Sediment Size Research Articles

Development of a geomorphic monitoring strategy for stage 0 restoration in the South Fork McKenzie River, Oregon, USA

AbstractThe South Fork McKenzie River (SFMR) in western Oregon, USA hosts one of the largest Stage 0 stream restoration projects implemented to date. Stage 0 refers to a multichannel planform with strong hydrologic connectivity to the adjacent floodplain and surface–subsurface connectivity. Stage 0 restoration was implemented on a 900‐m‐long reach of the SFMR by re‐grading the channel and floodplain using 65,000 m3 of sediment to raise the channel bed. Thousands of large logs were added and the ends of some logs were buried in the sediment to provide foundations for future log jams. Our primary objective is to present a monitoring protocol based on randomly located sampling plots. We also analyze results from 2 years of data collection since project implementation. Within each plot, we measured canopy cover, wood volume, flow depth and velocity, organic cover (area covered by coarse and fine organic material), and substrate grain size. We used intracluster correlation coefficients and variance of measured variables to assess heterogeneity at three spatial scales: within plots, between adjacent plots, and across the entire site. Here, we evaluate changes in the first 2 years after restoration (i.e., not pre‐ vs. post‐restoration). We hypothesized that heterogeneity within a plot would decrease as the plot adjusted to local‐scale hydraulics and sediment and particulate material transport. We hypothesized that heterogeneity would increase between adjacent plots and across the entire site. We found that spatial heterogeneity of geomorphic variables decreased within plots. Heterogeneity of organic cover, sediment size, and flow depth increased between adjacent plots, although other variables did not change. Site‐scale heterogeneity decreased for all variables except organic cover and substrate. We interpret the observed geomorphic responses to reflect decreased longitudinal connectivity and increased lateral and vertical connectivity at the restoration site.

Hydro-environmental Characteristics for Flows Over Inclined Block Carpet

A significant oxygenation is associated with flows over most of the hydraulic structures due to the entrainment of air into the flow. Block carpets are low-head hydraulic structures, which aim to control the sediment transport, dissipation of flow energy and contribute to considerable oxygenation. Studies have been conducted to investigate the effects of block carpet on the hydraulic jump, scouring phenomenon and variation in the hydro-environmental parameters. The study also investigates the aeration efficiency created by the hydraulic jump inflows over block carpet. Dissolved oxygen as a principal hydro-environmental parameter was measured and analysed upstream of the block carpet, along the BC (heel, mid and toe) and post hydraulic jump in the channel bed. The results show that in the tested range of slopes (20%, 25% and 30%) and block carpet material, the flow has attained a maximum aeration efficiency of 0.181. The characteristics of the hydraulic jump for different inclinations of block carpet and for two-channel bed sediment sizes were observed. Predominantly, for higher discharges and steep slopes, considerable scouring takes place downstream of the block carpet. Based on the physical features of the downstream scour, a qualitative description of three scour forms has been distinguished.

Prediction of temporal variation of scour hole dimensions due to plane wall jets: Application of new soft computing techniques

Scour due to wall jet is one of the important problems in hydraulic engineering field. Prediction of the scour hole dimensions with acceptable accuracy is necessary for the structures around the jets. In this issue, use of soft computing (SC) methods is unavoidable due to the complex process of jet scour. In this research, SC techniques such as random forests (RF), particle swarm optimization based fuzzy inference system (PSOFIS), slime mould algorithm based fuzzy inference system (SMAFIS) and adaptive neuro fuzzy inference system (ANFIS) were implemented for predicting temporal variation of the scour hole dimensions due to plane wall jets for the first time. The performance indices and the data distribution showed that among the above-mentioned methods, the RF could predict the scour hole dimensions with the highest accuracy. This is attributed to this fact that RF which is a substantial modification of Bootstrap averaging, increases the precision of estimated prediction by a collection of de-correlated regression trees. The hybrid methods, PSOFIS, SMAFIS and ANFIS were ranked from the best to the worst based on the performance indices of the test data. The sensitivity analysis showed that among the effective parameters, the scouring time and sediment standard deviation had the most and the least effects on the temporal variation of scour hole dimensions, respectively. Use of channel width ratio and jet Reynolds number along with other effective parameters such as densimetric Froude number, tailwater depth ratio, sediment size ratio in the models are recommended to reach appropriate accuracies. Comparison with the existing literature indicated that the accuracy of the proposed methods is considerably better than the previous researches.

On some aspects of flow characteristics of the bifurcated channel – An experimental approach

ABSTRACT The purpose of this research is to get an overall idea about the physical process of discharge and sediment distributions in channel bifurcations. A physical model has been used for the experimental study of channel bifurcation corresponding to the river Kangsabati in the field. The study describes sediment distribution of different sediment sizes for a bifurcation angle of 37° (the angle between the tip of the nose and the symmetrical line of a bifurcation). A total of three different sizes of sediment (0.190 mm, 0.260 mm, and 0.275 mm) have been used to investigate the influence of sediment distribution over the branches. For each sediment size, four different upstream discharges (0.002, 0.004, 0.006, and 0.008 m3/sec) have been used. From the experiments, a set of data on s1 /s 2 and q 1/q2 (where q 1, q 2, and s 1, s 2 are the discharge and sediment transport rate per unit width through respective bifurcated branches) have been collected. These data have been set to the nodal point relation (the relation between the ratio of downstream discharges and the ratio of the downstream sediment transport rates). The study so far performed is based on experimental data obtained from the physical model of channel bifurcation, and the results have been discussed in the present paper.

Continuous, High-Resolution Mapping of Coastal Seafloor Sediment Distribution

Seafloor topography and grain size distribution are pivotal features in marine and coastal environments, able to influence benthic community structure and ecological processes at many spatial scales. Accordingly, there is a strong interest in multiple research disciplines to obtain seafloor geological and/or habitat maps. The aim of this study was to provide a novel, automatic and simple model to obtain high-resolution seafloor maps, using backscatter and bathymetric multibeam system data. For this purpose, we calibrated a linear regression model relating grain size distribution values, extracted from samples collected in a 16 km2 area near Bagnoli–Coroglio (southern Italy), against backscatter and depth-derived covariates. The linear model achieved excellent goodness-of-fit and predictive accuracy, yielding detailed, spatially explicit predictions of grain size. We also showed that a ground-truth sample size as large as 40% of that considered in this study was sufficient to calibrate analogous regression models in different areas. Regardless of some limitations (i.e., inability to predict rocky outcrops and/or seagrass meadows), our modeling approach proved to be a flexible tool whose main advantage is the rendering of a continuous map for sediment size, in lieu of categorical mapping approaches which usually report sharp boundaries or rely on a few sediment classes.

Identification of the sources and influencing factors of the spatial variation of heavy metals in surface sediments along the northern Jiangsu coast

Determining the sources and factors influencing the spatial variation of heavy metals in the surface sediments of tidal flats is important for controlling and reducing heavy metal pollution. We used principal component analysis and partial least square regression to analyse the distribution characteristics, sources, and factors influencing the spatial variation of nine heavy metals (As, Co, Cr, Cu, Mn, Ni, Pb, V, and Zn) in the surface sediments of tidal flats along four sites located on the northern Jiangsu coast. Our results indicate that the northern three sampling areas had a high heavy metal content, whereas the southern sampling area had a low heavy metal content. The heavy metals Mn and Pb are related to both natural and anthropogenic sources, whereas V and Cr are primarily derivatives of human activities, and As, Co, Cu, Ni, and Zn are primarily a result of natural processes. The spatial variation of Mn and Pb was primarily affected by the total inorganic carbon and clay content (positive affect) as well as the sand and silt content (negative affect). The spatial variation of V and Cr was primarily related to silt, clay, and total phosphorus content (positive influence) as well as sand (negative influence). In addition, the spatial variation of As, Co, Cu, Ni, and Zn was primarily influenced by the total organic carbon and clay content (positive effect) as well as sand and pH (negative effect). The grain size of sediments plays an important role in the spatial variation of heavy metals in the surface sediments of tidal flats, with fine-grained clay materials being related to the enrichment of heavy metals. The results of our study are important for the control and reduction of heavy metal pollution in coastal sediments, protecting both the ecological environment and human health.

Factors affecting average grain size changes in rivers of a catchment area (Ardak catchment area, northeast Iran)

Investigation of sediment control factors in river channels of a catchment can play a very important role in the sustainable management of that catchment. For this purpose, Ardak catchment was selected, on which a reservoir dam was constructed for drinking and agricultural purposes large city of Mashhad in northeastern Iran. Then 57 samples were collected from the surface to the depth of 30 cm along the four rivers: A (14), B (23), C (13), and D (7). The samples were subsequently weighed and sieved for particle-size distribution. Cumulative curves were plotted followed by the determination of statistical parameters. Thirty-four representative fresh samples were selected for study using macroscopic features. Lithofacies were identified in the field using parametersand their mutual association following the classification scheme of Walker and Cant and Miall. Data on the textural parameters of different rivers showed that rivers A, D, B, and C produce coarse sediments. In terms of average grain size, river A has a greater role in the production of gravel sediments and river B has a greater role in the production of sand and mud sediments. According to the studies, the effect of formation of this catchment (Mozduran 3, Tirgan, and Mozduran 1) on the production of gravel sediments and other formation (Chaman Bid, Sarcheshmeh, and Shurijeh) which include more shale layers is more in the production of sand and mud sediments. Examination of sedimentary facies of alluvial terraces shows that river B is more effective in producing gravelly sediments and river A is more effective in producing sandy and mud sediments. Finally, a comparison of average grain size in sediments formed in the riverbeds of this catchment area and a comparison of this parameter in past sedimentary facies can show the effect of tectonic activity as the most important factor controlling textural parameters in this basin over time.

River flooding response to ENSO-related monsoon precipitation: Evidence from late Holocene core sediments in the Jianghan Plain

In the Jianghan Plain, known as the province of thousands of lakes, monsoon precipitation-induced floods carrying large amounts of sediments can shape the depositional landscape, particularly after frequent river flooding. Therefore, the sediments document abundant information on climate change and its interaction with the fluviolacustrine system and paleoflooding. To date, late Holocene paleoflood records are limited, as continuous paleoflood archives are scarce. Here, using grain size end-members and sensitive components in combination with element records from the JH001 sediment core in the Jianghan Plain, nine continuous paleoflood regimes were identified during 3400–3000, 2750–2550, 2050–1820, 1800–1650, 1550–1500, 1350–1100, 1050–1000, 800–750, and 620–600 cal yr BP, respectively. Exploration of the climatic driving factors on flood regimes indicated a good agreement among paleoflood regimes and El Niño-Southern Oscillation (ENSO)-related hydrological records in the Middle Yangtze Valley (MYV) and reconstructed ENSO records. This suggests that ENSO is the dominant influence on flood occurrence in the Jianghan Plain. Strong ENSO activity exerted a southward shift in the subtropical high in the western Pacific and produced a long-lasting rainbelt in the mid-lower Yangtze Valley, which induced the occurrence of floods in the Jianghan Plain. The evolution pattern of sedimentary environment demonstrated that the floods led to river overflow and overbank expansion, even causing the rivers to divert and bifurcate. The overflow channels carried and deposited silt sediments in the floodplain, which shaped the specific alluvial-lacustrine landscape of the Jianghan Plain. Our results indicate that the grain size of core sediments is sensitive to the occurrence of paleofloods, and that ENSO-related paleofloods significantly influenced the fluviolacustrine sedimentary evolution. These findings are highly useful for regional flood planning and environmental protection in the eastern Jianghan Plain in the context of global warming.

Environmental Assessment Impact of Acid Mine Drainage from Kizel Coal Basin on the Kosva Bay of the Kama Reservoir (Perm Krai, Russia)

The Kosva Bay is permanently affected by acid mine drainage (AMD) from Kizel Coal Basin in the Perm Krai of Russia. This discharge is released in the middle part of the Kosva River from the abandoned mines. This study investigates the current trace element (TE) concentrations for Zn, Cu, Pb, Ni, Cr, Cd, As, and Hg and the mineral composition, major oxides, grain size of sediments, and acute toxicity using two test organisms within the site of AMD downstream from the Kosva River and up to the Kosva Bay of Kama Reservoir. The objectives of this study were to analyze the quality of sediment and level pollution of Kosva Bay using pollution and ecotoxicological indices. The environmental indices, namely the contamination factor (CF), the geoaccumulation index (Igeo), and the potential ecological risk factor (Eri), indicate contamination by Cr and Pb in sediments at the site of AMD, with the highest values for Cr, Cu, and As in the Kosva Bay sediments downstream of abandoned coal mines. The results of Igeo and CF average values in bay of sediments showed different degrees of contamination, from moderate contamination to considerable contamination, respectively. According to the potential ecological risk index (RI) values, the Kosva Bay sediments exhibited low to moderate risk, and As and Cd have the highest contribution rate. According to LAWA and the Polish geochemical classification of sediments, sediments of the bay correspond to the highest levels (IV–III classes) for Cr, Ni, and Hg. Based on the SQGC, Hg, Cd, Cr, and Ni are the most probable for resulting in adverse effects on aquatic organisms in this study. The results of this study indicate that complex pollution and ecotoxicological indices must be supported by ecotoxicologal tests. High precipitation totals, low evaporation rates, and flow regulation stream by the Shirokovsky Reservoir located upstream from abandoned coal mines provide significant fluctuations in streamflow, which is probably the most important factor controlling the distribution and mobility of TE in the studied sediments.

Reliability of mangrove radiocarbon chronologies: A case study from Mahé, Seychelles

Mangrove sediments are valuable archives of paleoenvironmental and relative sea-level changes. The most widely applied method to obtaining chronologies of past changes in mangrove sediments is radiocarbon dating, because mangroves produce large amounts of organic matter in situ. However, there are many challenges to obtaining reliable radiocarbon chronologies because bioturbation processes from roots and crabs can rework mangrove sediments, resulting in ages that are not in stratigraphic order. Previous studies have suggested that methods that isolate specific sediment size fractions may yield ages closer to the age of the paleo depositional surface by removing younger carbon contamination from fine roots. This study examines which sample types are more likely to yield reliable radiocarbon ages using shallow cores from a mangrove environment on Mahé, Seychelles, in the Indian Ocean. We compare radiocarbon ages from bulk sediment, sieved organic concentrates and above-ground macrofossils collected from the same stratigraphic depths. Bulk sediment and organic concentrate ages are comparable, which suggests that methods that separate out different size fractions do not sample different carbon sources in Seychelles mangrove cores. Identifiable above-ground macrofossils are rare in Seychelles mangrove cores, but yield older radiocarbon ages than comparable bulk sediment or organic concentrate ages. We suggest that in Seychelles, limited accommodation space over the late-Holocene, determined by relatively stable relative sea levels, has resulted in poor preservation of above-ground macrofossils for radiocarbon dating due to low rates of burial and sediment accretion. Low accretion rates have likely resulted in a mangrove sediment sequence that is highly bioturbated and degraded, meaning both bulk sediment and organic concentrate samples are impacted by contamination from younger roots. We argue that the availability of accommodation space and sediment composition controls the reliability of mangrove radiocarbon chronologies, which has implications for sample choice and site selection.

Coastal reclamation mediates heavy metal fractions and ecological risk in saltmarsh sediments of northern Jiangsu Province, China

Coastal reclamation has created enormous extra land for the rapidly growing economy, but it has also caused serious environmental pollution problems and threatened the sustainable development of coastal areas. However, there are few studies focusing on the distribution patterns, geochemical speciation and ecological risks of heavy metals along the land-to-sea belt, as well as the differences between reclamation and non-reclamation. Here, we collected 69 sediment samples from four sediment types along the land-to-sea sampling belts in the reclaimed and non-reclaimed tidal flats of Jiangsu, China. Geochemical speciation and contents of heavy metals were determined to investigate their spatial distributions, ecological risks and effect factors. Results showed that As, Cd, Cr and Ni in the sediments posed considerable or moderate ecological risk according to the Ontario guidelines and sediment quality guidelines (SQGs) of USEPA, but they were lower than the SQGs of China. Higher geoaccumulation index and potential ecological risk index suggested that the sediments were moderately to heavily polluted by Cd and As. Generally, reclaimed sediments exhibited higher metal pollution levels. Additionally, reclaimed areas showed a unimodal pattern of metal content along the direction of land-to-sea, suggesting that Spartina alterniflora could accelerate the deposition and accumulation of metal pollutants caused by reclamation, and ultimately control the transfer of terrigenous metals to marine environment. We found that residual fraction was the dominant geochemical fraction for the metals determined. Reclamation processes have changed the composition of heavy metal fractions, especially Cd, Pb, Zn, and Ni. Approximately 20% of Cd existed in the acid extractable/exchangeable fraction and posed medium ecological risk according to the risk assessment code. The principal component analysis and correlation matrix further indicate that organic matter and particle size of sediment could be the major factors regulating the metal distribution, and Cd and Zn might be anthropogenic sources.

STATISTICAL PARAMETERS ANALYSIS OF SEDIMENT GRAIN SIZE FROM RAYA RIVER BENGKAYANG REGENCY, WEST BORNEO

The study of the statistical analysis parameters of grain size in the waters of Sungai Raya was carried out in order to understand the characteristic of the sediment in the river and coastal areas. The grain size by sieving method, and analyze the statistical parameters including the average grain size, sorting, skewness, and kurtosis. Sediment samples were acquired from six stations with each station consisting of three sampling points representing river west bank, river midstream, river east bank, and the coastal area consisting of five stations. The results of the sediment analyses showed that the average grain size in the river ranges from 1.23 to 2.77 mm, and on the beach area is between 1,52 - 2,59 mm, classified as fine sand, medium sand, very fine sand, and coarse sand with predominant fine sand in all stations. The results of the statistical parameter analysis of the grain size of the bottom sediment in the waters of Sungai Raya exhibit the average diameter value ranging from 1.23 to 2.77 mm, classified as fine sand to medium sand. This value indicates that the type of sediment in this location is dominated by silt with grain sizes ranging from < 0.05 - 0.002 mm. The sorting value ranges from 0.14 to 1.59 mm, categorized into moderately sorted, moderately well-sorted, very well sorted, and poorly sorted classes. The average value of skewness is 2.17 with the classification of the bed load being very fine and kurtosis value ranges from 0.72 to 1.67 indicates the classification in these waters is platycuric, mesokurtic, leptokurtic, and very leptokurtic. These finding concluded that in the study area there is a variation in the angularity of the sediment grains due to the different hydrodynamic processes

Prediction of Local Scour around Bridge Piers in the Cohesive Bed Using Support Vector Machines

Local scour around bridge piers is one of the most important factors threatening the life of bridges. The three-dimensional highly complicated horseshoe vortex and downflow are known to be the main agents responsible for pier scour. If the bed consists of cohesive sediment, it will add another level of complexity to the pier scour problem. Various approaches have attempted to predict scour depth, but no universal method is available to date. This study presents a prediction of local scour around bridge piers in the cohesive bed using support vector machines (SVMs), a machine learning technique. The maximum scour depth is predicted with seven dimensional variables, including velocity, flow depth, size of bed sediment, pier width, clay content, water content, and bed shear strength. The training and validation of the SVMs are conducted with 197 data from six datasets. Comparisons are made with the training and validation of the adaptive-network-based fuzzy inference system (ANFIS) method. The training of the ANFIS method appears successful, but the validation fails because of overfitting. The predictions with dimensionless variables are compared, and shown to be worse. In addition, the SVMs are found to predict the maximum scour depths better than three existing formulas, gene expression programming (GEP), and a non-linear regression model. The SVMs are applied to two datasets, revealing the importance of the coverage of the training data. Finally, to investigate the contributions of each variable, the mean absolute percent errors (MAPEs) and correlation coefficient are computed by predicting the maximum scour depths by excluding each variable.

Influence of sediment sources, water mass, and physical processes on the dynamics of flocs at a location between the mouth of a river and the head of a submarine canyon

A field experiment was conducted in the summer of 2011 to obtain detailed process–response data to understand the dynamics of suspended sediment off the Gaoping River mouth near the head of the Gaoping Submarine Canyon in Southern Taiwan. An instrumented tetrapod and a collocated floating platform were used to record the temperature, salinity, current and wave fields. Additionally, the volume concentration (VC) and mass concentration (SSC) of suspended sediments were recorded. Temperature and salinity signals over a tidal cycle distinguished water masses originating from the river plume and the canyon, which alternately dominated the surface dynamics of suspended sediment at the study area. Terrestrial–sourced suspended sediments aggregated into larger flocs, characterized by high VC, SSC, and low effective density values. Conversely, marine–sourced suspended sediments generally had smaller grain sizes, characterized by lower VC, SSC, and high effective densities. In the surface water, the effective density of suspended sediments decreased exponentially with size. In the bottom water, values of VC and SSC were higher under energetic wave conditions and lower under nonenergetic wave conditions, whereas mean size of suspended sediments showed an opposite trend. The hydrodynamics also affected the sediment–water interface, which was reflected in the grain size composition of surficial sediments. The silt and clay content on the seabed was lower under energetic wave conditions and higher under nonenergetic conditions. According to process–responses characteristics, suspended sediments in the bottom water were associated with two regimes: smaller mean size with lower effective densities formed under energetic wave conditions and larger mean size with higher effective densities formed under nonenergetic wave conditions. In the former regime, waves–induced turbulence dominated suspended sediment dynamics by entraining seafloor sediments into the bottom water and aggregating them into microflocs (<~125 μm) and macroflocs (> ~ 125 μm). However, the size distribution of suspended sediment showed a bimodal distribution, and the larger peak is close to the Kolmogorov microscale (around 250 μm). It suggests that strong turbulence associated with significant sediment suspension and flocculation also resulted in disaggregation of macroflocs. As the wave energy dissipated, most of suspended sediments including all fine ones were removed from the bottom water, via flocculation and deposition. Under nonenergetic wave conditions, suspended sediments in the bottom water were contributed from upcanyon water and river plumes, controlled by semidiurnal tidal currents. The size distributions of suspended sediment under nonenergetic conditions were mostly unimodal, with peaks around 100–300 μm, less than the Kolmogorov microscales of turbulence flow (350 μm). Therefore, it could be concluded that turbulence strength plays a key role in flocculation of suspended sediment in the bottom water.

Effects of Oil and Sediment Properties and Mixing States on the Formation and Settling of Oil‐Particle Aggregates

AbstractUnderstanding the interaction of oil droplets with suspended particulate matter is important not only for sunken oil modeling but also for emergency response. In this study, the effects of mixing time and energy, oil type, and sediment concentration and size on the oil content, morphology, and density of oil‐particle aggregates (OPAs) were investigated through a series of wave tank experiments and sedimentation tests. The results showed that loads of oil and particles in OPAs are high under high mixing energy. Under turbulent hydrodynamics, moderately viscous oils form OPAs more easily and sink rapidly to the seabed. Moreover, an increase in the density and oil capacity of OPAs is observed at a higher sediment concentration. More oil is captured by finer sediments. However, the corresponding oil‐sediment aggregates generally show lower density compared with those formed by larger sediments. The oil‐seawater interfacial tension (IFTow) diminishes with the addition of sediments, further promoting oil dispersion. The increasing duration and mixing energy produce more flake OPAs and multiple‐droplet OPAs. Oil droplets tend to be surrounded by several small particles but attach to the surface of large particles. Regardless of oil type and sediment concentration, the structure of OPAs does not change significantly.

Adsorption of Plutonium onto Several Natural Sediments.

The adsorption of plutonium (Pu) onto several natural sediments was studied using batch experiments to determine the different factors influencing Pu adsorption. These factors include the possible effect of different methods for adding Pu solution, the initial oxidation state of Pu, the particle size of the sediments, the pH, and the ionic strength of solution. The method used for adding Pu solution greatly influenced the species of Pu in sediment-groundwater systems and the adsorption behavior of Pu onto the sediments. Initial oxidation state of Pu, clay mineral content, particle size of sediment, pH, and ionic strength all appear to impact adsorption. The sediments preferred to adsorb Pu(IV) rather than Pu(V). The adsorption of Pu depended on the particle size and clay mineral content of the sediments; the higher the clay mineral content and the smaller the particle size, the more adsorption for Pu. The insoluble species of Pu formed in sediment-groundwater systems at pH 9.3 resulted in the decrease of adsorption capacity. The adsorption capacity increased with pH increasing at pH < 9. Ion exchange was the dominant mechanism for Pu adsorption onto the sediments at pH < 7.5. It appeared that the ionic strength had a stronger influence on adsorption capacity than pH.

Influence of beaver mimicry restoration on habitat availability for fishes, including Arctic grayling (Thymallus arcticus)

AbstractBeaver dam mimicry is an emergent conservation practice. We evaluated the influence of constructed riffles, a unique type of beaver mimicry aimed to store water and allow fish passage, on habitat for fishes in one control reach and one manipulated reach with mimicry structures added. The beaver mimicry reach had deeper pool habitats and deeper and wider riffle habitats compared to an unmanipulated control reach. Dissolved oxygen was similar among reaches, averaging 8.7 ± 0.2 and 8.9 mg/L in the beaver mimicry and control reaches, respectively. Sediment size was also similar among reaches, with a D50 of 8.1 and 10.6 mm in the beaver mimicry and control reaches, respectively. The beaver mimicry reach had little to no overhanging bank vegetation or riparian vegetation shade cover, while the control had 38% of its bank covered by canopy and 56% overhung by vegetation. These riparian characteristics result from a legacy of livestock grazing and lack of consistent vegetation planting during restoration. Longnose dace (Rhinichthys cataractae) and white sucker (Catostomus commersonii) dominated in the beaver mimicry reach, together comprising 70% of the fish assemblage post‐structure installation. Arctic grayling (Thymallus arcticus) was not found in the beaver mimicry reach but was present in the control, albeit in small numbers of only 3% of the assemblage post‐structure installation. These results highlight the need to consider both in‐stream and riparian habitat features for fishes, as well as timescales of both hydrological and ecological outcomes in restoration design.

Coarsening of sediments from the Huanghe (Yellow River) delta-coast and its environmental implications

We studied temporal-spatial variations in the grain size of sediments from the Huanghe (Yellow River) delta-coast. Four sediment push-cores and more than 200 surface sediment samples were collected. Key factors that control the sediment variability were revealed, as well as their environmental significance. Analytical results indicated that sediments of the Huanghe delta-coast have coarsened over the past decades, and that this coarsening has intensified in recent years. The average mean grain size (Mz) of two cores in the offshore area from the abandoned delta lobe increased by approximately 18%–32% in the 2010s compared to the 1990s. Surface sediments in the nearshore area were coarsened by about 25% on average from 28.6 μm in 1992 to 35.7 μm in 2000. The sediment coarsening of the abandoned delta lobe began in the 1990s due to the extensive erosion caused by the absence of riverine-sediment supply. Coarse-grained sediments that were resuspended and transported offshore also made the sediment of the abandoned delta lobe coarser. In contrast, sediments of two cores in the offshore area of the active delta lobe were coarsened by more than 30% in the 2010s compared to the 1990s. The average Mz of surface sediments in the nearshore area increased by more than 22% from 23.5 μm in 1992 to 28.7 μm in 2000. The sediment coarsening of the active delta lobe began in the 1990s and became more significant in the 2000s. This trend was due to the rapid decrease of the sediment load from the Huanghe, as well as the coarsening of river-delivered sediments (from 17.7 μm to 22.9 μm) caused by the Water-Sediment Regulation Scheme that has been in place since 2002. Increasing coastal hydrodynamics and the loss of riverine sediment also account for the coarsening of sediments of the delta lobe. Our data clearly indicate that the critical bed-shear stress of the Huanghe delta-coast increased significantly. As a result, it was more difficult to initiate motion of the seabed sediments, leading to the decline of resuspension and erosion. Moreover, since the content of sedimentary organic carbon is negatively correlated with sediment grain size, the coarsening sediment of the study area will have inevitably degraded the carbon-related biogeochemical processes of the Huanghe delta-coast. Our findings have significant implications for the evolution of large river deltas, which are now threatened by sediment starvation and erosion.

Effect of non-uniformity of sediment size on the Movability Number

Sediment on a channel bed is generally not composed of particles of the same size. This non-uniformity affects its incipient motion condition. As a model of an otherwise very complicated situation, two sediment sizes are considered here. A single parameter of non-uniformity is the ratio d/D of the two sizes, where d is the overlying moving sediment size and D the size of the underlying sediment. This study, with the help of experimental data of previous researchers, examines the influence of non-uniformity of sediment on the parameter of incipient motion, critical Movability Number. The empirical curves given by three different studies for uniform sediment are examined in the more general non-uniform context. It is found that the critical Movability Number decreases when the d/D ratio increases, that is, as the overlying sediment size increases and there is less likelihood of grains being hidden in interstices of the underlying layer. However, other factors like specific gravity, size, and the sediment surface features of the sediment have their individual influence on its determination.

Study on reservoir physical properties of Nadanhada terrane

The Nadanhada terrane is basically a large tectonic sedimentary hybrid, which is an accretionary complex belt formed by the subduction of the Pacific plate to the Eurasian plate. Through field geological survey, paleomagnetic analysis, paleontological analysis and microscopic observation of core slices, its structural and petrological characteristics were studied. The results show that the accretionary complex is mainly composed of 7 parts, including undeformed sedimentary rocks, shear deformed sedimentary rocks, shear deformed volcanic rocks, turbidites, deformed siliceous rocks, limestone blocks and basic ultrabasic rocks. Shear deformation structures of deformed sedimentary rocks and volcanic rocks are developed. The sediment grain size of the Lower Cretaceous reservoirs in each basin in the northern region is relatively coarse, the sorting is moderately deviated, and the rounding is poor, mainly secondary to angular. The grain size of the lower Cretaceous sediments of each basin in the southern region is relatively fine, with coarse, medium and fine sandstones, but mainly medium fine sandstones, with medium sorting preference and sub angular to sub round roundness.