves invaded the tidal flats. After the expansion of the mangroves, the tidal channels gradually transformed into a straight shape with a narrower width. After the mangroves developed into forests, the tidal channels maintained a straight and stable pattern. Since mangroves promote siltation and increase the elevation of the surrounding mudflats, the habitat suitability for mangroves in the neighbouring tidal flat areas may vary. These processes may help expand mangrove habitats, thereby compressing the area of flats and changing the shape of tidal channels. Due to tidal current effects, the unit stream power of a straight tidal channel is approximately twice that of a meandering channel, indicating that straight tidal channels have a stronger anti-siltation capability. Our research also found that the tidal channels may return to a meandering pattern when mangroves are degraded or die and their area decreases. This study provides key evidence that mangroves affect tidal channel types and hydrodynamic characteristics, thus providing a useful reference for restoring and managing estuarine mangrove ecosystems. [Display omitted] • Remote sensing binary imagery is used to monitor mangroves and tidal channels. • Mangrove area is inversely proportional to tidal channel sinuosity and width. • Tidal channels maintain a straight pattern after mangrove forest development. • Tidal channels may return to a meandering pattern on mangrove degradation or death. • A straight tidal channel has twice the unit stream power of a meandering channel. [ABSTRACT FROM AUTHOR]

Concrete grade-control structures (CGCSs) have broad application prospects in the restoration of large rivers. But there is a lack of indicators to evaluate CGCSs at laboratory study. In this study, we proposed two evaluation indicators from the perspective of the impact of CGCSs on geomorphology change and fish habitat, namely the spatial-averaged occurrence probability of sweep events near the bed and flow diversity. To verify the reasonableness of these indicators, flume experiments were conducted with CGCSs built by modified fish-nest bricks in different Reynolds number and layout condition. Data of the flow field around structures in streamwise, transverse and vertical direction was obtained and analyzed. Results of mean flow field show that large recirculation zones are found in the cavity and behind the element. The mechanism of suspended sediment deposition around CGCSs in the flow can be further clarified by combining sweep and ejection according to quadrant analysis. In the vertical direction, the ratio of sweep to total events near bed after spatial-averaged processing is found to be higher for the staggered array. According to the Shannon's entropy, water flow diversity was calculated to quantify the fish habitat. The water flow diversity index around the CGCSs is higher for the staggered. It can be concluded that the elements of CGCSs in staggered manners have a better protection for riverbed and can provide a more stable fish habitat suitability. The results anticipated by the spatial-averaged occurrence probability of sweep events near bed and flow diversity in the experiment are consistent with the result of previous research on landform change and fish habitat. The research could provide a theoretical basis for the application of CGCSs for river restoration. • Concrete grade-control structures (CGCSs) were examined in a lab-based study. • Two indicators are proposed to evaluate the CGCSs. • Elements among the CGCSs laid in staggered manner have a better performance. [ABSTRACT FROM AUTHOR]

Accessible sediment provenance information is highly desirable for guiding targeted interventions for reducing excess diffuse agricultural sediment losses to water. Conventional sediment source fingerprinting methods can provide this information, but at high cost, thereby limiting their widespread application for catchment management. The use of sediment colour measured using an office document scanner represents an easy, fast, and inexpensive alternative method to trace sediment sources. However, the potential for poor source discrimination and its non-conservatism due to enrichment in sediment organic matter content during sediment transport represent possible limitations to its use. As such, the treatment of samples using hydrogen peroxide to remove organic matter can potentially improve source discrimination based upon geology or soil type, and the mapping of differences in colour between source and sediment samples removing the need for a priori source groups, were trialled in a new colour-based tracing framework. The River Avon in southwest England and Holbeck/Wath Beck in northeast England were studied as they have been identified as being of high priority for the targeting of on-farm advice delivered through a long-running agri-environment initiative. In both catchments, colour was effective at identifying that a small proportion of each which would be considered as being low erosion risk was the dominant source of the sampled sediment. This was due to poor connectivity between fields deemed to be at high risk of erosion and stream channels. The hydrogen peroxide sample treatment confirmed that sediment colour was not significantly altered by enrichment in organic matter content. This treament and the mapped comparison between source and suspended sediment colour improved source discrimination allowing for the more spatially-refined identification of critical sediment source areas. It is argued that this new inexpensive procedure can potentially deliver more precise and reliable information to catchment managers than costly quantitative sediment source fingerprinting methods. This method can greatly increase the availability of catchment-specific sediment source data and therefore the robust targeting of management efforts on a national scale. • Colour was effective at tracing sediment sources in both catchments. • Hydrogen peroxide treatment significantly improved source discrimination. • Sediment losses were from a small part of each catchment with a low erosion risk. • The proposed method can out perform quantiative fingerprinting methods. • The inexpensively generated data can improve catchment management support. [ABSTRACT FROM AUTHOR]

The distribution, partitioning behavior, and diffusion of polycyclic aromatic hydrocarbons (PAHs) within sediment–porewater system were determined in two cores obtained from the Min-Zhe coastal mud of the East China Sea (ECS). Depth profiles of apparently dissolved PAH levels exhibited greater variabilities, with their elevated levels at depth and a high abundance of two-to three-ring PAHs observed. These distribution and composition patterns were inconsistent with the corresponding sediment PAHs, indicating differences in controlling factors for PAHs present in the system. In addition to compound's hydrophobicity, low detection of heavier PAHs in porewater was possibly correlated with the sediment transport process, as indicated by a relatively high weathering ratio in southern Min-Zhe coastal mud. PAH sorption affinity to the collected core sediments exhibited a generally decreasing trend downcore, as expressed by sediment–porewater partition coefficients. This was consistent with the higher content of porewater PAHs in deep core sediment. The established sediment total organic carbon (TOC)–porewater partitioning profiles in cores were predicted with amorphous organic carbon (AOC)-, coal tar-, and TOC-based distribution models, suggesting a dominant nonlinear sorption of PAHs to AOC. Through activity determinations, PAH diffusion within porewater was elucidated, with significant upward and downward mass transfer for PAHs occurring in both cores. The upward diffusion in the core collected from northern Min-Zhe coastal mud was in significant association with sediment TOC. This suggests that sediment TOC (especially AOC)-desorption of lighter PAHs into porewater, and therefore the possibility of their participation in environmental cycling. Baseline toxicity potential and toxic unit calculations indicated a relatively low exposure risk for benthic organisms to porewater PAHs. • Profiles and dominating factors of PAH levels in sediment and porewater differed. • Sorption of PAHs to amorphous organic carbon prevailed overall sorptive process. • Porewater PAHs presented upward and downward diffusion based on activity profiles. • PAH diffusion tendency in porewater was correlated with core sediment sorption. [ABSTRACT FROM AUTHOR]

Wildfire is a common disturbance that can significantly alter vegetation in watersheds and affect the rate of sediment and nutrient transport to adjacent nearshore oceanic environments. Changes in runoff resulting from heterogeneous wildfire effects are not well-understood due to both limitations in the field measurement of runoff and temporally-limited spatial data available to parameterize runoff models. We apply replicable, scalable methods for modeling wildfire impacts on sediment and nonpoint source pollutant export into the nearshore environment, and assess relationships between wildfire severity and runoff. Nonpoint source pollutants were modeled using a GIS-based empirical deterministic model parameterized with multi-year land cover data to quantify fire-induced increases in transport to the nearshore environment. Results indicate post-fire concentration increases in phosphorus by 161 percent, sediments by 350 percent and total suspended solids (TSS) by 53 percent above pre-fire years. Higher wildfire severity was associated with the greater increase in exports of pollutants and sediment to the nearshore environment, primarily resulting from the conversion of forest and shrubland to grassland. This suggests that increasing wildfire severity with climate change will increase potential negative impacts to adjacent marine ecosystems. The approach used is replicable and can be utilized to assess the effects of other types of land cover change at landscape scales. It also provides a planning and prioritization framework for management activities associated with wildfire, including suppression, thinning, and post-fire rehabilitation, allowing for quantification of potential negative impacts to the nearshore environment in coastal basins. [ABSTRACT FROM AUTHOR]

The identification of critical source areas (CSAs) is a key element in a cost-effective mitigation of diffuse emissions of phosphorus from agricultural soils into surface waters. One of the challenges related to CSAs is how to couple complex, data-intensive fate and transport models with easy-to-use information on field level for management purposes at the scale of large watersheds. To fill such a gap and create a bridge between the two tasks, this study puts forward the new Particulate PhozzyLogic Index (PPLI) based on the innovative combination of the results of a complex watershed model (in this case the PhosFate model) with fuzzy logic. Its main feature is the ability to transform the results of diverse scenarios or even models into a final map showing a catchment-wide ranking of the possibility of high PP emissions reaching surface waters for all agricultural fields. Further, this study enhances the PhosFate model with a new algorithm for the allocation of particulate phosphorus (PP) loads entering surface waters to their sources of origin. This is a basic requirement for the identification of critical PP source areas and in consequence for a cost-effective implementation of mitigation measures. By means of a sensitivity analysis, this study investigates the impacts of storm drains, discharge frequencies and flow directions on the designation of CSAs with the help of present-day scenarios for a case study catchment with an area of several hundred square kilometres. The upfront model calibration exhibits a Nash-Sutcliffe efficiency (NSE) of about 0.95 and a modified Nash-Sutcliffe efficiency (mNSE) of around 0.83. A core result of the sensitivity analysis is that the scenarios at least partially disagree on the identified CSAs and suggest that especially open furrows at field borders have the potential to lead to deviating outcomes. All scenario results nevertheless support the 80:20 rule, which states that about 80% of the phosphorus inputs into the surface waters of a catchment originate from only about 20% of its area. [Display omitted] • Presentation of a source allocation algorithm for PP loads entering surface waters. • Coupling of the PhosFate with the STREAM model. • Application of fuzzy logic for the identification of critical source areas. • Validation of the Pareto principle for critical PP source areas. • Development of the Particulate PhozzyLogic Index (PPLI) for policy makers. [ABSTRACT FROM AUTHOR]

Non-point source pollution from agricultural lands is a significant contributor of sediment pollution in United States lakes and streams. Therefore, quantifying the impact of individual field management strategies at the watershed-scale provides valuable information to watershed managers and conservation agencies to enhance decision-making. In this study, four methods employing some of the most cited models in field and watershed scale analysis were compared to find a practical yet accurate method for evaluating field management strategies at the watershed outlet. The models used in this study including field-scale model (the Revised Universal Soil Loss Equation 2 – RUSLE2), spatially explicit overland sediment delivery models (SEDMOD), and a watershed-scale model (Soil and Water Assessment Tool – SWAT). These models were used to develop four modeling strategies (methods) for the River Raisin watershed: Method 1) predefined field-scale subbasin and reach layers were used in SWAT model; Method 2) subbasin-scale sediment delivery ratio was employed; Method 3) results obtained from the field-scale RUSLE2 model were incorporated as point source inputs to the SWAT watershed model; and Method 4) a hybrid solution combining analyses from the RUSLE2, SEDMOD, and SWAT models. Method 4 was selected as the most accurate among the studied methods. In addition, the effectiveness of six best management practices (BMPs) in terms of the water quality improvement and associated cost were assessed. Economic analysis was performed using Method 4, and producer requested prices for BMPs were compared with prices defined by the Environmental Quality Incentives Program (EQIP). On a per unit area basis, producers requested higher prices than EQIP in four out of six BMP categories. Meanwhile, the true cost of sediment reduction at the field and watershed scales was greater than EQIP in five of six BMP categories according to producer requested prices. [Copyright &y& Elsevier]

Coarse sediment transport in fluvial systems serves an important role in determining in-stream physical habitat, spawning potential and benthic community structure. However, despite more than a decade of pressure in Europe to restore stream continuity under the Water Framework Directive (WFD), there have been relatively few empirical studies on how low-head, run-of-river structures (i.e., weirs) disrupt the processes and dynamics of bedload conveyance. In this study we present an investigation into how coarse sediment is transferred through a low-head dam via the real-time monitoring of bedload transport over a weir in southeast Ireland. Critical discharge values for particle entrainment over the structure were derived from the novel use of a stationary RFID antenna, coupled with continuous recording of water levels and sediment captured downstream using pit-style sediment traps. The stationary RFID antenna was installed along a weir crest using both 'pass-under' and 'pass-over' configurations as a means of detecting the moment bedload tracers moved over the dam crest. Results show that 10% of tracers deployed upstream were detected passing over the weir, while a further 15% that were not detected were recovered downstream. These results indicate bedload material as large as the upstream D 70 (i.e., 90 mm) can move over the structure during infrequent high-flow events. However, thorough searches of the seeded area upstream of the dam also suggest that as many as 43% of the total number may have passed downstream, indicating that tracers moved over the weir after the antenna was damaged during a high-flow event, or were missed due to either particle velocity or signal collision. In addition, 30 of the tracers that remained upstream were shown to have either been buried due to the subsequent influx of sediment entering the reservoir, or were reworked though the surface material. Critical discharge values indicate size-selective transport patterns may dominate and a strong correlation between event peak discharge and total bedload captured downstream. These findings provide more evidence that low-head structures may eventually adopt a morphology that allows for the intermittent storage and later export of a channel's bedload downstream as hypothesized by other authors. Building upon these findings and those of other recent field studies, we present a set of possible schematic models that offer a basis for understanding the unique ways low-head dams can continue to disrupt sediment conveyance long after they have reached their functional storage capacity. The limitations of using a stationary RFID antenna and possible recommendations for future studies are discussed. • Bedload transport over a low-head dam was assessed using sediment traps and a stationary RFID antenna positioned along a weir crest. • Tracers as large as the D 70 (90 mm) were observed passing over the weir. • Critical flow conditions for particle export indicated size-selective transport. • Presented are a number of possible conceptual models that may offer a basis for understanding temporary storage dynamics. [ABSTRACT FROM AUTHOR]

Soil erosion and sediment transport are controlled by complex factors promoting variable responses in catchment's erosion rates and sediment yields. To mitigate eventual negative effects derived from altered fluxes, integrated catchment management plans should assess the sediment cascade from upstream erosive processes, sediment mobilization through hillslopes and within the channel, up to downstream sediment yields. This study links hydro-sedimentary dynamics with sediment fingerprinting source ascription in a mid-mountainous Mediterranean catchment during five hydrological years (2013–2018). Soil colour parameters and fallout radionuclides were used as tracers to predict dominant suspended sediment sources using (i) a Bayesian mixing model (MixSIAR) and (ii) an End Member Mixing Analysis (EMMA). MixSIAR suggested that crops were the dominant source in most of the collected samples. EMMA showed similar results, clustering all except one sediment samples close to the crop and channel bank signatures. In addition, a quantitative hysteresis index was calculated and floods were clustered in function of their hydro-sedimentary characteristics. Despite different patterns were associated to each of the four identified clusters (e.g. different sediment loads and maximum suspended sediment concentrations), correlation between sediment origin and hydro-sedimentary variables was not significant due to the little seasonal variation in source type ascription. • Combination of continuous water and sediment monitoring with sediment fingerprinting were tested as catchment management tools. • The MixSIAR Bayesian mixing model and End Member Mixing Analysis showed similar results. • End Member Mixing Analysis provided valuable insights to determine dominant suspended sediment sources. • Source ascription homogeneity did not allow the link of hydro-sedimentary response to sediment source contributions. [ABSTRACT FROM AUTHOR]

Instream-flow scientists embrace streamflow as the master variable driving aquatic and riparian ecosystems, and that natural flow variability is imperative for river conservation and restoration efforts. Sediment transport, which is critical for maintenance of physical habitats in rivers and floodplains, has received less direct attention from instream-flow practitioners. This article serves to highlight the roles of sediment-transport evaluations in modifying or verifying instream-flow prescriptions based on hydrology alone. Two examples of sediment-transport evaluations are discussed in relation to the Texas Senate Bill 3 Environmental Flows allocation process, a mandate to “develop environmental flow analyses and a recommended flow regime” that “maintain(s) the viability of the state's streams, rivers, and bay and estuary systems” using “reasonably available science”. The first example provides an evaluation of effective discharge of suspended-sediment load of the lower Brazos River. The magnitude and frequency of effective discharge occurs between typical high-flow pulses and overbank flows, indicating that hydrologic and physical processes are not optimally coupled in some flow-regime models. The second example utilizes the Hydrology-Based Environmental Flow Regime (HEFR) model to prescribe instream flows for the lower Sabine River, and compares modeled bed-material loads for observed and HEFR-prescribed flow regimes. Results indicate that annual water and sediment yields are greatly reduced for the modeled flow regime. It should be noted, however, that different input variables to the HEFR model would have resulted in different computations of water and sediment yields, reinforcing that instream-flow practitioners should exercise great caution when applying rule-of-thumb procedures to generate flow prescriptions. [ABSTRACT FROM AUTHOR]

Soil erosion due to water and wind results in the loss of valuable top soil and causes land degradation and environmental quality problems. Site specific best management practices (BMP) are needed to curb erosion and sediment control and in turn, increase productivity of lands and sustain environmental quality. The aim of this study was to investigate the effectiveness of three different types of biodegradable erosion control blankets- fine compost, mulch, and 50–50 mixture of compost and mulch, for soil erosion control under field and laboratory-scale experiments. Quantitative analysis was conducted by comparing the sediment load in the runoff collected from sloped and tilled plots in the field and in the laboratory with the erosion control blankets. The field plots had an average slope of 3.5% and experiments were conducted under natural rainfall conditions, while the laboratory experiments were conducted at 4, 8 and 16% slopes under simulated rainfall conditions. Results obtained from the field experiments indicated that the 50–50 mixture of compost and mulch provides the best erosion control measures as compared to using either the compost or the mulch blanket alone. Laboratory results under simulated rains indicated that both mulch cover and the 50–50 mixture of mulch and compost cover provided better erosion control measures compared to using the compost alone. Although these results indicate that the 50–50 mixtures and the mulch in laboratory experiments are the best measures among the three erosion control blankets, all three types of blankets provide very effective erosion control measures from bare-soil surface. Results of this study can be used in controlling erosion and sediment from disturbed lands with compost mulch application. Testing different mixture ratios and types of mulch and composts, and their efficiencies in retaining various soil nutrients may provide more quantitative data for developing erosion control plans. [Copyright &y& Elsevier]

Rivers crossing coastal plains are often inefficient conveyors of sediment, so that changes in upstream sediment dynamics are not evident at the river mouth. Extensive accommodation space and low stream power often result in extensive alluvial storage upstream of estuaries and correspondingly low sediment loads at the river mouth. However, gaging stations with sediment records are typically well upstream of the coast, and thus tend to overestimate sediment yields by under-representing the lower coastal plain and because there is often a net loss of sediment in lower coastal plain reaches. Studies of alluvial sediment storage have generally focused on accommodation space, but, using examples from Texas, we show that low transport capacity controlled largely by slope is a crucial factor. [Copyright &y& Elsevier]

Forest fires are common in Mediterranean environments and may become increasingly more frequent as the climate changes. Destruction of the forest cover and litter layer leads to greater overland flow and increased erosion rates. The greatest risk occurs during the first rainstorms following a major fire, so local authorities must act quickly to put erosion control methods in place in order to avoid excessive post-fire sediment loads in river channels. Deciding on which methods to use requires accurate knowledge of their impact on sediment load and an estimate of their cost efficiency. The objective of this study was to evaluate the efficiency of Log Debris Dams (LDDs) and a sedimentation basin for their effectiveness in trapping sediments. Paired sub-catchments were studied to quantify the amount of sediments trapped in stream channels by a series of LDDs and a sedimentation basin. Cost efficiency was evaluated for each of the measures as a function of the cost per unit volume of sediments trapped. In addition, grain size analyses were performed to characterise the nature of the sediments trapped. A third sediment trapping method, Log Erosion Barriers (LEBs) was evaluated more superficially than the first two and conclusions regarding this method are tentative. LDDs trapped a mean volume of 1.57m3 per unit (median=1.28m3); mean LDD height was 105.4cm (std. dev.=21.9cm), and mean height of trapped sediments was only 50.0cm (std. dev.=22.9cm), showing that the traps were only half filled. Sediment height was limited by the presence of gaps between logs or branches that allowed runoff to flow through. Comparison of the textural characteristics of slope and trapped sediments showed distinct sorting: particles greater than 20mm were not mobilised from the slopes during the study period, sediments in the medium to coarse sand size fractions were trapped preferentially by the LDDs, and sediments in the sedimentation basin were enriched by clay and silt sized (<0.050mm) particles as coarser sediments were trapped upstream by the LDDs. Cost efficiency of LDDs was estimated at about 143 €m−3 for the LDDs and 217 €m−3 for the sedimentation basin at the time of sampling. The LDDs are therefore a cost effective method of trapping sediments, but they can only be used when pine trees or straight-trunked trees are locally available. In this case, they should be combined with LEBs, which had a cost efficiency estimated at about 250 €m−3. Installation of the LEBs had not been optimised and they have the advantage of trapping sediments on the slopes where they can continue to play an ecological role, so this method can give better results with more care. Sedimentation basins can be emptied if necessary and are useful in areas where pine trees are not available and where the site can be secured. [Copyright &y& Elsevier]

There is increasing awareness of the damage caused to valuable and often unique sensitive habitats by people pressure as degradation causes a loss of plant species, disturbance to wildlife, on-site and off-site impacts of soil movement and loss, and visual destruction of pristine environments. This research developed a new perspective on the problem of recreational induced environmental degradation by assessing the physical aspects of soil erosion using the fallout radionuclide caesium-137 (137Cs). Temporal sampling problems have not successfully been overcome by traditional research methods monitoring footpath erosion and, to date, the 137Cs technique has not been used to estimate longer-term soil erosion in regard to sensitive recreational habitats. The research was based on-sites within Dartmoor National Park (DNP) and the South West Coast Path (SWCP) in south-west England. 137Cs inventories were reduced on the paths relative to the reference inventory (control), indicating loss of soil from the path areas. The Profile Distribution Model estimated longer-term erosion rates (ca. 40 years) based on the 137Cs data and showed that the combined mean soil loss for all the sites on ‘paths’ was 1.41 kg m−2 yr−1 whereas the combined ‘off path’ soil loss was 0.79 kg m−2 yr−1, where natural (non-recreational) soil redistribution processes occur. Recreational pressure was shown to increase erosion in the long-term, as greater soil erosion occurred on the paths, especially where there was higher visitor pressure. [Copyright &y& Elsevier]

Abstract: A model associated with the formation of sedimentary ocean deltas is presented. This model is a generalized one-dimensional Stefan problem bounded by two moving boundaries, the shoreline and the alluvial-bedrock transition. The sediment transport is a non-linear diffusive process; the diffusivity modeled as a power law of the fluvial slope. Dimensional analysis shows that the first order behavior of the moving boundaries is determined by the dimensionless parameter —the ratio of the fluvial slope to bedrock slope at the alluvial-bedrock transition. A similarity form of the governing equations is derived and a solution that tracks the boundaries obtained via the use of a numerical ODE solver; in the cases where the exponent θ in the diffusivity model is zero (linear diffusion) or infinite, closed from solutions are found. For the full range of the diffusivity exponents, , the similarity solution shows that when there is no distinction in the predicted speeds of the moving boundaries. Further, within the range of physically meaningful values of the diffusivity exponent, i.e., , reasonable agreement in predictions extents up to . In addition to the similarity solution a fixed grid enthalpy like solution is also proposed; predictions obtained with this solution closely match those obtained with the similarity solution. [Copyright &y& Elsevier]

The low productivity of salmonids in many river systems across the UK is testament to their intolerance of water quality perturbations including those associated with excessive sedimentation. Catchment and fishery managers concerned with combating such issues require reliable information on the key sources of the sediment problem to target management and on the efficacy of the mitigation options being implemented. In recognition of the latter requirement, a pre- and post-remediation sediment sourcing survey was used to examine the potential for using sediment tracing to assemble preliminary information on the efficacy of riparian fencing schemes for reducing sediment contributions from eroding channel banks to salmonid spawning gravels in the Rivers Camel, Fal, Lynher, Plym, Tamar and Tavy in the south west of the UK. Respective estimates of the overall mean proportion (±95% confidence limits) of the interstitial sediment input to salmonid spawning gravels originating from eroding channel banks during the pre- (1999–2000) and post-remediation (2008–2009) study periods were computed at 97±1% vs. 69±1%, 94±1% vs. 91±1%, 12±1% vs. 10±1%, 92±1% vs. 34±1%, 31±1% vs. 16±1% and 90±1% vs. 66±1%. Whilst the study demonstrates the potential utility of the fingerprinting approach for helping to assemble important information on the efficacy of bank fencing as a sediment source control measure at catchment scale, a number of limitations of the work and some suggestions for improving experimental design are discussed. Equivalent data are urgently required for many sediment mitigation options to help inform the development of water quality policy packages designed to protect aquatic ecosystems. [Copyright &y& Elsevier]

Acoustic equipment, including interferometric sonar and parametric sub-bottom profiler, have been used to determine the volume and lateral spread of dredged sediments disposed in the natural submarine depression in the Bekkelag Basin, inner Oslofjord since the beginning of the Oslo Harbor remediation project in 2006. This natural depression is used as a subaqueous confined disposal facility (CDF). Calculation of the volume of disposed sediments in the CDF is based on elevation change, derived from two high-resolution bathymetric datasets obtained in 2004, i.e. before the onset of the remediation project, and in April 2008. Seismic profiles across the CDF have been used to estimate the settlement of the original seabed, caused by loading-induced dewatering and compaction of the seabed sediments under the disposed masses. Detailed bathymetry and backscatter data demonstrate the lateral spread of disposed sediments within a well-confined area covering ca. 195,000m2. The sea bottom within this area is distinctly softer than the surrounding seabed as shown by very low acoustic backscatter amplitude, signifying a very loose surface character of the disposed sediments. The thickness of the disposed sediments reaches 6m the deepest part of the original depression. The volume calculation of the disposed sediments in the CDF, based solely on bathymetry data, gives a value of ca. 310,000–320,000m3. Settlement of the original seabed as a result of loading has been estimated to be 30cm at 5m thickness of the disposed sediments. Under the condition that the settlement rate is linearly correlated to the thickness of disposed sediments, the settlement corrected volume of disposed sediments is ca. 330,000–340,000m3. Presented results demonstrate high accuracy and good reproducibility of acoustic seafloor data, and indicate a great potential of such methods as monitoring tools in environmental projects that involve dredging and subaqueous disposal. [Copyright &y& Elsevier]

The study presents an approach that combined objective information such as sampling or experimental data with subjective information such as expert opinions. This combined approach was based on the Analytic Network Process method. It was applied to evaluate soil erosion risk and overcomes one of the drawbacks of USLE/RUSLE soil erosion models, namely that they do not consider interactions among soil erosion factors. Another advantage of this method is that it can be used if there are insufficient experimental data. The lack of experimental data can be compensated for through the use of expert evaluations. As an example of the proposed approach, the risk of soil erosion was evaluated in olive groves in Southern Spain, showing the potential of the ANP method for modelling a complex physical process like soil erosion. [Copyright &y& Elsevier]

This study measured runoff and sediment concentration from the tire track and from the non-tire track to determine infiltration, interrill erodibility, and vegetative cover impacts of reopening an abandoned forest road. Runoff was lowest on the non-track portion of the abandoned road and highest on the reopened road. Sediment concentrations were significantly higher on the reopened road. Increased sediment concentrations were attributed to decreased vegetative cover, rather than traffic-induced changes in the physical soil properties of the reopened road. Thirty years of no traffic and vegetation regrowth was not sufficient to allow recovery of infiltration to values similar to an undisturbed forest. The study also found a significant dynamic behavior in interrill erodibility with respect to antecedent rainfall. Forest road erosion models that fail to account for this change will overestimate sediment yields. [Copyright &y& Elsevier]

Soil erosion on agricultural land is a growing problem in Western Europe and constitutes a threat to soil quality and to the ability of soils to provide environmental services. The off-site impacts of runoff and eroded soil, principally eutrophication of water bodies, sedimentation of gravel-bedded rivers, loss of reservoir capacity, muddy flooding of roads and communities, are increasingly recognised and costed. The shift of funding in the European Union (EU) from production-related to avoidance of pollution and landscape protection, raises issues of cross-compliance: public support for agriculture has to be seen to give value-for-money. In this context risk-assessment procedures have been introduced to help farmers recognise sites where either certain crops should not be grown or anti-erosion measures are required. In England, Defra [Defra, 2005a. Controlling Soil Erosion: A Manual for the Assessment and Management of Agricultural Land at Risk of Water Erosion in Lowland England. Revised September 2005. Department for Environment, Food and Rural Affairs, London] sets out a system of risk-assessment, including ranking of crops susceptible to erosion and anti-erosion measures, that may be selected. We assess this system using field data for an area of erodible soils in the Rother valley, Sussex. The Defra approach correctly identifies most at-risk fields and, taken together with land-use maps, allows non-compliance with advice to be highlighted. We suggest a simple extension to the system which would further identify at-risk fields in terms of possible damage to roads and rivers from muddy runoff. The increased risk of erosion in the study area is associated with certain crops: potatoes, winter cereals, maize and grazed turnips and seems unlikely to be the result of changes in rainfall which over the last 130 years are minimal. We have not evaluated proposed anti-erosion measures in the area because few have been put into practice. The European Water Framework Directive will increasingly focus attention on agricultural fields as a source of river pollution. Assessing the risk of erosion and the need for field testing of suggested approaches, are not simply issues for the EU, but for the management of global agricultural systems. [Copyright &y& Elsevier]

The transport of nutrients and soil sediments in runoff has been recognized as a noteworthy environmental issue. Vegetative Filter Strips (VFS) have been used as one of the best management practices (BMPs) for retaining nutrients and sediments from surface runoff, thus preventing the pollutants from reaching receiving waters. However, the effectiveness of a VFS when combined with a subsurface drainage system has not been investigated previously. This study was undertaken to monitor the retention and transport of nutrients within a VFS that had a subsurface drainage system installed at a depth of 1.2 m below the soil surface. Nutrient concentrations of NO3-N (Nitrate Nitrogen), PO4 − (Orthophosphorus), and TP (Total Phosphorus) were measured in surface water samples (entering and leaving the VFS), and subsurface outflow. Soil samples were collected and analyzed for plant available Phosphorus (Bray P1) and NO3-N concentrations. Results showed that PO4 −, NO3-N, and TP concentrations decreased in surface flow through the VFS. Many surface outflow water samples from the VFS showed concentration reductions of as much as 75% for PO4 − and 70% for TP. For subsurface outflow water samples through the drainage system, concentrations of PO4 − and TP decreased but NO3-N concentrations increased in comparison to concentrations in surface inflow samples. Soil samples that were collected from various depths in the VFS showed a minimal buildup of nutrients in the top soil profile but indicated a gradual buildup of nutrients at the depth of the subsurface drain. Results demonstrate that although a VFS can be very effective in reducing runoff and nutrients from surface flow, the presence of a subsurface drain underneath the VFS may not be environmentally beneficial. Such a combination may increase NO3-N transport... [Copyright &y& Elsevier]

The city of Angkor, capital of the Khmer empire from the 9th to 15th century CE, is well known for its impressive temples, but recent research has uncovered an extensive channel network stretching across over 1000km2. The channel network with large reservoirs (termed baray) formed the structure of the city and was the basis for its water management. The annual long dry season associated with the monsoon climate has challenged water management for centuries, and the extensive water management system must have played an important role in the mitigation of such marked seasonality. However, by changing the natural water courses with off-take channels the original catchments were also reshaped. Moreover, severe problems of erosion and sedimentation in human built channels evolved and impacted on the whole water management system. This paper describes the present hydrology of the area and discusses the impacts of water management on hydrology during the Angkor era. The paper, moreover, attempts to summarise lessons that could be learnt from Angkorian water management that might apply to present challenges within the field. [Copyright &y& Elsevier]

Sediment transport, turbidity, and dissolved oxygen were evaluated during six consecutive water years (2013–2018) of drawdowns of a flood control reservoir in the upper Willamette Valley, Oregon, USA. The drawdowns were conducted to allow volitional passage of endangered juvenile chinook salmon through the dam's regulating outlets by lowering the reservoir elevation to a point where the historical streambed was exposed and transported water and sediment through the reservoir dam. Sediment loads during the drawdown were highest in the first year of monitoring, with a computed value of 40,200 metric tons over a 5-day drawdown, followed by 5 years of lower sediment loads and lower sediment transport rates, suggesting that much of the stored sediment within the reservoir thalweg was transported out of the reservoir in the early years of the consecutive drawdowns. Suspended sediment concentrations (SSC) computed using turbidity and streamflow data resulted in maximum SSC at the onset of the drawdowns, with the highest computed values occurring during the water year 2017 drawdown at 17,500 mg/L (turbidity = 2,990 FNU), and average drawdown SSC values ranging from 654 to 3,950 mg/L for the six years of monitoring. Computed SSC were on the lower range of concentrations that could be harmful to out-migrating juvenile salmon published in other studies. High amounts of particulate organic matter and sand-sized material in drawdown SSC samples affected relations between turbidity and SSC, requiring the use of multiple surrogate regression models over short time frames. Dissolved oxygen minimum values were recorded in two of the monitoring years, with a minimum value of 0.71 and 3.4 mg/L recorded at the onset of the drawdowns in water years 2016 and 2018, respectively. Dissolved oxygen values below 4 mg/L lasted for 1 h, suggesting a rapidly expressed chemical oxygen demand. The response of suspended sediment loads and SSC highlight the site-specific nature of reservoir drawdowns, and the need for evaluation of expected sediment responses for drawdowns being considered at other locations. • Sediment transport rates over six years suggest decreasing sediment supply. • Reservoir morphology controls sediment transport during drawdown. • Most of the reservoir sediment was transported in the first two drawdowns. • Anoxia and hypoxia occurred for limited durations at the start of the drawdowns. [ABSTRACT FROM AUTHOR]

Sediment transport in mountain streams can be a major hazard to downstream infrastructure. Consequently, sediment traps are a common feature in many high gradient streams to retain large volumes of sediment and protect settlements from major sediment transport events. Despite the wide application of these instream structures, there is little knowledge regarding the environmental and ecological effects on streams. Here, we investigated the hydromorphological effects of sediment traps on instream habitats and associated macroinvertebrate communities in four impacted and three non-impacted streams in Switzerland. Sediment traps significantly disrupted the sediment regime homogenising grain size percentiles compared to the natural stepwise downstream fining in control streams. This disruption in the sediment regime resulted in finer grain size distributions upstream of the sediment trap, and reduced substrate diversity in the sediment retention basin and just downstream of the trap. The reductions in substrate diversity resulted in an altered macroinvertebrate community composition. Further, the disconnection in sediment transport led to a lack of longitudinal correlation in macroinvertebrate communities. Refugia provision downstream of the sediment trap, and resource availability within the retention basin, were diminished, potentially reducing resilience of macroinvertebrate assemblages to instream disturbances. The effects of sediment traps were most likely localised in three of the four streams with substrate diversity recovering to comparable control values within 8 wetted widths (ca. 50 m) downstream of the trap associated with natural longitudinal fining. In contrast, ecological and environmental effects propagated downstream in one impacted stream with no recovery being evident. Sediment retention basins in the impacted streams provided a local artificially unique habitat of dynamic-braided channels. Our results indicate that sediment traps can significantly disrupt the sediment regime with important consequences for instream ecology and environmental conditions, although these effects can be system specific. Further work is needed to fully understand the effects of sediment traps in mountain streams to assist resource managers in the mitigation and future construction of these structures. • Sediment traps disrupt sediment transport processes. • Sediment traps can reduce habitat diversity within and downstream of the trap. • Sediment traps can reduce refugia provision and ecological resilience downstream. • Local effects were found in 3 of 4 impacted streams but propagated downstream in 1 stream. • Retention basins themselves may offer an artificially unique localized habitat. [ABSTRACT FROM AUTHOR]

Mercury (Hg) is one of the most dangerous pollutants worldwide. In the European Union (EU), we recently estimated the Hg distribution in topsoil using 21,591 samples and a series of geo-physical inputs. In this manuscript, we investigate the impact of mining activities, chrol-alkali industries and other diffuse pollution sources as primary anthropogenic sources of Hg hotspots in the EU. Based on Hg measured soil samples, we modelled the Hg pool in EU topsoils, which totals about 44.8 Gg, with an average density of 103 g ha−1. As a following step, we coupled the estimated Hg stocks in topsoil with the pan-European assessment of soil loss due to water erosion and sediment distribution. In the European Union and UK, we estimated that about 43 Mg Hg yr−1 are displaced by water erosion and c. a. 6 Mg Hg yr−1 are transferred with sediments to river basins and eventually released to coastal Oceans. The Mediterranean Sea receives almost half (2.94 Mg yr−1) of the Hg fluxes to coastal oceans and it records the highest quantity of Hg sediments. This is the result of elevated soil Hg concentration and high erosion rates in the catchments draining into the Mediterranean Sea. This work contributes to new knowledge in support of the policy development in the EU on the Zero Pollution Action Plan and the Sustainable Development Goal (SDGs) 3.9 and 14.1, which both have as an objective to reduce soil pollution by 2030. • Hg pool in EU topsoils totals about 44.8 Gg, with an average density of 103 g ha−1. • Coupling Hg stocks in topsoil with soil losses and sediment distribution in Europe. • Hg displaced by water erosion is c.a. 43 Mg yr−1 and c.a. 6 Mg Hg yr−1 reach the rivers. • Agricultural lands contributes to more than 85% of Hg losses. • The Mediterranean Sea receives almost half of the Hg fluxes followed by Black Sea. [ABSTRACT FROM AUTHOR]

It is generally accepted that the sand mining industry causes severe destruction in river basin environments. In this study, six sediment cores were collected, and sequential extraction was applied in conjunction with the diffusive gradients in the thin films (DGT) technique to explore the effect of sand mining on the remobilization of Cu and Zn in the sediments. The results showed that Cu and Zn were mainly bound in the residual fraction in the sediments. C DGT -Cu/Zn in the sediments presented obvious increasing trends at the bottom (−9 to −12 cm) at the four sites that experienced sand mining and a decreasing trend at the sites with no sand mining disturbance. Cu and Zn also tended to be transported from the sediments to the overlying water at the four sand mining sites. A correlation analysis found that F1 and F3 correlated well with C DGT -Cu/Zn, indicating that the water/exchangeable fraction and oxidized fraction were the main fractions that led to increases in DGT-labile Cu and Zn in the sediments. Further analysis found that the introduction of oxygen (O 2) was the main reason for the simultaneous release of sulfur (S), Cu and Zn in the sediments, as indicated by the "dark area" of AgI gel appearing at the same position as the "hot spot area" of Chelex gel. Two main sand mining effects on the release of Cu and Zn were hypothesized: (1) intense sand disturbance leads to the transfer of the water/exchangeable fraction (F1) to the DGT-labile fraction and (2) O 2 introduction promotes the reaction of stable sulfide (F3), thus transferring it to the DGT-labile fraction. The above results indicated that the sand mining industry should be paid much attention in the Jialing River, as it can obviously cause labile Cu and Zn release into the water. • Sand mining caused the release of labile Cu and Zn in sediments as measured by DGT probes. • The released Cu and Zn mainly originate from the water/acid exchangeable fraction and oxidized fraction, respectively. • Sediment disturbance and oxygen introduction into sediment are the two main reasons for Cu and Zn remobilization. [ABSTRACT FROM AUTHOR]

Abstract: The measurement of the bed shear stress along vegetated river beds is essential for accurately predicting the water level, velocity and solute and sediment transport fluxes in computational hydroenvironmental models. Details are given herein of an experimental and theoretical study to determine the bed boundary shear stress along vegetated river beds introducing a novel field measuring method, namely the FliessWasserStammtisch (FST)-hemispheres. Although investigations have been conducted previously for sedimentary channels using the FST-hemispheres, this preliminary study is thought to be the first time that such hemispheres have been used to investigate the bed shear stresses in vegetated channels. FST-hemispheres were first developed by Statzner and Müller [1989. Standard hemispheres as indicators of flow characteristics in lotic benthos research. Freshwater Biology 21, 445–459] to act as an integrated indicator of the gross hydrodynamic stresses present near the bed. Test and validation data were found to be at least of the same order of magnitude for the stresses predicted from literature for sedimentary channels, with this study establishing the commencement of a database of calibrated FST-hemisphere laboratory data for vegetated channel beds. In a series of experiments, depths ranging from 0.1 to 0.28m were considered, equating directly to comparable conditions in small rivers or streams. The results of this study provide a basis for enabling the FST-hemispheres to be used to evaluate the boundary shear stress for a wider range of applications in the future, including vegetated river beds. [Copyright &y& Elsevier]

Abstract: This paper describes the parallel simulation of sediment dynamics in shallow water. By using a Lagrangian model, the problem is transformed to one in which a large number of independent particles must be tracked. This results in a technique that can be parallelised with high efficiency. We have developed a sediment transport model using three different sediment suspension methods. The first method uses a modified mean for the Poisson distribution function to determine the expected number of the suspended particles in each particular grid cell of the domain over all available processors. The second method determines the number of particles to suspend with the aid of the Poisson distribution function only in those grid cells which are assigned to that processor. The third method is based on the technique of using a synchronised pseudo-random-number generator to generate identical numbers of suspended particles in all valid grid cells for each processor. Parallel simulation experiments are performed in order to investigate the efficiency of these three methods. Also the parallel performance of the implementations is analysed. We conclude that the second method is the best method on distributed computing systems (e.g., a Beowulf cluster), whereas the third maintains the best load distribution. [Copyright &y& Elsevier]

Abstract: We present an existence theorem of a two-dimensional sedimentation model coupling a shallow water system with a sediment transport equation. The shallow water system includes Coriolis and friction terms. A Galerkin method is used to obtain a finite-dimensional problem which is solved using a Brouwer fixed point theorem. We prove that the limits of the resulting solution sequences satisfy the model equations. [Copyright &y& Elsevier]

Abstract: Water-quality managers desire information on the temporal and spatial variability of contaminant concentrations and the magnitudes of watershed and bed-sediment loads in San Francisco Bay. To help provide this information, the Regional Monitoring Program for Trace Substances in the San Francisco Estuary (RMP) takes advantage of the association of many contaminants with sediment particles by continuously measuring suspended-sediment concentration (SSC), which is an accurate, less costly, and more easily measured surrogate for several trace metals and organic contaminants. Continuous time series of SSC are collected at several sites in the Bay. Although semidiurnal and diurnal tidal fluctuations are present, most of the variability of SSC occurs at fortnightly, monthly, and semiannual tidal time scales. A seasonal cycle of sediment inflow, wind-wave resuspension, and winnowing of fine sediment also is observed. SSC and, thus, sediment-associated contaminants tend to be greater in shallower water, at the landward ends of the Bay, and in several localized estuarine turbidity maxima. Although understanding of sediment transport has improved in the first 10 years of the RMP, determining a simple mass budget of sediment or associated contaminants is confounded by uncertainties regarding sediment flux at boundaries, change in bed-sediment storage, and appropriate modeling techniques. Nevertheless, management of sediment-associated contaminants has improved greatly. Better understanding of sediment and sediment-associated contaminants in the Bay is of great interest to evaluate the value of control actions taken and the need for additional controls. [Copyright &y& Elsevier]

Assesses the catchment-wide mining-related impacts on sediment movement in the Swift Creek catchment in Northern Territory. Techniques used for the assessment; Application of geographic information system on catchment-wide basis in the region; Results of the preliminary assessment of landform evolution in the Swift Creek catchment.

Grasses and shrubs occupy large areas of fragile ecosystems following ecological restoration. Therefore, it is increasingly important to assess and monitor the environmental safety of pastures. However, previous studies on this topic lacked systematicity and directionality. In this study, we reviewed the literature on runoff and erosion to summarise the core issues for future research, resolve the current research bottleneck, and promote the balance of soil, water, and energy in fragile ecological areas. The results of the review indicate that coverage remained the main vegetation feature considered when characterising rangeland slope erosion and runoff. Erosion energy should be comprehensively considered based on the influence of vegetation on rainfall distribution and runoff erosivity. Rangeland slope erosion and runoff changes can only be explained by integrating the above- and below-ground characteristics of vegetation. Additionally, the impact of vegetation on runoff separation and the sediment transport processes at different erosion stages under rainfall conditions vary. Therefore, studying the comprehensive indicators of vegetation at different erosion stages in response to erosion and runoff will be vital in rangeland erosion research. From the perspective of disciplinary development, this study can promote the further development of soil erosion, ecology, soil science, hydrology, hydraulics, and other disciplines. • Research on soil erosion and overland flow on rangeland slopes lacks systematicity. • Effect of plants on runoff separation under rainfall varies between erosion stages. • Vegetation also affects sediment transport differently under rainfall. • Responses of comprehensive vegetation indicators to erosion and runoff are important. • Vegetation indicators will offer a breakthrough in rangeland research. [ABSTRACT FROM AUTHOR]