Extent Of Erosion Research Articles

Feeding and Mobility Traits Influence Grasshopper Vulnerability to Agricultural Production in the Cape Floristic Region Biodiversity Hotspot.

To be able to foretell which species will be at risk of extinction from possible expansion of agriculture into natural areas, we need to determine how land use affects animal groups especially insects with different life history traits. Intuitively, we can predict that the proportion of specialist versus generalist grasshoppers and widespread versus localised species can be an indicator of change in vegetation patterns in a landscape. As a result, the study examined the relationship between the extent of range distribution and mobility of grasshoppers and land-use type in the Cape Floristic Region (CFR) biodiversity hotspot. It aimed at examining grasshopper assemblage composition in association with different land uses. We specifically related the number and type of sites occupied by grasshopper species to their mobility and distribution type to find out which characters improve species survival under highly modified habitats. Grasshopper assemblages were dominated by highly mobile generalists that tolerated transformed landscapes, and mostly geographically widespread. This contrasts with the low- to medium-mobile, range-restricted specialists, which make up close to 30% of the total collection, with a lower tolerance for anthropogenically modified landscapes in the CFR. This study also reveal that the fynbos biome is an important habitat for low-mobility and range-restricted species, and hence require conscious conservation efforts to conserve such species to prevent possible future biotic erosion and homogenisation in this hotspot. This result can be used to assess the possible extent of biotic erosion or otherwise in order to recommend better conservation efforts in the CFR.

The effects of topographic surveying technique and data resolution on the detection and interpretation of geomorphic change

Change detection of high resolution topographic data is commonly used in river valleys to quantify reach- and site-scale sediment budgets by estimating the erosion/deposition volume, and to interpret the geomorphic processes driving erosion and deposition. Field survey data are typically collected as point clouds that are often converted to gridded raster datasets and the ultimate choice of grid resolution is left to the user. This choice may have important implications for both the quantification and interpretation of geomorphic change. Here we used concurrent topographic data collected by terrestrial laser scanning (TLS) and structure-from-motion (SfM) photogrammetry to quantify the influence of grid resolution and sampling technique on (a)the sediment budget and (b)the presence and role of geomorphic processes (i.e.,alluvial, colluvial, aeolian, and fluvial transport) driving topographic change at four sites along the Colorado River in Grand Canyon, Arizona, USA. We found that while both techniques produced similar estimates for site-scale sediment budgets, the magnitude of detected topographic change was dampened at coarser pixel resolutions. An overall decrease in the areal extent of erosion and deposition were observed, respectively, when coarsening pixel size from 5cm to 1m among all sites. Coarser resolution data tended to affect interpretation of landscape change along the margins of river valleys. For example, when changing from 5cm to 1m pixel resolution, the inferred contribution of aeolian changes to total site-scale geomorphic change increased in area by 7.9%, whereas the inferred contribution of alluvial and colluvial processes decreased in area by 97.9% and 88.2%, respectively. More generally, we found that coarsening pixel sizes disproportionately attributed geomorphic change to one or more of the most common processes operating at a site. We also found that coarsening pixel resolution amplified the net sediment imbalance at the site scale, driving the imbalance at erosional sites further into erosion and vice versa for depositional sites. Our results have implications both for point cloud data collection and for raster dataset processing. We argue that selecting the finest obtainable resolution is not always warranted to accurately quantify and interpret geomorphic change, because remote sensing technique, topographic data resolution, and analysis procedure can be optimized to capture the spatial scale of those processes driving landscape change. However, in landscapes at or near sediment equilibrium (i.e.,equal amounts of erosion and deposition), thefinest obtainable topographic data resolution is warranted to avoid amplifying sediment imbalance and erroneously inferring that sites are trending toward erosion or deposition.

Rift structures and its related unconformities on and adjacent the Dongsha Rise: insights into the nature of the high-velocity layer in the northern South China Sea

It is curious that the typical feature of high-velocity layer (HVL) underneath the crust for the magma-rich margin was found in the magma-poor margin of the South China Sea. In order to better understand the nature and age of the HVL in the South China Sea, here we provide seismic imaging on the Cenozoic structure and sedimentation using a regional seismic reflection profile combined with existing drilling data and seismic refraction lines in the northeastern South China Sea. An important finding is that the extent of erosion since Neogene is only on the Dongsha Rise and is much smaller than that of the HVL observed across the northern margin of the South China Sea, which suggests the occurrence of the HVL has no influence on the erosion on Dongsha Rise through Neogene. On the regional seismic profiles, the different structures between the deepwater rifted margins and the continental shelf were also observed. The faults in the Zhuyi Sub-basins on the continental shelf are imaged to be high-angle and bound a series of grabens and horsts. In contrast, the deepwater region is characterized by tilted fault blocks and an array of listric normal faults, which extremely thinned the crust to be ~ 5–10 km. After middle Miocene, active magmatism occurred in the deepwater region at the time of post-spreading of oceanic crust. These listric faults on the hyper-extended crust is interpreted to be conduits for magma migration to the shallower levels. This typical structure in the deepwater region changed the geophysical nature of the HVL underneath the extreme thinned crust, which should be formed before the event of hyper-extension and is likely to be associated with the subduction of the paleo-Pacific toward the Asia in the late Cretaceous. Our study will answer the question why the South China Sea with the HVL underneath the crust is a magma-poor passive margin.

Soil loss due to crop harvesting in the European Union: A first estimation of an underrated geomorphic process

Over the last two decades or so, there has been many research carried out to understand the mechanics and spatial distribution of soil loss by water erosion and to a lesser extent of wind, piping and tillage erosion. The acquired knowledge helped the development of prediction tools useful to support decision-makers in both ex-ante and ex-post policy evaluation. In Europe, recent studies have modelled water, wind and tillage erosion at continental scale and shed new light on their geography. However, to acquire a comprehensive picture of soil erosion threats more processes need to be addressed and made visible to decision-makers. Since 1986, a small number of studies have pointed to an additional significant soil degradation process occurring when harvesting root and tuber crops. Field observations and measurements have shown that considerable amounts of soil can be removed from the field due to soil sticking to the harvested roots and the export of soil clods during the crop harvest. This study aims to scale up the findings of past studies, carried out at plot, regional, and national level, in order to obtain some preliminary insights into the magnitude of soil loss from cropland due to sugar beets and potatoes harvesting in Europe. We address this issue at European Union (EU) scale taking into account long-term (1975–2016) crop statistics of sugar beet and potato aggregated at regional and country levels.During the period 2000–2016, sugar beets and potatoes covered in average ca. 4.2 million ha (3.81%) of the EU-28 arable land estimated at 110 million ha. The total Soil Loss by Crop Harvesting (SLCH) is estimated at ca. 14.7 million tons yr−1 in the EU-28. We estimate that ca. 65% of the total SLCH is due to harvesting of sugar beets and the rest as a result of potatoes harvesting.

Application of unmanned aircraft system (UAS) for monitoring bank erosion along river corridors

Excessive streambank erosion is a significant source of fine sediments and associated nutrients in many river systems as well as poses risk to infrastructure. Geomorphic change detection using high-resolution topographic data is a useful method for monitoring the extent of bank erosion along river corridors. Recent advances in an unmanned aircraft system (UAS) and structure from motion (SfM) photogrammetry techniques allow acquisition of high-resolution topographic data, which are the methods used in this study. To evaluate the effectiveness of UAS-based photogrammetry for monitoring bank erosion, a fixed-wing UAS was deployed to survey 20 km of river corridors in central Vermont, in the northeastern United States multiple times over a two-year period. Digital elevation models (DEMs) and DEMs of difference allowed quantification of volumetric changes along selected portions of the survey area where notable erosion occurred. Results showed that UAS was capable of collecting high-quality topographic data at fine resolutions even along vegetated river corridors provided that the surveys were conducted in early spring, after snowmelt but prior to summer vegetation growth. Longer term estimates of streambank movements using the UAS showed good comparison to previously collected airborne lidar surveys and allowed reliable quantification of significant geomorphic changes along rivers.

Impact of an Extreme Storm Event on River Corridor Bank Erosion and Phosphorus Mobilization in a Mountainous Watershed in the Northeastern United States

AbstractMovement of sediment, and associated phosphorus, from stream banks to freshwater lakes is predicted to increase with greater frequency of extreme precipitation events. This higher phosphorus load may accelerate harmful algal blooms in affected water bodies, such as Lake Champlain in Vermont, New York, and Québec. In the Mad River, a subwatershed in central Vermont's Lake Champlain Basin, extreme flooding from Tropical Storm Irene in 2011 caused extensive erosion. We measured stream channel change along the main stem between 2008 and 2011 by digitizing available prestorm and poststorm aerial imagery. Soils were sampled post Irene at six active stream erosion sites, using an experimental design to measure differences in soil texture and phosphorus both with depth (90 cm) and distance from the stream. In addition to total phosphorus (TP), we determined bioavailable (soil test) phosphorus (STP) and the degree of phosphorus saturation (DPS). The six sites represented a 0.87‐km length of stream bank that contributed an estimated 17.6 × 103 Mg of sediment and 15.8 Mg of TP, roughly the same as average annual watershed export estimates. At four sites, the STP and DPS were low and suggested little potential for short‐term phosphorus release. At two agricultural sites where the lateral extent of erosion was high, imagery showed a clear loss of well‐established riparian buffer. Present‐day near‐stream soils were elevated in STP and DPS. An increase in these extreme events will clearly increase sediment loads. There will also be increasing concentration of sediment phosphorus if stream banks continue to erode into actively managed agricultural fields.

Graptolite biostratigraphy and dating of the Ordovician–Silurian shale succession of the SW slope of the East European Craton

This paper deals with the graptolite biostratigraphy and age determination of the Ordovician and Silurian lithological successions of the Baltic, Podlasie and Lublin basins that existed during the early Palaeozoic on the SW slope of the East European Craton. The biostratigraphic research described was conducted on core material coming from old boreholes and cores from several new wells. Graptolite zones were identified and the chronostratigraphic succession was constrained, with the depths to the stratigraphic units, especially those considered prospective for petroleum, being determined in the individual borehole sections. Old local stratigraphic schemes of the Silurian used for many years in the Polish geological literature are correlated with the standard schemes. The most complete succession of graptolite zones, both in the Ordovician and the Silurian, is observed in the Baltic region. The number of stratigraphic gaps increases towards the east and southeast of the regions. The stratigraphic range of the Sasino Shale Formation decreases in this direction; in the Podlasie and Lublin regions, it comprises only the Katian Stage. The stratigraphic range of the Jantar Formation in the western part of the area spans not only the Rhuddanian but also part or the whole of the Aeronian. In the Podlasie and especially the Lublin regions, sedimentation of the Jantar Formation began in the latest Rhuddanian–Aeronian. A large stratigraphic gap, spanning part or the whole of the Llandovery and increasing eastwards, was documented in the Podlasie-Lublin region. The biostratigraphic research allowed a more precise constraint on the temporal and spatial extent of erosion of Pridoli deposits and the beginning of coarse-grained, siliciclastic sedimentation (Kociewie Formation) in the Baltic Basin.

Compositional variations of Titan's impact craters indicates active surface erosion

Titan, the only moon in the solar system with a considerable atmosphere, is host to a variety of exogenic processes that shape its surface. These processes form features that are quite similar to features on Earth, including sand dunes, rivers, and lakes. The combination of a thick atmosphere and active surface processes also leads to a scarcity of impact craters on the surface of Titan. The compositions of these craters vary and may relate to the type and extent of erosion occurring at their location. In this work, we examined the composition of 12 impact features on Titan using Cassini's Visible and Infrared Mapping Spectrometer (VIMS) and 2.18 cm emissivity data from the RADAR radiometer on board the probe. Comparisons were made between crater composition as inferred from VIMS and composition as inferred from emissivity data with corresponding crater characteristics such as latitude, longitude and erosional state. We see a correlation between crater subsurface composition as inferred from the emissivity data and its erosional state and location. Well-preserved craters typically are more enriched in water-ice than degraded, organic-rich craters, suggesting that variations in composition are partially controlled by erosion and infilling. Moreover, craters located in dune fields show more subsurface organic enrichment than craters within the plains, which indicates that the efficiency of erosion and infilling varies with location and geologic context. VIMS data provide complementary information about crater surficial composition. We note that VIMS spectra do not change with erosional state, but rather appear to depend on the crater location on the moon. We suggest that there are active surface processes occurring on Titan, such as wind or rain, which are actively clearing off its surface and filling in subsurface fractures with organic materials. These processes would act to change the emissivity of the craters over time but leave the surface sensed by VIMS unchanged.

Coastal Morphology and Long-term Shoreline Changes along the Southwest Coast of India

The part of southwest coast of India extending from Poovar in the south to Kasaragod in the north is considered as one of the highly dynamic coastal areas of Indian peninsula. Over the years due to rapid urbanization as well as other natural and anthropogenic activities, the coast is under severe pressure which in turn has reduced the percentage status of healthy / stable coast. Unscientific shoreline protection methods adopted without conducting appropriate studies to assess the suitability of the said method to a particular coastal stretch has often led to negative impacts. As a result, many areas that were once stable have turned eroding and in certain cases, the observed extent of erosion is severe warranting immediate protection measures. In this context, a study was carried out to assess the long-term shoreline changes along the southwest coast and to decipher the causative factors responsible for these changes. Accordingly, a 46 year period from 1968 to 2014 was studied using multi-dated shoreline images and Survey of India (SOI) topographic charts. The DSAS software (USGS) is used to compute the rate of shoreline changes along different sectors of the coast and accordingly the entire coastal stretch is classified into 7 classes depicting the present status (stable / dynamically stable / unstable) of the coast. The analysis revealed that almost 60 % of the coastline is eroding with about 29 % showing an accreting trend.

Geospatial assessment of soil erosion intensity and sediment yield: a case study of Potohar Region, Pakistan

Estimation of spatial extent of soil erosion, one of the most serious forms of land degradation, is critical because soil erosion has serious implications on soil fertility, water ecosystem, crop productivity and landscape beauty. The primary objective of the current study was to assess and map the soil erosion intensity and sedimentation yield of Potohar region of Pakistan. Potohar is the rainfed region with truncated and complex topography lying at the top of the Indus Basin, the world’s largest irrigation networks of canals and barrages. Spatially explicit Revised Universal Soil Loss Equation (RUSLE) Model integrated with Remote Sensing-GIS techniques was used for detecting/mapping of erosion prone areas and quantification of soil losses. The results show that the Potohar region is highly susceptible to soil erosion with an average annual soil loss of 19 tons ha−1 year−1 of which the maximum erosion (70–208 tons ha−1 year−1) was near the river channels and hilly areas. The sediment yield due to the erosion is as high as 148 tons ha−1 year−1 with an average of 4.3 tons ha−1 year−1. It was found that 2.06% of the total area falls under severe soil erosion, 13.34% under high erosion, 15.35% under moderate soil erosion while 69.25% of the area lies in the low (tolerable) soil erosion. Chakwal and Jhelum districts of the region are seriously affected by erosion owing to their topography and soil properties. The information generated in this study is a step forward towards proper planning and implementation of strategies to control the erosion and for protection of natural resources. It is, hence, necessary that suitable water harvesting structures be made to control water to prevent soil erosion and provision of water in the lean season in this region. Tree plantation and other erosion control practices such as strip cropping can also minimize soil erosion in this region.

Simultaneous quantification of bone erosions and enthesiophytes in the joints of patients with psoriasis or psoriatic arthritis - effects of age and disease duration

BackgroundComprehensive simultaneous quantification of bone erosion and enthesiophytes in the joints of patients with psoriatic arthritis (PsA) has not been performed. Herein, we aimed to compare the extent of bone erosion and enthesiophytes in patients with PsA, psoriasis (PSO) and healthy controls, assess the influence of age and disease duration on the development of erosions and enthesiophytes and define their impact on physical function.MethodsPatients with PsA or with PSO and controls were analysed by high-resolution peripheral quantitative computed tomography (HR-pQCT). The extent of bone erosions and enthesiophytes was assessed and plotted according to different categories of age, duration of PSO and duration of PsA, respectively. In addition, demographic and disease-specific data, including physical function (health assessment questionnaire) were collected.ResultsA total of 203 patients were analysed; 101 had PsA, 55 had PSO and 47 were healthy individuals. Patients with PsA had significantly more and larger erosions (p = 0.002/p = 0.003) and enthesiophytes (p < 0.001) compared to patients with PSO and healthy controls. Patients with PSO and healthy controls did not differ in erosions, while enthesiophytes were more frequent in patients with PSO than in healthy controls. Bone erosions, but not enthesiophytes, showed strong age-dependency in all three groups. In contrast, enthesiophytes were mostly influenced by the duration of PSO and PsA and, in contrast to bone erosions, were associated with poorer physical function.ConclusionsBone erosions are age-dependent, enhanced in PsA and increase with disease duration. Enthesiophytes are less age-dependent, are enhanced in both PSO and PsA and strongly influenced by disease duration. Enthesiophytes impact physical function in PsA suggesting the need for early therapeutic interventions to prevent damage.

Global long-term observations of coastal erosion and accretion

Changes in coastal morphology have broad consequences for the sustainability of coastal communities, structures and ecosystems. Although coasts are monitored locally in many places, understanding long-term changes at a global scale remains a challenge. Here we present a global and consistent evaluation of coastal morphodynamics over 32 years (1984–2015) based on satellite observations. Land losses and gains were estimated from the changes in water presence along more than 2 million virtual transects. We find that the overall surface of eroded land is about 28,000 km2, twice the surface of gained land, and that often the extent of erosion and accretion is in the order of km. Anthropogenic factors clearly emerge as the dominant driver of change, both as planned exploitation of coastal resources, such as building coastal structures, and as unforeseen side effects of human activities, for example the installment of dams, irrigation systems and structures that modify the flux of sediments, or the clearing of coastal ecosystems, such as mangrove forests. Another important driver is the occurrence of natural disasters such as tsunamis and extreme storms. The observed global trend in coastal erosion could be enhanced by Sea Level Rise and more frequent extreme events under a changing climate.

Soil erosion alters soil chemical properties and limits grassland plant establishment on an oceanic island even after goat eradication

Soil erosion after vegetation degradation induced by disturbance by feral goats, an invasive mammal, can lead to loss or accumulation of soil at a local scale and can alter soil chemical properties. This alteration of soil properties can in turn affect the establishment of plant species. We evaluated relationships among the extent of soil erosion, soil chemical properties, and the distribution of plant species in grassland ecosystems after goat eradication on Nakodo‐jima Island in the northwestern Pacific. In 105 1 × 1–m quadrats, changes were measured in the position of topsoil over 2 years. Surface soils were sampled for analysis of chemical properties, and plant species in the quadrat were recorded. Changes in the position of topsoil were related to the area of bare ground. Soil loss occurred at sites where areas of bare ground were extremely large. Significantly higher values of soil exchange acidity and smaller amounts of available phosphorus, total carbon, and total nitrogen were detected in soils at sites with large soil losses. Most of the 11 dominant plant species were absent from sites with large losses of soil. The presence of eight species was significantly negatively related to soil exchange acidity, and three species were significantly positively related to available phosphorus. Our results indicated that exposure of subsoils at the soil surface after vegetation degradation can increase soil loss, which can alter soil chemical properties, and this alteration can continue to limit the establishment of plant species, even long after goat eradication.

Corrosion behavior of alumina-carbon composite brick in typical blast furnace slag and iron

The corrosion behavior of alumina-carbon composite brick (ACCB) in CaO-8%MgO-14%Al2O3-SiO2 blast furnace slag and iron was investigated at different slag basicity and time via rotating immersion method. The results show that the erosion caused by slag is lightest and increases with the increase of basicity, while the slag and iron region is the most eroded area. The erosion caused by iron decreases with increasing basicity, and the whole erosion extent increases with time elapsing. The penetration of slag into ACCB is mainly appears on the boundary of corundum and mullite, while some unwashed-away high melting point phase like MgAl2O4 can mitigate the corrosion. The dissolution of carbon from ACCB into iron is one of the erosion reasons of ACCB, and the reaction between carbon and silica in ACCB can also be promoted by the appearance of iron. A synthetic action caused by slag and iron in this region leads to the worst erosion. And the reduction of SiO2 on the slag-iron interface relates the basicity of slag to the iron erosion degree.

Hydro-abrasive erosion in Pelton turbine injectors: A numerical study

Numerical simulations were performed to investigate how the design and the operation conditions of a Pelton turbine injector affect its vulnerability to hydro-abrasive erosion, alongside with its flow control capacity. Use was made of a Volume Of Fluid (VOF) model for simulating the free nozzle jet, a Lagrangian particle tracking model for reproducing the trajectories of the solid particles, and two erosion models for estimating the mass removal. The comparison against earlier studies and the experimental evidence, integrated with a careful sensitivity analysis, gave strength to the reliability of the numerical model. Nozzle seat and needle were the injector components most vulnerable to erosion. As the valve was closing, the erosion of the needle strongly increased, whilst that of the nozzle seat remained broadly constant. The influence of the injector design was also explored, suggesting that a reduction of the needle vertex angle is likely to enhance the risk of erosive wear. Finally, it was found that the possibility to condense the effects of the needle stroke and the needle vertex angle in a single parameter (i.e. the effective opening area) is no more allowed when hydro-abrasive erosion is considered, thereby assessing the need for case-specific wear prediction analyses. • Particle-laden jets generated by Pelton injector nozzles were numerically simulated. • The regulation characteristics of the injectors were estimated. • The injector components most vulnerable to hydro-abrasive erosion were identified. • The extent of erosion was assessed for different operation and design parameters. • A physical interpretation of the obtained results was provided.

The sheep in wolf's clothing? Recognizing threats for land degradation in Iceland using state‐and‐transition models

AbstractLand degradation and extensive soil erosion are serious environmental concerns in Iceland. Natural processes associated with a harsh climate and frequent volcanic activity have shaped Icelandic landscapes. However, following human settlement and the introduction of livestock in the ninth century, the extent of soil erosion rapidly escalated. Despite increased restoration and afforestation efforts and a considerable reduction in sheep numbers during the late 20th century, many Icelandic rangelands remain in poor condition. A deeper understanding of the ecology of these dynamic landscapes is needed, and state‐and‐transition models (STMs) can provide a useful conceptual framework. STMs have been developed for ecosystems worldwide to guide research, monitoring, and management but have been used at relatively small spatial scales and have not been extensively applied to high‐latitude rangelands. Integrating the best available knowledge, we develop STMs for rangelands in Iceland, where sheep grazing is often regarded as a main driver of degradation. We use STMs at a countrywide scale for 3 time periods with different historical human influence, from presettlement to present days. We also apply our general STM to a case‐study in the central highlands of Iceland to illustrate the potential application of these models at scales relevant to management. Our STMs identify the set of possible states, transitions and thresholds in these ecosystems, and their changes over time and suggest increasing complexity in recent times. This approach can help identify important knowledge gaps and inform management efforts and monitoring programmes, by identifying realistic and achievable conservation and restoration goals.

Erosion behaviour of raw bentonites under compacted and confined conditions: Relevance of smectite content and clay/water interactions

The quantification of colloid erosion from compacted bentonite barrier, in a high-level waste repository, is considered especially relevant because erosion may compromise its performance and because eroded colloids may contribute to radionuclide transport.The erosion behaviour of different raw bentonites, compacted at high density, was analysed in a confined system under favourable chemical conditions. A complete physical and geochemical characterisation of clays was carried out to overall relate clay physico-chemical characteristics and structure to their erosion behaviour.The mass eroded under compacted and confined conditions were in all cases lower than those obtained under free-dispersed conditions; indicating that compacted and confined conditions were limiting erosion. Maximum erosion was below a 1% of the initial mass.Results clearly showed that clay erosion under compacted state was hindered for those bentonites with high content of bivalent cations in exchangeable positions ((Ca + Na) > 90%), low smectite content (Sm. < 70 wt %) and high tetrahedral charge (|τ| > 0.1 e/h.u.c.). In addition, it was demonstrated that, at high solid to liquid ratios, dissolution of salts present in the clay and cation exchange reactions decrease the extent of erosion.

Effects of the particle Stokes number on wind turbine airfoil erosion

Under natural conditions, wind turbines are inevitably eroded by the action of sand-wind flow. To further investigate the effects of dust drift on the erosion of the wind turbine blades in sand-wind environments, the effects of the wind velocity, particle diameter, and particle density on the erosion of wind turbine airfoils are studied, and the effects of the particle Stokes number on the airfoil erosion are discussed. The results show that, when the angle of attack (AOA) is 6.1°, there will be no erosion on the airfoil surface if the particle Stokes number is lower than 0.013 5, whereas erosion will occur if the particle Stokes number is higher than 0.015 1. Therefore, there exists a critical range for the particle Stokes number. When the particle Stokes number is higher than the maximum value in the critical range, airfoil erosion will occur. The result is further confirmed by changing the particle diameter, particle density, and inflow speed. It is shown that the erosion area on the airfoil and the maximum erosion rate are almost equal under the same particle Stokes number and AOA. The extent of airfoil erosion increases when the particle Stokes number increases, and the critical particle Stokes number increases when the AOA increases. Moreover, the geometric shape of the airfoil pressure surface greatly affects the airfoil erosion, especially at the curvature near the leading edge.

Pengukuran erosi pada pertanaman kentang dan jagung padabeberapa kemiringan di desa Guru SingaKabupaten Karo dengan metode USLE

The type of plant and selection of conservation techniques greatly influence the extent of erosion. The aim of this study was to measure the value of the erosion in the field of potato and corn with the slopes by using USLE method (Universal Soil Loss Equation). This study had been implemented in the fields of potato and corn with a slope 0-3, 3-8%,8-15%, 15-25% and 25-45% in Guru Singa village, Berastagi sub-district, Karo district started on April until October 2016. Soil analysis was carried out in Research Laboratories and Technological Faculty of Agriculture, Universitas Sumatera Utara. The result showed that the amount of erosion occurred in the potato field. The field planted by contour direction in slope 0 – 3 % was 4,55 ton ha-1 yr-1 with the low level of erosion hazard. The highest level of erosion hazard in slope 8 – 15 % was 112,57ton ha-1 yr-1. The highest level of erosion hazard in slope 15 – 25 % was 160,97ton ha-1 yr-1. Based on data from the cornfield planted by cutting on contour, the amount of erosion in slope 3 – 8 % was 15,61ton ha-1 yr-1with the middle level of erosion hazard. The highest level of erosion hazard in slope 25 – 45% was 106,08ton ha-1 yr-1. It is required to do the changing of land conservation in order to minimize the risk of erosion or at least equal to the soil erosion tolerated.

Experimental study on gravitational erosion process of vegetation slope under freeze–thaw

Freeze–thaw is the major factor in gravitational erosion creep of slopes in cold regions, but gravitational erosion is influenced remarkably by vegetation cover. In order to investigate the phenomenon of the gravitational erosion process of vegetation slopes under freeze–thaw in seasonally frozen soil regions, on-site freeze–thaw tests of different vegetation slopes were conducted in the frozen soil testing ground of Kitami Institute of Technology (KIT, Hokkaido, Japan). Slope vegetation is divided into an external-soil spray seeding section and a turfed section according to its method of formation. Through field tests of four cycles, the slope temperature, frost depth, amount of frost-heave, and amount of movement were observed dynamically in real-time, initially revealing the regularity of the gravitational erosion process of the vegetation slope, which provided a scientific basis for slope stability control in cold regions. The experimental results show that the gravitational erosion of the slope is a process of irreversible gradual evolution, that the extent of erosion has a periodical fluctuation in time, that the target point of the slope surface moves in a jagged trajectory down the slope year after year, and that the maximum values of the amount of movement of the external-soil spray seeding section and the turfed section are −13.1 and –6.1 cm, respectively, after four freeze–thaw cycles. The space distribution of the slope surface has inhomogeneity. The difference in temperature and water content of each part of the slope surface is the main reason why the freezing front of the slope is not parallel to the slope surface. The amount of frost-heave of the slope toe was greater than that of the slope crest, which caused upward displacement along the slope during early freezing. The movement of the slope is closely related to the development of vegetation, and the heat insulation and reinforcement of vegetation cover effectively restrain the displacement of the slope's shallow soil. The results of this study have a certain significance in the prevention and treatment of shallow slope sliding in cold regions.