Remote sensing and GIS for artificial recharge study, runoff estimation and planning in Ayyar basin, Tamil Nadu, India

This paper focuses on artificial groundwater recharge study in Ayyar basin, Tamil Nadu, India. The basin is covered by hard crystalline rock and overall has poor groundwater conditions. Hence, an artificial recharge study was carried out in this region through a project sponsored by Tamil Nadu State Council for Science and Technology. The Indian Remote Sensing satellite 1A Linear Imaging Self Scanning Sensor II (IRS 1A LISS II) satellite imagery, aerial photographs and geophysical resistivity data were used to prioritize suitable sites for artificial recharge and to estimate the volume of aquifer dimension available to recharge. The runoff water available for artificial recharge in the basin is estimated through Soil Conservation Service curve number method. The land use/land cover, hydrological soil group and storm rainfall data in different watershed areas were used to calculate the runoff in the watersheds. The weighted curve number for each watershed is obtained through spatial intersection of land use/land cover and hydrological soil group through GeoMedia 3.0 Professional GIS software. Artificial recharge planning was derived on the basis of availability of runoff, aquifer dimension, priority areas and water table conditions in different watersheds in the basin.     

RETRACTED ARTICLE: Assessment of soil erosion using RUSLE and GIS: a case study of the Maotiao River watershed,Guizhou Province,China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

Assessment of soil erosion in a tropical mountain river basin of the southern Western Ghats,India using RUSLE and GIS

Revised Universal Soil Loss Equation(RUSLE) model coupled with transport limited sediment delivery(TLSD) function was used to predict the longtime average annual soil loss, and to identify the critical erosion-/deposition-prone areas in a tropical mountain river basin, viz., Muthirapuzha River Basin(MRB; area=271.75 km~2), in the southern Western Ghats, India. Mean gross soil erosion in MRB is 14.36 t ha~(-1) yr~(-1), whereas mean net soil erosion(i.e., gross erosion-deposition) is only 3.60 t ha~(-1) yr~(-1)(i.e., roughly 25% of the gross erosion). Majority of the basin area(~86%) experiences only slight erosion(5 t ha~(-1) yr~(-1)), and nearly 3% of the area functions as depositional environment for the eroded sediments(e.g., the terraces of stream reaches, the gentle plains as well as the foot slopes of the plateau scarps and the terrain with concordant summits). Although mean gross soil erosion rates in the natural vegetation belts are relatively higher, compared to agriculture, settlement/built-up areas and tea plantation, the sediment transport efficiency in agricultural areas and tea plantation is significantly high,reflecting the role of human activities on accelerated soil erosion. In MRB, on a mean basis, 0.42 t of soil organic carbon(SOC) content is being eroded per hectare annually, and SOC loss from the 4th order subbasins shows considerable differences, mainly due to the spatial variability in the gross soil erosion rates among the sub-basins. The quantitative results, on soil erosion and deposition, modelled using RUSLE and TLSD, are expected to be beneficial while formulating comprehensive land management strategies for reducing the extent of soil degradation in tropical mountain river basins.     

Soil erosion prediction using the Revised Universal Soil Loss Equation (RUSLE) in a GIS framework,Chania, Northwestern Crete,Greece

Soil erosion is a growing problem in southern Greece and particularly in the island of Crete, the biggest Greek island with great agricultural activity. Soil erosion not only decreases agricultural productivity, but also reduces the water availability. In the current study, an effort to predict potential annual soil loss has been conducted. For the prediction, the Revised Universal Soil Loss Equation (RUSLE) has been adopted in a Geographical Information System framework. The RUSLE factors were calculated (in the form of raster layers) for the nine major watersheds which cover the northern part of the Chania Prefecture. The R-factor was calculated from monthly and annual precipitation data. The K-factor was estimated using soil maps available from the Soil Geographical Data Base of Europe at a scale of 1:1,000,000. The LS-factor was calculated from a 30-m digital elevation model. The C-factor was calculated using Remote Sensing techniques. The P-factor in absence of data was set to 1. The results show that an extended part of the area is undergoing severe erosion. The mean annual soil loss is predicted up to ∼200 (t/ha year⁻¹) for some watersheds showing extended erosion and demanding the attention of local administrators.     

遥感与GIS支持下的南桐矿区水土流失评价与区划

以重庆市南桐矿区为研究对象,运用遥感和GIS技术获取对水土流失影响较大的植被覆盖度、地形坡度、土地利用类型等信息并进行空间叠加分析,计算了水土流失类型及面积。研究结果表明,南桐矿区水土流失面积262.91km2,侵蚀模数2281t/(km2?a),水土流失强度以轻度和中度为主,其中轻度流失132.37km2,中度流失108.95km2。根据区域地貌类型以及水土流失特征,将研究区水土流失划分为盆边低山丘陵中强度流失区、北部坪状低山中轻度流失区和盆边中山轻度流失区三个类型区,盆边低山丘陵中强度流失区以中度流失为主;北部坪状低山中轻度流失区以轻度流失为主;盆边中山轻度流失区虽然以轻度流失为主,但微度流失也占有相当部分的比重。      

Assessing soil erosion in Mediterranean karst landscapes of Lebanon using remote sensing and GIS

Maps showing the potential for soil erosion at 1:100,000 scale are produced in a study area within Lebanon that can be used for evaluating erosion of Mediterranean karstic terrain with two different sets of impact factors built into an erosion model. The first set of factors is: soil erodibility, morphology, land cover/use and rainfall erosivity. The second is obtained by the first adding a fifth factor, rock infiltration. High infiltration can reflect high recharge, therefore decreasing the potential of surface runoff and hence the quantity of transported materials. Infiltration is derived as a function of lithology, lineament density, karstification and drainage density, all of which can be easily extracted from satellite imagery. The influence of these factors is assessed by a weight/rate approach sharing similarities between quantitative and qualitative methods and depending on pair-wise comparison matrix.The main outcome was the production of factorial maps and erosion susceptibility maps (scale 1:100,000). Spatial and attribute comparison of erosion maps indicates that the model that includes a measure of rock infiltration better represents erosion potential. Field investigation of rills and gullies shows 87.5% precision of the model with rock infiltration. This is 17.5% greater than the precision of the model without rock infiltration. These results indicate the necessity and importance of integrating information on infiltration of rock outcrops to assess soil erosion in Mediterranean karst landscapes.     

Application of a resistivity survey and geographical information system (GIS) analysis for hydrogeological zoning of a piedmont area, Himalayan foothill region, India

A Geographical Information System (GIS) has been used for the integration of the results of 70 vertical electrical soundings and hydrogeological data in the piedmont zone of the Himalayan foothills region of Uttaranchal, India. Indian remote sensing (IRS) LISS-III data has been used to prepare thematic maps for the geomorphology and slope maps of the area. The ranges of electrical resistivity values have been assigned to the different formations by calibrating electrical resistivity values with the borehole data. Electrical resistivity, groundwater level monitoring, and borehole and remote sensing data have been integrated in the GIS analysis to delineate the hydrogeological zoning in the study area. Suitable weights were assigned to the different features affecting the groundwater potential. The total score for a particular location is translated in terms of groundwater potential of the area. The results indicate that the southern part of the study area has a very good groundwater potential for meeting the demand of water for irrigation and domestic purposes whereas the steeply sloping area in the northern part, having high relief, has a poor groundwater potential. The resulting delineation of groundwater potential zones are in general agreement with the available yield data of the tube wells.

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Resumen Se ha utilizado un Sistema de Información Geográfica (SIG) para la integración de los resultados de 70 sondeos eléctricos verticales y datos hidrogeológicos en la zona piamonte de la región al pie de los Himalaya de Uttaranchal, India. Se han utilizados datos de sensores remotos Indios (IRS) LISS-III para elaborar mapas temáticos de la geomorfología y mapas de pendientes del área. Se han asignado los rangos de valores de resistividad eléctrica a diferentes formaciones mediante la calibración de valores de resistividad eléctrica con datos de barrenos. Se han integrado datos de resistividad eléctrica, monitoreo de niveles de agua subterránea, y barrenos, y datos de sensores remotos mediante un análisis SIG para delimitar la zonificación hidrogeológica del área de estudio. Se asignaron pesos apropiados a las diferentes características que afectan el potencial del agua subterránea. El puntaje total de un lugar particular se ha transformado en términos de potencial de agua subterránea del área. Los resultados indican que la parte sur del área de estudio tiene muy buen potencial de agua subterránea para satisfacer la demanda de agua por riego y uso doméstico mientras que el área de pendientes pronunciadas en la parte norte, de alto relieve, tiene potencial pobre de agua subterránea. La delimitación de zonas potenciales de agua subterránea encaja muy bien con los datos disponibles de rendimiento de pozos entubados.

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Résumé Un système d’information géographique (SIG) a été utilisé pour l’intégration de résultats en provenance de 70 sondages électriques et données hydrogéologiques dans la zone de piedmont, au pied de l’Himalaya dans la région de Uttaranchal en Inde. Des données du satellite IRS LISS-III ont été utilisées pour préparer des cartes thématiques sur la géomorphologie et les pentes de la zone d’étude. Les valeurs de résistivités électriques ont été assignées aux différentes formations en les calibrant sur les données de sondages. La résistivité électrique, la piézométrie, et les données de sondages et de télédétection ont été intégrées dans une analyse par SIG pour délimiter les zones hydrogéologiques de l’aire d’étude. Des poids ont été assignés aux différents éléments affectant le potentiel en eau souterraine. Le résultat final pour une localisation particulière est traduit en terme de potentiel en eau souterraine. Les résultats indiquent que la partie Sud a un potentiel très bon pour la demande en eau domestique et eau d’irrigation, tandis que les zones plus pentues dans la partie Nord, caractérisée par un relief élevé, présente un potentiel assez pauvre. La délinéation globale des zones à différents potentiels s’accorde assez bien avec les données disponibles concernant la capacité des puits.

     

基于GIS RS与AHP耦合技术的矿山水力侵蚀研究

晋陕蒙(西)地区的水力侵蚀受控于多种因素。在详尽地分析了影响水力侵蚀的各种因子基础上,确定母质类型、植被覆盖、地貌类型、沟壑密度、地形坡度、土地利用类型、矿山开发面积、降雨强度、水土保持、大风强度作为其主控致灾因子。根据遥感(RS)解译成果,应用GIS分别建立了各主控因子的专题层图,利用先进的层次分析方法(AHP),确定影响水力侵蚀的各致灾因子的权重系数。通过GIS、RS与AHP耦合技术的应用,对各子专题层图进行加权复合叠加,利用频率和频数分布直方图,确定出水力侵蚀的分区阈值,构建水力侵蚀的危险度评价的多源地学信息复合叠加模型,并对水力侵蚀危险度进行了分区评价。水力侵蚀模型的建立,为水力侵蚀的分区评价与预测提供了理论依据,使评价结果更加科学、合理、准确。     

Surface runoff in a torrent catchment area in Middle Europe and its prevention

The Schesa, a sinister contributory torrent to the Ill river near Bludenz (federal province of Vorarlberg) is the largest basin-shaped gully of Middle Europe and endangers the underlying villages by torrential debris flow and gigantic mass movements. The catchment is characterized by a complex geological situation, high annual precipitation and torrential rains from spring to early autumn, which cause enormous amounts of surface runoff. Based on field investigations comprising rain simulation experiments on representative plots, investigations on land-use, vegetation cover, soil physical characteristics, geology, hydrogeology and other features of the catchment area, surface runoff coefficient maps were developed. They formed the basis for assessment of runoff potential for different scenarios in vegetation cover and land-use intensity. Calculation of runoff for the recurrent design event by use of an improved run-time method showed the urgent necessity of runoff reduction measures in large parts of the catchment area above the gully. Based on the modelling results a concept for reduction of both, surface runoff and amount of deep percolating water has been elaborated.     

Use of GIS for optimalization of human activity in a catchment area: An example of the Beauce region (France)

The quality of groundwater often represents a limiting factor for its exploitation. The chemical composition of groundwater is a very complicated process involving geochemical, hydrochemical, and biochemical interaction between the water and the rock with which it is in contact. In addition, as a result of human activity, the deterioration of groundwater quality is a serious problem. The use of a geographic information system (GIS) combining various data may help solve this problem. The article describes multicriterion analysis applied to the Beauce basin in France, which is a part of the SAGE project of the BRGM Orléans.     

Comparison of soil erosion and deposition rates using radiocesium, RUSLE, and buried soils in dolines in East Tennessee

 Three dolines (sinkholes), each representing different land uses (crop, grass, and forest) in a karst area in East Tennesse, were selected to determine soil erosional and depositional rates. Three methods were used to estimate the rates: fallout radiocesium (¹³⁷Cs) redistribution, buried surface soil horizons (Ab horizon), and the revised universal soil loss equation (RUSLE). When ¹³⁷Cs redistribution was examined, the average soil erosion rates were calculated to be 27 t ha^–1 yr^–1 at the cropland, 3 t ha^–1 yr^–1 at the grassland, and 2 t ha^–1 yr^–1 at the forest. By comparison, cropland erosion rate of 2.6 t ha^–1 yr^–1, a grassland rate of 0.6 t ha^–1 yr^–1, and a forest rate of 0.2 t ha^–1 yr^–1 were estimated by RUSLE. The ¹³⁷Cs method expressed higher rates than RUSLE because RUSLE tends to overestimate low erosion rates and does not account for deposition. The buried surface horizons method resulted in deposition rates that were 8 t ha^–1 yr^–1 (during 480 yr) at the cropland, 12 t ha^–1 yr^–1 (during 980 yr) at the grassland, and 4 t ha^–1 yr^–1 (during 101 yr) at the forest site. By examining ¹³⁷Cs redistribution, soil deposition rates were found to be 23 t ha^–1 yr^–1 at the cropland, 20 t ha^–1 yr^–1 at the grassland, and 16 t ha^–1 yr^–1 at the forest site. The variability in deposition rates was accounted for by temporal differences;¹³⁷Cs expressed deposition during the last 38 yr, whereas Ab horizons represented deposition during hundreds of years. In most cases, land use affected both erosion and deposition rates – the highest rates of soil redistribution usually representing the cropland and the lowest, the forest. When this was not true, differences in the rates were attributed to differences in the size, shape, and closure of the dolines. Received: 10 October 1995 · Accepted: 13 October 1995     

Rapid erosion of the coast of Sagar island, West Bengal - India

The coastal zone of the Sagar island has been studied. The island has been subjected to erosion by natural processes and to a little extent by anthropogenic activities over a long period. Major landforms identified in the coastal area of the Sagar island are the mud flats/salt marshes, sandy beaches/dunes and mangroves. The foreshore sediments are characterized by silty, slightly sandy mud, slightly silty sand and silty sand. Samples 500 m inland from high waterline are silty slightly sandy mud, and by clayey slightly sandy mud. The extent of coastline changes are made by comparing the topographic maps of 1967 and satellite imageries of 1996, 1998 and 1999. Between 1967 and 1999 about 29.8 km² of the island has been eroded and the accreted area is only 6.03 km². Between 1996 and 1998 the area underwent erosion of 13.64 km² while accretion was 0.48 km². From 1998 to 1999, 3.26 km² additional area was eroded with meager accretion. Erosion from 1997 to 1999 was estimated at 0.74 km² /year; however, from 1996 to 1999, the erosion rate was calculated as 5.47 km²/year. The areas severely affected by erosion are the northeastern, southwestern and southeastern faces of the island. As a consequence of coastal erosion, the mud flats/salt marshes, sandy beaches/dunes and mangroves have been eroded considerably. Deposition is experienced mainly on the western and southern part of the island. The island is built primarily by silt and clay, which can more easily be eroded by the waves, tides and cyclonic activities than a sandy coast. Historic sea level rises accompanied by land subsidence lead to differing rates of erosion at several pockets, thus periodically establishing new erosion planes.     

Groundwater-recharge estimation using a surface electrical resistivity method in the Himalayan foothill region, India

A new method for the estimation of groundwater recharge is presented using a surface resistivity method and isotope technique. A linear relationship was obtained between the resistivity of the unsaturated top layer and the recharge estimated using a tritium tagging technique for the piedmont zone in the Himalayan foothill region, India. The relation can be used for the estimation of recharge using surface electrical resistivity measurements for the same geological formation. The data used for the study are 32 vertical electrical resistivity sounding measurements at a station interval of 2 km, tritium tagging studies at six selected sites and pre- and post-monsoon water-level monitoring in the piedmont zone of the Himalayan foothill region (India). The results of this study were mapped using GIS techniques. In the study area, a well-defined empirical relationship between unsaturated zone resistivity and recharge per cent was obtained. The method suggests a new application of surface electrical resistivity data in determining recharge per cent due to infiltration. The technique of estimating groundwater recharge using surface electrical resistivity measurement is efficient, economic, less time consuming and easy to use compared with other methods used for this purpose.

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Resumen Se presenta un método nuevo para estimar recarga de agua subterránea utilizando un método superficial de resistividad y una técnica de isótopos. Se ha obtenido una relación linear entre la resistividad de la capa superior no saturada y la recarga estimada utilizando la técnica de tritio marcado etiquetado para la zona de piedemontes en la región de colinas al pie del Himalaya, India. La relación puede utilizarse para estimar recarga usando mediciones superficiales de resistividad eléctrica para la misma formación geológica. Los datos utilizados en el estudio consisten de treinta y dos mediciones de sondeos eléctricos verticales de resistividad en un intervalo de estaciones de dos km, estudios de tritio marcado en seis sitios seleccionados y monitoreo de niveles de agua, pre-monzón y post-monzón, en la zona piedemontes de la región de colinas al pie del Himalaya (India). Se mapearon los resultados de este estudio utilizando técnicas SIG. Se obtuvo para el área una relación empírica bien definida entre la resistividad de la zona no saturada y el porcentaje de recarga. El método sugiere una aplicación nueva de los datos superficiales de resistividad eléctrica en la determinación del porcentaje de recarga ocasionado por infiltración. La técnica de estimar recarga de agua subterránea utilizando mediciones superficiales de resistividad eléctrica es eficiente, económica, demanda poco tiempo, y fácil de utilizar en comparación con otros métodos que se utilizan para este propósito.

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Resumé Une nouvelle méthode permettant destimer la recharge des eaux souterraines a été présentée, utilisant une méthode de résistivité de surface et des méthodes isotopiques. Une relation linéaire a été obtenue entre la résistivité de la zone non saturée et la recharge estimée grâce au Tritium dans la zone du Piedmont au pied de lHimalaya, Inde. La relation peut être utilisée pour lestimation de la recharge en utilisant la méthode de résistivité de surface dans la même formation géologique. Les données utilisées pour létude sont vingt-deux sondages électriques réalisés tous les deux kilomètres, létude de la signature du tritium en six endroits sélectionnés, et la comparaison des niveaux piézométriques pré et post moussons. Les résultats de cette étude ont été cartographiés en utilisant les techniques SIG. Dans la zone détude une relation très bien définie entre la recharge (%) et la résistivité de la zone non saturée a été obtenue. La méthode suggère une nouvelle application de la résistivité de surface, pour déterminer le pourcentage de la recharge due à linfiltration. Cette technique est efficace, économique, rapide et facile à mettre en oeuvre, en comparaison dautres techniques utilisées pour atteindre le même objectif.

     

黄土丘陵区土壤侵蚀链垂直带水沙流空间分布

采用多坡段组合模型、人工模拟降雨实验研究了土壤侵蚀链垂直带水沙流空间分布变化特征。结果表明:愈向下坡方向的坡段产流量愈大,单位面积、单位时间的产流量按坡段排列为:谷坡>梁峁坡下部>梁峁坡中部>梁峁坡上部。雨强为29.7mm/h时,坡面上没有沟蚀发育;雨强为60.5mm/h时,细沟主要分布在梁峁坡下部和谷坡处;雨强为90 2mm/h时,各种侵蚀形态在坡面均有较好发育,细沟的出现部位一直伸展到梁峁坡中部和上部之间。由于上坡来水来沙的作用,梁峁坡的产沙量增大了20.2%～63.5%,谷坡的产沙量增大了42.9%～74.5%。     

Dendrochronological reconstruction of snow avalanche activity in the Lahul Himalaya,Northern India

Mass wasting and avalanche events substantially impact the landscape morphology and consequently human habitation throughout the Himalaya. There is, however, a paucity of snow avalanche documentation for the region. The application of dendrochronologic research methods introduces a sensitive approach to document the recurrence of snow avalanche events in a region where historical records are either non-existent or difficult to access. An exploratory dendrochronologic study was undertaken in the Lahul Himalaya of Northern India during the summer of 2006. Included within the fieldwork was an assessment of avalanche track morphology to enable identification of the slope characteristics that might be associated with an increase in avalanche activity. Thirty-six trees growing on the Ratoli avalanche track were sampled. The oldest tree was a Cedrus deodara with a pith date of 1950. A tree-ring-derived avalanche response curve highlights four avalanche events that occurred from 1972 to 2006. The successful scientific results based on the application of the method used provide the basis for local planners to quantify slope failure hazards in forested areas throughout the western Himalaya.     

Identification of hotspots for potential pyrethroid runoff: a GIS modeling study in San Joaquin River Watershed of California, USA

This paper attempts to identify the high-risk areas for potential runoff of pyrethroid pesticides in the San Joaquin River Watershed. Pyrethroid pesticides have been detected in water and fluvial sediments in this watershed, creating concerns about potential negative impacts on water quality. However, little documentation exists regarding the distributions or the extent of the adverse effects caused by the use of pyrethroids. This study developed a geographic information systems (GIS) model to identify areas with high potential for pyrethroid runoff during the rainy season. The model was then validated using field-monitoring data. Nine factors were identified for the runoff risk assessment: amount of active ingredient used, soil erodibility factor, hydrologic group, surface layer depth, seasonal rainfall, seasonal number of rainy days, seasonal number of storm events, stream density, and land cover. The results indicated that high pyrethroid runoff risks were associated with basins such as the Stanislaus River Sub-basin, Newman Gustine Sub-basin and South Merced Sub-basin. This study demonstrated that the GIS model is capable of predicting high-risk areas of pyrethroid runoff at sub-basin scale. The model can be used to prioritize sites for water quality monitoring and guide implementations of best management practices. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Temporal and spatial variations in water discharge and sediment load in the Alaknanda and Bhagirathi Rivers in Himalaya, India

The Alaknanda and Bhagirathi Rivers originate in the mountainous regions of the Himalayas (Garhwal) and result in high sediment yields causing flood hazards downstream of the Ganga River and high sediment flux to the Bay of Bengal. The rivers are perennial, since runoff in these rivers is controlled by both precipitation and glacial melt. In the present study, three locations in the upper reaches of the Ganga River were monitored for 1 yr (daily observations of, more than >1000 samples) for suspended sediment concentrations. In addition, more than one hundred samples were collected from various locations of the Alaknanda and Bhagirathi Rivers at different periods to observe spatial and temporal variations in river suspensions. Further, multi-annual data (up to 40 yrs) of water flow and sediment concentrations were used for inferring the variations in water flow and sediment loads on longer time scales. In most previous studies of Himalayan Rivers, there has been a general lack of long term water flow and sediment load data. In the present study, we carried out high frequency sampling, considered long term discharge data and based on these information, discussed the temporal and spatial variations in water discharge and sediment loads in the rivers in the Himalayan region. The results show that, >75% of annual sediment loads are transported during the monsoon season (June through September). The annual physical weathering rates in the Alaknanda and Bhagirathi River basins at Devprayag are estimated to be 863 tons km⁻² yr⁻¹ (3.25 mm yr⁻¹) and 907 tons km⁻² yr⁻¹ (3.42 mm yr⁻¹) respectively, which are far in excess of the global average of 156 tons km⁻² yr⁻¹ (0.58 mm yr⁻¹).     

辽宁铁岭市土壤侵蚀时空演变研究

近年来,人为活动的加剧造成铁岭地区水土流失日益严重。本文采用遥感和GIS技术,以部颁标准SL190-96对铁岭地区1991年和2001年的土壤侵蚀情况进行研究,并结合1986年和1996年的土壤侵蚀调查数据,分析了铁岭地区近15年来土壤侵蚀强度的时空变化,结果表明铁岭地区在此期间土壤侵蚀面积缓慢增长,其中强度侵蚀面积在1986~1996年间持续增长,2001年明显下降;中度侵蚀面积在1986~1996年间持续下降,2001年则明显增强;空间分析显示明显恶化的区域有西丰、开原和清河区,具明显改善的为铁岭县,而昌图和调兵山地区基本保持稳定。今后该区水保的重点应放在强度侵蚀的治理,以及土壤侵蚀等级增强的区域。     

Soil erosion assessment and its verification using the Universal Soil Loss Equation and Geographic Information System: a case study at Boun,Korea

This study is aimed at the evaluation of the hazard of soil erosion and its verification at Boun, Korea, using a Geographic Information System (GIS) and remote sensing. Precipitation, topographic, soil, and land use data were collected, processed, and constructed into a spatial database using GIS and remote sensing data. Areas that had suffered soil erosion were analysed and mapped using the Universal Soil Loss Equation (USLE). The factors that influence soil erosion are rainfall erosivitiy (R) from the precipitation database, soil erodibility (K) from the soil database, slope length and steepness (LS) from the topographic database, and crop and management (C) and conservation supporting practices (P) from the land use database. Land use was classified from Landsat Thematic Mapper satellite images. The soil erosion map verified use of the landslide location data. Landslide locations were identified in the Boun area from interpretation of aerial photographs and field surveys.     

基于GIS和层次分析法的冲积扇油气管道段坡面侵蚀性评价

坡面侵蚀是管道穿越冲积扇地质灾害的重要类型之一。通过对青海省乌兰县希里沟北山山前冲积扇油气管道建立坡面侵蚀单体模型,以遥感影像解译为基础,结合野外调查,沿管线得到40个灾害点。获取坡度、来水量、地表抗冲性、渗透性、植被等7个指标因子,用层次分析法确定各因子权重,发现坡度所占权重最高,达35.1%。借助Arc GIS软件,建立数据库,方便属性查询。通过加权叠加,将最终栅格图层按自然断点法进行分级,分为五级,得到调查点侵蚀强度等级图。比较分析结果与实际管线调查情况较吻合,表明该方法在坡面侵蚀研究中值得推广,从而为油气管道运营期主要治理区域及新管线的选线提供一定的理论支持。