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1.
在农业非点源污染研究中,确定农业非点源污染的关键源区或危险区域是开展有针对性研究和控制农业非点源污染的首要问题之一.本文在地理信息系统的支持下,综合考虑了影响于桥水库流域农业非点源磷流失的源因子和迁移因子,通过建立评价指标体系,计算磷污染危险性指数,对农业非点源磷流失危险性进行定量化评价,识别具有极高危险性或较高危险性的区域为磷流失的关键源区,将其作为控制和管理的优先区域和重点区域.结果表明:流域中磷流失危险性极高和较高的区域即关键源区不到全流域面积的6.0%,危险性中等的地区占到整个流域面积的20.52%;具有高和中等危险性的地区主要分布在流域河流两岸,且具有极高或较高的土壤有效磷含量或化肥磷施用量或高的土壤侵蚀强度,大部分为流域中部丘陵平原区的农田,少部分为地形较陡的山区农田.  相似文献   

2.
Geographical information systems (GIS)-based soil erosion risk assessment models continue to play an important role in soil conservation planning. In the present study, soil erosion risk of Istanbul–Elmalı dam watershed was determined within GIS-based COoRdination of INformation on the Environment (CORINE) soil erosion risk assessment method. Initially soil texture, soil depth, and surface stoniness maps were created and were intersected in GIS environment in order to generating erodibility map. Then, Fournier precipitation and Bagnouls–Gaussen drought indices determined based on meteorological data and erosivity were calculated. The composed erodibility map was co-evaluated within erosivity value and slope map of the site for composing potential erosion risk map. At the final step, the previous yearly land use maps which belong to years 1984, 1992, and 2003 intersected with potential erosion risk maps and temporal actual erosion risk alteration were assessed. In conclusion, according to our results in Elmalı watershed dam in 1984 there have been low, medium, and high erosion risks at rates 29.67, 52.49, and 17.84%, respectively, whereas in 2003 the erosion risk values have changed from low to high as 26.43, 46.57, and 27.00%, respectively. Inter-year comparison alteration to the advantage of the high erosion risk could have resulted from over degradation and high exposure to anthropogenic activities.  相似文献   

3.
The spatial pattern of soil erosion can provide valuable insights into the soil erosion processes that require a rapid assessment in practical applications. Generally, quantitative technique is expensive and time-consuming. The objective of this paper is to reveal the spatial pattern of erosion with a rapid assessment method. The affecting factors such as land cover, vegetation fraction and slope gradient are integrated into this method using a qualitative means. Beijing-1 images in 2006 were used to produce land-cover and vegetation fraction, and 1:50,000 topographic maps were used to calculate slope gradient. The study area was classified into six grades. Results show that the upstream area of Guanting Reservoir, in general, is exposed to a moderate risk; there are 17,740.33 km2 of land that suffered from water soil erosion in 2006, occupied 40.69% of the total area, and most of the soil erosion area is on the light and moderate risk, which occupied 25.05 and 62.83% of the eroded area, respectively. Eight elevation zones and six slope gradient zones were overlaid with the assessed risk. The analyzed results show that: (1) the areas above 2,000 m have the lowest erosion risk, which is only 0.75% of the eroded area; 1,250–1,500 m elevation zone has the highest erosion risk, which is 34.72% of the eroded area. (2) The slope gradient zone less than 5 degrees and greater than 35 degrees have the lowest erosion risk, which is 0.02 and 0.75% of the eroded area, respectively; the slope gradient zone with 8–15 degrees has the highest erosion risk, which is 36.40% of the eroded area. These results will be useful for water and soil conservation management and the planning of mitigation measures.  相似文献   

4.
This paper applied the Revised Universal Soil Loss Equation (RUSLE), remote-sensing technique, and geographic information system (GIS) to map the soil erosion risk in Miyun Watershed, North China. The soil erosion parameters were evaluated in different ways: the R factor map was developed from the rainfall data, the K factor map was obtained from the soil map, the C factor map was generated based on a back propagation (BP) neural network method of Landsat ETM+ data with a correlation coefficient (r) of 0.929 to the field collected data, and a digital elevation model (DEM) with a spatial resolution of 30 m was derived from topographical map at the scale of 1:50,000 to develop the LS factor map. P factor map was assumed as 1 for the watershed because only a very small area has conservation practices. By integrating the six factor maps in GIS through pixel-based computing, the spatial distribution of soil loss in the upper watershed of Miyun reservoir was obtained by the RUSLE model. The results showed that the annual average soil loss for the upper watershed of Miyun reservoir was 9.86 t ha−1 ya−1 in 2005, and the area of 47.5 km2 (0.3%) experiences extremely severe erosion risk, which needs suitable conservation measures to be adopted on a priority basis. The spatial distribution of erosion risk classes was 66.88% very low, 21.90% low, 6.19% moderate, 2.90% severe, and 1.84% very severe. Among all counties and cities in the study area, Huairou County is in the extremely severe level of soil erosion risk, about 39.6% of land suffer from soil erosion, while Guyuan County in the very low level of soil erosion risk suffered from 17.79% of soil erosion in 2005. Therefore, the areas which are in the extremely severe level of soil erosion risk need immediate attention from soil conservation point of view.  相似文献   

5.
Water erosion is a serious and continuous environmental problem in many parts of the world. The need to quantify the amount of erosion, sediment delivery, and sediment yield in a spatially distributed form has become essential at the watershed scale and in the implementation of conservation efforts. In this study, an effort to predict potential annual soil loss and sediment yield is conducted by using the Revised Universal Soil Loss Equation (RUSLE) model with adaptation in a geographic information system (GIS). The rainfall erosivity, soil erosivity, slope length, steepness, plant cover, and management practice and conservation support practice factors are among the basic factors that are obtained from monthly and annual rainfall data, soil map of the region, 50-m digital elevation model, remote sensing (RS) techniques (with use of Normalized Difference Vegetation Index), and GIS, respectively. The Ilam dam watershed which is located southeast part of Ilam province in western Iran is considered as study area. The study indicates that the slope length and steepness of the RUSLE model are the most effective factors controlling soil erosion in the region. The mean annual soil loss and sediment yield are also predicted. Moreover, the results indicated that 45.25%, 12.18%, 12.44%, 10.79%, and 19.34% of the study area are under minimal, low, moderate, high, and extreme actual erosion risks, respectively. Since 30.13% of the region is under high and extreme erosion risk, adoption of suitable conservation measures seems to be inevitable. So, the RUSLE model integrated with RS and GIS techniques has a great potential for producing accurate and inexpensive erosion and sediment yield risk maps in Iran.  相似文献   

6.
Wind-erosion risk is a challenge that threatens land development in dry-land regions. Soil analysis, remote sensing, climatic, vegetal cover and topographic data were used in a geographic information system (GIS), using multi-criteria analysis (MCA) to map wind-erosion risk (Rwe) in Laghouat, Algeria. The approach was based on modelling the risk and incorporating topographic and climatic effects. The maps were coded according to their sensitivity to wind erosion and to their socio-economic potential, from low to very high. By overlapping the effects of these layers, qualitative maps were drawn to reflect the potential sensitivity to wind erosion per unit area. The results indicated that severe wind erosion affects mainly all the southern parts and some parts in the north of Laghouat, where wind-erosion hazard (Hwe) is very high in 43% of the total area, and which was affected mainly by natural parameters such as soil, topography and wind. The results also identified features vulnerable to Rwe. The product of the hazard and the stake maps indicated the potential risk areas that need preventive measures; this was more than half of the study area, making it essential to undertake environmental management and land-use planning.  相似文献   

7.
Soil erosion by water is recognised as a worldwide land degradation issue, particularly in arid and semi-arid regions. The aim of this study is to apply the powerful capabilities of advanced remote sensing and geographic information system techniques to identify the areas at risk to water erosion. This study presents the assessment of water erosion in mountainous areas (eastern Aures, Algeria) based on three main factors: the friability of the bedrock, degree of slope and density of vegetation cover. Alsat1 image was used to produce land use and vegetation (NDVI) maps. Digital elevation model was used in constructing the slope gradient map. The erosion risk map was obtained by the combination of indices assigned to thematic layers following multicriteria decision rules. Water erosion was generally not concerning in the eastern Aures (slight risk = 33 %, moderate risk = 44 % of the area). This simple–qualitative approach gave good results for assessing soil erosion equally to quantitative methods since 89.55 % of field verifications were accurate. The non-alarming state and the low rate of severe and extremely severe risk to erosion are due to (1) the low steep slopes, (2) the good quality of vegetation (forests with thick undergrowth), and which are occurring on (3) resistant materials of the substratum, and (4) the low human pressure. Results of this study, which may be conducted with reasonable costs and accuracy over large areas, are of significant help in prioritising areas in decision making and sustainable planning.  相似文献   

8.
The Wadi Mina Watershed, western area of Algeria is characterized by rare and irregular rains and a fragile and weak vegetable cover. The sediments resulting from erosion are transported and contributed to silting dam Sidi Mhamed Benaouda. The combination of the thematical maps of the various erosive factors according to the Revised Universal Soil Loss Equation (RUSLE) in SIG by ArcGIS 10.2 software provided a reliable forecast of the annual rates of soil loss by delimiting the areas prone to erosive risk in the catchment above mentioned. The estimated potential average annual soil loss is 11.2 t/ha/yr., and the potential erosion rates from recognized erosion classes ranged from 0.0 to plus 100 t/ha/yr. About 50% of the catchment area was predicted to have very low to low erosion risk, with soil loss between 0 and 7.4 t/ha/yr. Erosion risk is moderate over 13.9% of the catchment, where calculated soil loss is between 7.4 and 12 t/ha/yr. Erosion risk is high to dangerous over 36.1% of the catchment, where calculated soil loss is more than 12 t/ha/yr. According to this study, it appeared clearly that we must intervene quickly by using reliable and effective conservation techniques.  相似文献   

9.
Tsunamis can represent a significant risk to the population and cause huge economic damage in many costal regions. In order to be able to identify risk hot spots and implement targeted risk reduction measures, decision makers need to have a clear picture of the risk situation in their countries or regions. This work reviews existing approaches for tsunami risk assessment and recommends a five-step process for assessing tsunami risk. As a case study, a qualitative risk assessment for a worst-case tsunami scenario was carried out to understand the tsunami risk to the population in Cádiz. Moreover, a sensitivity analysis of the tsunami hazard input parameters was performed as a strong influence of the variability of the input parameters on the resultant tsunami hazard and risk zonation maps was observed. The study shows that regardless of the assumptions made a non-negligible tsunami risk to Cádiz exists.  相似文献   

10.
Land degradation is still a very common problem in the mountains of Asia because of inappropriate land use practice in steep topography. Many studies have been carried out to map shifting cultivation and areas susceptible to soil erosion. Mostly, estimated soil loss is taken as the basis to classify the level of soil loss susceptibility of area. Factors that influence soil erosion are: rainfall erosivity, soil erodibility, slope length and steepness, crop management and conservation practices. Thus the reliability of estimated soil loss is based on how accurately the different factors were estimated or prepared. As each and every small pixel of our earth surface is different from one area to another, the manner in which the study area was discretized into smaller homogenous sizes and how the most accurate and efficient technique were adopted to estimate the soil loss are very important. The purpose of this study is to produce erosion susceptibility maps for an area that has suffered because of shifting cultivation located in the mountainous regions of Northern Thailand. For this purpose, an integrated approach using RS and GIS-based methods is proposed. Data from the Upper Nam Wa Watershed, a mountainous area of the Northern Thailand were used. An Earth Resources Data Analysis System (ERDAS) imagine image processor has been used for the digital analysis of satellite data and topographical analysis of the contour data for deriving the land use/land cover and the topographical data of the watershed, respectively. ARCInfo and ARCView have been used for carrying out geographical data analysis. The watershed was discretized into hydrologically, topographically, and geographically homogeneous grid cells to capture the watershed heterogeneity. The soil erosion in each cell was calculated using the universal soil loss equation (USLE) by carefully determining its various parameters and classifying the watershed into different levels of soil erosion severity. Results show that during the time of this study most of the areas under shifting cultivation fell in the highest severity class of susceptibility.  相似文献   

11.
This study was aimed at predicting soil erosion risk in the Buyukcekmece Lake watershed located in the western part of Istanbul, Turkey, by using Revised Universal Soil Loss Equation (RUSLE) model in a GIS framework. The factors used in RUSLE were computed by using different data obtained or produced from meteorological station, soil surveys, topographic maps, and satellite images. The RUSLE factors were represented by raster layers in a GIS environment and then multiplied together to estimate the soil erosion rate in the study area using spatial analyst tool of ArcGIS 9.3. In the study, soil loss rate below 1 t/ha/year was defined as low erosion, while those >10 t/ha/year were defined as severe erosion. The values between low and severe erosion were further classified as slight, moderate, and high erosion areas. The study provided a reliable prediction of soil erosion rates and delineation of erosion-prone areas within the watershed. As the study revealed, soil erosion risk is low in more than half of the study area (54%) with soil loss <1 t/ha/year. Around one-fifth of the study area (19%) has slight erosion risk with values between 1 and 3 t/ha/year. Only 11% of the study area was found to be under high erosion risk with soil loss between 5 and 10 t/ha/year. The severe erosion risk is seen only in 5% of the study area with soil loss more than 10 t/ha/year. As the study revealed, nearly half of the Buyukcekmece Lake watershed requires implementation of effective soil conservation measures to reduce soil erosion risk.  相似文献   

12.
Soil erosion by water is a serious environmental problem which affects particularly the agriculture of developing countries. Due to specific factors, such as high rainfall intensity, steep slopes and vegetation scarcity, Tunisia is prone to soil erosion. Taking this into account, the main objective of this study was to estimate the soil erosion risk in the Batta watershed in Tunisia using qualitative and quantitative erosion model with remote sensing data and geographic information system (GIS). Moreover, a developed method that deals with evaluating the impact of vegetation on soil erosion by water is also applied. This method used multi-temporal satellite images with seasonal variability and the transformed soil adjusted vegetation index (TSAVI) which is appropriate in arid and semi-arid areas. For both erosion models, the results show that a large area of the Batta watershed is seriously affected by erosion. This potentially high risk is due especially to severe slopes, poor vegetation coverage and high soil erodibility in this watershed. Furthermore, the use of multi-temporal satellite images and vegetation index show that the effect of vegetation is a significant factor to protect the soil against erosion. The risk is especially serious in the summer season, but it decreases with the growth of vegetation cover in spring. Erosion model, combined with a GIS and remote sensing, is an adequate method to evaluate the soil erosion risk by water. The findings can be used by decision makers as a guideline to plan appropriate strategies for soil and water conservation practices.  相似文献   

13.
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.  相似文献   

14.
Three Gorges Reservoir in China was running since June 2003, and its impacts on soil erosion (SE) and soil conservation (SC) have attracted major public attentions. We quantified the soil conservation service of ecosystems in the Three Gorges Reservoir Area (TGRA) based on a GIS platform using the universal soil loss equation. We revealed the changes of spatial and temporal patterns of soil conservation (SC) and soil erosion (SE) after project construction as well as impact factors on local SE and SC. Results showed that the total amounts and mean capacity of soil conservation services in the TGRA were 15.38-billion t a?1 and 2134.73 t ha?1 a?1, respectively. Northeast reservoir area owned better services than the southwest, and the regions with a capacity of >5000 t ha?1 a?1 were primary located in mountain areas. An increasing trend in SC appeared in the TRGA and “with increasing SC” totaled 22690.5 km2 (38.9%), while the areas “with decreasing SC” amounted to 3460.4 km2 (5.9%) between 2000 and 2010. Moreover, the pattern of changing SC was continuous in this area. The spatial characteristics of soil conservation service in the TGRA were primarily affected by slope, climate and terrain features. In addition, the reforestation and/or forest protection would contribute to soil erosion control in the TGRA. The results revealed a great spatial heterogeneity of soil conservation service in this region, which may provide useful suggestions for land management, soil erosion control and ecosystem protection in the TGRA in China.  相似文献   

15.
Soil erosion is a serious environmental problem in Indravati catchment. It carries the highest amount of sediments compared with other catchments in India. This catchment spreading an area of 41,285 km2 is drained by river Indravati, which is one of the northern tributaries of the river Godavari in its lower reach. In the present study, USLE is used to estimate potential soil erosion from river Indravati catchment. Both magnitude and spatial distribution of potential soil erosion in the catchment is determined. The derived soil loss map from USLE model is classified into six categories ranging from slight to very severe risk depending on the calculated soil erosion amount. The soil erosion map is linked to elevation and slope maps to identify the area for conservation practice in order to reduce the soil loss. From the model output predictions, it is found that average erosion rate predicted is 18.00 tons/ha/year and sediment yield at the out let of the catchment is 22.30 Million tons per annum. The predicted sediment yield verified with the observed data.  相似文献   

16.
Soil erosion is a serious global environmental problem which limits the survival and development of human beings. In our country, due to the special physical geography and socio-economic conditions, soil erosion intensity is great, which is particularly prominent in Loess Plateau region. Therefore, preventing and controlling soil erosion, as well as reducing soil erosion in Loess Plateau have become the key to solving environmental problems in the region. Soil erosion on Loess Plateau is serious, and grassland vegetation has good effects on soil and water conservation, which can improve ecological environment well. After the implementation of the project about returning farmland to grassland on Loess Plateau, the ecological benefits mainly focused on soil and water conservation benefits, soil improvement benefits, water conservation benefits and species diversity benefits, etc. Grassland vegetation has an irreplaceable role in the construction of the ecological environment on Loess Plateau. Therefore, the role of grassland in preventing soil erosion has received more and more attention. Scholars have done lots of research involved in the relationship between grassland coverage and soil erosion, impacts of grassland on hydrodynamic parameters, effects of grassland on soil properties, reduction effects of grassland on runoff and sediment, and soil erosion process on grassland slope. However, there is little research on erosion effect induced by grassland cover. This paper mainly pointed out the following questions: First, grassland cover is influenced by many factors, but the relationship with soil erosion from the dynamic mechanism is rarely discussed; Second, there is no well-developed theory of overland flow erosion at present, which limits the study of hydrodynamic parameters on grassland slope; Third, establishment of mathematical model between grassland cover and soil resistance can accelerate the quantitative analysis of grassland influence on erosion; Fourth, comprehensive analysis of influencing factors on water reduction and sediment reduction effect on grassland are insufficient; Fifth, there are not many mechanisms to analyze the erosion process of grassland slope by using the hydrodynamic characteristics of slope; sixth, research results on grassland-induced erosion are mainly focused on leading to soil dry layer and we should continue to strengthen in the future. This paper summarized the previous results, and supplemented some studies about erosion caused by grassland, then pointed out the existing problems in current research and the areas that need to be strengthened in the future, aiming at reducing soil erosion on the Loess Plateau.  相似文献   

17.
Soil erosion is considered as the most widespread form of soil degradation which causes serious environmental problems. This study investigates the performance of the maximum entropy (ME) in mapping rill erosion susceptibility in the Golgol watershed, Ilam province, Iran. To this end, ten rill erosion conditioning factors were selected to be employed in the modelling process based on an investigation of the literature. These layers are: elevation, slope percent, aspect, stream power index, topographic wetness index, distance from streams, plan curvature, lithology, land use, and soil. Then, a training dataset of rill erosion locations was used for modelling this phenomenon. The area under receiver operating characteristics curve was used for evaluating the performance of the ME model. In addition, Modified Pacific South-West Inter Agency Committee (MPSIAC) framework was applied and sediment yield was determined for different hydrological units in the study area. At last, Jackknife test was implemented to show the contribution of the factors in the modelling process. The results depicted that area under ROC curve for training and validation datasets were 0.867, and 0.794, respectively. Therefore, this conclusion can be achieved that ME worked well and could be a good tool for generating rill erosion susceptibility maps and its output could be employed for soil conservation in similar areas.  相似文献   

18.
Estimation of soil erosion using RUSLE in Caijiamiao watershed,China   总被引：4，自引：1，他引：3  
Jinghu Pan  Yan Wen 《Natural Hazards》2014,71(3):2187-2205
Soil erosion is a serious environmental and production problem in China. In particular, natural conditions and human impact have made the Chinese Loess Plateau particularly prone to intense soil erosion area. To decrease the risk on environmental impacts, there is an increasing demand for sound, and readily applicable techniques for soil conservation planning in this area. This work aims at the assessment of soil erosion and its spatial distribution in hilly Loess Plateau watershed (northwestern China) with a surface area of approximately 416.31 km2. This study was conducted at the Caijiamiao watershed to determine the erosion hazard in the area and target locations for appropriate initiation of conservation measures using the revised universal soil loss equation (RUSLE). The erosion factors of RUSLE were collected and processed through a geographic information system (GIS)-based approach. The soil erosion parameters were evaluated in different ways: The R-factor map was developed from the rainfall data, the K-factor map was obtained from the soil map, the C-factor map was generated based on Landsat-5 Thematic Mapper image and spectral mixture analysis, and a digital elevation model with a spatial resolution of 25 m was derived from topographic map at the scale of 1:50,000 to develop the LS-factor map. Support practice P factor was from terraces that exist on slopes where crops are grown. By integrating the six-factor maps in GIS through pixel-based computing, the spatial distribution of soil loss in the study area was obtained by the RUSLE model. The results showed that spatial average soil erosion at the watershed was 78.78 ton ha?1 year?1 in 2002 and 70.58 ton ha?1 year?1 in 2010, while the estimated sediment yield was found to be 327.96 × 104 and 293.85 × 104 ton, respectively. Soil erosion is serious, respectively, from 15 to 35 of slope degree, elevation area from 1,126 to 1,395 m, in the particular area of soil and water loss prevention. As far as land use is concerned, soil losses are highest in barren land and those in waste grassland areas are second. The results of the study provide useful information for decision maker 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 river watershed scale on a cell basis in Chinese Loess Plateau and for planning of conservation practices.  相似文献   

19.
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.  相似文献   

20.
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