Evaluate Soil Loss Research Articles

Influence of vegetation cover on the assessment of erosion and erosive potential in the Isser marly watershed in northwestern Algeria—comparative study of RUSLE and PAP/RAC methods

The present article aims to evaluate soil losses due to water erosion and to contribute to the knowledge about the impact of vegetation cover on the Isser watershed that is located in northwestern Algeria. For this purpose, two predictive models were used, namely the Priority Actions Program by the Regional Activity Center (PAP/RAC) model and the revised universal soil loss equation (RUSLE) model, using the geographic information system (GIS). To illustrate the level of protection in that watershed, it was decided to use two approaches for the estimation of factor C; the first one is the classical method and the second consists of calculating the normalized difference vegetation index (NDVI) during two periods (dry and wet). The map of erosive states, which was obtained from using by the PAP/RAC model, shows the areas that are potentially most vulnerable to erosion and which cover more than 60% of the total area of the basin. The results for vegetation cover (factor C) by the conventional method during the dry period present an average land loss equal to 14 (t ha−1 year−1), whereas this rate decreases to 7.9 (t ha−1 year−1) during the wet period. According to the NDVI approach, the factor C results for the dry season are 25.53 (t ha−1 year−1) with an annual land loss of up to 3 million tons. This study provided the qualitative and quantitative estimates needed for the development of the environmental management; it also helps to control the different impacts on that watershed.

Application of Geomorphologic Factors for Identifying Soil Loss in Vulnerable Regions of the Cameron Highlands

The main purpose of this study is to propose a methodology for identifying vulnerable regions in the Cameron Highlands that are susceptible to soil loss, based on runoff aggregation structure and the energy expenditure pattern of the natural river basin, within the framework of power law distribution. To this end, three geomorphologic factors, namely shear stress and stream power, as well as the drainage area of every point in the basin of interest, have been extracted using GIS, and then their complementary cumulative distributions are graphically analyzed by fitting them to power law distribution, with the purpose of identifying the sensitive points within the basin that are susceptible to soil loss with respect to scaling regimes of shear stress and stream power. It is observed that the range of vulnerable regions by the scaling regime of shear stress is much narrower than by the scaling regime of stream power. This result seems to suggest that shear stress is a scale-dependent factor, which does not follow power law distribution and does not adequately reflect the energy expenditure pattern of a river basin. Therefore, stream power is preferred as a more reasonable factor for the evaluation of soil loss. The methodology proposed in this study can be validated by visualizing the path of soil loss, which is generated from the hillslope process (characterized by the local slope) to the valley through a fluvial process (characterized by the drainage area as well as the local slope).

Modelagem da erosão hídrica nas bacias hidrográficas dos rios Lontra e Manoel Alves Pequeno, Tocantins

Water erosion is one of the main factors that lead to the process of soil degradation, with impacts ranging from reducing productivity to losses of natural resources. Thus, this work aimed to estimate soil losses performing RUSLE model and to verify the effect of changes in land use changes, from 1990 to 2007, in the watersheds of the rivers Lontra and Manoel Alves Pequeno,Tocantins State-Brazil. Water erosion in the river Lontra ranged from “slight” (51.3%) in the central region of the basin (dominance of flat relief and forest land use), to “extremely high” (24.6%), in the range that goes from the north to the west (dominance of pasture land use and more declining relief). In the watershed of Manoel Alves Pequeno the erosion class “slight” (52%) was distributed along the basin, due to most soils had low erodibility and with most of the area covered by cerrado. While the “extremely high” class (6.7%), occurred in the northern and western part due to pasture land use, and in the eastern part due to the greater slope. Temporal evaluation of soil loss evidenced that there were no significant variations in the period studied. However, in the watershed of river Lontra, from 2000 to 2007, occurred a 0.3% reduction of the “extremely high”; at the wathershed Manoel Alves Pequeno, from 1990 to 2007, there was a gradual increase in the soil erosion rate.

СОВРЕМЕННЫЙ ТРЕНД ЭРОЗИОННО-АККУМУЛЯТИВНЫХ ПРОЦЕССОВ В МАЛОМ РАСПАХАННОМ ВОДОСБОРЕ, РЕСПУБЛИКА ТАТАРСТАН, "Геоморфология"

Анализ аккумуляции наносов в днищах долин первого порядка позволяет дать достаточно надежную количественную оценку общей интенсивности и временн й изменчивости эрозионных процессов на сельскохозяйственных землях, подходящих практически вплотную к этим долинам. С использованием радиоактивного цезия-137 в качестве хрономаркера, а также усовершенствованных эрозионных моделей USLE и Государственного гидрологического института, изучение аккумулированных наносов в днище малой долины “Темева речка” (площадь водосбора - 1.13 км2), расположенной в северо-западной части Республики Татарстан (бассейн р. Мёша), показало заметное снижение темпов смыва почв с пахотной части водосбора за последние десятилетия. Так, если за период 1963-1986 гг. темпы аккумуляции в днище малой долины смытого со склонов водосбора почвенного материала составляли 0.92-1.81 см/год, то за период 1987-2015 гг. - 0.17-0.50 см/год, т.е. сократились как минимум в 3-5 раз. Причиной отмеченного уменьшения темпов смыва почв и аккумуляции наносов явилось сокращение объемов поверхностного стока со склонов в период снеготаяния, вызванное повышением температуры воздуха в весеннее время года, уменьшением глубины промерзания почв и снижением частоты выпадения экстремальных ливней со слоем 40-50 мм. Влияние хозяйственной деятельности на уменьшение темпов эрозионно-аккумулятивных процессов было, по всей видимости, несущественным, хотя некоторое изменение севооборотов с увеличением доли многолетних трав, очевидно, повлияло на снижение темпов смыва в теплое время года. Данная эрозионная тенденция и климатические причины, ее обусловившие, имели региональный характер и ранее выявлены в ряде регионов южной половины Европейской территории России.

Evaluation of Soil Erosion and Sustainable Land Use Management in the Sarısu Basin

Land use management requires controlling natural resources for sustainability. Soil erosion related to improper land use is a major issue around the world. Land degradation may harm the health of ecosystems. Defining the soil loss in a basin is the starting point in the restoration of soil quality for crop production. Reducing soil losses to a tolerable rate is one of the primary objectives for sustainability and soil conservation. Central Anatolia is under considerable risk due to an increase in the cultivation of marginal lands for food production. Cultivated lands have already been reached the final limits throughout the last 50 years. Moreover, forests and considerable areas of pasture have recently been converted to ploughed fields due to agricultural expansion. This study was conducted in the Sarısu basin to evaluate soil losses and land use management for sustainability. The Universal Soil Loss Equation model and Geographic Information System techniques were used to estimate the soil losses. The mean potential soil loss of the basin was calculated to be 1.88 t ha-1 per year with the Universal Soil Loss Equation model. These results are comparatively small when compared to the average value for Turkey of 13 t ha-1 yearly. Our calculated results are closer to the value for the Sakarya river basin, which is approximately 2.77 t ha-1 y-1. In this study, land usages in the Sarısu basin were evaluated in terms of soil losses, tolerable soil loss rates and soil conservation precautions.

Evaluation of soil losses and sediment yield using modified PSIAC model

Evaluation of soil losses and sediment yield using modified PSIAC model

Soil loss in an olive grove in Central Spain under cover crops and tillage treatments, and farmer perceptions

Purpose Soil erosion is a threat for the sustainability of the grove production all over the world, and olive groves are where the highest erosion is achieved. This study aimed to (1) evaluate soil loss from water erosion in microplots (1 m2) under natural rainfall events in an olive grove managed with tillage and three different cover crops; (2) determine the main climatic factors on soil loss and selective transportation; and (3) survey the willingness of local farmers to adopt cover crops.

Soil Erosion Assessment of the Poyang Lake Basin, China: Using USLE, GIS and Remote Sensing

Soil erosion is one of the most critical eco-environmental issues in the Poyang Lake basin, China. The purpose of this study is to discover the spatial pattern of soil erosion, and predict soil loss and sediment yield, and evaluate soil loss impacts on main reservoirs by using Universal Soil Loss Equation (USLE), GIS and Remote Sensing (RS). Firstly, five erosion factors including rainfall erosivity (R), soil erodibility (K), topographic factor (LS), cover and management factor(C), and conservation supporting practice factor (P) were calculated and analyzed, respectively. Secondly, annual soil erosion and its spatial distribution were evaluated, and sediment yield was subsequently predicted. Next, soil erosion was classified into five erosion categories according to Industry Standard of Water Resources of China. Then, the relationship among soil erosion, landform and land use and land cover (LULC) were analyzed. Finally, the influence of soil erosion on main reservoirs in the basin were assessed. The result showed that: 28.3% of the total watershed area appears soil loss; the average annual soil loss amount is approximate 2.7 × 107 t; soil erosion modulus ranged from 0 to 394.8 t/ha/y, with a mean value of 1.82 t/ha/y. 71.7% of the watershed area are undergoing minimal erosion, primarily appear in surrounding the lake area, both sides of river valley and plains of five main rivers; 24.1% of the watershed area are undergoing low erosion, mainly found in the west, east, central hilly and mountain areas; 3.4% of the watershed area was observed moderate soil erosion; 0.83% of the watershed area are undergoing high, very high and extreme soil erosion, which located in the northeastern and northwestern corner, and the upstream of the Ganjiang river and Fuhe river sub-watershed. Low and moderate soil erosion most frequently occurred at the plains and hills zone in this basin. Soil loss happens on needleleaved forest, rainfed croplands and shrub land use type are greater than that of other LULC types; soil erosion modulus descends on the different land use types, orderly by bare lands, grass lands, shrub lands, rainfed croplands, needleleaved forest, spares vegetation, broadleaved deciduous forest, artificial surface, irrigated croplands and water bodies. Present main reservoirs are undergoing a big threat from the upstream sediment load, especially as the Qiyi, Da’ao, Qixing and Tuolin reservoir.

Evaluación comparativa de pérdidas de suelo en el corredor biológico entre parques nacionales Puracé y Cueva de los Guácharos en el Huila

El propósito de la investigación fue evaluar las pérdidas de suelo en parcelas experimentales del corredor biológico entre Parques Nacionales Naturales Puracé y la Cueva de los Guácharos en el departamento del Huila, en cultivos con manejo tradicional frente a manejo alternativo, resultados que fueron validados mediante la Ecuación Universal de Pérdidas de Suelo. Se realizó la medición de las pérdidas de suelo y se registraron las lluvias en un periodo de cuatro meses, calificando el periodo de lluvias como suaves, resultando mayor la erosión en el cultivo de café convencional (1,14 t.ha -1 .año -1 ), seguido de mora convencional (0,99 t.ha -1 .año -1 ) con diferencias significativas atribuidas al manejo de las coberturas. En cultivos con prácticas de labranza cero resultaron las menores pérdidas (0,37 t.ha -1 .año -1)en comparación con el manejo convencional (0,53 t.ha -1 .año -1 ), estos últimos incluyen quema, remoción de la cobertura y movimiento superficial del suelo. En los tratamientos con ganadería extensiva y semi-estabulada no se presentaron diferencias significativas en la erosión del suelo. No existe correlación significativa entre las pérdidas de suelo estimadas USLE y las medidas en las parcelas de escorrentía.

Evaluation of Soil Loss with Surface Covering Methods Using Strip Tillage Seeding Device

Most fields in highland areas are covered with rye or hairy vetch for conservation during a fallow. However, using cover crops needs an effort to sow, and this makes top soil more vulnerable to loss due to surface disturbances. The aims of this study were to develop an automatic seeding-regulator device using a low-price, extensive-use GPS sensors and a DC motors and to evaluate a working efficiency of it after adaptation to partial tillage machine for reducing seeding effort. The amount of runoff water and soil loss was evaluated with partial tillage and simultaneous-seeding after harvesting soybean, in 17% slope lysimeters. In results, the seeding amount with the machine speed was stable between 0.5~0.8 m s -1 of working sections. The automatic control device of seeding-rate could be enough to solve the slip problems of power selecting supply system or five four-wheel drive device. In partial tillage and simultaneous seeding, runoff water was 11.6% (1.8 m³ ha -1 ) of the scatter-seeding control (15.5 m³ ha -1 ) and soil loss was 13.2% (7 kg ha -1 ) of the scatter-seeding control (53 kg ha -1 ). These results suggest that partial tillage and simultaneous-seeding methods are very effective in decreasing work effort and soil loss of sloped land.

PERDA DE SOLO EM DIFERENTES CULTURAS AGRÍCOLAS SOBRE LATOSSOLO VERMELHO NO MUNICÍPIO DE PATROCÍNIO, MG - DOI: 10.13083/1414-3984.v22n05a05

Os processos erosivos, apesar de naturais, vêm sendo intensificados pelo uso inadequado do solo provocando a perdas anuais de bilhões de toneladas de solos férteis em todo o mundo. Assim, compreender este processo é fundamental para um desenvolvimento sustentável da atividade agrícola. Este trabalho avaliou as perdas de solo por erosão laminar em sete parcelas, sob diferentes tratamentos (mata; cultivo de soja, milho e cafeeiro, pastagem e solo exposto), em Latossolos vermelhos da Fazenda Esmeril, em Patrocínio, MG. As parcelas de solo exposto apresentaram os maiores valores de perdas de solo, com mais de 23 Mg ha-1 ano-1. Em relação aos demais tratamentos, a mata apresentou os menores totais, aproximadamente 38%; dentre as culturas, o milho (79%), seguido da soja (68%), foram os que apresentaram os maiores valores para as perdas de solo, bem superiores ao da área de cafezal e pasto, com 47% e 45%, respectivamente. Apesar do sistema de plantio direto nas culturas de soja e milho ter reduzido a produção de sedimentos nestas áreas, estas ainda continuam perdendo muito material durante as fases de preparação do solo e plantio. Já o valor elevado apresentado na cultura do cafeeiro é reflexo do grande espaçamento entre plantas.

Soil erosion by snow gliding – a first quantification attempt in a subalpine area in Switzerland

Abstract. Snow processes might be one important driver of soil erosion in Alpine grasslands and thus the unknown variable when erosion modelling is attempted. The aim of this study is to assess the importance of snow gliding as a soil erosion agent for four different land use/land cover types in a subalpine area in Switzerland. We used three different approaches to estimate soil erosion rates: sediment yield measurements in snow glide depositions, the fallout radionuclide 137Cs and modelling with the Revised Universal Soil Loss Equation (RUSLE). RUSLE permits the evaluation of soil loss by water erosion, the 137Cs method integrates soil loss due to all erosion agents involved, and the measurement of snow glide deposition sediment yield can be directly related to snow-glide-induced erosion. Further, cumulative snow glide distance was measured for the sites in the winter of 2009/2010 and modelled for the surrounding area and long-term average winter precipitation (1959–2010) with the spatial snow glide model (SSGM). Measured snow glide distance confirmed the presence of snow gliding and ranged from 2 to 189 cm, with lower values on the north-facing slopes. We observed a reduction of snow glide distance with increasing surface roughness of the vegetation, which is an important information with respect to conservation planning and expected and ongoing land use changes in the Alps. Snow glide erosion estimated from the snow glide depositions was highly variable with values ranging from 0.03 to 22.9 t ha−1 yr−1 in the winter of 2012/2013. For sites affected by snow glide deposition, a mean erosion rate of 8.4 t ha−1 yr−1 was found. The difference in long-term erosion rates determined with RUSLE and 137Cs confirms the constant influence of snow-glide-induced erosion, since a large difference (lower proportion of water erosion compared to total net erosion) was observed for sites with high snow glide rates and vice versa. Moreover, the difference between RUSLE and 137Cs erosion rates was related to the measured snow glide distance (R2 = 0.64; p < 0.005) and to the snow deposition sediment yields (R2 = 0.39; p = 0.13). The SSGM reproduced the relative difference of the measured snow glide values under different land uses and land cover types. The resulting map highlighted the relevance of snow gliding for large parts of the investigated area. Based on these results, we conclude that snow gliding appears to be a crucial and non-negligible process impacting soil erosion patterns and magnitude in subalpine areas with similar topographic and climatic conditions.

Experimental Study of Rill Evolution Processes and Relationships between Runoff and Erosion on Clay Loam and Loess

Rill erosion accounts for approximately 70% of the total erosion of upland areas in China's Loess Plateau. A laboratory rainfall experiment with deionized water was conducted to examine the process of rill evolution and the relationship between runoff, rill evolution, and erosion rates for clay loam and loess soils given a fixed slope gradient (10°) and two rainfall intensities (1.5 and 2.0 mm min−1). The results show that rills evolved from a series of parallel drop‐pit chains along the down‐slope direction. Clay loam soil produced rills under a rainfall intensity of 1.5 mm min−1, and loess soil produced rills only under higher rainfall intensity. The temporal change in sediment concentration and erosion rate shows good consistency with the emergence of drop pits and rills. An increase in rainfall intensity had little effect on the sediment concentration and erosion rate for clay loam soil, whereas for loess soil, both increased rapidly and exceeded those of clay loam soil, with the emergence of a rill when the rainfall intensity was higher. Rills have a much greater effect on sediment concentration and erosion rate for loess soil than for clay loam soil. This study indicates that soil texture has a major impact on rill formation; clay loam soil is more subject to rill formation, but the rills formed are generally small and do not substantially increase soil loss. In contrast, the well‐developed rills in silt loam soil can result in intensive soil loss, though rills occur infrequently. Basic understanding of these results, causes, and quantification are essential for the prediction and evaluation of soil loss.

Retraction Note: Assessment of soil erosion using RUSLE and GIS: a case study of the Maotiao River watershed, Guizhou Province, China

Due to the existence of fragile karst geo-ecological environments, such as environments with extremely poor soil cover, low soil-forming velocity, and fragmentized terrain and physiognomy, as well as inappropriate and intensive land use, soil erosion is a serious problem in Guizhou Province, which is located in the centre of the karst areas of southwestern China; evaluation of soil loss and spatial distribution for conservation planning is urgently needed. This study integrated the revised universal soil loss equation (RUSLE) with a GIS to assess soil loss and identify risk erosion areas in the Maotiao River watershed of Guizhou. Current land use/cover and management practices were evaluated to determine their effects on average annual soil loss and future soil conservation practices were discussed. Data used to generate the RUSLE factors included a Landsat Thematic Mapper image (land cover), digitized topographic and soil maps, and precipitation data. The results of the study compare well with the other studies and local data, and provide useful information for decision makers and planners to take appropriate land management measures in the area. It thus indicates the RUSLE–GIS model is a useful tool for evaluating and mapping soil erosion quantitatively and spatially at a larger watershed scale in Guizhou.

Identification et évaluation du risque d’érosion sur le bassin versant du K’sob (Est Algérien)

The estimated of soil losses by erosion in semi-arid regions is often difficult due to the complex interaction of many factors such as climate, geology, land use, topography and human activities. RUSLE, Gravilovic and ICONA models are used to evaluate soil losses and characterize degraded areas in the K’sob watershed (1,482 km2), located north eastern Algeria, in order to implement management intervention. The results show that 90 % of the basin surface is subject to low to moderate risk erosion and only 10 % is vulnerable to erosion with sediment loss estimated at 4.6 t ha−1 year−1. Areas with excessive risk of gully and sheet erosion cover respectively 10 and 1 % of the basin and zones suffering the combined effects of these two processes would total more than 3 % of the basin. Finally, the sites subject to potential landslide cover just over 0.3 km2. The K’sob dam’s reservoir is surrounded by potentially sides degraded by sheet erosion and gully. However, larger areas degraded by these processes are located near urban areas as Rabta, Bordj Ghdir and K’sour. Spatial differences in erosion rates in the K’sob watershed are mainly caused by differences in the type of land cover and slope gradient. RUSLE, Gravilovic and ICONA models provide a useful tool for identifying soil erosion and can be successfully used for prioritization of vulnerable areas in semi-arid watersheds.

Evaluation of Soil Loss According to Surface Covering and Tillage Methods in Corn Cultivation

Corn was mainly cultivated in slope land during summer season when heavy rain falls so that soil loss occurs severely. Especially, soil disturbance and exposure of topsoil by conventional tillage intensifies soil loss by heavy rain. The aim of this study was to develop surface covering and tillage methods for reducing soil loss in corn cultivation. The experiment was conducted in 17% sloped lysimeter with 8 treatments including strip tillage after surface covering with rye residue, strip tillage after residue covering of several crops and sod culture, black polyethylene film covering after conventional tillage and control. Amount of runoff water and eroded soil, and corn growth were investigated. Amounts of runoff water in all plots except black polyethylene plot ranged from 152 to 375 m³ ha -1 , accounting for 13~32% of 1,158 m³ ha -1 in control. Amount of eroded soil decreased by 94 to 99% (3 to 89 kg ha-1) in plots of strip tillage after covering with crop residues compared to control with 1,739 kg ha -1 . Corn yields in plots of strip tillage after covering with crop residues ranged from 6.0 to 6.9 Mg ha -1 , while that of control was 6.5 Mg ha -1 . The results suggest that strip tillage methods after surface covering with crop residues are very effective on soil conservation of slope land in corn cultivation.

MODELLING AND MAPPING OF SOIL EROSION ON THE OUED EL MALLEH CATCHMENT USING REMOTE SENSING AND GIS

In Morocco, the spectacular expansion of erosive processes shows increasingly alarming aspects. Due to the considerable costs of detailed ground surveys for studying this phenomenon, remote sensing is an appropriate alternative for analyzing and evaluating the risks of the expansion of soil degradation. According to an FAO study (2001), Erosion threatens 13 million ha of cropland and rangeland in northern Morocco and induces an estimated average water storage capacity loss of 50 million m3 each year through dam silting. The lost water volume could potentially be used to irrigate 5000 to 6000 ha / year.
 This study analyses soil erosion on the Oued El Malleh catchment, a 34 km2 catchment located in the north of Fez (Morocco). This contribution aims at mapping the spatio-temporal evolution of land use and modelling the erosion and sedimentation processes using the well known RUSLE model. Land use changes were assessed using Landsat-5 TM and Landsat-7 ETM+ images, from the 1987-2011 periods which were validated by field studies. The images were first georeferenced and projected into the Moroccan coordinate system (Merchich North) then processed to evaluate soil loss through a GIS package (Idrisi Andes Software). These static assessments of soil loss were then used in a deposition/sedimentation algorithm to model soil loss propagation to the downstream. The soil loss averages determined by the model vary between 1.09 t/ha/yr as a minimum value for the reforested lands and 169.4 t/ha/yr as a maximum value for the uncultivated lands (badlands). The latter generally correspond to Regosols or low protected soils located on steep slopes. In comparison with RUSLE, the sedimentation model yields lower values of soil losses; only 97.3 t/h/year for the uncultivated lands, and -0.34 t/ha/year in the reforested land, indicating an on-going sedimentation process.
 By taking into account the temporal variability of erosion and deposition jointly lower values of soil erosion are calculated by the RUSLE model. However, despite this decline, land degradation problems are still important due to the combination of land use and local lithology. The results of this study were used to indentify areas where interventions are needed to limit land degradation processes.

MODELLING AND MAPPING OF SOIL EROSION ON THE OUED EL MALLEH CATCHMENT USING REMOTE SENSING AND GIS

In Morocco, the spectacular expansion of erosive processes shows increasingly alarming aspects. Due to the considerable costs of detailed ground surveys for studying this phenomenon, remote sensing is an appropriate alternative for analyzing and evaluating the risks of the expansion of soil degradation. According to an FAO study (2001), Erosion threatens 13 million ha of cropland and rangeland in northern Morocco and induces an estimated average water storage capacity loss of 50 million m3 each year through dam silting. The lost water volume could potentially be used to irrigate 5000 to 6000 ha / year.
 This study analyses soil erosion on the Oued El Malleh catchment, a 34 km2 catchment located in the north of Fez (Morocco). This contribution aims at mapping the spatio-temporal evolution of land use and modelling the erosion and sedimentation processes using the well known RUSLE model. Land use changes were assessed using Landsat-5 TM and Landsat-7 ETM+ images, from the 1987-2011 periods which were validated by field studies. The images were first georeferenced and projected into the Moroccan coordinate system (Merchich North) then processed to evaluate soil loss through a GIS package (Idrisi Andes Software). These static assessments of soil loss were then used in a deposition/sedimentation algorithm to model soil loss propagation to the downstream. The soil loss averages determined by the model vary between 1.09 t/ha/yr as a minimum value for the reforested lands and 169.4 t/ha/yr as a maximum value for the uncultivated lands (badlands). The latter generally correspond to Regosols or low protected soils located on steep slopes. In comparison with RUSLE, the sedimentation model yields lower values of soil losses; only 97.3 t/h/year for the uncultivated lands, and -0.34 t/ha/year in the reforested land, indicating an on-going sedimentation process.
 By taking into account the temporal variability of erosion and deposition jointly lower values of soil erosion are calculated by the RUSLE model. However, despite this decline, land degradation problems are still important due to the combination of land use and local lithology. The results of this study were used to indentify areas where interventions are needed to limit land degradation processes.

토양 손실 평가에 의한 식생매트의 허용 소류력 결정

By the activation of environment-friendly river works, application of vegetation mats is increasing, however, evaluation techniques for hydraulic stability of vegetation mats are not presented. This study is conducted to develop the objective test method for vegetation mats. Two kind of vegetation mats are tested by the real scale experiments, and hydraulic quantities are measured and analyzed to evaluate acting shear stresses. To evaluate soil loss, Terrestrial 3D LiDAR measurement is conducted and soil loss index are calculated from changes of bed elevation. Quantified evaluation for permissible shear stresses is conducted by graphical method for acting shear stresses and soil loss index. By the results of precision survey, changes of sub soil are limited to local range in stable cases and relatively large changes of sub soil which is similar to natural river bed are detected in unstable cases. From the study, evaluation of permissible shear stresses by ASTM D 6040 is avaliable in the failure mechanism and failure criteria by soil loss index.

Resultados preliminares de las pérdidas de suelo en zona agrícola del Penedés (Cataluña, España)

This concerns the evaluation of soil loss through runoff erosion in the agricultura! zones. The area of ·study is situated in the tectonic trench of Penedes (Province of Barcelona), basically made up of neoge and quaternary materials. The quantification of the erosive processes is carried out on experimental plots intalled on prívate estates. It is based on the data obtained from two fundamental variables: climate and runoff. For this purpose we have set up a series of typical meteorological instruments and gathering devices to collect both solid and liquid discharge brought down by the overland flow. These are similar to Gerlach troughs but on a larger scale. During 1983 the soil losses in this experimental zone were 2.4 kg/m2 . The erosion took place atan uneven rate. From a total of 46 rainy days only 11 produced results and 3 of these were responsible for 92% of the total erosion.