Erosion Regions Research Articles

Shear strength characteristics of collapsed walls and influencing factors in the Benggang erosion region of Southern China

Shear strength characteristics of collapsed walls and influencing factors in the Benggang erosion region of Southern China

Alterações nas dunas da Praia de Boa Viagem - Recife (PE) originadas por Ação Antrópica

O ambiente de dunas com a vegetação na região costeira tem se tornado uma das áreas do espaço geográfico que mais sofre com a ação antrópica mal planejada, ficando exposto à degradação dos seus componentes naturais. A preservação dos cordões de dunas frontais ainda é apontada como a melhor solução para prevenir uma região da erosão costeira. Para obtenção dos dados teóricos da pesquisa foi utilizado como motor de busca o site Google e as imagens de campo foram obtidas por sensoriamento remoto. O arco praial da Praia de Boa Viagem pode ser descrito como um sistema dominado por ondas e ventos, agentes responsáveis pela dinâmica sedimentar e modeladores da linha da costa. Observou-se uma perda significativa de dunas com a cobertura vegetal aceleradas por ação antrópica. Conclui-se que há uma necessidade de implantação de um manejo adequado de recuperação da área degradada que aumenta sua extensão há cada ano. Buscou-se no presente estudo entender as consequências da ação antrópica no ambiente natural da praia de Boa Viagem, Recife-PE.

The effects of tillage on sheet erosion on sloping fields in the wind-water erosion crisscross region of the Chinese Loess Plateau

Tillage complicates erosion on sloping fields, especially in regions of combined wind and water erosion. The wind-water erosion crisscross region of the Chinese Loess Plateau is an example of such a region wherein erosion is caused by the stimulating effects of tillage, rainfall, and wind. Sheet erosion is an important form of cropland soil erosion and is closely correlated to the productive capacity of land. It is important to better understand the influence of tillage on soil sheet erosion in order to estimate the loss of fertile surface soil and to provide suitable tillage recommendations for the cultivation of sloping cropland in this region, which is susceptible to multiple erosion factors. This study aims to clarify spatial distribution and variation of sheet erosion rates as affected by different tillage patterns on sloping cropland under different slope conditions. We applied beryllium-7 measurements and sediment collection methods to estimate sheet erosion rates to reveal the distribution of sheet erosion on bare sloping fields, to determine correlations between sheet erosion rates and slopes (0°, 5°, 10°, 15°, 20°, and 25°), and to analyze variation in sheet erosion affected by tillage patterns on a plot scale. Results show that sheet erosion increased in a top-down direction and achieved maximum values at the mid- or lower-mid section of slopes, then erosion rates decreased or sediment deposition occurred at the base of slopes. Sheet erosion intensified with an increase in slope gradient fitting to linear or exponential functions regardless of the tillage pattern used (i.e., whether solely applying autumn plowing or a combination of autumn and spring plowing). However, tillage patterns had an obvious effect on sheet erosion. Differences in sheet erosion caused by tillage patterns increased from 5° to between 15° and 20° before decreasing at 25°. This demonstrates that steep slope gradients will weaken tillage pattern effects on sheet erosion, thus becoming a significant impacting factor on sheet erosion. Based on sheet erosion rates, we recommend that cropland be converted to grassland or shrubland when slope gradients are greater than 20° in the study region. Notably, a decrease in tillage intensity (frequency) helped in the reduction of sheet erosion on sloping croplands, and further tillage practices associated with conservation tillage should be applied on sloping cropland to obtain better soil erosion control results.

Ecological restoration of eroded karst utilizing pioneer moss and vascular plant species with selection based on vegetation diversity and underlying soil chemistry

Soil erosion in karst areas not only destroys the natural environment but also accelerates the decline in land productivity together with the associated increase in poverty for local communities. There are no simple or straightforward answers to controlling soil erosion on karst. Such erosion has become a serious problem in China. This study addresses both the diversity of vegetation (mosses, herbs, shrubs and trees) on karst and the underlying soil chemical characteristics, in order to provide a scientific basis by which suitable plant species can be selected for recovery and restoration of karst degraded by soil erosion. Vegetation diversity and soil chemistry were assessed in areas with five different grades of soil erosion in Guiyang Karst Park, Guizhou, China. Mosses are more tolerant than vascular plants of soil erosion and associated environmental degradation of karst and the order of species diversity was: mosses > herbs > shrubs > trees. Mosses were found to play a major role in ecological restoration of microhabitats on karst. Soil microbial biomass carbon was found to be significantly higher in soil under mosses than in bare soil associated with other plant categories. Mosses were more effective in converting unavailable potassium to available potassium. Vascular plants were found to have a positive effect on total nitrogen fixation and the availability of phosphorus in the soil. Increasing soil degradation was associated with lower levels of total Nitrogen in soil underlying mosses than in soil underlying vascular plants. Thus, based on their different but complementary contributions to soil chemistry, mosses and vascular plants in combination can provide the most practical outcome for the repair and restoration of areas of karst affected by soil erosion. The combination of the moss species, Homomallium plagiangium, Cyrto-hypnum pygmaeuman and Brachythecium perminusculum, the herbs Veronica arvensis and Youngia japonica, and the tree Prunus salicina, are recommended as suitable pioneer plant species to cultivate for use in restoration of regions of karstic soil erosion.

Effects of plant residue management on soil properties, surface runoff, and soil loss under rainfall simulation in a semi-arid region in Iran

A 5-year field study was conducted on the effect of plant residue management on soil erosion, runoff, bulk density, penetration resistance, and organic carbon. There were three treatments: burning residues on field (BR), returning residues unto the soil surface after harvesting (TR), and removing residues from soil surface (RR) (control treatment). At the end of the 5-year treatment, a rainfall simulation at 90 mm h−1 was applied to each plot. After rainfall simulation started, the runoff volume and soil loss amount in samples were collected at four sampling times. The results showed that the runoff volume for BR (from 145.5 ± 12.2 to 190.0 ± 11.8 mL) differed significantly (p ≤ 0.01) from that of RR (from 32.3 ± 5.5 to 67.5 ± 11.1 mL) and TR (from 10.0 ± 0.7 to 16.7 ± 3.3 mL). A significant difference (p ≤ 0.01) was also observed between RR and TR regarding runoff volume and soil loss amount in different sampling times, except for the first sampling time (2–4 min). The runoff volume in BR and TR was 215% higher and 294% lower than that of the control (RR), respectively. As compared to the control (RR), soil loss decreased by 96.5% in TR but increased by 192% in BR. The BR increased soil bulk density and penetration resistance by 4.9% and 12.4%, whereas TR reduced them by 2.1% and 15.8%, respectively, as compared to the control (RR). The results indicated that the highest (0.35) and lowest (0.03) runoff coefficients were obtained for BR and TR treatments, respectively. It is concluded that returning plant residues to soil is the best residue management practice in decreasing soil runoff volume and controlling soil erosion in semi-arid regions.

Effects of mosaic-pattern shrub patches on runoff and sediment yield in a wind-water erosion crisscross region

Shrub patch fragmentation makes a substantial contribution to soil erosion in sandy regions. This study aimed to analyze the effects of mosaic-pattern shrub patch size on runoff and sedimentation in a wind-water erosion crisscross region. The influence of shrub patch size on runoff and sedimentation, and on several soil physical and vegetation factors was evaluated in a sandy Chinese landscape. Based upon the canopy diameter of Artemisia ordosica, a xerophytic shrub, three different patch sizes were set as the treatments, such as small (Ø < 60 cm), medium (60 < Ø < 160 cm) and large (Ø > 160 cm) shrub patches. Bare land served as control conditions. Three runoff plots were established for each shrub size, and runoff (Q) and sediment (SY) yields were monitored under natural rainfall conditions. The results indicated that rainfall distribution was uneven in the study area. Low-intensity (0–5 mm/h) and short-duration (0–5 h) rainfall events accounted for 82.6% and 71.7% of all events, respectively, during the 6-month test period, from May to October 2016. Linear regression indicated that Q and SY increased with increasing rainfall depth at the slope scale. The impact of rainfall erosion on bare land was the greatest. Compared with control plots, Q and SY reduction owing to the small, medium, and large shrub patches was 19.7% and 49.3%, 31.4% and 62.4%, and 35.9% and 94.9%, respectively. These results confirmed the different effects of shrub patches of different sizes on soil quality, runoff and sediment reduction. Besides, this study suggested that shrub patches could modify soil microhabitats on sandy soils, reducing the soil erosion rates and as well as favoring vegetation regeneration.

Wind tunnel experiment and CFD analysis of sand erosion/deposition due to wind around an obstacle

A wind tunnel experiment on sand erosion/deposition around a cube was performed to clarify the basic phenomena and obtain validation data for computational fluid dynamics (CFD) analysis. The experiment was conducted in the atmospheric boundary layer wind tunnel at the Niigata Institute of Technology in Japan. A cubic model with width 200 mm was located on the sand surface with depth 30 mm, and the erosion and deposition patterns on the sand surface were measured following the blowing of wind. Considerable wind erosion was observed near the windward corners of the cube, in contrast to small deposition in other areas. Primary CFD analysis of wind erosion was then conducted to reproduce the results of the experiment. The results confirmed that the various shapes of large erosion regions near the upwind corners of the cube were accurately reproduced by CFD, even when performing relatively simple modeling of sand transport. However, the erosion area in the prediction result was horizontally wider than that of the experiment. These differences are mainly the result of not considering that the horizontal movement of the sand particles relates to the angle of repose in the CFD simulation.

Effects of vegetation restoration on soil quality in degraded karst landscapes of southwest China

Vegetation restoration was implemented to control soil erosion in the karst regions of southwest China. It is essential to assess the soil function and quality scientifically during this process and to adopt suitable management practices for this area. However, few studies have been conducted to comprehensively evaluate the effect of vegetation restoration on soil quality in this severely eroded karst area. By taking 302 soil samples from 11 vegetation types, this study investigated the influence of different types of vegetation restoration on soil quality using an integrated soil quality index (SQI) and a generalized linear model (GLM). Vegetation types had significant effects on soil properties and thus on soil quality. SQI was developed by using TN, TP, TK, AP, and clay content; TN had highest weighting values (0.58), which indicated that it contributed the most to final SQI. The highest and lowest SQI values were observed for primary forest and cropland, respectively. Overall, vegetation restoration (e.g., natural restoration, artificial forests and artificial grassland) improved soil quality significantly. A GLM model explained 73.20% of the total variation in SQI, and vegetation type explained the largest proportion (46.39%) of the variation, which implies that the vegetation restoration practices can greatly enhance the soil quality in karst landscapes of southwest China. The results of this study may be used to improve implication of ecological restoration and management in degraded regions.

Parameters of a Microstructure of Erosion Regions during the Action of a Spark Discharge on a Copper Electrode Surface in Air

The parameters of a microstructure of regions of action of a spark discharge on a copper plane electrode surface in air at atmospheric pressure in the spike–plane gap both for positive and negative polarity of a spike have been studied using scanning electron microscopy. It has been found that regions of action have the appearance of rounded spots or groups of spots with an internal structure in the form of agglomeration of a large number of microcraters. It has been shown that the statistical distributions of microcrater diameters and intermicrocrater distances are characterized by several local maximums that determine the presence of several predominant values of these parameters in a spot. It has been revealed that the microstructure of a spot is characterized by the fractal behavior and the fractal dimensionalities of the microstructure have been determined.

Feedbacks of flow and bed morphology from a submerged dense vegetation patch without upstream sediment supply

Laboratory experiments were performed to investigate how flow patterns and bed morphology are affected around a submerged vegetation patch in the condition without an upstream sediment supply. Five patches with different submergences, including four submerged patches and one emergent patch, were considered. In all cases, a wake region with depressed velocity and turbulent kinetic energy (TKE) occurred directly behind the vegetation patches. Beyond the end of the wake region, the presence of Karman vortices contributed to the recovery of the velocity and the peak of the TKE. However, a distinct von Karman vortex street was present at the ratio h/D > 1 with patch height h and diameter D, and the ratio was not influenced by the change in the channel bed. Because of the presence of stem-scale turbulence, net erosion was observed inside the patch in all cases. The motion of the colored sediment (placed inside the patch) indicated that the sediment inside the patch moved downstream and deposited in the patch wake. For a deeply submerged patch, a net deposition region was observed in the patch wake. For slightly submerged and emergent patches, a net erosion region was observed in both the patch wake and the adjacent region. Although the sand inside the patch was transported in the wake, the degree of net deposition was smaller than the degree of net erosion, which caused significant bed erosion. The greatest net erosion in the adjacent region was related to both the submergence (h/H) and the solid volume fraction (φ) of the patch. A greater h/H and φ resulted in a higher maximum net erosion value.

Effect of environmental policies in combating aeolian desertification over Sejzy Plain of Iran

Abstract Wind erosion in arid and semi-arid regions is a serious concern because it can cause land degradation and consequently affect the land use pattern. The aim of this study was to assess the variations of aeolian sediments and gypsum sediment surfaces (ASGSS) during 1992–2017 in Sejzy Plain and to analyze the impact of plans against desertification, as well as human and environmental activities on the variations of these surfaces. In the current study, Landsat satellite images were classified using the multiple layer perceptron (MLP) neural network. Finally, the logistic regression model has been used to study the impact and role of plans against desertification, human and environmental activities on the ASGSS variations in the studied area. The ASGSS decreased from 37.9% in 1992 to 24.3% in 2017 in the study area. Investigation of the effect of aeolian desertification in the region showed that planting stabilizing species and preventive measures taken in controlling gypsum-mining activities and grill areas, especially in the northern parts of the region has prevented further variation in the gypsum sediment cover. The results indicate that the planting of stabilizing species in lands outside the ASGSS has a greater effect on reducing ASGSS, in comparison with the planting of stabilizing species in the interior lands of the and ASGSS. Also, the results show that policies related to plans against desertification have been useful in reducing lands with ASGSS.

Point bar sedimentation and erosion produced by an extreme flood in a sand and gravel-bed meandering river

In fluvial environments, extreme floods are often catalysts for substantial geomorphologic planform change. Despite the significant sediment erosion and deposition associated with high-magnitude, low-frequency floods, their sedimentological products often lack distinctive characteristics. However, the sedimentological expression of extreme floods in sand and gravel-bed meandering rivers has yet to be fully described. The sedimentological characteristics of a 1 in 100 year flood on a point bar of the South Saskatchewan River in Alberta, Canada, are investigated. Digital elevation models from multitemporal LiDAR surveys, field sediment sampling, measured sections, shallow boreholes, and aerial photographs were used to identify regions of sediment deposition and erosion, quantify the amount of vertical elevation change, and describe the sedimentology, stratigraphy and grain-size distribution of the flood deposit. The upstream portion of the point bar was dominated by high-velocity flow and erosion. The majority of sedimentation occurred at the meander-bend apex in lee and scroll bars composed of medium- to coarse-grained sand. Downstream of the bend apex, very fine- to fine-grained sand beds accumulated on ridges and lee bars. Silt, <10 cm thick, was deposited in the point bar interior. No single grain size or sedimentary structure typifies the flood deposit. Sedimentological evidence of extreme floods on point bars are likely best preserved in floodplain strata (rather than in-channel strata) and consist of beds with a coarser texture than what is normally dominant at that position on the point bar. In particular, the presence of gravel beds at high stratigraphic elevations appears indicative of an extreme-flood event. These criteria have been used to identify extreme-flood sediments in other coarse-grained point-bar deposits and may be applicable to the deposits of braided and wandering rivers, or lower-competence meandering rivers.

Assessment of the potential of semi-arid plants to reduce soil erosion in the Konartakhteh watershed, Iran

Soil erosion is a major environmental problem in arid and semi-arid areas. Although bioengineering is important in preventing soil erosion, plant architecture and mechanical properties in these areas are rarely studied. In this study, in order to evaluate the potential of native plants to reduce soil erosion in semi-arid regions, their above-ground (e.g., stem density, radius of the stem, etc.) and below-ground (e.g., root area ratio, root tensile strength, etc.) characteristics were measured in the field and laboratory. Five indicators, namely, stem density (SD), sediment obstruction potential (SOP), plant stiffness (MEI), relative soil detachment (RSD), and root cohesion (Cr), were taken into account. Each indicator was scored according to a five-point scale (0 = low, 4 = high), and then, the score of each indicator was represented on an ameba diagram. Finally, for understanding traits of plants and evaluating their potential to control rill and gully erosion, the area occupied by the ameba diagram was studied. The results indicated that the shrub Ziziphus spina-christi (MEI = 108.35 N, RSD = 0.398, Cr = 8.34 kPa, SOP = 0.097, and SD = 0.00270) is a very suitable native plant species for controlling both the gully and rill erosion. In addition, Scariola orientalis is effective for sediment obstruction, but its low scores on the MEI and RSD indicators imply that it is not able to control gully development. Furthermore, Noaea mucronata, Platychaete glaucescens, Astragalus gummifer, Alhagi persarum, Lycium shawii, and Prosopis farcta have a distinct potential to reduce the rate of gully erosion. These results have wide applicability for adopting soil conservation measures to other semi-arid environments.

Identifying the factors and status of land degradation in a tropical plateau region

The systematic decline of land quality due to the mismatch between land quality and land use is called land degradation. It is the consequences of different physical factors but accelerated by human activities. The processes and factors of land degradation are different in different morpho-climatic regions of the world. Present study is primarily concerned in identifying the factors and status of land degradation in a tropical plateau region. Tropical plateaus are one of the most water erosion related land degraded areas of world. Chotanagpur plateau in tropical eastern India is one of the vulnerable soil degraded areas of the tropical environment. The Precambrian geological formation, undulating topography, immature soil, increasing aridity sets natural settings for land degradation in tropical plateau areas. However, induced degradation results from inappropriate land use, clearance of forest land and heavy land pressure related anthropogenic factors accelerates the processes of land degradation. Kangsabati River basin of eastern Chotanagpur plateau bears all of the above characteristics has been taken for present study as a degraded tropical plateau region. Water erosion and vegetal degradation are the major factors of land degradation in Kangsabati basin. The physical factors responsible for land degradation in the studied area includes physiographic formations, edaphic maturity, hydrologic characteristics, and vegetation cover dynamics etc. This land degradation processes is accelerated by different anthropogenic factors like, land use land cover dynamics, deforestation, agricultural pressure. Multispectral remote sensing data, digital elevation data, thematic maps, recorded climatological data, secondary data and field observation have been utilised to understand the different factors of land degradation in a typical tropical plateau region. The less developed soil profile over Precambrian geology with undulated landforms causes high soil erosion in upper plateau proper regions of the basin. High agricultural pressure, forest and groundwater decline with associated land use land cover dynamics creates decline of land quality in lower basin regions of tropical plateau. The varying intensities of land degraded areas for the basin has been identified through the multiplication of different physical and anthropogenic factor overlaying rasters in GIS environment. Before multiplying, each of these input factor rasters has assigned with weightage after considerable importance of land degradation. The lower basin area with accelerated human interference is the most vulnerable land degraded area for the Kangsabati River basin.

Degradation of physical and mechanical properties of sandstone subjected to freeze-thaw cycles and chemical erosion

Rocks are often exposed to chemical erosion and extreme temperature changes in cold regions. In this study, the deterioration of sandstone is investigated under rapid freeze-thaw (F-T) cycles. To do so, physical and mechanical properties of sandstone specimens immersed in different chemical solutions were studied after 10, 20 and 30 freeze-thaw cycles. It was found that after applying freeze-thaw cycle specimens' mass, tensile strength and point load strength decrease at different extent while porosity increases. Coupled effects of chemical erosion and freeze-thaw cycles were observed to have a destructive damage on physical and mechanical properties. In this regard, the samples experienced deterioration at different extend when immersed in different chemical solutions. The maximum deterioration was observed for samples being immersed in NaOH solution, followed by that of NaCl solution, H2SO4 solution and pure water. Finally, a decay function model is used to further investigate the variations of splitting tensile strength and point load index with freeze-thaw cycles and predict deterioration of rock integrity.

In situ monitoring and analysis of enamel demineralisation using synchrotron X-ray scattering

Dental caries is one of the most common chronic diseases that affect human teeth. It often initiates in enamel, undermining its mechanical function and structural integrity. Little is known about the enamel demineralisation process caused by dental caries in terms of the microstructural changes and crystallography of the inorganic mineral phase. To improve the understanding of the carious lesion formation process and to help identify efficient treatments, the evolution of the microstructure at the nano-scale in an artificially induced enamel erosion region was probed using advanced synchrotron small-angle and wide-angle X-ray scattering (SAXS and WAXS). This is the first in vitro and time-resolved investigation of enamel demineralisation using synchrotron X-ray techniques which allows in situ quantification of the microstructure evolution over time in a simulated carious lesion. The analysis revealed that alongside the reduction of mineral volume, a heterogeneous evolution of hydroxyapatite (HAp) crystallites (in terms of size, preferred orientation and degree of alignment) could be observed. It was also found that the rate and direction of dissolution depends on the crystallographic orientation. Based on these findings, a novel conceptual view of the process is put forward that describes the key structural parameters in establishing high fidelity ultrastructure-based numerical models for the simulation of the enamel demineralisation process. Statement of significanceHydroxyapatite (HAp) crystallites in the enamel dissolve during dental caries although little is known about the structural-chemical relationships that control the dynamic demineralisation process. For the first time this work investigated the in situ evolution of nano-scale morphology and the spatial distribution of ultrastructural HAp crystallites of human enamel during demineralisation in simulated caries. Advanced synchrotron SAXS and WAXS techniques showed that the heterogeneous evolution of crystallites (size, preferred orientation and degree of alignment) could be attributed to crystallographic-orientation-dependent anisotropic dissolution. Hence we propose a novel conceptual schematic diagram to describe the demineralisation process. These findings have important implications for understanding the detailed mechanisms of enamel demineralisation and provide insight into potential enamel remineralisation that could restore structural integrity and function.

Sediment Yield of Kamchatka Krai Rivers into the Pacific Ocean and the Seas of Bering and Okhotsk

Sediment yield of Kamchatka Krai rivers into the Pacific Ocean and the seas of Bering and Okhotsk, is evaluated, including that from the drainage basins that are not covered by regular observations. Regression dependences of specific suspended sediment yield (SSSY) on factors determining it were constructed for erosion regions identified in Kamchatka Krai. The total average many-year yield of suspended sediments of Kamchatka Krai rivers into the Pacific is 11.4 × 106 t/year, 73.9% of which is transported by rivers of the eastern coast and 26.1%, by those of the western coast. Among other factors, such distribution is attributed to the location of the majority of volcanoes on Kamchatka eastern coast. About one third of all sediments transported from Kamchatka Krai territory is discharged by the two largest rivers in the region, i.e., the Penzhina and Kamchatka.

Ligament, hinge, and shell cross-sections of the Atlantic surfclam (Spisula solidissima): Promising marine environmental archives in NE North America.

The Atlantic surfclam (Spisula solidissima) is a commercially important species in North American waters, undergoing biological and ecological shifts. These are attributed, in part, to environmental modifications in its habitat and driven by climate change. Investigation of shell growth patterns, trace elements, and isotopic compositions require an examination of growth lines and increments preserved in biogenic carbonates. However, growth pattern analysis of S. solidissima is challenging due to multiple disturbance lines caused by environmental stress, erosion in umbonal shell regions, and constraints related to sample size and preparation techniques. The present study proposes an alternative method for describing chronology. First, we analyzed growth patterns using growth lines within the shell and hinge. To validate the assumption of annual periodicity of growth line formation, we analyzed the oxygen isotope composition of the outer shell layer of two specimens (46°54'20"N; 56°18'58"W). Maximum δ18Oshell values occurred at the exact same location as internal growth lines in both specimens, confirming that they are formed annually and that growth ceases during winter. Next, we used growth increment width data to build a standardized growth index (SGI) time-series (25-year chronology) for each of the three parts of the shell. Highly significant correlations were found between the three SGI chronologies (p < 0.001; 0.55 < τ < 0.68) of all specimens. Thus, ligament growth lines provide a new method of determining ontogenetic age and growth rate in S. solidissima. In a biogeographic approach, the shell growth performance of S. solidissima in Saint-Pierre and Miquelon was compared to those in other populations along its distribution range in order to place this population in a temporal and regional context.

Change analysis on historical shorelines extracted from medium resolution satellite images: a case study on the southern coast of Peninsular Malaysia

Information on changes of coastal zones such as erosions and accretions can be monitored by identifying conditions of shorelines. Shorelines provide the boundary information of land and water, which can be performed by using satellite images rather than by using traditional ground survey, which is known as laborious and expensive. In this study, the historical satellite images of Landsat sensors were gathered from year 1977 to 2017. Additionally, one image of SPOT-5 was also included to get more data for analysis. For each satellite image acquired, supervised machine learning techniques were used to classify the image into land and water classes. Then, the shoreline GIS vector were extracted after locating boundaries of both classes and applying post-processing stages on the classified images. The historical shorelines extracted were used to do further change analysis using End Point Rate method to examine the differences between the older shorelines and the newer shorelines. At this stage, two baselines were created for inner and outer baselines to control the analysis boundary limit. Then, transects of the historical shorelines were created for every 50 m interval. The rate of change statistics represent a cumulative summary of the processes affected during the observation duration. The research findings observed that the southern region of Peninsular Malaysia which known as Tanjung Piai was affected mostly by erosion while the western coast was affected by accretion. The erosion regions were affected by the living population along the coastal areas while the accretion was caused by land reclamation against erosion or built-up area expansion. This study was conducted to observe the most affected areas in the southern Peninsular Malaysia for more than 30 years’ duration, potentially due to sea level rises besides natural processes and anthropogenic activities.

Surface erosion and underground leakage of yellow soil on slopes in karst regions of southwest China

AbstractSurface erosion and underground leakage loss simultaneously exist on slopes with a double‐layered structure (surface and underground) and have caused rocky desertification in karst regions. Because of the great difficulty of directly determining the underground leakage loss of soil and water, soil erosion processes in this region remain unclear, especially underground leakage loss. The aim of this study was to reveal the plot‐scale characteristics of surface soil erosion and underground leakage loss of yellow soils on karst slopes. Simulated rainfall tests and field runoff plot monitoring were conducted to achieve this aim. We found that surface erosion formed on steep slopes (30°) or at greater rainfall intensities (over 50 mm hr−1) and that surface runoff and surface soil loss dominated the total runoff and soil loss on karst slopes at greater rainfall intensities. However, underground leakage loss always occurred at different slopes and rainfall intensities. For small rainfall intensity cases (lower than 80 mm hr−1), underground runoff and underground soil leakage loss dominated the total runoff and soil loss and showed an underground runoff ratio of over 90% and an underground soil leakage ratio of over 44%. Rainfall intensity had significant effects on surface runoff depth and surface soil loss rates but an insignificant influence on underground leakage loss. Slope gradient and slope length influenced the runoff yield, and slope degree had a greater effect on the surface soil loss than had slope length. This study improves our understanding of surface erosion and underground leakage loss in karst rocky desertification regions.