This study provides a map of glacial geomorphology of Mt. Asralt Khairkhan and Mt. Baga Khentii Saridag in Khentii Mountain Range in northeastern Mongolia. In the Khentii Mountain Range, only two types of glacial land...This study provides a map of glacial geomorphology of Mt. Asralt Khairkhan and Mt. Baga Khentii Saridag in Khentii Mountain Range in northeastern Mongolia. In the Khentii Mountain Range, only two types of glacial landforms including glacial cirques and terminal moraines are observed for the paleoglacial reconstructions of Mt. Asralt Khairkhan and Mt. Baga Khentii Saridag, and are mapped based on a mapping from 30 m resolution ASTER DEM and Landsat 8 satellite imagery. Spatial distribution of the glacial landforms indicates that the Khentii Mountain Range has experienced valley glaciations with small ice caps centered on the high mountains. The glacial cirques mark numerous glacial erosional landforms, while the terminal moraines indicate glacial advances and depositional landforms at outlets of valleys. Outer limits of these glacial landforms show their maximum glaciation of 10.0 km2 and 0.7 km2 for Mt. Asralt Khairkhan and Mt. Baga Khentii Saridag, respectively. This study demonstrates that spatial analysis of the glacial landforms is crucial for reviewing the paleoglacier extent. The map of the glacial geomorphology will be a key for further detailed studies in paleoglaciology and paleoclimate of the mountain range.展开更多
The Kumaun Himalaya is well-known as a geologically and tectonically complex region that amplifies mass wasting processes,particularly landslides.This study attempts to investigate the interplay between landslide dist...The Kumaun Himalaya is well-known as a geologically and tectonically complex region that amplifies mass wasting processes,particularly landslides.This study attempts to investigate the interplay between landslide distribution and the lithotectonic regime of Darma Valley,Kumaun Himalaya.A landslide inventory comprising 295 landslides in the area has been prepared and several morphotectonic proxies such as valley floor width to height ratio(Vf),stream length gradient index(SL),and hypsometric integral(HI)have been used to infer tectonic regime.Morphometric analysis,including basic,linear,aerial,and relief aspects,of 59 fourth-order sub-basins,has been carried out to estimate erosion potential in the study area.The result demonstrates that 46.77%of the landslides lie in very high,20.32%in high,21.29%in medium,and 11.61%in low erosion potential zones respectively.In order to determine the key parameters controlling erosion potential,two multivariate statistical methods namely Principal Component Analysis(PCA)and Agglomerative Hierarchical Clustering(AHC)were utilized.PCA reveals that the Higher Himalayan Zone(HHZ)has the highest erosion potential due to the presence of elongated sub-basins characterized by steep slopes and high relief.The clusters created through AHC exhibit positive PCA values,indicating a robust correlation between PCA and AHC.Furthermore,the landslide density map shows two major landslide hotspots.One of these hotspots lies in the vicinity of highly active Munsiyari Thrust(MT),while the other is in the Pandukeshwar formation within the MT's hanging wall,characterized by a high exhumation rate.High SL and low Vf values along these hotspots further corroborate that the occurrence of landslides in the study area is influenced by tectonic activity.This study,by identifying erosionprone areas and elucidating the implications of tectonic activity on landslide distribution,empowers policymakers and government agencies to develop strategies for hazard assessment and effective landslide risk mitigation,consequently safeguarding lives and communities.展开更多
Located in Southeastern Chad. The Iro lake offers a great opportunity for the study of Precambrian formations and their Phanerozoic cover. Pluton is a Cal-alkaline granite. Due to its geographical location and geologi...Located in Southeastern Chad. The Iro lake offers a great opportunity for the study of Precambrian formations and their Phanerozoic cover. Pluton is a Cal-alkaline granite. Due to its geographical location and geological features, it holds crucial information for understanding the evolution of the Saharan Meta craton (central Africa), which remains poorly studied. One of the objectives is to map the formations Precambrian age in Southeastern Chad. Based on the petrographic and geochemical results, we identified granitoids of pan-African age (biotite granite, aplite granite and pegmatite granite). This Precambrian basement is covered with sedimentary formations (clays, argillites, lateritic cuirasses, etc.). The mineral assemblage is characteristic of acid rocks. Geochemistry reveals rocks with a high SiO2 range (62% - 77%) giving sub-alkaline to calc-alkaline acid rocks with high k (4.62% to 6.39%). The granitoids are classified as S-type hyperaluminous granites. This classification is supported by the presence of peraluminous minerals (e.g., muscovite) within the Iro granitoids, which also have high (>1%). Geochemical variation within the granites is largely due to extensive crystal fractionation. The Pattern of REEs normalized to the primitive mantle shows a pronounced negative Eu anomaly, reflecting the crystallization process and fractional crystallization of plagioclase in the rock, and a positive Yb anomaly. The role of plagioclase fractionation was relatively major during the earlier intrusive stages (consistent with the presence of Eu anomalies) and slightly increased, together with biotite and K-feldspar fractionation, during the later (granitic) rock crystallization. The Pattern of the spider normalized to MORBs shows two pronounced negative anomalies in TiO2 and Cs and a slight negative anomaly in Ba. The loss of Ba, Ti and Cs may be caused by the plagioclase fractionation, apatite and ilmenite crystal. The Ba anomaly is also controlled by the presence of K-feldspar and mica. The observed Ti anomalies are due to the fractionation of magnetite indicating a subduction environment (or remelting of a source from a subduction environment).展开更多
A total of 393 potholes(368 fluvial and 25 marine potholes)were studied at seven different sites in both the fluvial and marine environments.Diverse bedrock properties and large-scale delivery of tools and grinders re...A total of 393 potholes(368 fluvial and 25 marine potholes)were studied at seven different sites in both the fluvial and marine environments.Diverse bedrock properties and large-scale delivery of tools and grinders regulate the dynamic growth,truncation,and amalgamation of potholes.Therefore,the principal objectives of the study are(i)to examine the relationship between the growth of potholes and substrate lithological with structural characteristics(applying geospatial and Schmidt hammer for rock strength analysis)and(ii)to measure the morphology,and size of tools and grinders,processes of truncation and amalgamation in hydro-geomorphic environment using various indices and field techniques.The result showed that large potholes are stretched in the direction of lineament axes and roughly parallel to the river flow direction.Here,the steady growth of pothole depth-diameter is controlled by active bedrock structures,tools,or grinders,and monsoonal high-velocity bank full discharge.Consequently,the deepening and widening of potholes are relatively slow at Bindu,Deuli,and marine beach Neil Island due to fewer structures and little supply of tools or grinders.In small stretches,(Damodar,Subarnarekha,and Rarhu)canyons and gorge-like features(bedrock incision)are formed at Rajrappa,Bhakuyadi,and Guridih sites due to cyclic truncation and amalgamation.Truncation and amalgamation processes restrict the vertical depth threshold value of potholes within 3m,particularly at Rajrappa,Bhakuyadi,and Guridih sites.Scientific study of the pothole's dynamic growth is greatly necessary for the different environmental engineering and river hydraulic projects like excavation,dredging,and dam or barrage construction.Successively,it is essential to compute the cost of rock excavation or dredging,primarily for the mechanical strength of the bedrock river channel and its stability.展开更多
Very few studies have benefited from the synergetic implementation of visible,near-infrared,and shortwave infrared(VNIR-SWIR)spectra and terrain attributes in predicting Pb content in agricultural soils.To fill this g...Very few studies have benefited from the synergetic implementation of visible,near-infrared,and shortwave infrared(VNIR-SWIR)spectra and terrain attributes in predicting Pb content in agricultural soils.To fill this gap,this study aimed to predict lead(Pb)contents in agricultural soils by combining machine learning algorithms(MLAs)with VNIR-SWIR spectra or/and terrain attributes under three distinct approaches.Six MLAs were tested,including artificial neural network(ANN),partial least squares regression,support vector machine(SVM),Gaussian process regression(GPR),extreme gradient boosting(EGB),and Cubist.The VNIR-SWIR spectral data were preprocessed by methods of discrete wavelet transformation,logarithmic transformation-Savitzky Golay smoothing,standard normal variate(SNV),multiplicative scatter correction,first derivative(Fi D),and second derivative.In approach 1,MLAs were combined with the preprocessed VNIR-SWIR spectral data.The Cubist-Fi D combination was the most effective,achieving a coefficient of determination(R2)of 0.63,a concordance correlation coefficient(CCC)of 0.51,a mean absolute error(MAE)of 6.87 mg kg^(-1),and a root mean square error(RMSE)of8.66 mg kg^(-1).In approach 2,MLAs were combined with both preprocessed VNIR-SWIR spectral data and terrain attributes,and the EGB-SNV combination yielded superior results with R2of 0.75,CCC of 0.65,MAE of 5.48 mg kg^(-1),and RMSE of 7.34 mg kg^(-1).Approach 3 combined MLAs and terrain attributes,and Cubist demonstrated the best prediction results,with R^(2) of 0.75,CCC of 0.66,MAE of 6.18 mg kg^(-1),and RMSE of 7.71 mg kg^(-1).The cumulative assessment identified the fusion of terrain properties,SNV-preprocessed VNIR-SWIR spectra,and EGB as the optimal method for estimating Pb content in agricultural soils,yielding the highest R2value and minimal error.Comparatively,GPR,ANN,and SVM techniques achieved higher R2values in approaches 2 and 3 but also exhibited higher estimation errors.In conclusion,the study underscores the significance of using relevant auxiliary datasets and appropriate MLAs for accurate Pb content prediction with minimal error in agricultural soils.The findings contribute valuable insights for developing successful soil management strategies based on predictive modeling.展开更多
Groundwater is the main source of drinking water for large cities in most African countries. In Moundou, for example, the conventional groundwater supply system is failing. To compensate for this state failure, the po...Groundwater is the main source of drinking water for large cities in most African countries. In Moundou, for example, the conventional groundwater supply system is failing. To compensate for this state failure, the population is building boreholes and wells, most of which tap the surface water table, generally referred to as the “water table”. The aim of this study is to characterize these waters in order to assess their level of contamination and, by extension, the degree of pollution of the water table. Major elements such as: Chloride (Cl<sup>-</sup>), Sulfate (SO<sub>4</sub><sup>2-</sup>), Nitrate (NO<sub>3</sub><sup>-</sup>), Calcium (Ca<sup>2+</sup>), magnesium (Mg<sup>2+</sup>), sodium (Na<sup>+</sup>) and potassium (K<sup>+</sup>) were analysed by Liquid Chromatography and the Bicarbonate ion (HCO<sub>3</sub><sup>-</sup>) was determined by the titrimetric method. The methodology applied is based on a combination of hydrochemical techniques and statistical analysis (PCA and CHA). A sampling campaign was carried out during high-water periods. The results of the physico-chemical analyses show mineralization ranging from 7.29 to 3670 μS/cm, with an average of 487.44 μS/cm. The groundwater studied is generally acidic, with a pH ranging from 3.26 to 6.41. Based on their anions, they are classified into four main hydrochemical facies: chloride and sulphate facies, calcium and magnesium facies, sodium and potassium facies and bicarbonate facies. The various correlations between major ions and statistical analyses have enabled us to identify three hydrogeochemical processes involved in water mineralization. The dominant process is silicate hydrolysis, followed by cation exchange, then anthropogenic input, which influences mineralization by polluting the water.展开更多
Geomorphological and Quaternarygeological field- and laboratory data (Fig.1) are introduced and interpreted with regard to the maximum Ice Age (LGM) glaciation of the Central-and South Karakoram in the Braldu-, Basna-...Geomorphological and Quaternarygeological field- and laboratory data (Fig.1) are introduced and interpreted with regard to the maximum Ice Age (LGM) glaciation of the Central-and South Karakoram in the Braldu-, Basna-, Shigar-and Indus valley system as well as on the Deosai plateau between the Skardu Basin and the Astor valley (Fig.2). These data result from two research expeditions in the years 1997 and 2000. They show that between c. 60 and 20 Ka the Central Karakorum and its south slope were covered by a continuous c. 125,000 km2 sized ice stream network. This ice stream network flowed together to a joint parent glacier, the Indus glacier. The tongue end of the Indus glacier reached down to 850 ～ 800 m a.s.l. In its centre the surface of this Indus ice stream network reached a height of a good 6000 m. Its most important ice thicknesses amounted to c. 2400 ～ 2900 m.展开更多
Like for most parts of High Asia,researches concerning the Pleistocene landscape evolution of the Leh Basin(34°03' N/77°38' E) have also left contradictions.To push this topic,three up to now unexplo...Like for most parts of High Asia,researches concerning the Pleistocene landscape evolution of the Leh Basin(34°03' N/77°38' E) have also left contradictions.To push this topic,three up to now unexplored Ladakh Range tributaries of the Leh Basin(Stagmo-,Arzu-and Nang-Valley) have been investigated.U-shaped profiles,transfluence passes,moraine mantled and glacially rounded peaks and ridges,roches moutonnées,glacial flank polishings and ground moraines document the former glaciation of the study area.The ice fillings of these tributaries reached a minimum thickness up to 540 m.Even at the valley outlets and on the orographic right side of the Leh Basin,the glaciation was more than 350 m thick.Based on these empirically extracted results,theoretical snow line considerations lead to the conclusion that the whole Leh Basin was filled up by a former Indus-Valley glacier.An ice injection limited to the nourishment areas of the Ladakh Range valleys could not have caused the reconstructed ice cover(down to 3236 m a.s.l.),which is proved by extended ground moraine complexes.Only an Indus ice stream network(most likely during the LGP),nourished by inflowing glaciers of the Ladakh-and Stok Range,explains the widespread existence of the glacial sediments at the outlets of the investigated valleys.展开更多
In this study, a novel approach of the landslide numerical risk factor(LNRF) bivariate model was used in ensemble with linear multivariate regression(LMR) and boosted regression tree(BRT) models, coupled with radar re...In this study, a novel approach of the landslide numerical risk factor(LNRF) bivariate model was used in ensemble with linear multivariate regression(LMR) and boosted regression tree(BRT) models, coupled with radar remote sensing data and geographic information system(GIS), for landslide susceptibility mapping(LSM) in the Gorganroud watershed, Iran. Fifteen topographic, hydrological, geological and environmental conditioning factors and a landslide inventory(70%, or 298 landslides) were used in mapping. Phased array-type L-band synthetic aperture radar data were used to extract topographic parameters. Coefficients of tolerance and variance inflation factor were used to determine the coherence among conditioning factors. Data for the landslide inventory map were obtained from various resources, such as Iranian Landslide Working Party(ILWP), Forestry, Rangeland and Watershed Organisation(FRWO), extensive field surveys, interpretation of aerial photos and satellite images, and radar data. Of the total data, 30% were used to validate LSMs, using area under the curve(AUC), frequency ratio(FR) and seed cell area index(SCAI).Normalised difference vegetation index, land use/land cover and slope degree in BRT model elevation, rainfall and distance from stream were found to be important factors and were given the highest weightage in modelling. Validation results using AUC showed that the ensemble LNRF-BRT and LNRFLMR models(AUC = 0.912(91.2%) and 0.907(90.7%), respectively) had high predictive accuracy than the LNRF model alone(AUC = 0.855(85.5%)). The FR and SCAI analyses showed that all models divided the parameter classes with high precision. Overall, our novel approach of combining multivariate and machine learning methods with bivariate models, radar remote sensing data and GIS proved to be a powerful tool for landslide susceptibility mapping.展开更多
Various soil surface components, such as trees, shrubs and biological crusts, and human recreational activities, e.g., barbecues and trampling by visitors, may divide the area of the urban park into smaller fragments/...Various soil surface components, such as trees, shrubs and biological crusts, and human recreational activities, e.g., barbecues and trampling by visitors, may divide the area of the urban park into smaller fragments/mieroenvironments, differentiated by their microenvironmental conditions, which may differ in soil and vegetation characteristics. The spatial changes in the soil and vegetation characteristics and their causes were investigated in an urban park located south of Tel Aviv-Jaffa, Israel. The area of the park is 0.5 km^2, including groves, a lake, lawns, and rest areas. Soil was sampled in nine microenvironments, of which seven were within the park： under Ceratonia siliqua trees （CsU）, under Ficus sycomorus trees （FLU）, rest area between tables under F. sycomorus （FIB）, rest area under tables under F. sycomorus （FIT）, open area with bare soil （OaS）, open area with biological crust cover （OaC）, and open area covered by herbaceous vegetation （OaV）. Two more microenvironments, planar and sloping open areas （CoP and CoS, respectively） in the vicinity of the park, were used as the controls. Electrical conductivity, concentrations of soluble ions （Mg^2＋, Ca^2＋, Na^＋, K^＋ and HCO3）, pH, contents of organic carbon, calcium carbonate and moisture, and grain size distribution were determined. In addition, herbaceous vegetation cover, number and diversity of herbaceous vegetation species were measured. It was found that soil properties and herbaceous vegetation characteristics varied within the park. Soil organic carbon, electrical conductivity, soluble salts, penetration depth, and vegetation characteristics were affected by human activities, mainly in the rest area between the tables. In contrast, the above characteristics were affected by natural factors mainly in the rest of the microenvironments, which were subjected to low levels of anthropogenic intervention. The heterogeneous structure of the park, as represented by the various microenvironments, offered new habitats and promoted the preservation of natural vegetation.展开更多
The ecogeomorphic processes occurring on semiarid rangelands are reviewed, with emphasis on the source-sink relations and positive feedback loops that existed between shrub patches and intershrub areas, and the way li...The ecogeomorphic processes occurring on semiarid rangelands are reviewed, with emphasis on the source-sink relations and positive feedback loops that existed between shrub patches and intershrub areas, and the way livestock presence affected these interactions. Compared with intershrub areas, the shrub patches had a higher soil porosity, infiltration capacity, water-holding capacity, hydraulic conductivity, structural stability, and organic matter content, and lower bulk density. These differences derived from a host of processes whose intensity was less in the shrub patches, including raindrop impact, mechanical crust formation, overland water flow, soil erosion, evaporative moisture loss, and flock trampling. There was also greater shading of the soil surface; soil and litter deposition; water accumulation; microbial, fungal, and mesofaunal activities in the shrub patches. The overland flow of water carried soil and litter from the intershrub areas to the shrub patches and resulted in microtopographic modifications that tended to strengthen these source-sink relations. Grazing had an impact on these processes, not only at the shrub-intershrub scale but also within the intershrub areas, through the creation of highly compacted trampling routes. The combined role of the above ecogeomorphic processes was to maintain the rangeland＇s functionality. Without these inter-relationships, water loss, soil erosion, and nutrient depletion would occur at the hillside scale, causing degradation of the landscape.展开更多
At a global scale, tree growth in alpine treeline ecotones is limited by low temperatures. At a local scale, however, tree growth at its upper limit depends on multiple interactions of influencing factors and mechanis...At a global scale, tree growth in alpine treeline ecotones is limited by low temperatures. At a local scale, however, tree growth at its upper limit depends on multiple interactions of influencing factors and mechanisms. The aim of our research was to understand local scale effects of soil properties and nutrient cycling on tree growth limitation, and their interactions with other abiotic and biotic factors in a near-natural Himalayan treeline ecotone. Soil samples of different soil horizons, litter, decomposition layers, and foliage samples of standing biomass were collected in four altitudinal zones along three slopes, and were analysed for exchangeable cations and nutrient concentrations, respectively. Additionally, soil and air temperature, soil moisture, precipitation, and tree physiognomy patterns were evaluated. Both soil nutrients and foliar macronutrient concentrations of nitrogen(N), magnesium(Mg), potassium(K), and foliar phosphorus(P) decrease significantly with elevation. Foliar manganese(Mn) concentrations, bycontrast, are extraordinarily high at high elevation sites. Potential constraining factors on tree growth were identified using multivariate statistical approaches. We propose that tree growth, treeline position and vegetation composition are affected by nutrient limitation, which in turn, is governed by low soil temperatures and influenced by soil moisture conditions.展开更多
For the reconstruction of past climate variations,investigations on the history of glaciers are necessary.In the Himalaya,investigations like these have a rather short tradition in comparison with other mountains on e...For the reconstruction of past climate variations,investigations on the history of glaciers are necessary.In the Himalaya,investigations like these have a rather short tradition in comparison with other mountains on earth.At the same time,this area on the southern margin of Tibet is of special interest because of the question as to the monsoon-influence that is connected with the climate-development.Anyhow,the climate of High Asia is of global importance.Here for the further and regionally intensifying answer to this question,a glacial glacier reconstruction is submitted from the CentralHimalaya,more exactly from the Manaslu-massif.Going on down-valley from the glacial-historical investigations of 1977 in the upper Marsyandi Khola(Nadi) and the partly already published results of field campaigns in the middle Marsyandi Khola and the Damodar- and Manaslu Himal in the years 1995,2000,2004 and 2007,new geomorphological and geological field- and laboratory data are introduced here from the Ngadi(Nadi) Khola and the lower Marsyandi Nadi from the inflow of the Ngadi(Nadi) Khola down to the southern mountain foreland.There has existed a connected ice-stream-network drained down to the south by a 2,100-2,200 m thick and 120 km long Marsyandi Nadi main valley glacier.At a height of the valley bottom of c.1,000 m a.s.l.the Ngadi Khola glacier joined the still c.1,300 m thick Marsyandi parent glacier from the Himalchuli-massif(Nadi(Ngadi) Chuli) – the south spur of the Manaslu Himal.From here the united glacier tongue flowed down about a further 44 km to the south up to c.400 m a.s.l.(27°57'38 "N/84°24'56" E) into the Himalaya fore-chains and thus reached one of or the lowest past ice margin position of the Himalayas.The glacial(LGP(Last glacial period),LGM(Last glacial maximum) Würm,Stage 0,MIS 3-2) climatic snowline(ELA = equilibrium line altitude) has run at 3,900 to 4,000 m a.s.l.and thus c.1,500 altitude meters below the current ELA(Stage XII) at 5,400-5,500 m a.s.l.The reconstructed,maximum lowering of the climatic snowline(ΔELA = depression of the equilibrium line altitude) about 1,500 m corresponds at a gradient of 0.6°C per 100 altitude meters to a High Glacial decrease in temperature of 9°C(0.6 × 15 = 9).At that time the Tibetan inland ice has caused a stable cold high,so that no summer monsoon can have existed there.Accordingly,during the LGP the precipitation was reduced,so that the cooling must have come to more than only 9°C.展开更多
Over the past few years, OSL and TCN datings of glacial material from High Asia have come into fashion. To this day, however, these techniques do not permit safe calibration. The intensity of the cosmic ray flux is be...Over the past few years, OSL and TCN datings of glacial material from High Asia have come into fashion. To this day, however, these techniques do not permit safe calibration. The intensity of the cosmic ray flux is being modulated by the solar and terrestrial magnetic fields and their secular fluctuations in the past. So far, these variations cannot be converted into the respective local TCN production rates for High Asia. We have reason to believe that the ages that are being calculated despite these uneertainties are generally overestimated. This assessment is supported by eonventional radiocarbon dates and above＂ all by the glacial chronology developed independently on the basis of the Quaternary geological method. The strongly emerging evidence for a much more extensive LGM glaciation of High Asia is, however, either being ignored or rejected by many authors, solely on the basis of the above-mentioned uncalibrated datings. This self-conceit based on the ＂dating fallacy＂, as we call it, should be avoided since it goes decidedly against the standards of the scientific method established in Quaternary geology and makes a fundamental scientific discussion impossible.展开更多
The geomorphic studies are extremely dependent on the quality and spatial resolution of digital elevation model(DEM)data.The unique terrain characteristics of a particular landscape are derived from DEM,which are resp...The geomorphic studies are extremely dependent on the quality and spatial resolution of digital elevation model(DEM)data.The unique terrain characteristics of a particular landscape are derived from DEM,which are responsible for initiation and development of ephemeral gullies.As the topographic features of an area significantly influences on the erosive power of the water flow,it is an important task the extraction of terrain features from DEM to properly research gully erosion.Alongside,topography is highly correlated with other geo-environmental factors i.e.geology,climate,soil types,vegetation density and floristic composition,runoff generation,which ultimately influences on gully occurrences.Therefore,terrain morphometric attributes derived from DEM data are used in spatial prediction of gully erosion susceptibility(GES)mapping.In this study,remote sensing-Geographic information system(GIS)techniques coupled with machine learning(ML)methods has been used for GES mapping in the parts of Semnan province,Iran.Current research focuses on the comparison of predicted GES result by using three types of DEM i.e.Advanced Land Observation satellite(ALOS),ALOS World 3D-30 m(AW3D30)and Advanced Space borne Thermal Emission and Reflection Radiometer(ASTER)in different resolutions.For further progress of our research work,here we have used thirteen suitable geo-environmental gully erosion conditioning factors(GECFs)based on the multi-collinearity analysis.ML methods of conditional inference forests(Cforest),Cubist model and Elastic net model have been chosen for modelling GES accordingly.Variable’s importance of GECFs was measured through sensitivity analysis and result show that elevation is the most important factor for occurrences of gullies in the three aforementioned ML methods(Cforest=21.4,Cubist=19.65 and Elastic net=17.08),followed by lithology and slope.Validation of the model’s result was performed through area under curve(AUC)and other statistical indices.The validation result of AUC has shown that Cforest is the most appropriate model for predicting the GES assessment in three different DEMs(AUC value of Cforest in ALOS DEM is 0.994,AW3D30 DEM is 0.989 and ASTER DEM is 0.982)used in this study,followed by elastic net and cubist model.The output result of GES maps will be used by decision-makers for sustainable development of degraded land in this study area.展开更多
The prediction of incipient motion has had great importance to the theory of sediment transport. The most commonly used methods are based on the concept of critical shear stress and employ an approach similar, or iden...The prediction of incipient motion has had great importance to the theory of sediment transport. The most commonly used methods are based on the concept of critical shear stress and employ an approach similar, or identical, to the Shields diagram. An alternative method that uses the movability number, defined as the ratio of the shear velocity to the particle＇s settling velocity, was employed in this study. A large amount of experimental data were used to develop an empirical incipient motion criterion based on the movability number. It is shown that this approach can provide a simple and accurate method of computing the threshold condition for sediment motion.展开更多
Water trapped in glaciers and in lakes impounded by landforms created by glaciers (glacial lakes) are an important component of the hydrology and water resources in high mountain areas of Central Asia. Changes in mode...Water trapped in glaciers and in lakes impounded by landforms created by glaciers (glacial lakes) are an important component of the hydrology and water resources in high mountain areas of Central Asia. Changes in modern glaciers and glacial lakes are an important component of the hydrology of watersheds in the Mongolian Altai and Khuvsgul Mountain Ranges, western and northern Mongolia, respectively. Here we focus on Mt. Ikh Turgen and Mt. Munkh Saridag, isolated mountains of the Mongolian Altai and Khuvsgul Mountain Ranges, respectively. We use remote sensing to track changes in modern glaciers over time with mapping at scales of 1:200,000 for Mt. Ikh Turgen and 1:90,000 for Mt. Munkh Saridag based on imagery from Google Earth, 30 m resolution Aster Digital Elevation Model (DEM) and 30 m resolution Landsat 5 TM. Mt. Ikh Turgen lost 45.6% of its total glacier area between 1970 (41.4 km2) and 2011 (18.9 km2) and the Equilibrium Line Altitude (ELA) of the glaciers increased in elevation by 98 m and 144 m on north and south aspects, respectively. Mt. Munkh Saridag lost 57.3% of its total glacier area between 1970 (901 m2) and 2007 (381 m2) and the local ELA rose by 47 m and 80 m on north and south aspects, respectively. These mountains are located at similar latitudes, and so the greater percentage loss of glacier area in Mt. Munkh Saridag and faster changes in ELAs in Mt. Ikh Turgen may reflect variations in elevation and aspect, duration of solar radiation, and vulnerability to solar radiation, as well as variations in glacier scale. This study demonstrates the importance of spatial analyses of modern glaciers in understanding the context of hydrological changes within which any sustainable water resource management plan must be situated.展开更多
Flood probability maps are essential for a range of applications,including land use planning and developing mitigation strategies and early warning systems.This study describes the potential application of two archite...Flood probability maps are essential for a range of applications,including land use planning and developing mitigation strategies and early warning systems.This study describes the potential application of two architectures of deep learning neural networks,namely convolutional neural networks(CNN)and recurrent neural networks(RNN),for spatially explicit prediction and mapping of flash flood probability.To develop and validate the predictive models,a geospatial database that contained records for the historical flood events and geo-environmental characteristics of the Golestan Province in northern Iran was constructed.The step-wise weight assessment ratio analysis(SWARA)was employed to investigate the spatial interplay between floods and different influencing factors.The CNN and RNN models were trained using the SWARA weights and validated using the receiver operating characteristics technique.The results showed that the CNN model(AUC=0.832,RMSE=0.144)performed slightly better than the RNN model(AUC=0.814,RMSE=0.181)in predicting future floods.Further,these models demonstrated an improved prediction of floods compared to previous studies that used different models in the same study area.This study showed that the spatially explicit deep learning neural network models are successful in capturing the heterogeneity of spatial patterns of flood probability in the Golestan Province,and the resulting probability maps can be used for the development of mitigation plans in response to the future floods.The general policy implication of our study suggests that design,implementation,and verification of flood early warning systems should be directed to approximately 40%of the land area characterized by high and very susceptibility to flooding.展开更多
The use of remote sensing techniques and subsequent analysis by means of geographical information system (GIS) offers an effective method for monitoring temporal and spatial changes of landscapes. This work studies th...The use of remote sensing techniques and subsequent analysis by means of geographical information system (GIS) offers an effective method for monitoring temporal and spatial changes of landscapes. This work studies the urbanization processes and associated threats to natural ecosystems and resources in the metropolitan areas of Berlin and Erlangen-Fürth-Nürnber?Schwabach (EFNS). To compute the land use/cover (LULC) of the study areas, a supervised classification of “maximum likelihood” using Landsat data for the years of 1972, 1985, 1998, 2003, and 2015 is used. Results show that the built-up area is the dominant land use in both regions throughout the study period. This land use has increased at the expense of green and open areas in EFNS and at the expense of agricultural land in Berlin. Likewise, 5% of forest in EFNS is replaced with urban infrastructure. However, the amount of forest in Berlin increased by 3%. While EFNS experienced relatively big changes in its water bodies from 1972 to 1985, changes in water bodies in Berlin were rather slight during the last 40 years. The overall accuracy of our remotely sensed LULC maps was between 88% and 94% in Berlin and between 85.87% and 87.4% for EFNS. The combination of remote sensing and GIS appears to be an indispensable tool for monitoring changes in LULC in urban areas and help improving LU planning to avoid environmental and ecological problems.展开更多
文摘This study provides a map of glacial geomorphology of Mt. Asralt Khairkhan and Mt. Baga Khentii Saridag in Khentii Mountain Range in northeastern Mongolia. In the Khentii Mountain Range, only two types of glacial landforms including glacial cirques and terminal moraines are observed for the paleoglacial reconstructions of Mt. Asralt Khairkhan and Mt. Baga Khentii Saridag, and are mapped based on a mapping from 30 m resolution ASTER DEM and Landsat 8 satellite imagery. Spatial distribution of the glacial landforms indicates that the Khentii Mountain Range has experienced valley glaciations with small ice caps centered on the high mountains. The glacial cirques mark numerous glacial erosional landforms, while the terminal moraines indicate glacial advances and depositional landforms at outlets of valleys. Outer limits of these glacial landforms show their maximum glaciation of 10.0 km2 and 0.7 km2 for Mt. Asralt Khairkhan and Mt. Baga Khentii Saridag, respectively. This study demonstrates that spatial analysis of the glacial landforms is crucial for reviewing the paleoglacier extent. The map of the glacial geomorphology will be a key for further detailed studies in paleoglaciology and paleoclimate of the mountain range.
基金CSIR for providing financial assistance(09/0420(11800)/2021EMR-I)。
文摘The Kumaun Himalaya is well-known as a geologically and tectonically complex region that amplifies mass wasting processes,particularly landslides.This study attempts to investigate the interplay between landslide distribution and the lithotectonic regime of Darma Valley,Kumaun Himalaya.A landslide inventory comprising 295 landslides in the area has been prepared and several morphotectonic proxies such as valley floor width to height ratio(Vf),stream length gradient index(SL),and hypsometric integral(HI)have been used to infer tectonic regime.Morphometric analysis,including basic,linear,aerial,and relief aspects,of 59 fourth-order sub-basins,has been carried out to estimate erosion potential in the study area.The result demonstrates that 46.77%of the landslides lie in very high,20.32%in high,21.29%in medium,and 11.61%in low erosion potential zones respectively.In order to determine the key parameters controlling erosion potential,two multivariate statistical methods namely Principal Component Analysis(PCA)and Agglomerative Hierarchical Clustering(AHC)were utilized.PCA reveals that the Higher Himalayan Zone(HHZ)has the highest erosion potential due to the presence of elongated sub-basins characterized by steep slopes and high relief.The clusters created through AHC exhibit positive PCA values,indicating a robust correlation between PCA and AHC.Furthermore,the landslide density map shows two major landslide hotspots.One of these hotspots lies in the vicinity of highly active Munsiyari Thrust(MT),while the other is in the Pandukeshwar formation within the MT's hanging wall,characterized by a high exhumation rate.High SL and low Vf values along these hotspots further corroborate that the occurrence of landslides in the study area is influenced by tectonic activity.This study,by identifying erosionprone areas and elucidating the implications of tectonic activity on landslide distribution,empowers policymakers and government agencies to develop strategies for hazard assessment and effective landslide risk mitigation,consequently safeguarding lives and communities.
文摘Located in Southeastern Chad. The Iro lake offers a great opportunity for the study of Precambrian formations and their Phanerozoic cover. Pluton is a Cal-alkaline granite. Due to its geographical location and geological features, it holds crucial information for understanding the evolution of the Saharan Meta craton (central Africa), which remains poorly studied. One of the objectives is to map the formations Precambrian age in Southeastern Chad. Based on the petrographic and geochemical results, we identified granitoids of pan-African age (biotite granite, aplite granite and pegmatite granite). This Precambrian basement is covered with sedimentary formations (clays, argillites, lateritic cuirasses, etc.). The mineral assemblage is characteristic of acid rocks. Geochemistry reveals rocks with a high SiO2 range (62% - 77%) giving sub-alkaline to calc-alkaline acid rocks with high k (4.62% to 6.39%). The granitoids are classified as S-type hyperaluminous granites. This classification is supported by the presence of peraluminous minerals (e.g., muscovite) within the Iro granitoids, which also have high (>1%). Geochemical variation within the granites is largely due to extensive crystal fractionation. The Pattern of REEs normalized to the primitive mantle shows a pronounced negative Eu anomaly, reflecting the crystallization process and fractional crystallization of plagioclase in the rock, and a positive Yb anomaly. The role of plagioclase fractionation was relatively major during the earlier intrusive stages (consistent with the presence of Eu anomalies) and slightly increased, together with biotite and K-feldspar fractionation, during the later (granitic) rock crystallization. The Pattern of the spider normalized to MORBs shows two pronounced negative anomalies in TiO2 and Cs and a slight negative anomaly in Ba. The loss of Ba, Ti and Cs may be caused by the plagioclase fractionation, apatite and ilmenite crystal. The Ba anomaly is also controlled by the presence of K-feldspar and mica. The observed Ti anomalies are due to the fractionation of magnetite indicating a subduction environment (or remelting of a source from a subduction environment).
文摘A total of 393 potholes(368 fluvial and 25 marine potholes)were studied at seven different sites in both the fluvial and marine environments.Diverse bedrock properties and large-scale delivery of tools and grinders regulate the dynamic growth,truncation,and amalgamation of potholes.Therefore,the principal objectives of the study are(i)to examine the relationship between the growth of potholes and substrate lithological with structural characteristics(applying geospatial and Schmidt hammer for rock strength analysis)and(ii)to measure the morphology,and size of tools and grinders,processes of truncation and amalgamation in hydro-geomorphic environment using various indices and field techniques.The result showed that large potholes are stretched in the direction of lineament axes and roughly parallel to the river flow direction.Here,the steady growth of pothole depth-diameter is controlled by active bedrock structures,tools,or grinders,and monsoonal high-velocity bank full discharge.Consequently,the deepening and widening of potholes are relatively slow at Bindu,Deuli,and marine beach Neil Island due to fewer structures and little supply of tools or grinders.In small stretches,(Damodar,Subarnarekha,and Rarhu)canyons and gorge-like features(bedrock incision)are formed at Rajrappa,Bhakuyadi,and Guridih sites due to cyclic truncation and amalgamation.Truncation and amalgamation processes restrict the vertical depth threshold value of potholes within 3m,particularly at Rajrappa,Bhakuyadi,and Guridih sites.Scientific study of the pothole's dynamic growth is greatly necessary for the different environmental engineering and river hydraulic projects like excavation,dredging,and dam or barrage construction.Successively,it is essential to compute the cost of rock excavation or dredging,primarily for the mechanical strength of the bedrock river channel and its stability.
基金supported by an institutional Ph.D.grant(No.21130/1312/3131)from the Faculty of Agrobiology,Food,and Natural Resources at the Czech University of Life Sciences Prague(CZU),Czech Republic。
文摘Very few studies have benefited from the synergetic implementation of visible,near-infrared,and shortwave infrared(VNIR-SWIR)spectra and terrain attributes in predicting Pb content in agricultural soils.To fill this gap,this study aimed to predict lead(Pb)contents in agricultural soils by combining machine learning algorithms(MLAs)with VNIR-SWIR spectra or/and terrain attributes under three distinct approaches.Six MLAs were tested,including artificial neural network(ANN),partial least squares regression,support vector machine(SVM),Gaussian process regression(GPR),extreme gradient boosting(EGB),and Cubist.The VNIR-SWIR spectral data were preprocessed by methods of discrete wavelet transformation,logarithmic transformation-Savitzky Golay smoothing,standard normal variate(SNV),multiplicative scatter correction,first derivative(Fi D),and second derivative.In approach 1,MLAs were combined with the preprocessed VNIR-SWIR spectral data.The Cubist-Fi D combination was the most effective,achieving a coefficient of determination(R2)of 0.63,a concordance correlation coefficient(CCC)of 0.51,a mean absolute error(MAE)of 6.87 mg kg^(-1),and a root mean square error(RMSE)of8.66 mg kg^(-1).In approach 2,MLAs were combined with both preprocessed VNIR-SWIR spectral data and terrain attributes,and the EGB-SNV combination yielded superior results with R2of 0.75,CCC of 0.65,MAE of 5.48 mg kg^(-1),and RMSE of 7.34 mg kg^(-1).Approach 3 combined MLAs and terrain attributes,and Cubist demonstrated the best prediction results,with R^(2) of 0.75,CCC of 0.66,MAE of 6.18 mg kg^(-1),and RMSE of 7.71 mg kg^(-1).The cumulative assessment identified the fusion of terrain properties,SNV-preprocessed VNIR-SWIR spectra,and EGB as the optimal method for estimating Pb content in agricultural soils,yielding the highest R2value and minimal error.Comparatively,GPR,ANN,and SVM techniques achieved higher R2values in approaches 2 and 3 but also exhibited higher estimation errors.In conclusion,the study underscores the significance of using relevant auxiliary datasets and appropriate MLAs for accurate Pb content prediction with minimal error in agricultural soils.The findings contribute valuable insights for developing successful soil management strategies based on predictive modeling.
文摘Groundwater is the main source of drinking water for large cities in most African countries. In Moundou, for example, the conventional groundwater supply system is failing. To compensate for this state failure, the population is building boreholes and wells, most of which tap the surface water table, generally referred to as the “water table”. The aim of this study is to characterize these waters in order to assess their level of contamination and, by extension, the degree of pollution of the water table. Major elements such as: Chloride (Cl<sup>-</sup>), Sulfate (SO<sub>4</sub><sup>2-</sup>), Nitrate (NO<sub>3</sub><sup>-</sup>), Calcium (Ca<sup>2+</sup>), magnesium (Mg<sup>2+</sup>), sodium (Na<sup>+</sup>) and potassium (K<sup>+</sup>) were analysed by Liquid Chromatography and the Bicarbonate ion (HCO<sub>3</sub><sup>-</sup>) was determined by the titrimetric method. The methodology applied is based on a combination of hydrochemical techniques and statistical analysis (PCA and CHA). A sampling campaign was carried out during high-water periods. The results of the physico-chemical analyses show mineralization ranging from 7.29 to 3670 μS/cm, with an average of 487.44 μS/cm. The groundwater studied is generally acidic, with a pH ranging from 3.26 to 6.41. Based on their anions, they are classified into four main hydrochemical facies: chloride and sulphate facies, calcium and magnesium facies, sodium and potassium facies and bicarbonate facies. The various correlations between major ions and statistical analyses have enabled us to identify three hydrogeochemical processes involved in water mineralization. The dominant process is silicate hydrolysis, followed by cation exchange, then anthropogenic input, which influences mineralization by polluting the water.
文摘Geomorphological and Quaternarygeological field- and laboratory data (Fig.1) are introduced and interpreted with regard to the maximum Ice Age (LGM) glaciation of the Central-and South Karakoram in the Braldu-, Basna-, Shigar-and Indus valley system as well as on the Deosai plateau between the Skardu Basin and the Astor valley (Fig.2). These data result from two research expeditions in the years 1997 and 2000. They show that between c. 60 and 20 Ka the Central Karakorum and its south slope were covered by a continuous c. 125,000 km2 sized ice stream network. This ice stream network flowed together to a joint parent glacier, the Indus glacier. The tongue end of the Indus glacier reached down to 850 ～ 800 m a.s.l. In its centre the surface of this Indus ice stream network reached a height of a good 6000 m. Its most important ice thicknesses amounted to c. 2400 ～ 2900 m.
文摘Like for most parts of High Asia,researches concerning the Pleistocene landscape evolution of the Leh Basin(34°03' N/77°38' E) have also left contradictions.To push this topic,three up to now unexplored Ladakh Range tributaries of the Leh Basin(Stagmo-,Arzu-and Nang-Valley) have been investigated.U-shaped profiles,transfluence passes,moraine mantled and glacially rounded peaks and ridges,roches moutonnées,glacial flank polishings and ground moraines document the former glaciation of the study area.The ice fillings of these tributaries reached a minimum thickness up to 540 m.Even at the valley outlets and on the orographic right side of the Leh Basin,the glaciation was more than 350 m thick.Based on these empirically extracted results,theoretical snow line considerations lead to the conclusion that the whole Leh Basin was filled up by a former Indus-Valley glacier.An ice injection limited to the nourishment areas of the Ladakh Range valleys could not have caused the reconstructed ice cover(down to 3236 m a.s.l.),which is proved by extended ground moraine complexes.Only an Indus ice stream network(most likely during the LGP),nourished by inflowing glaciers of the Ladakh-and Stok Range,explains the widespread existence of the glacial sediments at the outlets of the investigated valleys.
基金supported by the Centre for Advanced Modelling and Geospatial Information Systems(CAMGIS),UTS under grant numbers 321740.2232335,323930,and 321740.2232357
文摘In this study, a novel approach of the landslide numerical risk factor(LNRF) bivariate model was used in ensemble with linear multivariate regression(LMR) and boosted regression tree(BRT) models, coupled with radar remote sensing data and geographic information system(GIS), for landslide susceptibility mapping(LSM) in the Gorganroud watershed, Iran. Fifteen topographic, hydrological, geological and environmental conditioning factors and a landslide inventory(70%, or 298 landslides) were used in mapping. Phased array-type L-band synthetic aperture radar data were used to extract topographic parameters. Coefficients of tolerance and variance inflation factor were used to determine the coherence among conditioning factors. Data for the landslide inventory map were obtained from various resources, such as Iranian Landslide Working Party(ILWP), Forestry, Rangeland and Watershed Organisation(FRWO), extensive field surveys, interpretation of aerial photos and satellite images, and radar data. Of the total data, 30% were used to validate LSMs, using area under the curve(AUC), frequency ratio(FR) and seed cell area index(SCAI).Normalised difference vegetation index, land use/land cover and slope degree in BRT model elevation, rainfall and distance from stream were found to be important factors and were given the highest weightage in modelling. Validation results using AUC showed that the ensemble LNRF-BRT and LNRFLMR models(AUC = 0.912(91.2%) and 0.907(90.7%), respectively) had high predictive accuracy than the LNRF model alone(AUC = 0.855(85.5%)). The FR and SCAI analyses showed that all models divided the parameter classes with high precision. Overall, our novel approach of combining multivariate and machine learning methods with bivariate models, radar remote sensing data and GIS proved to be a powerful tool for landslide susceptibility mapping.
文摘Various soil surface components, such as trees, shrubs and biological crusts, and human recreational activities, e.g., barbecues and trampling by visitors, may divide the area of the urban park into smaller fragments/mieroenvironments, differentiated by their microenvironmental conditions, which may differ in soil and vegetation characteristics. The spatial changes in the soil and vegetation characteristics and their causes were investigated in an urban park located south of Tel Aviv-Jaffa, Israel. The area of the park is 0.5 km^2, including groves, a lake, lawns, and rest areas. Soil was sampled in nine microenvironments, of which seven were within the park： under Ceratonia siliqua trees （CsU）, under Ficus sycomorus trees （FLU）, rest area between tables under F. sycomorus （FIB）, rest area under tables under F. sycomorus （FIT）, open area with bare soil （OaS）, open area with biological crust cover （OaC）, and open area covered by herbaceous vegetation （OaV）. Two more microenvironments, planar and sloping open areas （CoP and CoS, respectively） in the vicinity of the park, were used as the controls. Electrical conductivity, concentrations of soluble ions （Mg^2＋, Ca^2＋, Na^＋, K^＋ and HCO3）, pH, contents of organic carbon, calcium carbonate and moisture, and grain size distribution were determined. In addition, herbaceous vegetation cover, number and diversity of herbaceous vegetation species were measured. It was found that soil properties and herbaceous vegetation characteristics varied within the park. Soil organic carbon, electrical conductivity, soluble salts, penetration depth, and vegetation characteristics were affected by human activities, mainly in the rest area between the tables. In contrast, the above characteristics were affected by natural factors mainly in the rest of the microenvironments, which were subjected to low levels of anthropogenic intervention. The heterogeneous structure of the park, as represented by the various microenvironments, offered new habitats and promoted the preservation of natural vegetation.
文摘The ecogeomorphic processes occurring on semiarid rangelands are reviewed, with emphasis on the source-sink relations and positive feedback loops that existed between shrub patches and intershrub areas, and the way livestock presence affected these interactions. Compared with intershrub areas, the shrub patches had a higher soil porosity, infiltration capacity, water-holding capacity, hydraulic conductivity, structural stability, and organic matter content, and lower bulk density. These differences derived from a host of processes whose intensity was less in the shrub patches, including raindrop impact, mechanical crust formation, overland water flow, soil erosion, evaporative moisture loss, and flock trampling. There was also greater shading of the soil surface; soil and litter deposition; water accumulation; microbial, fungal, and mesofaunal activities in the shrub patches. The overland flow of water carried soil and litter from the intershrub areas to the shrub patches and resulted in microtopographic modifications that tended to strengthen these source-sink relations. Grazing had an impact on these processes, not only at the shrub-intershrub scale but also within the intershrub areas, through the creation of highly compacted trampling routes. The combined role of the above ecogeomorphic processes was to maintain the rangeland＇s functionality. Without these inter-relationships, water loss, soil erosion, and nutrient depletion would occur at the hillside scale, causing degradation of the landscape.
文摘At a global scale, tree growth in alpine treeline ecotones is limited by low temperatures. At a local scale, however, tree growth at its upper limit depends on multiple interactions of influencing factors and mechanisms. The aim of our research was to understand local scale effects of soil properties and nutrient cycling on tree growth limitation, and their interactions with other abiotic and biotic factors in a near-natural Himalayan treeline ecotone. Soil samples of different soil horizons, litter, decomposition layers, and foliage samples of standing biomass were collected in four altitudinal zones along three slopes, and were analysed for exchangeable cations and nutrient concentrations, respectively. Additionally, soil and air temperature, soil moisture, precipitation, and tree physiognomy patterns were evaluated. Both soil nutrients and foliar macronutrient concentrations of nitrogen(N), magnesium(Mg), potassium(K), and foliar phosphorus(P) decrease significantly with elevation. Foliar manganese(Mn) concentrations, bycontrast, are extraordinarily high at high elevation sites. Potential constraining factors on tree growth were identified using multivariate statistical approaches. We propose that tree growth, treeline position and vegetation composition are affected by nutrient limitation, which in turn, is governed by low soil temperatures and influenced by soil moisture conditions.
文摘For the reconstruction of past climate variations,investigations on the history of glaciers are necessary.In the Himalaya,investigations like these have a rather short tradition in comparison with other mountains on earth.At the same time,this area on the southern margin of Tibet is of special interest because of the question as to the monsoon-influence that is connected with the climate-development.Anyhow,the climate of High Asia is of global importance.Here for the further and regionally intensifying answer to this question,a glacial glacier reconstruction is submitted from the CentralHimalaya,more exactly from the Manaslu-massif.Going on down-valley from the glacial-historical investigations of 1977 in the upper Marsyandi Khola(Nadi) and the partly already published results of field campaigns in the middle Marsyandi Khola and the Damodar- and Manaslu Himal in the years 1995,2000,2004 and 2007,new geomorphological and geological field- and laboratory data are introduced here from the Ngadi(Nadi) Khola and the lower Marsyandi Nadi from the inflow of the Ngadi(Nadi) Khola down to the southern mountain foreland.There has existed a connected ice-stream-network drained down to the south by a 2,100-2,200 m thick and 120 km long Marsyandi Nadi main valley glacier.At a height of the valley bottom of c.1,000 m a.s.l.the Ngadi Khola glacier joined the still c.1,300 m thick Marsyandi parent glacier from the Himalchuli-massif(Nadi(Ngadi) Chuli) – the south spur of the Manaslu Himal.From here the united glacier tongue flowed down about a further 44 km to the south up to c.400 m a.s.l.(27°57'38 "N/84°24'56" E) into the Himalaya fore-chains and thus reached one of or the lowest past ice margin position of the Himalayas.The glacial(LGP(Last glacial period),LGM(Last glacial maximum) Würm,Stage 0,MIS 3-2) climatic snowline(ELA = equilibrium line altitude) has run at 3,900 to 4,000 m a.s.l.and thus c.1,500 altitude meters below the current ELA(Stage XII) at 5,400-5,500 m a.s.l.The reconstructed,maximum lowering of the climatic snowline(ΔELA = depression of the equilibrium line altitude) about 1,500 m corresponds at a gradient of 0.6°C per 100 altitude meters to a High Glacial decrease in temperature of 9°C(0.6 × 15 = 9).At that time the Tibetan inland ice has caused a stable cold high,so that no summer monsoon can have existed there.Accordingly,during the LGP the precipitation was reduced,so that the cooling must have come to more than only 9°C.
文摘Over the past few years, OSL and TCN datings of glacial material from High Asia have come into fashion. To this day, however, these techniques do not permit safe calibration. The intensity of the cosmic ray flux is being modulated by the solar and terrestrial magnetic fields and their secular fluctuations in the past. So far, these variations cannot be converted into the respective local TCN production rates for High Asia. We have reason to believe that the ages that are being calculated despite these uneertainties are generally overestimated. This assessment is supported by eonventional radiocarbon dates and above＂ all by the glacial chronology developed independently on the basis of the Quaternary geological method. The strongly emerging evidence for a much more extensive LGM glaciation of High Asia is, however, either being ignored or rejected by many authors, solely on the basis of the above-mentioned uncalibrated datings. This self-conceit based on the ＂dating fallacy＂, as we call it, should be avoided since it goes decidedly against the standards of the scientific method established in Quaternary geology and makes a fundamental scientific discussion impossible.
文摘The geomorphic studies are extremely dependent on the quality and spatial resolution of digital elevation model(DEM)data.The unique terrain characteristics of a particular landscape are derived from DEM,which are responsible for initiation and development of ephemeral gullies.As the topographic features of an area significantly influences on the erosive power of the water flow,it is an important task the extraction of terrain features from DEM to properly research gully erosion.Alongside,topography is highly correlated with other geo-environmental factors i.e.geology,climate,soil types,vegetation density and floristic composition,runoff generation,which ultimately influences on gully occurrences.Therefore,terrain morphometric attributes derived from DEM data are used in spatial prediction of gully erosion susceptibility(GES)mapping.In this study,remote sensing-Geographic information system(GIS)techniques coupled with machine learning(ML)methods has been used for GES mapping in the parts of Semnan province,Iran.Current research focuses on the comparison of predicted GES result by using three types of DEM i.e.Advanced Land Observation satellite(ALOS),ALOS World 3D-30 m(AW3D30)and Advanced Space borne Thermal Emission and Reflection Radiometer(ASTER)in different resolutions.For further progress of our research work,here we have used thirteen suitable geo-environmental gully erosion conditioning factors(GECFs)based on the multi-collinearity analysis.ML methods of conditional inference forests(Cforest),Cubist model and Elastic net model have been chosen for modelling GES accordingly.Variable’s importance of GECFs was measured through sensitivity analysis and result show that elevation is the most important factor for occurrences of gullies in the three aforementioned ML methods(Cforest=21.4,Cubist=19.65 and Elastic net=17.08),followed by lithology and slope.Validation of the model’s result was performed through area under curve(AUC)and other statistical indices.The validation result of AUC has shown that Cforest is the most appropriate model for predicting the GES assessment in three different DEMs(AUC value of Cforest in ALOS DEM is 0.994,AW3D30 DEM is 0.989 and ASTER DEM is 0.982)used in this study,followed by elastic net and cubist model.The output result of GES maps will be used by decision-makers for sustainable development of degraded land in this study area.
文摘The prediction of incipient motion has had great importance to the theory of sediment transport. The most commonly used methods are based on the concept of critical shear stress and employ an approach similar, or identical, to the Shields diagram. An alternative method that uses the movability number, defined as the ratio of the shear velocity to the particle＇s settling velocity, was employed in this study. A large amount of experimental data were used to develop an empirical incipient motion criterion based on the movability number. It is shown that this approach can provide a simple and accurate method of computing the threshold condition for sediment motion.
文摘Water trapped in glaciers and in lakes impounded by landforms created by glaciers (glacial lakes) are an important component of the hydrology and water resources in high mountain areas of Central Asia. Changes in modern glaciers and glacial lakes are an important component of the hydrology of watersheds in the Mongolian Altai and Khuvsgul Mountain Ranges, western and northern Mongolia, respectively. Here we focus on Mt. Ikh Turgen and Mt. Munkh Saridag, isolated mountains of the Mongolian Altai and Khuvsgul Mountain Ranges, respectively. We use remote sensing to track changes in modern glaciers over time with mapping at scales of 1:200,000 for Mt. Ikh Turgen and 1:90,000 for Mt. Munkh Saridag based on imagery from Google Earth, 30 m resolution Aster Digital Elevation Model (DEM) and 30 m resolution Landsat 5 TM. Mt. Ikh Turgen lost 45.6% of its total glacier area between 1970 (41.4 km2) and 2011 (18.9 km2) and the Equilibrium Line Altitude (ELA) of the glaciers increased in elevation by 98 m and 144 m on north and south aspects, respectively. Mt. Munkh Saridag lost 57.3% of its total glacier area between 1970 (901 m2) and 2007 (381 m2) and the local ELA rose by 47 m and 80 m on north and south aspects, respectively. These mountains are located at similar latitudes, and so the greater percentage loss of glacier area in Mt. Munkh Saridag and faster changes in ELAs in Mt. Ikh Turgen may reflect variations in elevation and aspect, duration of solar radiation, and vulnerability to solar radiation, as well as variations in glacier scale. This study demonstrates the importance of spatial analyses of modern glaciers in understanding the context of hydrological changes within which any sustainable water resource management plan must be situated.
基金conducted by the Basic Research Project of the Korea Institute of Geoscience and Mineral Resources(KIGAM)funded by the Ministry of Science and ICT。
文摘Flood probability maps are essential for a range of applications,including land use planning and developing mitigation strategies and early warning systems.This study describes the potential application of two architectures of deep learning neural networks,namely convolutional neural networks(CNN)and recurrent neural networks(RNN),for spatially explicit prediction and mapping of flash flood probability.To develop and validate the predictive models,a geospatial database that contained records for the historical flood events and geo-environmental characteristics of the Golestan Province in northern Iran was constructed.The step-wise weight assessment ratio analysis(SWARA)was employed to investigate the spatial interplay between floods and different influencing factors.The CNN and RNN models were trained using the SWARA weights and validated using the receiver operating characteristics technique.The results showed that the CNN model(AUC=0.832,RMSE=0.144)performed slightly better than the RNN model(AUC=0.814,RMSE=0.181)in predicting future floods.Further,these models demonstrated an improved prediction of floods compared to previous studies that used different models in the same study area.This study showed that the spatially explicit deep learning neural network models are successful in capturing the heterogeneity of spatial patterns of flood probability in the Golestan Province,and the resulting probability maps can be used for the development of mitigation plans in response to the future floods.The general policy implication of our study suggests that design,implementation,and verification of flood early warning systems should be directed to approximately 40%of the land area characterized by high and very susceptibility to flooding.
文摘The use of remote sensing techniques and subsequent analysis by means of geographical information system (GIS) offers an effective method for monitoring temporal and spatial changes of landscapes. This work studies the urbanization processes and associated threats to natural ecosystems and resources in the metropolitan areas of Berlin and Erlangen-Fürth-Nürnber?Schwabach (EFNS). To compute the land use/cover (LULC) of the study areas, a supervised classification of “maximum likelihood” using Landsat data for the years of 1972, 1985, 1998, 2003, and 2015 is used. Results show that the built-up area is the dominant land use in both regions throughout the study period. This land use has increased at the expense of green and open areas in EFNS and at the expense of agricultural land in Berlin. Likewise, 5% of forest in EFNS is replaced with urban infrastructure. However, the amount of forest in Berlin increased by 3%. While EFNS experienced relatively big changes in its water bodies from 1972 to 1985, changes in water bodies in Berlin were rather slight during the last 40 years. The overall accuracy of our remotely sensed LULC maps was between 88% and 94% in Berlin and between 85.87% and 87.4% for EFNS. The combination of remote sensing and GIS appears to be an indispensable tool for monitoring changes in LULC in urban areas and help improving LU planning to avoid environmental and ecological problems.
