Regional soil erosion risk mapping using RUSLE,GIS, and remote sensing: a case study in Miyun Watershed,North China

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.     

毛乌素沙漠地震勘探历程及效果

总结陕西省煤田地质局物探测量队在毛乌素沙漠开展地震勘探攻关的三个阶段及各阶段取得的成果,认为该区虽然表浅层地震地质条件复杂,地震勘探难度较大,但勘探精度基本上可以达到解释5m断层的的精度。并以国家重大产业技术开发专项的依托工程,内蒙古鄂托克前旗新上海庙地区SZT井田三维地震勘探为例,对地震激发、接收技术进行改进,并采取精细静校、地表一致性振幅补偿等处理手段,结合多参数信息,进行资料精细解释。成果表明：依托工程野外原始资料甲级率达到70％以上,获得的三维数据体信噪比高,构造及煤层解释成果可靠、准确。     

基于遥感的毛乌素沙地红碱淖面积变化趋势及其影响因素分析

红碱淖是毛乌素沙地最大的内陆湖泊,是集旅游、渔业和生态湿地于一体的功能区。近年来,红碱淖面积萎缩,影响了其综合功能的发挥。为了查明红碱淖面积的变化趋势及其影响因素,在收集前人资料和研究成果的基础上,借助MODIS遥感数据反演了湖面面积,建立了2000年以来红碱淖面积的时间序列。在分析红碱淖面积的变化特征和影响因素后发现,早期红碱淖面积变化主要受气象因素的影响,湖泊面积呈周期性有规律的变化;后期在自然因素的基础上叠加了上游截流、地下水开采等人为因素的影响,湖泊面积在周期性变化的基础上总体呈现出萎缩的趋势。     

Fire danger assessment with remote sensing: a case study in Northern China

Every year several million hectares of forest and grassland in China are affected by wildfires. The majority of wildfires occur in the northern part of China, where grasslands and forests are ubiquitous. A critical step toward the protection of life, property, and natural resources from wildfires is the development of a fire danger rating system. This paper presents a new method to assess fire danger that capitalizes on the abundance of environmental data available via remote sensing and applies this new method to the northern part of China. Using an analytical hierarchy process, a fire danger index was developed based on five environmental factors that are known to affect fire frequency and severity, including land surface temperature, vegetation curing, equivalent water thickness, vegetation continuity degree, and fuel weight. Data for these five factors were derived from satellite imagery, instead of point data, allowing for predictions to be made over a large geographic area. Fire danger ratings were then mapped for the region based on the fire danger index. In addition, the accuracy of the fire danger index was evaluated by statistical analyses. The fire danger index was significantly correlated with air temperature and precipitation, suggesting that changes in these two environmental variables will affect the predictions of the index.     

Geochemical characteristics of Holocene aeolian deposits and their environmental significance in the Mu Us Desert,northern China

This paper addresses the surface and Holocene aeolian deposits in the southeastern Mu Us Desert, N. China, systematically analysing the evolution of the geochemical characteristics of aeolian sand–palaeosol sequences and their environmental significance. Our results indicate that the geochemical components of the Holocene aeolian deposits and surface deposits had the similar material sources, sediment transport and deposition processes in the study region, which were dominated by SiO₂, Al₂O₃, and Na₂O. In the weathering process of the Jinjie (JJ) profile, the Na, K, and Si presented the slight leaching and migration in general, while the other elements were relatively accumulated. The Holocene aeolian deposits and surface deposits incurred weaker geochemical weathering under cold and dry conditions and were only weakly leached, which implies a relatively arid environment in the Holocene epoch and the modern era. The weathering degree was controlled by the regional temperature and precipitation, and was probably more sensitive to the precipitation changes. In the sedimentary profile, the geochemical parameters and migration of elements demonstrated that there have been several alternating warm–wet and cold–dry intervals in the Mu Us Desert in the Holocene epoch; there were relatively warm and wet conditions prior to 4.6 ka, and it has been cold and dry since then. Six millennial‐scale dry events were recorded during the Holocene, which were not only accordant with the history of palaeoclimatic changes in the different latitudes and archives of the Northern Hemisphere, but also correspond to the millennial‐scale variation of cosmic radiation and solar activity during that period. Copyright © 2015 John Wiley & Sons, Ltd.     

Estimation of spatial patterns of soil erosion using remote sensing and GIS: a case study of Indravati catchment

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.     

Climate fluctuation on a kiloyear scale during the Late Last Glacial in Mu Us Desert,China: evidence from Rb and Sr contents and ratios

The MGS2 segment of the Milanggouwan stratigraphical section in China’s Salawusu River Valley records 5.5 sedimentary cycles consisting of dune sands alternating with fluviolacustrine facies or/and palaeosols. The high Rb and Sr contents and low Rb/Sr ratios in the fluviolacustrine facies indicate the presence of a warm and humid climate, and vice versa for a dry and cold climate. Rb and Sr appeared to have 5.5 element cycles that are consistent with the sedimentation changes, and each cycle lasts about 2 ka on average. This study suggests that the observed cycles mainly resulted from variations in the strength of the East Asian winter and summer monsoons, and the MGS2 segment experienced six cold-dry winter monsoons and five warm-humid summer monsoons during the OIS2. In addition, the millennial-scale monsoonal climate fluctuations revealed by the element cycles corresponded well with the Dansgaard–Oeschger cycles recorded in the Greenland ice cores and Heinrich events in the North Atlantic marine sediments. Therefore, the monsoonal climate fluctuations revealed by the Rb and Sr in the MGS2 segment were likely triggered by global climate change.     

Mapping soil erosion susceptibility using remote sensing and GIS: a case of the Upper Nam Wa Watershed,Nan Province,Thailand

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.     

The climate change during early Holocene recorded by trace elements of Shenmu section,Mu Us Desert

Through nine trace elements of the Shenmu section, Mu Us Desert is analyzed for the climate changes during Early Holocene. Except Sr, a migration process of P, Mn, Cr, Rb, Nb, Cu, Zn, and V is found in the dune sands, indicating the accumulation processes of the Asian winter monsoon-driven wind erosion and transport and deposition under the cold climatic phase. And accumulation of these elements in different layers of paleo sol dune sands is related to regional geomorphology and element properties. 8.5 winter-summer monsoon cycles in the early Holocene are observed. The duration time and climate of the stronger winter monsoon phases can be compared with the cold climate in the North Atlantic and other parts of China. The result of Red fit 3.8 power spectra shows 310a, 210a, 90a, and 70a centennial cycles for the element, which are consistent with the solar oscillation cycles. These suggest that the external solar activities of the Earth may have great influences on driving the winter and summer monsoon cycles during early Holocene.     

遥感技术在密云水库北部土壤侵蚀调查中的应用

密云水库是北京市的重要水源地之一。其上游地区的植被、地形、地质以及降雨等因素对该区的土壤侵蚀情况具有较大影响，可直接影响到密云水库的泥沙入库量及水质等。而在土壤侵蚀调查方面，遥感技术具有较大的优势。在北京市国土资源与地质环境遥感综合调查的基础上，对遥感技术在密云水库北部地区土壤侵蚀调查中的应用进行了探讨。首先根据建立的遥感解译标志对遥感图像进行判读并实地验证，然后，根据影响土壤侵蚀的生态环境因子，建立了数学评判模型，对该区的土壤侵蚀情况进行了评判。为该区的水土保持规划、管理和决策提供了科学依据。     

Spatial prediction of soil erosion risk by remote sensing,GIS and RUSLE approach: a case study of Siruvani river watershed in Attapady valley,Kerala, India

Siruvani watershed with a surface area of 205.54 km² (20,554 hectare), forming a part of the Western Ghats in Attapady valley, Kerala, was chosen for testing RUSLE methodology in conjunction with remote sensing and GIS for soil loss prediction and identifying areas with high erosion potential. The RUSLE factors (R, K, LS, C and P) were computed from local rainfall, topographic, soil classification and remote sensing data. This study proved that the integration of soil erosion models with GIS and remote sensing is a simple and effective tool for mapping and quantifying areas and rates of soil erosion for the development of better soil conservation plans. The resultant map of annual soil erosion shows a maximum soil loss of 14.917 t h⁻¹ year⁻¹ and the computations suggest that about only 5.76% (1,184 hectares) of the area comes under the severe soil erosion zone followed by the high-erosion zone (11.50% of the total area). The dominant high soil erosion areas are located in the central and southern portion of the watershed and it is attributed to the shifting cultivation, and forest degradation along with the combined effect of K, LS and C factor. The RUSLE model in combination with GIS and remote sensing techniques also enables the assessment of pixel based soil erosion rate.     

末次冰期毛乌素沙地湖泊消涨过程:沉积证据

毛乌素沙地位于东亚季风边缘区,对于气候变化响应敏感。基于沙地的侵蚀-堆积关系,在侵蚀作用为主的沙地西北部和中部很难找到沉积相对连续且分辨率较高的地层剖面,因此已有的末次冰期古气候环境研究多集中于堆积作用为主的沙地东南缘的萨拉乌苏河河谷地区。本文选取位于沙地腹地,厚度为3.5 m的风成砂-河湖相沉积序列——神水台（SSTG）剖面为研究对象,基于AMS¹⁴C和OSL年代数据,推测得出剖面中湖相层的上界和下界分别为约24.2 ka B.P.和42.7 ka B.P.,依据沉积地层和环境代用指标分析结果,针对末次冰期毛乌素沙地湖泊消涨的一般过程进行了探讨。结果表明,自约5万年以来,由神水台（SSTG）剖面指示了两次明显的湖泊主要发育期,时间分别约为42.7~34.3 ka B.P.和31.1~24.2 ka B.P.,期间粘土含量、有机质、红度均表现为低值,为含淡水螺壳化石的典型湖泊相沉积,且与毛乌素沙地已有湖泊发育的年代结果基本一致。在两期湖相层之间的砂层,平均粒径、砂含量表现为峰值,指示了一次明显的湖泊消退的过程,其时间约为34.3~31.1 ka B.P.;在湖相层上下可能均为风力作用为主导的风沙沉积。通过区域对比并初步探讨其可能的驱动机制,结果表明SSTG剖面记录的湖泊消涨过程主要受控于东亚季风强度的变化。

     

Integration of remote sensing data with the field and laboratory investigation for lithological mapping of granitic phases: Kadabora pluton, Eastern Desert, Egypt

In the current study, an integration of Enhanced Thematic Mapper Plus (ETM+), field, and laboratory data have been used for lithological mapping of different granitic phases in the Kadabora area, Eastern Desert, Egypt. Application of enhancement techniques, including a new proposed band ratio combination (ratio 5/3, 3/1, 7/5 in RGB, respectively) and supervised classification images are used in discriminating different granitic phases in the Kadabora pluton from each other and from their environs. The data have been proved with the help of field and geochemical investigations. The results revealed that: (1) the Kadabora granitic pluton could be distinguished into three phases that recognized by field and laboratory investigation including granodiorite (phase I), monzogranite (phase II), and syeno-alkali feldspar granite (phase III). These phases are arranged according to their relative ages while the country rocks include ophiolitic mélange and metagabbro–diorite complex. It is also confirmed that the granitic pluton is invaded by dyke swarms which is trending in N–S direction. Geochemically, results show that the granodiorite is calc-alkaline, I-type and formed under subduction tectonic regime. Monzogranite falls within the alkaline and highly fractionated calc-alkaline granites, whereas syeno-alkali feldspar granite extends into proper alkaline granitoids field. Monzogranite and syeno-alkali feldspar granite belong to the A₂-subtype granite. This A₂-subtype granite was probably formed in an extensional regime, subsequent to subduction which can lead to tensional break-up of the crust (i.e., post-collisional, post-orogenic granites). The monzogranite and the syeno-alkali feldspar granite were probably formed by partial melting of relatively anhydrous lower crust source and/or tonalite to granodiorite is viable alternative to the granulite source.     

Land transformation assessment using the integration of remote sensing and GIS techniques: a case study of Al-Anbar Province,Iraq

Human activities and climate changes significantly affect our environment, altering hydrologic cycles. Several environmental, social, political, and economical factors contribute to land transformation as well as environmental changes. This study first identified the most critical factors that affect the environment in Al-Anbar city including population growth, urbanization expansion, bare land expansion, and reduction in vegetation cover. The combination of remote sensing data and fuzzy analytic hierarch process (Fuzzy AHP) enabled exploration of land transformations and environmental changes in the study area during 2001 to 2013 in terms of long and short-term changes. Results of land transformation showed that the major changes in water bodies increased radically (94 %) from the long-term change in 2001 to 2013 because of water policies. In addition, the urban class expanded in two short-term periods (2001–2007 and 2007–2013), representing net changes of 46 and 60 %, respectively. Finally, barren land showed 25 % reduction in the first period because of the huge expansion of water in the lake; a small percentage of growth gain was observed in the second period. Based on the land transformation results, the environmental degradation assessment showed that the study area generally had high level of environmental degradation. The degradation was mostly in the center and the north part of the study area. This study suggested for further studies to include other factors that also responsible for environmental degradation such as water quality and desertification threatening.     

River bank erosion hazard study of river Ganga,upstream of Farakka barrage using remote sensing and GIS

This study has been carried out to analyze and report the river bank erosion hazard due to morphometric change of the Ganga River (also called Ganges in English) in the upstream of Farakka Barrage up to Rajmahal. Morphometric parameters, such as, Sinuosity, Braidedness Index, and percentage of the island area to the total river reach area were measured for the year of 1955, 1977, 1990, 2001, 2003, and 2005 from LANDSAT and IRS satellite images. The analysis shows that there is a drastic increase in all of those parameters over the period of time. This study has found that bank failure is because of certain factors like soil stratification of the river bank, presence of hard rocky area (Rajmahal), high load of sediment and difficulty of dredging and construction of Farakka Barrage as an obstruction to the natural river flow. For the increasing sinuosity, the river has been engulfing the large areas of left bank every year. The victims are mostly Manikchak and Kaliachak-II blocks of Malda district, with a loss of around 1,670 ha agricultural land since 1977. Temporal shift measurements for the river reach between Farakka and Rajmahal has been done with help of 22 cross-sections in this reach. Erosion impact area has also been estimated to emphasize the devastating nature of the hazard.     

遥感技术在断裂研究中的应用——以张家口—蓬莱断裂带为例

张家口一蓬莱断裂带是一条北西西向活动断裂带。本文选取ETM+光学影像和SRTM高程影像作为主要数据源,结合研究区已有地质资料研究发现该带断裂构造的北西西向线性特征明显。从水系分布和错断地形等地貌标志判断,该断裂具有左阶组合样式和左行走滑活动特征。据遥感影像综合特征,可将该带分为张家口段、延庆-怀来段和北京一天津段,影像特征分段性显著,并与断裂带的分段性一致。研究结果表明,张家口-蓬莱断裂具有左行走滑的运动学特征,限制或错断北北东或北东向断裂,并且控制该区域的左阶雁列式第四纪盆地群和第四纪冲洪积物的分布。该断裂带各段对不同规模的水系分布和形态影响比较大,且北京-天津地区的华北平原段断裂对第四纪冲洪积扇和沿海地区的贝壳堤的形态和分布有一定的控制作用。地球物理深部数据和野外地质考察资料也证实了遥感解泽的结果,证明遥感技术在探查断裂构造空间展布和活动性鉴定中有着广泛的应用前景。     

Study on the oasis landscape fragmentation in northwestern China by using remote sensing data and GIS: a case study of Jinta oasis

The purpose of this study is to investigate the oasis landscape fragmentation in northwestern China’s arid regions. Landscape maps of Jinta oasis were compiled by using GIS based on Landsat TM data of 1990 and 2000. Landscape indexes for evaluating fragmentation are patch area, patch density, corridor density and split index. Results indicated many difference. First, between the years 1990 and 2000, the landscape fragmentation in Jinta oasis decreased slightly. Second, the area of the matrix decreased at the class level. The landscape fragmentation of the matrix (bare soil) increased as a result of increased influence of human activities on matrix and was opposite to the irrigated farmland whose area is larger and more aggregated in 2000 than in 1990. Third, dense corridor system is one of the most prominent characteristics of the arid regions. It is one of the key factors resulting in the landscape fragmentation; especially the fragmentation within the same patch types. The corridor density of irrigated farmland, residential area and forestland were quite large in Jinta oasis both in 1990 and 2000. The pattern of Jinta oasis is characterized by agricultural oasis embedded in Gobi and in the desert, where the ecosystem was disturbed strongly by the intense human activities.