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过刊目录

  • 2021年, 18卷, 第10期
    刊出日期：2024-06-19
      
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  • Degradation of a protected mountain area by tourist traffic: case study of the Tatra National Park, Poland
    Joanna FIDELUS-ORZECHOWSKA, El?bieta GORCZYCA, Marcin BUKOWSKI, Kazimierz KRZEMIE?
    2021, 18(10): 2503-2519.
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    Mountain protected areas are characterized by high biodiversity, which makes it a great challenge for managers to maintain a balance between their use and the stability of natural ecosystems. Maintaining that balance is particularly difficult in areas with high tourism pressure. The expected volume of tourist traffic should be considered at the planning stage of the tourist infrastructure development process. Insufficient capacity of tourist infrastructure can lead to environmental degradation, which is hard, or at times impossible, to repair. In our research, we identified patterns of tourist footpath and road functioning in an environmentally protected area with high volumes of tourist traffic. Data from geomorphologic mapping was analyzed in order to identify tourist footpath and road structures in the Tatra National Park(TNP). Fieldwork was conducted in several stages between 1995 and 2019. Orthophotomaps from the years 1977, 2009, 2017 and 2019 were used to identify and compare degraded zones along selected tourist footpaths. Degraded zones were defined as areas surrounding a footpath or tourist road with a mean width larger than or equal to 10 meters, with heavily damaged or completely removed vegetation and exposed, weathered cover, where geomorphic processes that would not take place under normal conditions are readily observable. The examined tourist footpaths and roads vary in terms of their morphometric parameters. Research has shown important differences between mean and maximum footpath width as well as maximum incision depth for the forest zone versus the subalpine and alpine zones. A lack of differences in these parameters was noted between the alpine and subalpine zones. Research has shown that an increase in the surface area of degraded zones found adjacent to tourist footpaths occurred in all the studied geo-ecological zones in the study period. However, the largest increase occurred atop wide ridgelines found in the alpine zone. Degraded zones may be an indication of exceeding the tourist carrying capacity of a mountain tourist area. Mass tourism in TNP contributes to the formation of degraded zones adjacent to footpaths, whose continuous evolution may lead to irreversible changes in local relief.
  • Status and determinants of other gainful activities by farmers in mountainous rural regions of Gilgit-Baltistan, Pakistan
    SHAHZAD Muhammad Abid, AHMED Vaqar, FISCHER Christian
    2021, 18(10): 2520-2539.
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    Non-farm income sources are important for livelihood sustenance, especially in the mountainous regions of developing countries. To implement effective policies to improve economic development, policymakers need insights at the grassroots level. Yet, there is a lack of empirical evidence in the context of Pakistan. This study examines the current situation and the factors influencing the decision by farmers to engage in other gainful activities(OGAs) such as farm diversification and off-farm work in the northern mountainous regions of Pakistan. The study is based on quantitative survey data obtained from 459 farm managers and qualitative data from 24 key informants from five different districts in GilgitBaltistan. Utilizing a logistic regression model, a statistical analysis is conducted on farmer and farm characteristics to investigate the probability of farm managers to engage in OGAs. The survey results show that around 71% of farm managers are engaged in OGAs(with 24% in farm diversification, 61% in offfarm work and 15% in both). The share of female farm managers is 51% in farm diversification while male farm managers dominate off-farm activities(69%). The most prevalent types of farm diversification are the processing of farm products and tourism-related farm work, while the main off-farm activities are setting up grocery stores outside the farm, having salaried jobs or engaging in other non-agricultural business. There are significant differences between farmers with and without OGAs particularly regarding farmer characteristics, agricultural income and some other variables. The logit model results show that farmer characteristics mainly determine off-farm work activities while farm(and other) characteristics mostly explain farm diversification. These findings suggest that OGAs primarily exist as livelihood strategies. Farm diversification is linked with the long-term sustenance of agricultural activities while off-farm work is predominantly driven by economic needs. Both types of OGAs require specific support policies while attention needs to be given not to threaten regional food supply.
  • Landslide mapping and analysis along the China-Pakistan Karakoram Highway based on SBAS-InSAR detection in 2017
    SU Xiao-jun, ZHANG Yi, MENG Xing-min, YUE Dong-xia, MA Jin-hui, GUO Fu-yun, ZHOU Zi-qiang, REHMAN Mohib Ur, KHALID Zainab, CHEN Guan, ZENG Run-qiang, ZHAO Fu-meng
    2021, 18(10): 2540-2564.
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    The Karakoram Highway(KKH), a part of the China–Pakistan Economic Corridor(CPEC), is a major highway connecting northern Pakistan to China. The inventorying and analysis of landslides along KKH are challenging because of poor accessibility, vast study area, limited availability of ground-based datasets, and the complexity of landslide processes in the region. In order to preserve life, property, and infrastructure, and to enable the uninterrupted and efficient operation of the KKH, it is essential to strengthen measures for the prevention and control of geological disasters. In the present study, SBASInSAR(Small Baseline Subsets-Interferometric Synthetic Aperture Radar) was used to process 150 scenes of Sentinel 1-A images in the year 2017 along the Karakoram Highway. A total of 762 landslides, including 57 complex landslides, 126 rock falls, 167 debris slides, and 412 unstable slopes, ranging in size between 0.0017 and 10.63 km2 were identified. Moreover, this study also gains an inventory of 40 active glacier movements in this region. Landslide categorization, displacements characteristics, spatial distribution, and their relationship with various contributing factors have been successfully investigated along the entire KKH using image interpretation and frequency-area statistics. The criteria adopted for landslides categorization is presented in the study. The results showed that the 2-D ground deformation derived in Hunza valley echoes well with the general regional landslides characteristics. The spatial distribution analysis revealed that there are clumped distributions of landslides in the Gaizi, Tashkurgan, and Khunjerab in China, as well as in Hunza valley, and north of Chilas city in Pakistan. Statistical results indicated that these landslides mainly occur on south-facing slopes with a slope angle of 20°– 45° and elevation relief of 550 – 2,100 m. Landslide development is also related to low vegetation cover and weathering effects in mountain gullies. Overall, our study provides scientific data support and theoretical references for prevention, control, and mitigation of geological disasters in the Karakoram region.
  • Triggering mechanism and dynamic process of water-rock flow in Nanfen waste dump in 2010
    CAO Chun-hui, FENG Ji-li, TAO Zhi-gang
    2021, 18(10): 2565-2579.
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    Water-rock flow is a kind of debris flow with more coarse particles and low viscosity, which occurs in many areas of the world. In this work, the water-rock flow that occurred on May 24, 2010, at Nanfen's open-pit mine of China was investigated by combining field investigation, meteorological and hydrological survey with numerical simulation to understand its triggering mechanism and dynamic process. The field data shows that the short-term high-intensity rainfall is the most direct inducement to trigger water-rock flow in the waste dump. The loose shallow gravel soil and the V-shaped valley with a certain slope provide the necessary conditions of the occurrence of water-rock flow in the waste dump. Moreover, the possibility criterion of water-rock flow is presented by analyzing the historical rainfall data. In addition, the smoothed particle hydrodynamics(SPH) method was employed to simulate the waterrock flow under the conditions of Newtonian fluid with uniform distribution of water and coarse-grained materials. The simulating results show that the flow distance, velocity, shape, and deposition profile of water-rock flow are in good agreement with the field observation. The present work is beneficial to the risk assessment and mitigation design of water-rock flow disaster in the waste dump.
  • Failure analysis on a heavy rainfall-induced landslide in Huay Khab Mountain in Northern Thailand
    Veerayut KOMOLVILAS, Weeradetch TANAPALUNGKORN, Panon LATCHAROTE, Suched LIKITLERSUANG
    2021, 18(10): 2580-2596.
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    On 28 th July 2018, a massive landslide occurred in a mountainous area in Northern Thailand. The landslide after ten days of heavy rainfall generated the movement of uphill mountain soil into the populated village. This study presents a comprehensive failure analysis of local rainfallinduced landslides based on topographical and geological information. Rainfall measurement data were gathered from two rainfall stations close to the study area. The rainfall records show that the total monthly rainfalls in 2018 were significantly higher than the average monthly rainfalls over the past decade. Site investigation started with an unmanned aerial photogrammetric survey to generate a digital elevation model. Then, dynamic probing test, microtremor survey, and electrical resistivity survey were carried out along undisturbed soils beside the failed slope to evaluate the thickness of the soft soil cover on top of the rock basement. During the site survey, residual soil samples were collected to determine engineering properties in the laboratory. Finally, a slope stability analysis was performed to assess the landslide hazard based on the results of aerial photogrammetric survey, field exploration, and laboratory tests. The slope stability analysis and rainfall records revealed that the Huay Khab landslide was mainly caused by an increase in the water content of residual soils due to the prolonged rainfall which led to a sharp decrease in the shear strength. This leads to the conclusion that the proposed landslide investigation program could be used to assess the potential of landslide failure due to prolonged rainfall on a local scale.
  • Dynamic prediction of landslide displacement using singular spectrum analysis and stack long short-term memory network
    LI Li-min, Zhang Ming-yue, WEN Zong-zhou
    2021, 18(10): 2597-2611.
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    An accurate landslide displacement prediction is an important part of landslide warning system. Aiming at the dynamic characteristics of landslide evolution and the shortcomings of traditional static prediction models, this paper proposes a dynamic prediction model of landslide displacement based on singular spectrum analysis(SSA) and stack long short-term memory(SLSTM) network. The SSA is used to decompose the landslide accumulated displacement time series data into trend term and periodic term displacement subsequences. A cubic polynomial function is used to predict the trend term displacement subsequence, and the SLSTM neural network is used to predict the periodic term displacement subsequence. At the same time, the Bayesian optimization algorithm is used to determine that the SLSTM network input sequence length is 12 and the number of hidden layer nodes is 18. The SLSTM network is updated by adding predicted values to the training set to achieve dynamic displacement prediction. Finally, the accumulated landslide displacement is obtained by superimposing the predicted value of each displacement subsequence. The proposed model was verified on the Xintan landslide in Hubei Province, China. The results show that when predicting the displacement of the periodic term, the SLSTM network has higher prediction accuracy than the support vector machine(SVM) and auto regressive integrated moving average(ARIMA). The mean relative error(MRE) is reduced by 4.099% and 3.548% respectively, while the root mean square error(RMSE) is reduced by 5.830 mm and 3.854 mm respectively. It is concluded that the SLSTM network model can better simulate the dynamic characteristics of landslides.
  • Microstructure evolution of loess under multiple collapsibility based on nuclear magnetic resonance and scanning electron microscopy
    WANG Hai-man, NI Wan-kui, YUAN Kang-ze, LI Lan, NIE Yong-peng, GUO Ye-xia
    2021, 18(10): 2612-2625.
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    In recent years, the acceleration of urbanization in loess areas has prompted frequent dismantling and reconstruction of old urban areas. Demolition and reconstruction of buildings involve multiple collapses of the foundation. To study microstructure evolution of loess under multiple collapsibility, this paper selects undisturbed loess samples from Guyuan, Northwest China for multiple compression tests. Using nuclear magnetic resonance(NMR) imaging and scanning electron microscopy(SEM) as auxiliary methods, a combination of qualitative and quantitative analyses was used to study the microstructure of loess samples before and after various number of collapses under different pressures. Results show that the loess does undergo multiple collapse under 200 kPa pressure. Pore is an important reason for loess collapse. The initial collapse comes primarily from the compression of macropores and mesopores, and the second collapse comes primarily from mesopore compression. The compression process of loess can be roughly divided into two stages. First, under the action of dissolution and compression, the relative displacement of soil particles occurs. Macropores and mesopores are destroyed first, generating small pores. Second, with increasing pressure and times of collapses, pore compression gradually transforms into small pore compression. During the first collapse, particle aggregates disintegrate due to water and pressure. However, with increasing times of collapses, the contact relationship between particles gradually changes from the point contact to face contact. Loess particles tend to gradually become rounded. The study of the microstructure provides the possibility to further reveal the mechanism of multiple collapsibility of loess.
  • Does polar amplification exist in Antarctic surface during the recent four decades?
    WANG Shi-meng, XIE Ai-hong, ZHU Jiang-ping
    2021, 18(10): 2626-2634.
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    There are numerous studies on polar amplification and its influence on mid-latitude weather and climate. However, assessments on whether polar amplification occurs in Antarctica are rarely conducted. Based on the latest atmospheric reanalysis of ERA5 produced by European Centre for Medium-Range Weather Forecasts(ECMWF), we have defined the Antarctic amplification index, and calculated the trend of annual and seasonal Surface Air Temperature(SAT) mean during 1979-2019 for Antarctic Ice Sheet(AIS) and the trend mean of different meridional sectors of Antarctic sub regions including East Antarctic Ice Sheet(EAIS), West Antarctic Ice Sheet(WAIS) and Antarctic Peninsula(AP). Antarctic amplification shows regional differences and seasonal variations. Antarctica shows a slight warming with the largest magnitude in AP. The temperature anomalies indicate the least fluctuations in austral summer, and the more fluctuations in winter and spring. In austral summer, the warming trend domains EAIS and WAIS, while the cooling trend appears over AP. The zonal mean in Southern Hemisphere maintains a warming trend in the low latitudes, and fluctuates greatly in the middle and high latitudes. The strongest Antarctic amplification phenomenon occurs in spring, with the amplification index of 1.20. For AP, the amplification occurs in austral autumn, and the amplification index is 2.16. At South Pole and the surrounding regions, SAT for land only fluctuates largely and shows different trends in different seasons. The mechanism of Antarctic amplification is unclear till now, and its research suffers from the limitation of measured data. This suggests that future research needs progress in comprehensive ground observation network, remote sensing data accumulation, and high-resolution climate modeling with better representation of both atmospheric and cryospheric processes in Antarctica.
  • Water resources response and prediction under climate change in Tao'er River Basin, Northeast China
    SUN Jia-qi, LI Hong-yan, WANG Xiao-jun, SHAHID Shamsuddin
    2021, 18(10): 2635-2645.
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    Climate change has significantly affected hydrological processes and increased the frequency and severity of water shortage, droughts and floods in northeast China. A study has been conducted to quantify the influence of climate change on the hydrologic process in the Tao'er River Basin(TRB), one of the most prominent regions in northeast China for water contradiction. The Soil and Water Assessment Tool(SWAT) model was calibrated and validated with observed land use and hydro-climatic data and then employed for runoff simulations at upper, middle and lower reaches of the river basin for different climate change scenarios. The results showed that a gradual increase in temperature and decrease in annual precipitation in the basin was projected for the period 2020-2050 for both representative concentration pathways(RCP) 4.5 and 8.5 scenarios. The climate changes would cause a decrease in annual average runoff at basin outlet by 12 and 23 million m3 for RCP4.5 and 8.5, respectively. The future runoff in the upstream and midstream of the basin during 2020-2050 would be-10.8% and-12.1% lower than the observed runoff compared to the base period for RCP4.5, while those would be-5.3% and-10.7% lower for RCP8.5. The future runoff will decrease at three hydrology stations for the assumed future climate scenarios. The results can help us understand the future temperature and precipitation trends and the hydrological cycle process under different climate change scenarios, and provide the basis for the rational allocation and management of water resources under the influence of future climate change in the TRB.
  • Apportioning above-and below-ground effects of moss biocrusts on soil detachment by overland flow in a subtropical climate
    ZHANG Guan-hua, YI Liang, DING Wen-feng, LEI Xu, WANG Yi-ran, SUN Bao-yang, LI Jian-ming
    2021, 18(10): 2646-2655.
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    Biocrusts affect soil detachment through above-ground(top crust's surface covering) and below-ground(sub-crust's binding and bonding, B&B) effects, which might vary with biocrust development or coverage. However, these effects in humid climates are still unclear. This study was conducted to apportion and quantify the surface covering and B&B effects of moss biocrusts with five coverage levels(1%–20%, 20%–40%, 40%–60%, 60%–80%, and 80%–100%) on soil detachment by overland flow in a subtropical humid climate. Two treatments with one being intact moss crusts and one removing the aboveground moss tissues were designed for each coverage level, and bare soil was used as the baseline. The results indicated that soil detachment capacity(Dc) and rill erodibility(Kr) decreased with biocrust coverage. After removing the above-ground moss tissues, the impeding effect of biocrusts on soil detachment weakened, but still increasing soil erosion resistance relative to bare soil. For intact crust, Dc was reduced by 50%–95% compared with bare soil, wherein 36%–55% and 14%–40% were attributed to the surface covering and B&B, respectively. The top crust contributed more than sub-crust to the soil detachment reduction, which were related to but not linear with biocrust coverage. When biocrust coverage reached mid-to-higher level(40%–100%), both top crust and sub-crust steadily contributed to soil detachment reduction with 60% and 40%, respectively. The findings advance a better understanding of the influencing mechanism of biocrusts on soil erosion in humid climates and highlight the importance of saving biocrusts as ecosystem functions.
  • Elevation change of the Urumqi Glacier No.1 derived from Sentinel-1A data
    LIU Jia-liang, ZHAO Jun, LI Zhong-qin, WANG Yan-qiang, SHEN Si-min
    2021, 18(10): 2656-2671.
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    Accurate measurements of glacier elevation changes play a crucial role in various glaciological studies related to glacier dynamics and mass balance. In this paper, glacier elevation changes of Urumqi Glacier No.1 between August 2015 and August 2017 were investigated using Sentinel-1 A data and DInSAR technology. Meanwhile, the atmospheric delay error was corrected with the MODIS MOD05_L2 products. The weight selection iteration method was applied to calibrate the glacier elevation changes in the mass balance years 2015-2016 and 2016-2017. Finally, the geodetic method was employed to calculate the elevation change values of individual stakes of Urumqi Glacier No.1. Moreover, the elevation change values corrected by the weight selection iteration method were verified. Results showed as follows:(1) the elevation of Urumqi Glacier No.1 glacier affected by atmospheric delay was 1.270 cm from 2015 to 2016. The glacier elevation affected by atmospheric delay from 2016 to 2017 was 1.071 cm.(2) The elevation change value of Urumqi Glacier No.1 was-1.101 m from 2015 to 2016, and the elevation of Urumqi Glacier No.1 decreased by 1.299 m from 2016 to 2017. The overall thickness of Urumqi Glacier No. 1 was thinning.(3) By comparing the elevation change results of individual stakes with corresponding points corrected by the weight selection iteration method, the mean squared errors of difference were 0.343 m and 0.280 m between the two mass balance years, respectively.(4) The accuracy of elevation change in non-glaciated areas was 0.039 m from 2015 to 2016 and 0.034 m from 2016 to 2017. Therefore, it is reliable to use Sentinel-1 A data and the study method proposed in this paper to calculate the elevation change of mountain glaciers with very low horizontal movement.
  • Spatial and temporal variations in nitrogen retention effects in a subtropical mountainous basin in Southeast China
    LIU Mei-bing, CHEN Xing-wei, CHEN Ying, GAO Lu, DENG Hai-jun
    2021, 18(10): 2672-2687.
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    Nitrogen retention within a watershed reduces the amount of N exported to the ocean; however, it worsens environmental problems, including surface water eutrophication, aquifer pollution, acid rain, and soil acidification. Here, we adopted the Soil and Water Assessment Tool(SWAT) model to describe the riverine N output and retention effects in the Shanmei Reservoir Basin, a subtropical mountainous basin located in Quanzhou City, Southeast China. The results revealed that farmlands and orchards in the upstream and central parts of the basin were the dominant land use types, which contributed large N yields. Fertilizer application was the key source of riverine N output and N retention within the basin. On average, approximately 64% of anthropogenic N inputs were retained within the basin, whereas 36% of total N was exported to the downstream and coastal areas. The average N retention efficiency was 80% in a dry year, and within the year, N retention occurred in spring and summer and N release occurred in autumn and winter. The annual variation in N retention within the basin was largely dominated by changes in rainfall and runoff, whereas the seasonal characteristics of N retention were mainly affected by fertilization. Even with a large decrease in fertilizer application, owing to the contributions of the residual N pool and river background, the riverine N output still maintained a certain base value. The effects of precipitation, land use types, and agricultural fertilizer on N retention should be comprehensively considered to implement reasonable N management measures.
  • Deep profile soil moisture distribution characteristics for different microtopographies on the semi-arid Loess Plateau, China
    GOU Qing-ping, ZHU Qing-ke, LI Yi-xuan, TIAN Xiang-lei, WANG Peng-xiang, XIN Yun-ling, LUO Shu-yuan
    2021, 18(10): 2688-2697.
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    Soil moisture is a limiting factor for vegetation restoration on the Loess Plateau, China. Micro-topography may cause heterogeneities in the distribution of soil moisture, but little is known about its effect on deep soil moisture. Our study aims to explore the distribution and impact of soil moisture within the upper 10 m of soil for different microtopographies. Taking undisturbed slope as the control, five micro-topographies were selected. Soil moisture over a depth of 0-10 m from 2017 to 2019 was investigated, and soil particle size and soil organic matter were measured. Variance analysis and multiple comparisons were used to analyze the difference in soil moisture for different microtopographies and multiple-linear regression was used to analyze the influence of micro-topography on soil moisture. There are significant differences in soil moisture within the different layers underlying the examined micro-topographies, while the inter-annual variation in soil water storage for the selected microtopographies increase with increased rainfall. The depth of influence of micro-topographic vegetation on soil moisture exceeded 1000 cm for a gully(GU), 740 cm for a sink hole(SH), 480 cm for a scarp(SC), 360 cm for an ephemeral gully(EG) and 220 cm for a platform(PL). Micro-topography will cause the heterogeneous distribution of soil moisture in the shallower layers, which changes the vegetation distribution differences between micro-topographies. This may be the survival strategy of herbaceous vegetation in response to climate change in the Loess Plateau. For future vegetation restoration efforts, we need to pay attention to the influence of microtopography on soil moisture.
  • Conservation of challenging endemic plant species at high risk of extinction in arid mountain ecosystems: a case study of Rosa arabica Crép. in Egypt
    Karim OMAR, Ibrahim ELGAMAL
    2021, 18(10): 2698-2721.
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    Rosa arabica Crép. is a perennial shrub belonging to the family Rosaceae. It is endemic to the high mountain area of St. Catherine Protected Area(SCPA) in southern Sinai, Egypt, and is listed as one of the most 100 threatened plants in the world. Recently, it has been listed as critically endangered by IUCN Red List due to its small extent of occurrence and tiny population size. We reported the continuous decline in habitat quality for this species and the urgent need to carry out on-ground conservation actions. So, this research aims to conserve Rosa arabica through in situ practices by implementing the following steps, respectively: a) evaluate the current conservation status through IUCN Red List to extract the environmental factors controlling the species' distribution necessary for establishing the recovery program, b) determine the potential species habitat suitability under the current climate conditions using Maxent, and c) based on the previous two steps, the translocation process for R. arabica in the suitable habitat will be done after the simple layering process as one of the most effective traditional vegetative methods for wild cultivation for this species. These steps aimed to reduce the impact of threats and the risk of extinction through increasing the population size, the Extent of Occurrence(EOO), and the Area of Occupancy(AOO). We extracted the environmental factors controlling the target species' distribution and habitat suitability range using the IUCN Red List assessment and Species Distribution Model(SDM). The most suitable habitat for R. arabica is predicted in the middle northern parts of SCPA, with the highest suitability in the High Mountains. Precipitation of driest quarter, precipitation of wettest month, precipitation of coldest quarter, and aspect are the highest mean contributors determining the distribution of R. arabica in SCPA. Rosa arabica potential distribution covers 324.4 km2(7.46%) of the total SCPA area(4350 km2). This area is divided into: 18.1 km2 high probability, 124.3 km2 moderate probability, and 182 km2 low probability. After one year of the simple layering process, ten branches rooted and were translocated into three sites that had been previously identified to cover three habitat suitability ranges(high, moderate, and low suitability). After a year of translocation in the wild, the survival rate ranged from 66% to 100%, the geographical range increased by 65%, and the population size by 6.8%. Therefore, if the new individuals continue to grow and adapt it may lead to the expansion of other environmental factors such as climatic and topographical factors that probably increase the resilience of the global population of the species to adverse events. Detailed information is provided in this research about the recovery program, from planning to implementation and monitoring, and recommendations for best practices.
  • Assessing resource vulnerability quadrants under changing precipitation trends in Uttarakhand, Central Himalayan region
    Ayushi VIJHANI, Vinay Shankar Prasad SINHA, Mini GOVINDAN
    2021, 18(10): 2722-2741.
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    The Central Himalayan region is vulnerable to the adverse effects of climate change and characterized by regional climatic conditions. The livelihood of the mountain communities across the Himalaya is at risk owing to the consequences of variable precipitation patterns. There exists limited empirical research on precipitation variability due to inadequate hydro-meteorological stations at highaltitude regions. The study uses a novel methodology which integrates precipitation variability with resource sensitivity over the three verticals of Central Himalaya: Himadri, Himachal and Shivaliks and across four major river basins: Yamuna, Upper Ganga, Ghaghar and Ramganga. The magnitude of the significant precipitation trends was estimated through time series analysis at a 95% confidence interval. To assess the sensitivity of natural resources(forest, water and land) and human resources, fourteen mountain-specific indicators were identified which captured resource index using data standardization and principal component analysis. Sen's slope and Resource index were plotted in a 2 D Cartesian coordinate to draw precipitation-resource quadrants with their effective coverage area: High Precipitation and Scarce Resources(35.92%); Low Precipitation and Abundant Resources(30.10%); Low Precipitation and Scarce Resources(22.33%) and High Precipitation and Abundant Resources(11.65%). This helped in developing quadrant-specific adaptation strategies under regional variability of precipitation. The methodology and the research findings will certainly assist water experts, resource managers and policy makers to strengthen adaptive capacity and improve the resilience of vulnerable communities across Himalaya.
  • Clustering gully profiles for investigating the spatial variation in landform formation on the Chinese Loess Plateau
    CHENG Yao, LI Jing-wei, XIONG Li-yang, TANG Guo-an
    2021, 18(10): 2742-2760.
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    The gully is the most dynamic and changeable landform unit on the Loess Plateau, and the characteristics of gully landforms are key indicators of gully evolution. Different gully profiles are connected and combined through runoff nodes. Thus, it is necessary to cluster gully profiles into a gully profile combination(GPC) to reveal the spatial variation in gully landforms throughout the Loess Plateau. First, the gradient and gully evolution index(GEI) of two sample areas in Changwu and Suide in Shaanxi Province, China are calculated and analysed based on GPC. Then, the gradient and GEI are calculated by using 90-m-resolution digital elevation model(DEM) data for the severe soil erosion area with the basin as the research unit. On this basis, the spatial variation in the development degree is analysed with Getis-Ord Gi*. The results show that the degree of gully undercutting decreases from southeast to northwest under the influence of rainfall. Due to the soil properties, the loess in the northwest is more prone to collapse, resulting in the decrease of GEI from northwest to southeast. The development degree of gullies is closely related to rivers. The strong erosive capacity of rivers leads to greater differences in gullies within the basin. At the same time, the skewness and kurtosis of the gully index in the basin are correlated; when the distribution of the gully index in the basin is less normal, the distribution of the gully index is more concentrated. These results reveal the spatial variation characteristics of the Loess Plateau based on GPC.
  • A new strategy combined HASM and classical interpolation methods for DEM construction in areas without sufficient terrain data
    WANG Jing, ZHAO Ming-wei, JIANG Ling, YANG Can-can, HUANG Xiao-li, XU Yan, LU Jie
    2021, 18(10): 2761-2775.
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    Spatial interpolation is an important method in the process of DEM construction. However, DEMs constructed by interpolation methods may induce serious distortion of surface morphology in areas lack of terrain data. In order to solve this problem, this paper proposes a strategy combining high-accuracy surface modeling(HASM) and classical interpolation methods to construct DEM. Firstly, a triangulated irregular network(TIN) is built based on the original terrain data, and the area of the triangles in the TIN is used to determine whether to add supplementary altimetric points(SA-Points). Then, classical interpolation methods, such as Inverse Distance Weighted(IDW) method, Kriging, and Spline, are applied to assign elevation values to the SA-Points. Finally, the SA-Points are merged with the original terrain data, and HASM is used to construct DEM. In this research, two test areas which are located in Nanjing suburb in Jiangsu Province and Guiyang suburb in Guizhou Province are selected to verify the feasibility of the new strategy. The study results show that:(1) The combination of HASM and classical interpolation methods can significantly improve the elevation accuracy of DEMs compared with DEM constructed by a single method.(2) The process of adding SA-Points proposed in this study can be repeated in many times. For the test areas in this paper, compared with the results with only one execution, the results with more executions are in much more accordance with the actual terrain.(3) Among all the methods discussed in this paper, the one combined HASM and Kriging produce the best result. Compared with the HASM alone, absolute mean error(MAE) and root mean square error(RMSE) of the best result were reduced from 1.29 m and 1.83 m to 0.68 m and 0.45 m(the first test area), and from 0.32 m and 0.38 m to 0.21 m and 0.28 m( The second test area).
  • Influence of grain segregation on the behavior of sand in triaxial tests
    YU Fang-wei, PENG Xiong-zhi, SU Li-jun
    2021, 18(10): 2776-2790.
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    As a common phenomenon in granular flow, grain segregation plays a great role in affecting the behavior of granular soil by causing a great change of grain-void distribution in granular soil. This paper presents an experimental study on the influence of grain segregation on the behavior of sand, by a number of triaxial tests to interpret the characteristic behavior, friction and dilatancy behavior, excess pore water pressure behavior and critical state behavior of sand incorporating grain segregation. An index-grain segregation index was proposed to quantify grain segregation. Grain segregation affected greatly the characteristic behavior of sand, causing the movement of void ratio-dilatancy relation of sand towards the increase of void ratio and dilatancy of sand. In the drained tests, the mobilized friction angle of sand showed a decrease followed by an increase but the mobilized dilatancy angle of sand increased, with increasing grain segregation index. An increase in grain segregation index impaired the basic friction of sand. In the undrained tests, the mobilized friction angle of sand showed an increase followed by a decrease with increasing grain segregation index. However, grain segregation caused an increase of the mobilized dilatancy of sand followed by a different development. An increase in grain segregation resulted in a higher summit of the dilatancy of sand but with a faster decrease along axial strain. In the q-p′ plane, grain segregation caused a reciprocating rotation of the dilatancy line and failure line of sand. Grain segregation resulted in enhancement of the peak-state dilatancy of sand, affecting greatly peakstate friction angle and peak-state basic friction angle of sand as well as the normalized excess pore water pressure. The excess friction angle of sand showed an increase followed by a decrease in the drained tests but increased linearly in the undrained tests, with increasing grain segregation index. The excess friction angle-over-maximum dilatancy angle of sand decreased in up convexity while increasing grain segregation index. Grain segregation resulted in rotation and translation of the critical state line of sand in the e-p′α=0.7 plane. However, in the q-p′ plane, the critical state line of sand showed an anticlockwise rotation followed by a clockwise rotation with increasing grain segregation index.
  • Settlement patterns of mountainous half-filled and half-cut widened subgrade with retaining wall
    FU Yong-guo, JIANG Xin, GU Han-yan, QIU Yan-jun
    2021, 18(10): 2791-2802.
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    The settlement of widened highway subgrade in mountainous area is not only affected by the interaction between new and existing subgrade, but also seriously restricted by the external retaining wall. Based on the practical engineering of half-filled and half-cut widened mountainous highway subgrade with external balance weight retaining wall(BWRW), a sophisticated finite element numerical model is established. The evolution law of subgrade settlement is revealed during the whole process of new subgrade filling and BWRW inclination after construction. The settlement component of subgrade is clarified considering whether the existing pavement continues to be used. The results show that the additional settlement caused by the BWRW inclination after construction cannot be ignored in the widening and reconstruction of mountainous highway subgrade. In addition, pursuant to the comprehensive design of subgrade and pavement, the component of subgrade settlement should be determined according to whether the existing pavement continues to be used, while considering the influence of BWRW inclination after construction. When the existing pavement continues to be used, the settlement of the existing subgrade is caused by the new subgrade filling and the BWRW inclination after construction. On the contrary, the settlement is only caused by the BWRW inclination after construction.