Erosion Characteristics Research Articles

Investigating the Acid Erosion Characteristics of Carbonate Rocks under Hydrodynamic Action.

In carbonate areas, the unique dissolution features bring a lot of resistance to engineering constructions. The acidic filtrate will definitely cause accelerated dissolution of the surrounding rocks, and the mechanism of accelerated dissolution of such rocks in acid is not clear. In order to explore the dissolution pattern of carbonate rocks after the alteration of their primary environments, a self-made rotating reaction device was used to conduct laboratory dissolution experiments on carbonate cores under three conditions. The mass loss, the change of pH, the molar concentration of Ca2+ and Mg2+, and the morphological changes before and after acid erosion were obtained. The results of correlation analysis show that the dissolution characteristics of carbonate are significantly related to dissolution time, composition of rocks, liquid flow rate, and acid concentration. Segmented characteristics were recorded between CaO/MgO and the reaction sequence (m). When 2 < CaO/MgO < 30, the increase of CaO/MgO has a significant contribution to the chemical dissolution rate; however, when 30 < CaO/MgO < 66, the increase of CaO/MgO does not contribute significantly to the chemical dissolution rate. The dissolution rate is positively correlated with the liquid flow rate. Also, liquid flow rate changes affect dolomite more than they do limestone. The mass loss rate (Rc) order of the rocks of the five carbonate formations was Maocaopu > Qingyan > Falang > Anshun > Dengying. Differences in dissolution induced by the acidic fluids in different formations will eventually form complex dissolution channels.

Assessing basin-wide soil erosion in the Citarum watershed using USLE method

Citarum is the largest watershed in West Java, which is home to 25 million people. In such a large and populated watershed, land conversion is an inevitability. This condition directly encouraged an increase in erosion rates, which impacted increasing sedimentation rates in rivers, lakes, and dams. This research aimed to assess the spatial characteristics of soil erosion in the Citarum Watershed using the USLE method. The results showed that 45 % of the land in the Citarum watershed was in class I erosion hazard with an erosion rate of ≤15 tons/ha/year, 18 % in class II (15–60 tons/ha/year), 26 % in class III (60–180 tons/ha/year), 5 % in class IV (180–480 tons/ha/year), and the remaining 6 % in class V (>480 tons/ha/year). Total annual erosion in the Citarum watershed reaches 80.1 million tons, of which 52 % is contributed by the Middle Citarum Watershed (42.0 million tons/year), 26 % is the Upper Citarum Watershed (21.2 million tons/year), and the remaining 22 % contributed by the Lower Citarum Watershed (17.0 million tons/year). The proposed control measures for erosion hotspot locations throughout the watershed, which include structural and nonstructural approaches, are also proposed.

Study on Dynamic Evolution and Erosion Characteristics of Cavitation Clouds in Submerged Cavitating Water Jets

The dynamic evolution behavior of submerged water jet cavitation clouds was studied by combining experiments and simulation. The formation, development, shedding, and collapsing process of a void cloud was analyzed by high-speed camera technology, and the influence of jet pressure was studied. Cavitation water jet erosion experiments were carried out on AL6061 specimens with standard cylindrical nozzles, and the correlation between cavitation cloud evolution and material erosion was studied by surface analysis. The results showed that the evolution of a cavitation cloud has obvious periodicity, that one period is about 0.8 ms, and its action region can be divided according to the attenuation rate of the jet velocity of the nozzle axis. The attenuation rate of the jet velocity at the nozzle axis in the central jet action zone is less than or equal to 82.5%, in the mixed action zone greater than 82.5% and less than 96%, and in the cavitation action zone greater than or equal to 96%. The erosion damage characteristics in different regions of the mixed action zone are significantly different.

Calibration of Oil Film Thickness Acoustic Reflection Coefficient of Bearing under Multiple Temperature Conditions

Rolling mill bearings are prone to wear, erosion, and other damage characteristics due to prolonged exposure to rolling forces. Therefore, regular inspection of rolling mill bearings is necessary. Ultrasonic technology, due to its non-destructive nature, allows for measuring the oil film thickness distribution within the bearing during disassembly. However, during the process of using ultrasonic reflection coefficients to determine the oil film thickness and distribution state of rolling mill bearings, changes in bearing temperature due to prolonged operation can occur. Ultrasonic waves are susceptible to temperature variations, and different temperatures of the measured structure can lead to changes in measurement results, ultimately distorting the results. This paper proposes using density and sound speed compensation methods to address this issue. It simulates and analyzes the oil film reflection coefficients at different temperatures, ultimately confirming the feasibility and effectiveness of this approach. The paper establishes a functional relationship between bearing pressure and reflection coefficients, oil film thickness, and reflection coefficients. This allows for the compensation of reflection coefficients under any pressure conditions, enhancing the accuracy of oil film thickness detection. The proposed method provides technical support for the maintenance of plate rolling processes in the steel industry.

Meander Morphologic Characteristics in an Alluvial Channel

Meander bends are one of the most common morphological features of rivers. Their formation is the result of interactions between bank erosion and several other river characteristics, such as the bed topography resulting from bank erosion, sinuosity, channel flow, and riffle-pool sequencing. Many studies have emphasized proportional relationships between channel widths and different aspects of meander morphology, such as wavelength, curvature of the radius, and belt width. These relationships have been studied for bankfull level width in high-order channels. It is not clear how such relationships vary in low-order headwater streams. This research addresses those gaps in low-order streams of which little is known. Field surveys were conducted in nine meander bends of a low-order alluvial channel in Virginia. The results suggest that in a low-order channel, the ratios of width with wavelength, the radius of curvature, and belt width are mostly similar between the meanders’ beginning and tail endpoints. The stream also has similar meander morphologic characteristics and ratios as anticipated from the literature on high-order streams.

Research on the solid particle erosion wear of pipe steel for hydraulic fracturing based on experiments and numerical simulations

Erosion wear is a common failure mode in the oil and gas industry. In the hydraulic fracturing, the fracturing pipes are not only in high-pressure working environment, but also suffer from the impact of the high-speed solid particles in the fracturing fluid. Beneath such complex conditions, the vulnerable components of the pipe system are prone to perforation or even burst accidents, which has become one of the most serious risks at the fracturing site. Unfortunately, it is not yet fully understood the erosion mechanism of pipe steel for hydraulic fracturing. Therefore, this article provides a detailed analysis of the erosion behavior of fracturing pipes under complex working conditions based on experiments and numerical simulations. Firstly, we conducted erosion experiments on AISI 4135 steel for fracturing pipes to investigate the erosion characteristics of the material. The effects of impact angle, flow velocity and applied stress on erosion wear were comprehensively considered. Then a particle impact dynamic model of erosion wear was developed based on the experimental parameters, and the evolution process of particle erosion under different impact angles, impact velocities and applied stress was analyzed. By combining the erosion characteristics, the micro-structure of the eroded area, and the micro-mechanics of erosion damage, the erosion mechanism of pipe steel under fracturing conditions was studied in detail for the first time. Under high-pressure operating conditions, it was demonstrated through experiments and numerical simulations that the size of the micro-defects in the eroded area increased as the applied stress increased, resulting in more severe erosion wear of fracturing pipes.

Numerical study on sediment erosion characteristics of Francis turbine runner

Sediment erosion is a prevalent and significant challenge to hydro turbines in mountainous rivers. In order to gain an insight into the erosion characteristics of Francis turbines, this study considers the influence of actual sediment gradation and emphasizes the erosion mechanism from the perspective of flow structure. Numerical results reveal a significant correlation between erosion distributions and the location of inter-blade vortices, which is dependent on operating conditions. Specifically, at small or optimal openings, inter-blade vortices predominantly form on the suction side of blades, which coincidentally experiences the most severe sediment erosion. Conversely, at a large guide vane opening, sediment erosion and vortices are primarily distributed at outlet of pressure side, aligning closely with actual site observations at a hydropower station. With increase of operating heads, the average erosion rate of suction side decreases at all guide vane openings, while that of pressure side elevates significantly. In addition, the effect of particle size on sediment erosion was discussed and the maximum erosion rate is demonstrated to be proportional to sediment diameter. These findings would provide important engineering insights for operation optimization to reduce sediment erosion.

Seismic investigation uncovers formation and spatial distribution of seafloor erosional features on the Changjiang (Yangtze) River subaqueous delta

River deltas face erosional challenges driven by global changes and human activities leading to diminished sediment supply. Despite extensive researches on erosional processes within the Changjiang River subaqueous delta (CRSD), there exists a knowledge gap concerning the comprehensive spatial distribution of erosional features throughout the CRSD. This study addresses this gap by utilizing a substantial dataset of high-resolution chirp data to analyze the characteristics, distributions, and stratigraphic terminations of seafloor erosional features within the CRSD. The results unveil an expansive erosion area spanning approximately 2900 km2, occurring at depths ranging from 10 to 40 m in the modern CRSD. These erosional features manifest as extensive truncations, low-relief scoured seafloor, and cut-and-fill structures, distributed variably across the CRSD. Particularly noteworthy is the identification of an alignment between the suspended sediment front and a 20 m water depth erosional area along the deltaic coast. Erosion in this area is dominated by truncations, extending ∼ 10 km in width, and followed by scoured (several hundred meters wide and ∼ 1–2 m deep on average) seafloor. Slope gradient also influences erosion, with cut-and-fill structures (2 km wide and around 5 m deep) that we attribute to sediment gravity flows are identified on steeper slopes offshore of North Channel. Beyond the 20 m water depth, extensive truncations spanning approximately 20 km wide and lead to outcrops of older strata. The spatial distribution of erosional features, coupled with river outlets and subsurface structure, suggests joint influences from reduced riverine sediments, estuarine engineering, wave actions, and tidal regimes. These findings emphasize the primary impact of sediment discharge reduction and underscore the collective influence of various anthropological and natural factors in shaping the spatial distribution of erosional features across different water depths in the subaqueous delta. Insights from this study contribute to a deep understanding of erosional processes and the ongoing evolution of erosional degradation in deltaic systems worldwide.

Decoding the Interplay Between Tidal Notch Geometry and Sea‐Level Variability During the Last Interglacial (Marine Isotope Stage 5e) High Stand

AbstractRelic coastal landforms (fossil corals, cemented intertidal deposits, or erosive features carved onto rock coasts) serve as sea‐level index points (SLIPs), that are widely used to reconstruct past sea‐level changes. Traditional SLIP‐based sea‐level reconstructions face challenges in capturing continuous sea‐level variability and dating erosional SLIPs, such as tidal notches. Here, we propose a novel approach to such challenges. We use a numerical model of cliff erosion embedded within a Monte Carlo simulation to investigate the most likely sea‐level scenarios responsible for shaping one of the best‐preserved tidal notches of Last Interglacial age in Sardinia, Italy. Results align with Glacial Isostatic Adjustment model predictions, indicating that synchronized or out‐of‐sync ice‐volume shifts in Antarctic and Greenland ice sheets can reproduce the notch morphology, with sea level confidently peaking at 6 m and only under a higher than present erosion regime. This new approach yields insight into sea‐level trends during the Last Interglacial.

Soil Erosion Modeling Using the Revised Universal Soil Loss Equation and a Geographic Information System in a Watershed in the Northeastern Brazilian Cerrado

Soils have an important task in maintaining vegetation cover and natural resources on Earth and are indispensable to societies. However, the accelerated soil erosion has become an environmental problem related to land settlement for agricultural practices and forestry and is linked to population growth. This study aimed to evaluate soil erosion in a watershed downstream of Parnaíba river, northwest of Piauí state, in the Brazilian Cerrado using geotechnology products and tools in order to understand the soil loss and map the potential erosion and actual erosion through qualitative and quantitative results to support the management and planning of the watershed in an effective and efficient way. As a modeling tool, this research used the Revised Universal Soil Loss Equation (RUSLE). The potential erosion ranged from very low to very high. The soil loss obtained by the integration of natural physical factors with land use (anthropic action) resulted in soil loss corresponding to the category slight (0–0.01 t.ha−1.year−1) to extremely high (&gt;100 t.ha−1.year−1). The areas with the greatest soil loss were identified in land uses linked to pasture, exposed soil, and cultivated land. It was also possible to identify erosion features in the field, indicating the need to implement soil conservation practices.

Erosion characteristics of water droplet machining

Water Droplet Machining (WDM) is a new manufacturing process, which uses a series of high-velocity, pure-water droplets to impact and erode solid workpieces, for the purpose of through-cutting, milling and surface profiling. The process is conducted within a vacuum environment to suppress aerodynamic drag and atomization of the waterjet and droplet train. This preserves droplet momentum and allows for a more efficient transfer of energy between the water and workpiece, than in standard atmospheric pressure. As a new manufacturing technique, parameter-specific details and characteristics of this process are absent from the scientific literature. Therefore, this study aims to elucidate the capabilities of WDM, and uncover its erosion characteristics. Experiments are performed using a custom-fabricated machine, where a range of waterjet-types (and droplet trains) are produced. The experiments are performed on two industrial-relevant metals: stainless steel SS 316 L and aluminum AA 6022-T4. The target shape is a partial-cut through the material, i.e., a trench. A parametric study investigates the effects of stand-off distance, orifice diameter, and feed-rate on the trench shape, material-removal-rate, and reveals the conditions which render WDM an effective machining process. It was found that, for orifice diameters of 100 μm, an effective stand-off distance is between 457 and 686 mm; below that, no material removal is observed. In this configuration, accurate through-cuts are produced and can be used for manufacturing purposes. For large orifice diameters, e.g., 250 μm, an atomized spray is produced, which features a comparatively large material removal rate, and can be used for surface profiling and milling.

Sediment production process and hydraulic characteristics of ephemeral gully erosion in granite hilly area

Ephemeral gully (EG) erosion represents the early stage of large-scale gully (locally named as “Benggang”) development on Ultisols in the granite hilly area. However, the EG erosion process and the mechanism underlying sediment production have not been fully elucidated. In this study, a series of field scouring experiments were conducted under different flow discharge levels (10, 15, 20, 25, and 30 L·min−1), and the primary EGs in three typical soil layers with different weathering degrees (red soil layer (RL), transition layer (TL), and sandy layer (SL)) was dynamically monitored. The results indicated that the ratio of width to depth of the EGs rapidly decreased as the flow discharge increased. At 30 L·min−1, the average sediment yield and transport rate (Sr) of the SL were 4.85 and 5.39 times, greater than those of the RL, respectively. The sediment particles were concentrated within the 1–2 mm particle size range, accounting for over 35 %. In addition, the mean weight diameter of the sediment particles in the RL was the largest. The sediment distribution characteristics did not respond to flow changes but were affected by EG morphological changes. With increasing flow discharge, the flow shear stress and stream power increased. Further analysis revealed that the coupling effect of flow hydraulic characteristics and EG morphological evolution drove the EG erosion sediment production process, and the Sr of the SL was highly sensitive to flow discharge changes. The soil disintegration rate was an internal factor that directly affected soil loss in the EGs, with a path coefficient of 0.71. The bulk density, organic matter content, and sand content were all indirect influencing factors. The RL exhibited greater anti-erodibility than the other layers and could serve as an effective protective layerfor granite hilly areas. These findings provide a theoretical basis for improving soil loss management systems.

Relationship among runoff, soil erosion, and rill morphology on slopes of overburdened stockpiles under simulated rainfall

Overburdened stockpiles are difficult to achieve natural stability in a short period time because of their complex and diverse composition of materials and significant differences in physical and chemical properties, causing numerous cases of water loss and soil loss events. We conducted a series of experiments at different rainfall intensities (30, 60, 90, and 120 mm h−1) and different gravel contents (0 %, 10 %, 20 %, 30 %, and 40 %) to study the runoff, soil erosion, and rill morphology characteristics and relationship among three of overburdened stockpiles in production and construction projects with simulated rainfall. The runoff rate and soil loss rate basically showed a trend of increasing and then decreasing with gravel content and lower gravel content had a certain degree of inhibition on the flow velocity. 20 %, 0 %, 0 %, and 20 % gravel contents had the most significant inhibition on the flow velocity at 30, 60, 90, and 120 mm h−1 rainfall intensities, respectively. Flow shear stress, stream power, unit energy of water cross-section, maximum rill length, width and depth all increased with increasing rainfall intensity. The stream power, unit stream power, and unit energy of water cross-section were larger at higher gravel content. The maximum rill length and depth were positively correlated with gravel content, which were the minimum at 0 % gravel content and all rainfall intensities. Gravel content played a more important role in the runoff, soil loss, and rill morphology. The relationship between runoff rate and soil loss rate, flow velocity and rill morphology parameters were all expressed as linear functions, and flow velocity and soil loss rate was quadratic function, with a correlation coefficient of 0.339. In contrast, runoff rate and rill morphology parameters, soil loss rate and rill morphology parameters, erosion dynamics parameters and rill morphology parameters were all expressed as power functions. In addition, the runoff rate can better describe the process of soil loss (R2 = 0.798, P < 0.05). The unit energy of water cross-section was more suitable to describe the development of maximum rill length and depth (with rill length was R2 = 0.781, and with rill depth was R2 = 0.723, P < 0.05). At the same time, the stream power was more suitable to describe the development of maximum rill width on the slope of overburdened stockpiles (R2 = 0.841, P < 0.05). These results contributed to preventing soil loss on overburdened stockpiles and helping the development of estimation models for soil erosion.

Study on Grease Lubrication and Electric Erosion Characteristics in AC Electric Fields

Protecting motor bearings from electric erosion is crucial as electric vehicles evolve. To better understand how lubrication interacts with electric discharge within motor bearings during varying speeds of vehicle operation, an optical ball-on-disk tribometer was modified to investigate the influence of alternating current (AC) electric fields on film thickness, friction force under various lubrication regions, and discharge characteristics. The study revealed that in AC electric fields, as the lubrication state shifts from mixed lubrication to fluid lubrication region, the electrical characteristic of the lubricating oil film changes from resistive to capacitive, accompanied by an increase in discharge frequency. Under the elastohydrodynamic lubrication (EHL) region, an electrical potential difference between the surfaces separated by the lubrication film leads to a reduction in film thickness, which can be attributed to the generation of Joule heating. If the potential difference across the oil film increases to the threshold voltage, destructive discharge occurs with the emission of a significant amount of purple light. Joule heating generated by the AC electric fields also results in a reduction in the friction coefficient under the fluid lubrication region. However, due to the reduction in film thickness, the lubrication state eventually moves to mixed lubrication, leading to a substantial increase in the friction coefficient. In addition, the study also investigated the use of grease with a nanographite conductive additive. It was found that inappropriate additive amounts can lead to discharge phenomena occurring outside the contact region.

SWE Modelling of Debris-flow body-sedimentation and Tail-flow Remobilization in a Check-dam Controlled Gully (Unzen Volcano, Japan) using UAV LiDAR, SfM-MVS

On 13th August 2021 at Unzen Volcano (Japan), an 81 mm.hr-1 peak-rainfall (1486 mm in 2 weeks) triggered series of erosion and deposition features in the Tansandani and the Gokurakudani gullies, all adding up to 57,800 m3 of erosion and 39,600 m3 of deposition. Upstream of the Sabo dam located at the exit of the Tansandani Gully, a large deposit has been visually identified as a potential debris-flow front candidate. However, the absence of direct observation leaves some uncertainty on the process that deposited the material and the magnitude of the flow. In the present contribution, the authors are investigating (1) the role of the debris-flow body in constructing the deposit and (2) the role of the tail of the debris-flow in eroding the fresh deposit. To reach this objective, the authors have combined a field investigation with direct observation, UAV (Unmanned Aerial Vehicle) LiDAR (Light Detection And Ranging) and Photogrammetry, and GIS (Geographic Information System) analysis of the field data. From this data, a 2D hydrodynamic simulation and sediment transport models were applied. The results show that the debris-flow ran beyond the first Sabo dam, with part of the material trapped on both sides of the gully. Afterwards, a central channel connected to sub-channels conveyed the diluted flow, most probably < 25 cm with maximum velocities between 4 to 5 m.s-1 at peak flow. Only the debris-flow phase went over the internal shoulders of the Sabo dam. A lobe occupies the top half of the study area and its deposition has been discussed to be related to the sudden widening of the gully, while the lower half is connected to the base-level created by the check dam.

Erosion Characteristics of Oil-Immersed On-Load Tap Changer Contacts Under Varying Contact Speeds and Pressures

Erosion Characteristics of Oil-Immersed On-Load Tap Changer Contacts Under Varying Contact Speeds and Pressures

Effect and mechanism of erosion in Pelton turbine and case studies—A review

Pelton turbines are widely used in hydropower stations located in mountainous regions, especially with water head drop of more than 2000 m. Due to the complex structure and working principle of the turbine, the flow is more complicated than reaction turbines, making the numerical simulation more difficult. The impulse action causes the occurrence of erosion phenomena in Pelton turbines, which will directly decrease the hydraulic efficiency and reduce the turbine's life. For investigating the erosion characteristics, computational fluid dynamics is widely used on variegated platforms according to their unique advantage. Thus, different platforms are introduced and compared in solving the multi-phase flow using a discrete element method or the other meshless methods. In addition, the erosion mechanism is studied and classified in different aspects such as impact angle and impact velocity. However, unlike the feasibility of numerical simulations, experimental work on the erosion mechanism is still challenging to reproduce. Furthermore, the state of experimental research is discussed by listing the various major facilities in operation and comparing their methods of experimental analysis. Case studies all over the world provide a very rich database of erosion patterns which would be highly useful in validation and verification of simulation and experimental results. Studies have shown that particle parameters, such as size, concentration, shape, velocity, and the interaction between particles and material surfaces, significantly impact the erosion of Pelton turbines. In response to this erosion, upgrading materials and implementing geometric optimization have proven to be effective strategies.

Hydrohelical ESP Gas Separator Increases Flow Range, Improves Reliability

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 214723, “New High-Performance ESP Gas Separator,” by Barry Nicholson, SPE, and Scott R. Harryman, SPE, Oxy, and Donn J. Brown, SPE, Halliburton, et al. The paper has not been peer reviewed. _ The complete paper presents research, design, and field testing of a new type of mechanical gas separator for electrical submersible pump (ESP) systems that increases operating flow range and separation efficiency while decreasing erosion problems and improving reliability. The hydrohelical separator system has been proved effective in different types of wells. Background Several methods and techniques exist for avoiding gas in ESPs, including inverted shrouds, passive separators, mechanical gas separators, and tandem gas separators. Most share the limitations of limited flow capabilities and reduced performance at higher total flow rates. The many variables associated with complex two-phase flow behavior, internal and external pressure variations, separation methods, velocity and viscosity of fluids, effect of the pump bolted above, inherent erosion issues, and single vs. tandem designs add to the challenge of basic mechanical gas-separator operation. In 2016, a program was initiated that featured investment in both experienced personnel and advanced testing technology to unravel the aforementioned challenges and improve understanding of the operation of downhole mechanical gas separation. The team investigated innovative methods of testing and created a transparent testing system that allowed visual observation of individual internal flow regimes as well as component performance. Using a combination of high-speed photography, computational fluid dynamics validation, and specialized instrumentation, every component of a mechanical separator system was enhanced for higher flow capabilities, improved separation efficiency, and higher reliability for a variety of downhole conditions. The result was the development of a new type of mechanical gas separator for ESP use. Development Most gas separators ingest multiphase fluid into a separation chamber, separate the gas and liquid phases, eject the separated gas phase into the well annulus, and provide sufficient liquid phase fluid to the pump to enable efficient pumping. Existing designs vary, but they share separation methods that result in decreased efficiency at higher flow rates and low maximum flow rates compared with the pumps they feed. The hydrohelical gas separator is the first downhole, dynamic gas-separator design improvement in more than 30 years designed to address these deficiencies (Fig. 1). The design was aimed at the following main objectives: - Increase total fluid flow rate through the separator - Maximize efficiency of every internal and external component of the system - Reduce erosion characteristics common in traditional gas-separator designs - Improve reliability The design of the hydrohelical gas separator is based on a stationary helical vortex inducer and pump stages that enable movement of large quantities of fluid while remaining immune to gas locking. The stationary helical vortex inducer design enables increased efficiency and flow rate through the separator by reducing turbulence in remixing regions within the helical inducer and separation chamber.

Soil Erosion Characteristics in Tropical Island Watersheds Based on CSLE Model: Discussion of Driving Mechanisms

Previous research has primarily focused on soil erosion issues in arid and semi-arid regions, with a limited understanding of soil erosion mechanisms in tropical areas. Additionally, there is a lack of a holistic perspective to determine the spatial attribution of soil erosion. The conversion of tropical rainforests into economically driven plantations, like rubber and pulpwood, has resulted in distinct soil erosion characteristics in specific regions. To enhance our knowledge of soil erosion patterns and mechanisms in tropical regions, it is necessary to examine soil erosion in the three major watersheds of Hainan Island from 1991 to 2021, which encompass significant geographical features such as tropical island water sources and tropical rainforest national parks. The study employed the China Soil Loss Equation (CSLE) model, slope trend analysis, Pearson correlation analysis, land-use transfer matrix, and spatial attribution analysis to examine soil erosion under different scenarios. The research results indicate that scenarios driven by the combination of natural and human factors have the greatest impact on soil erosion changes in the entire study area. Co-driven increases affected 53.56% of the area, while co-driven decreases affected 21.74%. The 31-year soil erosion showed an overall increasing trend. Human factors were identified as the primary drivers of increased soil erosion in the Nandu River basin, while a combination of climate and anthropogenic factors influenced the decrease in soil erosion. In the Changhua River basin, climate and human activities contributed to the soil erosion increase, while human activities primarily caused the decrease in soil erosion. In the Wanquan River basin, climate intensified soil erosion, whereas human activities mitigated it. This study underscores the significant combined impact of human activities and natural factors on soil erosion in tropical regions. It emphasizes the importance of considering human-induced factors when implementing soil erosion control measures in tropical regions.

Water Erosion Processes on the Geotouristic Trails of Serra da Bocaina National Park Coast, Rio de Janeiro State, Brazil

Conservation units are strategic territories that have a high demand for public use, as they protect attractions of great scenic beauty, geodiversity sites, and numerous leisure areas. However, when carried out in an intensive and disorderly manner, tourist activity in these areas tends to catalyze environmental degradation, triggering, for example, water erosion processes caused by intensive soil trampling on the trails. In this sense, the aim of this study was to determine the soil’s physicochemical characteristics, and to spatiotemporally monitor the microtopography of those areas degraded by erosion along two trails on Serra da Bocaina National Park coast of the Paraty Municipality. The findings verified that intensive trampling, the values of some soil physicochemical characteristics, and the specific meteorological conditions of the coastal region of this protected area were factors that contributed significantly to the evolution of erosion features monitored on these trails. Finally, strategies for appropriate management and recovery actions for these degraded areas are proposed in order to not only stop the erosive processes and re-establish the local ecosystem balance, but also avoid accidents involving the numerous tourists who visit the coastal region.