Application of digital image processing in slope surface runoff velocity analysis under simulated rainfall conditions

Velocity measurement of water flow within gravel layer with electrolyte tracer method under virtual boundary condition

Soil surface roughness decay under different topographic conditions

Application of tracer techniques to continuous-flow toxicity testing

Surface roughness and slope gradient are two important factors influencing soil erosion. The objective of this study was to investigate the interaction of surface roughness and slope gradient in controlling soil loss from sloping farmland due to water erosion on the Loess Plateau, China. Following the surface features of sloping farmland in the plateau region, we manually prepared rough surfaces using four tillage practices (contour drilling, artificial digging, manual hoeing, and contour plowing), with a smooth surface as the control measure. Five slope gradients (3°, 5°, 10°, 15°, and 20°) and two rainfall intensities (60 and 90 mm/hr) were considered in the artificial rainfall simulation experiment. The results showed that the runoff volume and sediment yield increased with increasing slope gradient under the same tillage treatment. At gentle slope gradients (e.g., 3° and 5°), the increase in surface roughness prevented the runoff and sediment production, that is, the surface roughness reduced the positive effect of slope gradient on the runoff volume and sediment yield to a certain extent. At steep slope gradients, however, the enhancing effect of slope gradient on soil erosion gradually increased and surpassed the reduction effect of surface roughness. This study reveals the existence of a critical slope gradient that influences the interaction of surface roughness and slope gradient in controlling soil erosion on sloping farmland. If the slope gradient is equal to or less than the critical value, an increase in surface roughness would decrease soil erosion. Otherwise, the increase in surface roughness would be ineffective for preventing soil erosion. The critical slope gradient would be smaller under higher rainfall intensity. These findings are helpful for us to understand the process of soil erosion and relevant for supporting soil and water conservation in the Loess Plateau region of China.

Effects of rainfall intensity and slope gradient on the dynamics of interrill erosion during soil surface sealing

There has been significant advances in the field of image and video processing over the past few decades. The term "image processing" is used to describe multiple signal-processing methodologies where images (such as video or picture frames) serves as the input, resulting to another image or a collection of image-related parameters or features. The majority of methodologies to image processing include reducing the picture to a two-dimensional signal and processing it in the same way as any other signal. The term "video processing" on the other hand is used to describe a particular type of signal processing where video files or video streams are utilized as output or input signals. Video recorders, televisions, video codecs, digital versatile, disc players, and other devices all utilize video processing algorithms. This paper provides a survey of the components of Digital Image Processing (DIP) as well as the recent developments in Image Processing technology and DIP applications.

There has been significant advances in the field of image and video processing over the past few decades. The term "image processing" is used to describe multiple signal-processing methodologies where images (such as video or picture frames) serves as the input, resulting to another image or a collection of image-related parameters or features. The majority of methodologies to image processing include reducing the picture to a two-dimensional signal and processing it in the same way as any other signal. The term "video processing" on the other hand is used to describe a particular type of signal processing where video files or video streams are utilized as output or input signals. Video recorders, televisions, video codecs, digital versatile, disc players, and other devices all utilize video processing algorithms. This paper provides a survey of the components of Digital Image Processing (DIP) as well as the recent developments in Image Processing technology and DIP applications.

Slope erosion in the Loess Plateau region has long been a concern, and vegetation plays an important role in slowing down erosion and controlling sedimentation. However, a single vegetation model shows some limitations when facing complex natural conditions and variable rainfall events. Therefore, this study investigated the influence mechanism of vegetation configuration on slope sand production at different slopes through theoretical analyses and indoor experiments. The results of the study showed that certain factors, such as vegetation configuration mode, flow rate, runoff power, runoff velocity, and runoff shear, are closely related to slope runoff sand production. The specific findings are as follows: (1) Under the condition of slope gradient of 2°, the sand reduction effect of the rigid–flexible single-row staggered configuration is the most significant, and the sediment production is reduced by 29.89%. (2) With the increase in the slope gradient and flow rate, the sand production on the slope surface rises significantly, and when the slope gradient is increased from 2° to 6°, the average sand production is increased from 1.43 kg to 2.51 kg.(3) The erosion reduction effects of different vegetation configurations were in the order of rigid–flexible single-row staggered combination > flexible vegetation single combination > rigid–flexible double-row staggered combination > rigid vegetation single combination > upstream rigid downstream flexible combination > bare slope. This study provides a theoretical basis for optimizing the vegetation configuration for effective sand reduction and provides an important reference for the sustainable development of the Yellow River Basin.

Understanding the spatial distribution patterns of soil organic carbon components in Ecological Vegetative Slopes (EVS) is crucial for optimizing restoration strategies, enhancing soil carbon sequestration capacity, and scientifically evaluating rehabilitation effectiveness. It is an important pathway for promoting sustainable development. This study investigated the effects of slope gradient, slope position, vegetation type, and cement content on the spatial distribution characteristics of soil total organic carbon (TOC) and its components (readily oxidizable organic carbon (ROC) and dissolved organic carbon (DOC)) through slope model experiments and laboratory analyses. The key findings revealed that (1) TOC, ROC, and DOC concentrations decreased with increasing slope gradient and upper slope positions, with steeper slopes amplifying positional effects and exhibiting surface-layer accumulation characteristics. (2) The highest TOC, ROC, and DOC content was achieved in the mixed planting slope with Bermudagrass and Magnolia under a substrate thickness of 3 cm and 3% cement content. Lastly, (3) soil pH increased with the slope gradient and upper positions, showing systematic variations across vegetation types and cement contents. Comparative analysis demonstrated that optimizing vegetation composition and cement dosage effectively enhanced SOC accumulation, while slope gradient and position dominated the spatial heterogeneity of carbon distribution. These results provide theoretical and practical guidance for the precision management of slope ecological restoration. These findings provide robust data support for the ecological sustainability of engineering slope restoration and the enhancement of soil carbon storage.

Hydraulic behavior and removal efficiency of settling tanks

Film-mulched rock outcrops are a proven way to effectively prevent preferential flow at the rock–soil interface in rocky karst areas, but the impact on rainwater redistribution and maize growth in farmland areas has never been studied. This paper used the dye tracer method at a sprinkling intensity of 1 mm min−1 to study the rainwater redistribution in soils for three different treatments: away from rock (AR), close to rock (CR), and close to film-mulched rock (CFMR). The growth situation of maize (Zea mays L.) according to the different treatments was also studied. It was shown in the study that the rainwater gathered by rock outcrops was mainly confined only within a narrow flow path at the rock–soil interface in the CR treatment, with a preferential flow fraction of 35.78~55.54% and dyeing depth of 15.37~20.00 cm across the three dye application amounts (850 mL, 1700 mL, and 3400 mL) in contrast to the uniform distribution of the rainwater in the soil of the AR treatment, with a preferential flow fraction of 12.31~37.15% and dyeing depth of 6.93~14.00 cm. Interestingly, in the CFMR treatment, there was no preferential flow at the rock–soil interface benefiting from the film’s blocking action, and the redistribution of rainwater was mainly based on the matrix flow, with a preferential flow fraction of 24.93~39.62% and dyeing depth of 10.27~18.00 cm, indicating that the film-mulched rock outcrops improved the rock’s output capability for gathering rainwater into the surrounding soil. In addition, film-mulched rock outcrops can promote the growth of maize, as indicated by the results for plant height, stem diameter, maximum leaf area, SPAD value, and floral development of maize, which increased in order from AR, CR, to CFMR. Our study suggests that film-mulched rock outcrops have important implications for the efficient use of rainwater and the growth of crops in rocky karst areas, as well as in regions with similar geological characteristics.

Effects of rainfall characteristics and contour tillage on ephemeral gully development in a field in Northeastern China

Land abandonment and slope gradient as key factors of soil erosion in Mediterranean terraced lands

Surface roughness has an important role in retarding the runoff velocity. The increase in paving blocks usage, particularly in urban areas, can change the surface roughness of the land. This study investigated the effects of four types of concrete block pavements (CBPs) in retarding the surface runoff velocity. Three design parameters based on CBP properties that considerably influenced the flow retardation were promoted. They were opening ratio (Or), void ratio (Vr) and straight channel ratio (Sr). A tilted plot equipped with a rainfall simulator was used to investigate the influence of surface slope and rainfall intensity to the flow on various CBPs. A modified dye tracing method in view was performed to monitor the surface flow velocity under various rainfall intensities. Flow retardation coefficient (Frd) were calculated based on velocity data on smooth pavement and on CBPs layer measured under the same slope and rainfall intensity. The results showed that flow retardation coefficient increased with an increase in openings ratio, rainfall intensity and surface slope. The relationship between flow retardation coefficient and all design parameters was expressed by a linear regression function. A further study is required to increase the accuracy of the model by modifying the regression function and increasing the variation of design parameters.

Through large-scale afforestation and reforestation, China has increased its forest area and improved forest quality, making considerable contributions to carbon stocks of the world’s forests. As one of the important indicators of forest quality and carbon potential, vegetation carbon density (VCD) is affected by different factors at different scales, but little is known about the effect of topographic factors on the VCD of subtropical forests in the southeast of China, especially at a large regional scale. Based on the national forest continuous inventory protocols, more than 2000 permanent samples (2061 samples in 2009, 2115 samples in 2014, and 2132 samples in 2016) of major forest types (Bamboo forests (BB), broad-leaved forests (BF), mixed forests (MF), coniferous forests (CF)) were grouped by topographic factors to compare the distribution of VCD in Zhejiang Province of China. The four topographic factors (altitude, slope gradient, aspect, and slope position) explained 16.2%~28.4% of the variance in different forest types in the random forest model and the importance order of the four terrain variables is basically corresponding to the significance in the radar charts. The VCD of each forest type varies significantly at different altitudes (p < .05, except for the BB samples in 2009). In general, VCD tends to be higher at high altitudes. The VCD in BB and BF varies significantly with slope gradient (p < .05, the largest on the steep slope and the smallest on the gentle slope); however, the VCD of CF and MF showed almost no difference in different slope gradients. We found significant differences in VCD between the eight aspects in the mixed forest (p < .05, the largest in the S and SW aspects), but not in the other three forest types. As for different slope positions, the VCD of ridges is relatively large, and the VCD of the upslope is generally larger than that of the downslope (more pronounced in BB and BF, all p < .05). This study made a detailed analysis of the greening distribution in different topographic factors, and the research conclusion could provide a scientific basis for the selection of afforestation location and forest scientific management, and contribute to the improvement of the capability of coping with climate change in subtropical forests.