Fine Deposits Research Articles

Shadow effect in dual‐source thermally evaporated perovskite patterns

AbstractPerovskite light‐emitting diodes (PeLEDs) have recently emerged as a potential next‐generation display technology due to their wide color gamut, high external quantum efficiency (EQE), and low fabrication cost. The thermal evaporation process with no solvent involvement and offers low substrate selectivity and high compatibility with production lines has attracted significant academic interest. However, in thermal evaporation processes, the shadow effect greatly affects the deposition size and positioning accuracy of the patterns, consequently impacting the effective device area and process repeatability of PeLEDs. In this study, we calculated the shadow distance during the dual‐source thermal evaporation and analyzed the issues of misalignment and size deviation caused by shadow effects. Based on the calculation of shadow distance, we increased the substrate height from 33 to 38 cm to enhance the deposition angle. This adjustment led to an improvement in the characteristic parameter W1/Wdot from 0.178 to 0.365 during perovskite deposition. As a result, we successfully obtained a high‐resolution perovskite array with uniform morphology and photofluorescence (PL) emission at 600 pixels per inch (ppi). This demonstrated the reliable calculation and analysis of shadow distance, which is effective for fine deposition of high‐resolution perovskite patterns and PeLEDs.

Controls on channel planform changes in rivers of the Atlantic Coastal Plain: Findings from the Congaree river valley (South Carolina, USA)

Rivers shaped the landscape of the Atlantic Coastal Plain during the last tens of thousands years. However, their spatial and temporal evolution is understudied. We conducted geophysical, geological and remote sensing surveys in the Congaree River valley, characterized by numerous traces of palaeochannels preserved in the floodplain. The age of the former channels was determined by AMS radiocarbon dating. The main goal of our study was to identify factors controlling the river planform changes and compare the findings with other rivers of the Atlantic Coastal Plain. We found that the Congaree floodplain was shaped by single-thread channels characterized by formation of levees and floodbasins at least 34,000 cal. BP. Large-scale meanders were active between 16,000 and 12,000 cal. BP. They were replaced by meandering channel belts shifting by avulsions between 12,000 and 3,000 cal. BP. Compound meanders have been formed during the last 3000 years. Traces of these channel planforms are also present in other rivers of the Atlantic Coastal Plain. The abandonment of the large-scale meanders was caused by increase in climate humidity, changes in vegetation cover, and inundation of the coastal plain by the ocean level rise, resulting in base-level rise. The avulsions of meander belts in the Early and Middle Holocene were formed in conditions of a humid climate, a series of flooding periods, and continued base-level rise. A relatively drier climate in the Late Holocene caused a change in the meanders’ evolution from the channel belts shifting by avulsions to compound meanders evolving by cutoffs. The last 200 years were dominated by a huge delivery and deposition of fines, caused by deforestation and land-use changes in the river valleys.

The Local Changes in the Physicochemical Properties during Cu Electrodeposition in an Ionic Liquid Composed of [CuCl2]–

The equimolar mixture of CuCl and 1-butyl-1-methylpyrrolidinium chloride (BMPCl) was found to yield an ionic liquid composed predominantly of BMP+ and [CuCl2]–. Fine deposits of metallic Cu were obtained by potentiostatic reduction of [CuCl2]– in CuCl-BMPCl (50.0-50.0 mol%). The change in the local physicochemical properties near the electrode during the electrodeposition of Cu was analyzed using electrochemical quartz crystal microbalance. The resonance resistance of a quartz crystal electrode increased with an increase in the local viscosity near the electrode, probably reflecting the change in the composition of the electrolyte.

Exploration of KCl deposition dynamics for the formation of coarse and fine layer deposits

In biomass and waste combustion, the release of KCl into the gas phase results in its deposition on heat exchanger surfaces, enhancing their stickiness and accelerating deposit buildup from incoming ash particles. Despite this, the mechanisms governing KCl deposition remain inadequately explored. KCl has been observed to form either a fine, powdery layer through thermophoresis of nucleated KCl particles or a crystal-like, coarse layer through heterogeneous condensation of KCl vapor. However, the quantitative assessment of coarse and fine layer formation has never been performed. In this study, an entrained flow reactor and mechanistic model were employed to analyze KCl deposition behavior, examining the effect of probe temperature and exposure time. Quantification of both the coarse and fine deposit layers was accomplished. Probe temperature was found to have no influence on the deposition in the range from 300 °C – 595 °C. For coarse layer formation, the critical factor was the development of a fine layer upon which the crystal-like structure of the coarse layer grows. Lower probe temperatures accelerate initial layer formation, initiating the coarse section sooner. Additionally, it slightly increases nucleation and condensation, however, nucleation is increased stronger resulting in a lower ratio of coarse to fine deposit. The quantification of the coarse mass, in conjunction with the simulation, provides a first estimation of the critical mass required to initiate heterogeneous condensation on a steel tube. In this study, a critical mass of 1.26e-3 g/cm2 was determined.

Numerical simulation of granular silicon growth and silicon fines formation process in polysilicon fluidized bed

Operating conditions strongly affect the yield and quality of polysilicon in a polysilicon fluidized bed. In this study, a new model of polysilicon fluidized bed was established using the Euler–Euler model coupled with population balance model (PBM), which was combined with fluid flow, heat, and mass transfer models, while considering the scavenging effect of silicon fines. The effects of different operating conditions on the deposition and formation rates of silicon fines were investigated. Results show that the model can correctly describe the particle growth process in the fluidized bed of polysilicon. The silicon fines and the interphase velocity difference show “N”- and “M”-shaped distributions along the axial direction, respectively. The particle temperature and concentration near the wall are higher than those in the central region. The decomposition of silane in the bottom region of the bed is dominated by heterogeneous deposition. The scavenging of silicon fines occurs in the dilute-phase region. The effects of operating conditions, i.e. inlet gas temperature, silane composition, and gas velocity, on the reactor performance were also explored comprehensively. Increasing the inlet gas composition and velocity enhances the formation rates of solid silicon and fines. Increasing the inlet gas temperature promotes the growth of solid silicon and inhibits the formation of silicon fines. High fluidization ratio, low inlet silane concentration, and high inlet gas temperature enhance the selectivity of silicon growth.

Leakage through a circular geomembrane hole overlain and underlain by silty sand tailings

Experiments are conducted to investigate leakage through circular GMB holes overlain and underlain by both tailings with various hole diameters and GMB thicknesses. Finite element analyses are performed to explore the effect of hydraulic conductivities (k) of subgrade (underliner) and tailings above the GMB (overliner) on water head contours dissipation. An analytical solution is developed for predicting leakage through circular GMB hole overlain and underlain by both tailings. Results show that the effect of subgrade on leakage is highly dependent on the ratio of k between the underliner and the overliner. If the ratio >100, no head loss occurs in the subgrade; if the ratio <0.01, all the head loss occurs in the subgrade. With the deposition of fines from overliner into subgrade, a low permeable filter cake is formed on the subgrade surface, notably increasing the impact of underliner on leakage. With the increasing ratio of k between underliner and overliner from 0.01, 0.1, 1, 10, and to 100, the ratio of leakage relative to a highly permeable subgrade increases from 0.01, 0.1, 0.56, 0.93, and to 1. An intimate interface contact can be achieved when the GMB is underlain by silty sand tailings as subgrade (foundation) material.

Understanding and predicting physical clogging at managed aquifer recharge systems: A field-based modeling approach

Managed aquifer recharge (MAR) techniques are in demand to cope with water scarcity challenges posed by climate change and groundwater overexploitation. One of the long-lasting technical issues associated with MAR systems is physical clogging. The intrusion and deposition of external fines during water recharge reduce the infiltration capacity of the site over time. Operation and maintenance (O&M) costs are experienced directly at the site to restore the original efficiency of infiltration rates. Thus, investors need reliable estimations of the risk of clogging during the planning of the site. As a rule, in MAR design, the main parameter of concern for physical clogging is the total suspended solids (TSS), and most clogging models rely on experiment calibrations in 1D sand columns. However, secondary processes can control the development and spatial distribution of physical clogging in field conditions. The proposed work aims to detect key clogging factors directly in the field and to model these processes for reproducibility at other sites. The fieldwork is conducted at the two-stage infiltration basin in Suvereto (Tuscany, Italy). Spatial factors are included in the analysis (i.e. basin topography) to explain clogging patterns in the field altered by erosion processes. The observed clogging profiles at two sampled locations exhibiting clogging are replicated by a mathematical model. Based on the computation of annual erosion rates in the pond and fines’ redistribution, the exceeding fines’ contents over depth are validated with an RMSE of 2.53% and 12.53%. The infiltration capacity of the site is estimated to reach a stable value of 90% of the initial infiltration capacity over 20 years, given the Suvereto basin features. The model's parameterisation from field measurements represents a great advantage over existing clogging models due to its transferability to other MAR sites. The assessment of the risk of clogging supported by field characterization and numerical modelling is cost-effective and assists the deduction of O&M schemes for MAR sites.

Effect of rare–earth (Ce, La) compounds on the microstructure, mechanical and electrochemical corrosion characteristics of electroplated Ni films

For optimizing the microstructure and performance of Ni–electroplating film, the soluble rare–Earth (RE) compounds CeCl3 or LaCl3 were introduced, which were electrodeposited on Cu substrate by direct current (DC) and pulse current (PC) methods, respectively. The surface characteristics of morphology, composition, and phase of obtained different deposits were investigated, and the relationship between the structure and the performance of internal stress, hardness, and electrochemical responses was discussed. The results show that both RE compounds were conducive to eliminating the surface pits by inhibiting the hydrogen evolution reaction, while did not co–deposit into the Ni film. Moreover, the preferred orientation of Ni (111) crystalline plane was altered into Ni (200) by LaCl3, and its combination with PC–electrodeposition further had a better grain refinement effect than CeCl3. Due to the formation of a relatively dense and fine deposit, the PC–electrodeposited Ni/LaCl3 film exhibited the highest hardness of 320 HV, lowest tensile stress of 55 MPa, and best electrochemical passivation protection, which effectively improved the comprehensive performance of Ni film and demonstrated a good prospect for industrial applications.

Influencing factors on fines deposition in porous media by CFD–DEM simulation

Influencing factors on fines deposition in porous media by CFD–DEM simulation

An NMR-assisted laboratory investigation of coal fines migration in fracture proppants during single-phase water production

Proppants are injected with the fracturing fluid to keep the hydraulic fractures open. However, deposition of coal fines in the void spaces between proppants significantly damage flow conductivity of the fractures. In this study, we experimentally model coal fines migration in a proppant pack. Standard quartz sand (16–20 mesh) is used to prepare the proppant pack. The proppant pack is installed within a low-field Nuclear Magnetic Resonance (NMR) facility to record NMR response before and after the experiment of fines suspension injection. The injected suspension consists of water with 500 ppm concentration of coal fines of radius from 2.8 to 142.9 µm. Coal fines are generated by crushing an anthracite coal sample. The permeability is damaged significantly by about 41% after 80 pore volume injection. NMR response suggests that volume of the large-size pores (radius rp > 60 um) decreases while that of the medium-size pores (0.9 um <rp < 60 um) increases. The pore structure change is caused by two possible mechanisms: (a) reducing pore size by fines occupying pore space and (b) developing inter-particulate pore space of fines gathering at the damaged pores. Although the fines size (radius from 2.8 to 142.9 um) is significantly smaller than the pore size (<1005.2 um), the large-size pores can still be damaged by the fines. The results of this study can help to understand mechanisms of fines migration and conductivity evolution in/of the hydraulic fractures during Coal Seam Gas production.

Fine sediment dynamics over a gravel bar. Part 2: Impact of hydro-meteorological conditions

In this study, the temporal evolution of fine sediment deposits on a gravel bar is analysed during a two-year period. The time-series of fine deposit surface area is obtained using the methodology proposed in Part 1 of this work. By combining the hydro-meteorological data, the main evolutions of the fine deposits observed on the bar surface are found to be triggered by events such as natural floods, dam flushes, and strong wind valley breezes, and are quantified for each of these events. A simple processed-based flow model is proposed to investigate the sediment dynamics during the flood events, which balances the erosional/depositional processes of fine sediments. Variability in the fine deposit evolution after floods is mainly due to the different flow and sediment concentration conditions. For small events for which the gravel bar is not totally submerged, a slight erosion generally occurs. For larger events for which the gravel bar is totally submerged, a large net deposition is often observed. The fine deposit surface area time-series also shows sharp decreases of the surface deposit coverage after some strong valley breeze events, with an evolution of the same order of magnitude than floods. The application of a wind transport model shows that strong wind valley breezes can transport fine particles from the bar surface to the river channel, thus leading to a loss of fine deposits on the bar surface. Also, the deposit initial moisture is a crucial element having impact on the fine sediment transport on the bar surface. Dry deposits are much more likely to be transported than wet deposits. A discussion is also provided on the potential impact of wind and vegetation on the long-term dynamics of fine sediment deposits.

Fine sediment dynamics over a gravel bar. Part 1: Validation of a new image-based segmentation method

In this paper, we present a new image processing algorithm to analyse fine sediment deposits on gravel bars. The method is based on pictures taken from the river bank with an average resolution of a few centimetres per pixel. The proposed image processing algorithm consists of two steps. In the first step, the raw image is orthorectified with a 5 cm pixel size. In second step, we used an original combination of two well-known image techniques to classify pixel. First, a high-pass filter is applied in the Fourier domain to correct grey-value potential bias, i.e. to merge wet and dry deposits. Then, an unsupervised classification process based on K-means clustering is conducted to partition image pixels into K classes. The area of fine sediment deposits is calculated by summing the area of each class multiplied by weighting parameters (surface area percentage of fine deposits for each class). The value of K and the weighting parameters are calibrated using local close range photos of the bar surface representing the spatial variation of surface fine sediment distribution. The algorithm is then validated with field measurement using the finest class (d<4 mm) of Wolman pebble count method. The impact of image resolution is investigated: the algorithm was found suitable for pixel size between 1 and 10 cm. The robustness of the present algorithm to images taken at different times and with different illuminations is studied by comparing it to two methods from the literature. The new method yields the most robust results with an average standard deviation lower than 5%. It yields larger surface of fine sediment since it includes all possible patches around coarse particles. Such results imply that the algorithm can be applied on a long image series to help us understand the temporal dynamics of fine sediment deposits on the bar surface.

Effect of Chlorine Salts on TiC Coating Morphology and Bonding Strength of Diamond Surface in Molten Salt Reaction

To obtain a high-quality TiC coating on the diamond (D) surface and improve the interfacial properties of metal matrix composites, the optimized molten salt method is used to prepare TiC coatings on the D surface. The effects of NaCl, KCl, and NaCl–KCl molten salts on the uniformity, surface morphology, composition, and bonding ability of TiC coatings are investigated by scanning electron microscopy, energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction, and cold–hot cycling experiments. The results show that the boiling and pickling processes after the molten salt reaction can effectively remove the residual chloride salts and Ti powders to obtain clean TiC-coated D. The TiC particles of the coating surfaces prepared by NaCl and KCl molten salts are finer and more uniform, which is due to their higher melting points and shorter real reaction time compared with NaCl–KCl mixed salts. The TiC coating prepared by KCl has the best bonding ability and can withstand 50 times as many cold–hot cycles due to its uniform fine deposition particles and appropriate thickness. And, during cold–hot cycles, it can be found that the TiC coating cracking and shedding occur primarily at the edges and corners of the D with internal thermal stress concentration.

Impact of Fine Solids on Hydrotreating of Bitumen-Derived Gas Oil

Bitumen-derived gas oils that enter hydrotreaters contain fine solids such as minerals, heavy metals, and coke. The deposition of these fines will eventually restrict the flow and result in pressure buildup across the hydrotreater, which eventually necessitate the premature shutting down of the reactor system. To determine if certain types of fine particles had a greater detriment to the hydrotreating process, a series of experiments were performed by accelerated fine deposition in a trickle bed catalytic reactor under industrial conditions using bitumen-derived light gas oil. Kaolinite, montmorillonite, pyrite, and petroleum coke fines had no significant impact on the catalyst activity and catalyst deactivation toward hydrodenitrogenation (HDN), hydrodesulfurization (HDS), and hydrodearomatization. Unlike the above fines, iron(III)oxide was found to convert into FeS under hydrotreating conditions, which provided a promoting effect for HDN and HDS reactions. When comparing the trends in pressure drop across the catalyst bed, there was a delayed period during the initial fine deposition where no change in pressure drop was observed, followed by an exponential increase in pressure due to the decrease in bed porosity. The difference found between these fines was the length of this delayed period, with iron(III)oxide and petroleum coke having the longest periods of no pressure growth. From inductively coupled plasma, scanning electron microscopy with energy-dispersive spectroscopy, X-ray diffraction, and Brunauer–Emmett–Teller analysis of the fresh and spent catalysts, it was determined that the deposition of all fines occurred within the packing material in the preheating zone, with only petroleum coke and iron(III)oxide fines being found on the surface of the catalysts.

Physical and Rheological Characteristics of Sediment for Nautical Depth Assessment in Bushehr Port and Its Access Channel

Sedimentation in ports and waterways covered with fine deposits is a significant challenge in harbor management. The top layer of the bed in such areas typically consists of fluid mud, for which dredging is complicated and less efficient. The goal of this paper is to investigate physical and rheological characteristics of sediment for nautical depth assessment in Bushehr Port and its access channel. In this study the fluid mud layer was detected by hydrographic surveys with a dual-frequency echo sounder. Moreover, sediment properties in various parts of the channel and port were analyzed through a comprehensive sediment sampling in the field and complementary laboratory studies, including sediment grain-size analysis and distribution, carbonate and organic matter content, rheometry, and consolidation and settling tests. It was found that water contents and concentration, and clay-size fractions are the most important factors in rheological characteristics of sediment in the study area. The results indicated that the clay-size fraction in the surficial bed was between 18 and 31%, which categorized it as fine and cohesive sediment. In terms of mineralogy, the sediment was mostly carbonate mud with carbonate content between 52.9 and 57.2%. The results showed that the sediment concentration and yield stress in most samples were lower than 1030 kg/m3 and 123 Pascals, respectively. Based on the hydrographic surveys and obtained sediment characteristics, it is concluded that the nautical bottom approach can be practically implemented in the Bushehr Port and its access channel.

Factors Affecting the Rates and Modes of Landslide Colluvium Removal in River Channels of Podhale (Western Carpathians)

This paper presented some hydrological factors affecting the course and rate of fluvial erosion of landslide colluvium at its contact with river flow. Volumes of colluvium eroded by rivers in the period 2013–2019 were measured at Podhale (a part of Polish West Carpathians) on four landslides representing various geological settings. At each landslide, changes in shape and position of the contact zone between colluvium and river water were registered after episodes of high river stage. The obtained data on changes in relief of the landslide fronts and adjacent river channels were used to calculate volumes of colluvium removed during each episode. The course of erosion and volumes of colluvium eroded were compared with the water stage records for the studied period of time. Intensity of colluvium erosion was found to be strongly dependent on the water levels and cohesion of colluvium. Volumes of removed colluvium were the greatest during short-lived (1–2 days) and prolonged (7–10 days) periods of high river stages. The rate of erosional removal was the highest for colluvium consisting of poorly consolidated Quaternary matrix-supported massive gravel and overlying fine deposits stored within river terraces. Colluvium composed of Neogene mudstones and sandstones was removed at a lower rate and the rate of removal was lowest for large blocks and slices composed of solid layers of alternating sandstone and shales belonging to the Podhale Flysch series. Erosion of the landslide toes was more intense at those sites where the river flow approached the landslide front at a wider angle.

Latest Pleistocene and Holocene Floodplain Evolution in Central Europe—Insights from the Upper Unstrut Catchment (NW-Thuringia/Germany)

The upper Unstrut River is located in Germany at the modern Central European climate boundary of Cfb and Dfb climate. The river drains a loess landscape, which has experienced important environmental changes throughout the last 12,000 years. To evaluate the impacts of these changes on floodplain evolution, a multi-proxy research program, consisting of 2D electrical resistivity tomography profiling (ERT), vibracoring, and sedimentological investigations, 14C and OSL dating were applied. From base to top the investigations the following fluvial deposits were revealed: (1) gravels embedded in a fine-grained sediment matrix (interpreted as fluvial bedload deposits); (2) silty sediment with pedogenic features (interpreted as overbank floodplain deposits); (3) peat and tufa deposits (interpreted as wetland deposits) intercalated by pedogenetically influenced silty sediments (interpreted as overbank deposits); (4) humic silty sediment with some pedogenic features (interpreted as overbank floodplain deposits); and (5) silty sediments (interpreted as overbank deposits). Radiocarbon and luminescence dates yielded the following periods for sediment formation: (1) Younger Dryas to Preboreal period (around 11.6 cal ka BP); (2) Preboreal to early Atlantic period (approx. 11.6 to 7.0 cal ka BP); (3) early Atlantic to late Subboreal period (approx. 7.3 to 3.4 cal ka BP); (4) late Subboreal to early Subatlantic period (2.9 to 2.3 cal ka BP); and (5) late Subatlantic period (approx. 1.0 to 0.6 cal ka BP). The results suggest that floodplain development during the latest Pleistocene and early Holocene (approx. 11.6 to 7.0 cal ka BP) was considerably controlled by climatic conditions and short-term climate variabilities, which caused gravel deposition and overbank sedimentation. Afterwards floodplain conditions varied between rather stable (peat and tufa development, initial soil formation) and active periods (deposition of overbank fines). In this context, active periods with increased sediment input prevailed from approx. 5.1 to 3.4 cal ka BP, 2.9 to 2.3 cal ka, and 1.0 to 0.6 cal ka BP, temporally corresponding well with increased land-use phases of the past. In conclusion this study demonstrates that the investigated Unstrut catchment has reacted very sensitively to natural and human-induced changes during the latest Pleistocene and Holocene. Consequently, this high vulnerability to external changes should be considered in future river predictions or river management.

Evaluación de respuesta sísmica usando la teoría de vibraciones aleatorias en tres perfiles de suelo de Lima, Perú

Seismic response analyses are performed using a minimum number of seismic records as input motions in order to achieve a statistically strong estimation. Unfortunately, the available information recorded from the current seismic networks is still scarce regarding events with considerable magnitude. In this context, the Random Vibration Theory (RVT) arises as an alternative tool for performing site response analyses without the need of seismic records, since it only requires adequate probabilistic seismic hazard assessment.&#x0D; In this study, RVT was applied to three shear-wave velocity profiles in Lima city with distinct geomorphological origin. These profiles are characteristic for gravelly, sandy and fine deposits so the influence of each soil type in their corresponding transfer function was taken into account. In that sense, the three RVT-based normalized response spectra show good agreement with the design spectra specified in the Peruvian code, despite some amplification in the short (below 0.10 s) and long (above 0.80 s) period ranges related to noise or far-field effects. Furthermore, RVT-based response spectra for La Punta and Villa el Salvador show good agreement with the time-series based analyses from a previous study.&#x0D; In addition, spectral acceleration values surpass those specified in the Peruvian code for a range beyond the corner period. This could suggest that the soil profile characterization based on the time-averaged shear wave velocity from the upper 30 m might be insufficient to evaluate the overall seismic behavior of a soil deposit. Therefore, additional parameters that account for the deeper soil substructure might be required.

Fine-sediment Supply Can Control Fluvial Deposit Architecture: An Example From the Blackhawk Formation-Castlegate Sandstone Transition, Upper Cretaceous, Utah, USA

The arrangement of channel and floodplain deposits in alluvial basins reflects the balance of subsidence, sediment supply, and channel avulsion behavior during accumulation. Approaches for reconstructing tectonic and climatic histories from alluvial architecture generally assume that floodplain preservation is primarily a function of channel mobility relative to long-term sediment-accumulation rate; however, the amount of mud supplied to a river network can significantly impact the baseline accumulation of fine-grained deposits in alluvial basins. Here we evaluate preserved fine-sediment volume fractions at the bedform, reach, and outcrop scale across the transition from the mudstone-dominated Blackhawk Formation to the sandstone-dominated Lower Castlegate Sandstone (Upper Cretaceous, Utah, USA). Results show a nearly 50% decrease in mud abundance across the Blackhawk-Castlegate transition at a range of morphodynamic scales (mud percent in bed material: 28.4% to 14.1%, interbar fine deposits: 39.6% to 22.1%, and outcrop architecture: 58% to 16%). This decrease in fine-grained sediment coincides with an abrupt increase in quartz abundance from Blackhawk to Castlegate sands, suggesting that unroofing quartz-rich source rock caused significant regional changes in the alluvial deposits. This result shows that changes in sediment supply grain size are detectable from bed to landscape scales and can cause major changes in stratigraphic architecture. This method of comparing sand-to-mud ratios can be broadly applied in other fluvial successions and in source-to-sink transects to better reconstruct mud fluxes through ancient fluvial networks and to investigate how rivers respond to changes in fine-sediment availability.

Spatial variability of the erodibility of fine sediments deposited in two alpine gravel-bed rivers: The Isère and Galabre

In mountainous environments, high suspended sediment load during runoff or dam flushing events can lead to important amounts of fine deposits in gravel bed rivers. Fine sediment deposits may contribute to bar elevation, riparian vegetation growth and consequently to bar stabilization. Despite their contribution to the morphodynamic of mountain rivers, the erosion properties of fine sediments in this context is not fully understood.In order to investigate the dynamics of re-suspension of these deposits, field monitoring campaigns were performed to explore both the spatial variability and the controlling factors of the erodibility of fine deposits. A cohesive strength-meter (CSM), along with moisture, grain sizes, geographical position and elevation were used to evaluate both the critical bed shear stress for erosion and erosion rate of fine sediment deposits in two rivers of the French Alps: the Isère and Galabre.The results highlight a large variety of fine sediment deposition areas, which are discontinuous compared to those in estuaries and lowland rivers. A high spatial variability of erodibility was observed on the reach, the bar and the metric scale. While no upstream–downstream trend was observed at the scale of both studied reaches, the locations of the deposits, elevation from the river surface and their moisture were inter-related variables and with the highest correlations to erodibility. Measurements showed that both dry and humid deposits located at the highest and lowest elevation from the river surface respectively, were more easily eroded than intermediate deposits with medium moisture.