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过刊目录

  • 2021年, 18卷, 第02期
    刊出日期：2024-06-19
      
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  • A review of modern treeline migration, the factors controlling it and the implications for carbon storage
    HANSSON Amanda, DARGUSCH Paul, SHULMEISTER Jamie
    2021, 18(02): 291-306.
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    Numerous studies have reported that treelines are moving to higher elevations and higher latitudes. Most treelines are temperature limited and warmer climate expands the area in which trees are capable of growing. Hence, climate change has been assumed to be the main driver behind this treeline movement. The latest review of treeline studies was published in 2009 by Harsch et al. Since then, a plethora of papers have been published studying local treeline migration. Here we bring together this knowledge through a review of 142 treeline related publications, including 477 study locations. We summarize the information known about factors limiting tree-growth at and near treelines. Treeline migration is not only dependent on favorable growing conditions but also requires seedling establishment and survival above the current treeline. These conditions appear to have become favorable at many locations, particularly so in recent years. The review revealed that at 66% of these treeline sites forest cover had increased in elevational or latitudinal extent. The physical form of treelines influences how likely they are to migrate and can be used as an indicator when predicting future treeline movements. Our analysis also revealed that while a greater percentage of elevational treelines are moving, the latitudinal treelines are capable of moving at greater horizontal speed. This can potentially have substantial impacts on ecosystem carbon storage. To conclude the review, we present the three main hypotheses as to whether ecosystem carbon budgets will be reduced, increased or remain the same due to treeline migration. While the answer still remains under debate, we believe that all three hypotheses are likely to apply depending on the encroached ecosystem. Concerningly, evidence is emerging on how treeline migration may turn tundra landscapes from net sinks to net sources of carbon dioxide in the future.
  • Paleoglacial and paleoclimate reconstructions during the global Last Glacial Maximum in the Longriba area, eastern Tibetan Plateau
    YANG Wei-lin, HAN Ye-song, PENG Xu, RAN Ze-ze, LIU Qing, LIU Geng-nian
    2021, 18(02): 307-322.
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    Owing to the remoteness of the Longriba area and the lack of dating records, it is extremely challenging to reconstruct the chronology and extent of the paleoglaciers in this area. In this paper, we combined limited observational data with automated modelling for paleoglacial reconstructions. We first identified a broadly distributed paleoglacier from satellite imagery and field investigation based on the sediment-landform assemblage principle and dated it to 23.1±1.4～19.5±1.2 ka by ~(10) Be exposure dating, corresponding to the global Last Glacial Maximum(gLGM). Then, we reconstructed the extent and ice surface of 171 paleoglaciers formed during the similar period based on geomorphological evidence and ‘ice surface profile' modelling. The results showed that the paleoglacial coverage was 426.5 km2, with an ice volume of 38.1 km3, in the Longriba area. The reconstructed equilibrium line altitudes(ELAs) based on modelled ice surfaces yielded an average of 4245±66 m above sea level(asl), ～725±73 m lower than the present ELA(4970±29 m asl). The temperature was ～5.51-6.68 ℃ lower, and the precipitation was ～30-34% less in Longriba, during the g LGM compared to the present day. This glacial advance was mainly driven by colder climate that was synchronous with Northern Hemisphere cooling events.
  • Characteristics of the active-layer under the China-Russia Crude Oil pipeline
    SERBAN Mihaela, LI Guo-yu, SERBAN Raul-David, WANG Fei, FEDOROV Alexander, VERA Samsonova, CAO Ya-peng, CHEN Peng-chao, WANG Wei
    2021, 18(02): 323-337.
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    Active layer is a key component for permafrost environment studies as many subsurface biological, biogeochemical, ecological, and pedogenic activities prevail in this layer. This study focuses on active layer temperature monitoring in an area with sporadic permafrost at two adjacent sites along China-Russia Crude Oil Pipeline(CRCOP), NorthEast China. Site T1 is located in disturbed ground on the right-of-way(on-ROW) 2 m away from the center of the oil pipeline. T2 is located in a natural and undisturbed site, around 16.6 m off-ROW. Our objective was to study seasonal variability of the active layer depth and thermal regime from October 2017 to September 2018. The monitoring sites consist of soil temperature probes arranged in a vertical array at different depths at both sites. The following parameters were computed: number of isothermal days(ID), freezing days(FD), thawing days(TD), freezing degree days(FDD), thawing degree days(TDD), number of freeze-thaw days(FTD). The mean air temperature in the monitoring period reached-3.2°C. The temperature profile indicates that the maximum active layer thickness observed during the study period was 10 m at T1 and 2 m at T2. The majority of the soil temperatures were above or close to 0°C, resulting in great values of TDD, especially in the first 4 m depth. TDD for T1 were predominant and ranged between 600-1160°C·days(0-4 m depth) reflecting the influence of oil temperature from the pipeline. In T2 borehole FDD were predominant for all the soil layer depths resulting in less permafrost degradation. This comparison emphasizes the significant influence of vegetation removal and the dispersed heat from the pipeline on the active layer thickness.
  • Numerical simulation of seasonal snow in Tianshan Mountains
    REN Yan-run, ZHANG Yao-nan, HAO Jian-sheng, SHEN Yong-ping, ZHAO Guo-hui, LI Cong
    2021, 18(02): 338-356.
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    Snowfall in the Tianshan Mountains in China is frequent during winter; thus, avalanches have become a severe issue in snow-covered areas. Accumulation and metamorphosis, as well as hydrothermal exchanges with the environment, considerably affect the stability of snow on slopes. Therefore, a hydrothermal model of snow cover and its underlying surfaces must be developed on the basis of meteorological data to predict and help manage avalanches. This study adopted the conceptual model of snow as a porous medium and quantitatively analysed its internal physical processes on the basis of the thermal exchanges amongst its components. The effects of local meteorological factors on snow structure and the redistribution of energy and mass inside the snow cover in the Tianshan Mountains were simulated. Simulation results showed that deformation as a result of overlying snow and sublimation of snow cover at the bottom is the main cause of density variation in the vertical profile of snow cover. Temperature drives water movement in snow. The low-density area of the bottom snow is the result of temperature gradient. The simulation results of the long-term snow internal mass distribution obtained by the method established in this study are highly consistent with the actual observed trend of variation. Such consistency indicates an accurate simulation of the physical characteristics of snow cover in small and microscale metamorphism in the Tianshan Mountains during the stable period.
  • Degradation significantly decreased the ecosystem multifunctionality of three alpine grasslands: evidences from a large-scale survey on the Qinghai-Tibetan Plateau
    XU Yu-dan, DONG Shi-kui, SHEN Hao, XIAO Jian-nan, LI Shuai, GAO Xiao-xia, WU Sheng-nan
    2021, 18(02): 357-366.
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    Owing to the joint effects of ecosystem fragility, anthropogenic disturbance and climate change, alpine grasslands(alpine meadow, alpine steppe and alpine desert) have experienced serious degradation during the past several decades. Grasslands degradation has severely affected the delivery of ecosystem multifunctionality(EMF) and services, and then threatens the livelihood of local herdsmen and ecological security of China. However, we still lack comprehensive insights about the effects of degradation and climatic factors on EMF of alpine grasslands, especially for alpine desert ecosystem. Therefore, we applied a large-scale field investigation to answer this question. Our results suggested grassland degradation significantly decreased the belowground ecosystem multifunctionality(BEMF) and EMF of alpine grasslands and aboveground ecosystem multifunctionality(AEMF) of alpine meadow, while did not reduce the AEMF of alpine steppe and desert. Except for the insignificant difference between degraded steppe and degraded desert in AEMF, the alpine meadow showed the highest AEMF, BEMF and EMF, alpine steppe ranked the second and alpine desert was the lowest. AEMF, BEMF and EMF of health alpine grasslands were strongly affected by mean annual precipitation(MAP)(19%-51%) and mean annual temperature(MAT)(9%-36%), while those of degraded meadow and degraded desert were not impacted by precipitation and temperature. AEMF and BEMF showed a synergistic relationship in healthy alpine grasslands(12%-28%), but not in degraded grasslands. Our findings emphasized the urgency of implementing the feasible ecological restoration project to mitigate the negative influences of grassland degradation on EMF of alpine ecosystems.
  • Size distribution of PM_(20) observed to the north of the Tibetan Plateau
    ZHOU Cheng-long, YANG Fan, HUO Wen, MAMTIMIN Ali, YANG Xing-hua
    2021, 18(02): 367-376.
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    The size distribution of airborne dust particles is an important parameter in the measurement of dust emissions due to wind erosion, and a quantitative and accurate description is necessary. Observations regarding the size distribution of airborne dust particles are currently lacking in Tibetan Plateau(TP). This study aims to obtain a dust particle size distribution and compare the difference in spatial distribution at a field site(FS) and two urban observation sites(Minfeng and Hetian), in the north of the TP, under the condition of the dust-days and clear-days. The observation data was collected from 5 July to 4 August, 2019. The mass concentration of dust(PM_(20)) was measured with a 10-stage quartz crystal microbalance cascade impactor. The results suggested that 91.9% of the particles were less than 1.4 μm on clear-days, and particles of d ≥ 1.4 μm increased to 27.2% with the occurrence of the dust events. More than 80% of the airborne dust particles were less than 1.4 μm for each friction velocity. The proportion of d < 0.7 μm was the greatest at 3.0 m(above the surface, similarly hereinafter) on dust-days, while the proportion of d > 0.7 μm was the greatest at 0.5 m on clear-days. During urban observation, with the occurrence of dust events, the concentration of a particle size greater than 2.5 μm increased most significantly in Minfeng, while the concentration of a particle size less than 0.7 μm increased most significantly in Hetian. Moreover, the proportion of particles with d < 0.7 μm had the smallest difference, while the proportion of particles with d > 1.4 μm had the most obvious difference among these three sites.
  • Sediment generation and soil mound denudation in areas of high-density tree throw along a river valley in the Jura Mountains, Switzerland
    Philip GREENWOOD, Jan BAUER, Nikolaus J KUHN
    2021, 18(02): 377-391.
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    A preliminary field-based investigation was undertaken in a small(< 10 km~2) river valley located in the mountainous Jura region of northwest Switzerland. The aims of the work were to assess sediment generation and annual sediment transport rates by tree throw on forested hillslopes, and to document surface hydrology characteristics on four fresh soil mounds associated with recent tree throws over a 24-day monitoring period. For the soil mounds, average sediment recovery ranged from 7.7-28.2 g(dry weight), equivalent to a suspended sediment concentration of 145.2-327.8 g L~(-1), and runoff coefficients ranged from 1.0%-4.2%. Based on a soil bulk density value of 1,044 kg m~(-3), upslope runoff generation areas were denuded by an average 0.14 mm by the end of the 24-day monitoring period, representing an erosion rate equivalent to 2.1 mm yr~(-1). A ca. 50 cm high soil mound could therefore feasibly persist for around 200-250 years. For tree throw work, the dimensions of 215 individual tree throws were measured and their locations mapped in 12 separate locations along the river valley representing a cumulative area equivalent to 5.3 ha(av. density, 43 per ha). Tree throws generated a total of 20.1 m3 of fine-sediment(< 2 mm diameter), or the equivalent of 3.8 × 10~(-4) m~3 m~(-2). The process of tree throw was originally attributed to two extreme weather events that occurred in west and central Europe in late December 1999. Taking the 18-year period since both storms, this represents an annual sediment transport rate of 2.7 × 10-~(-5) m~3 m~(-1) yr~(-1). Exploring the relationship with wind on fall direction, 65.5% of tree throws(143) generally fell in a downslope direction irrespective of hillslope aspect on which they were located. This infers that individual storms may not have been responsible for the majority of tree throws, but instead, could be associated with root failure. Given the high density of tree throws and their relative maturity(average age 41 years), we hypothesise that once trees attain a certain age in this river valley, their physiognomy(i.e. height, mass and centre of gravity) compromises their ability to remain securely anchored. We tentatively attribute this possibility to the presence of bedrock close to the surface, and to the shallow soil profile overlaying steep hillslopes.
  • Soil anti-scourability enhanced by herbaceous species roots in a reservoir water level fluctuation zone
    XU Wen-xiu, YANG Ling, BAO Yu-hai, LI Jin-lin, WEI Jie
    2021, 18(02): 392-406.
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    Revegetation is one of the successful approaches to soil consolidation and streambank protection in reservoir water level fluctuation zones(WLFZs). However, little research has been conducted to explore the impact of herbaceous species roots on soil anti-scourability during different growth stages and under different degrees of inundation in this zone. This study sampled two typical grasslands(Hemarthria compressa grassland and Xanthium sibiricum grassland) at two elevations(172 and 165 m a.s.l.) in the water level fluctuation zone(WLFZ) in the Three Gorges Reservoir(TGR) of China to quantify the changes in soil and root properties and their effects on soil anti-scourability. A simulated scouring experiment was conducted to test the soil anti-scourability in April and August of 2018. The results showed that the discrepancy in inundation duration and predominant herbaceous species was associated with a difference in root biomass between the two grasslands. The root weight density(RWD) values in the topsoil(0-10 cm) ranged from 7.31 to 13 mg cm~(-3) for the Hemarthria compressa grassland, while smaller values ranging from 0.48 to 8.61 mg cm~(-3) were observed for the Xanthium sibiricum grassland. In addition, the root biomass of the two herbs was significantly greater at 172 m a.s.l. than that at 165 m a.s.l. in the early recovery growth period(April). Both herbs can effectively improve the soil properties; the organic matter contents of the grasslands were 128.06% to 191.99% higher than that in the bare land(CK), while the increase in the water-stable aggregate ranged from 8.21% to 18.56%. Similarly, the topsoil antiscourability indices in both the herbaceous grasslands were larger than those in the CK. The correlation coefficients between the root length density(RLD), root surface area density(RSAD) and root volume density(RVD) of fine roots and the soil antiscourability index were 0.501, 0.776 and 0.936, respectively. Moreover, the change in the soil antiscourability index was more sensitive to alternations in the RLD with diameters less than 0.5 mm. Overall, the present study showed that the perennial herbaceous(H. compressa) has great potential as a countermeasure to reduce or mitigate the impact of erosion in the WLFZ of the Three Gorges Reservoir.
  • Initial colonisation by Rhizocarpon geographicum in the Tatra Mountains
    Stanis?aw K?DZIA
    2021, 18(02): 407-415.
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    Previous lichenometric dating of young geomorphological forms in the Tatra Mountains has been hindered by differences in the determination of initial colonisation of fresh rock surfaces by the Rhizocarpon geographicum lichen. In order to determine precisely the time needed for the first thalli to appear on newly exposed rock surfaces, two experimental sites were created in 2013. The results from these sites were compared with the measurements taken on boulders in debris formed by a 2013 debris flow. In 2018, the largest thalli measured within the experimental sites and the debris flow area reached a size of approximately 2 mm. Based on this, the time of initial colonisation of rock surfaces was determined to be 5 ± 1 years, which is about half the period previously described in the literature.
  • Forest cover dynamics in Palas Valley Kohistan, Hindu Kush-Himalayan Mountains, Pakistan
    Noor ul HAQ, Fazlur RAHMAN, Iffat TABASSUM, MEHRAN
    2021, 18(02): 416-426.
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    Forest cover change in the mountainous region is driven by a variety of anthropogenic and natural factors. The Hindu Kush-Himalayan Mountains has experienced a considerable vegetation cover change due to intensive human activities, such as population growth, proximate causes, accessibility, unstable political situations, government policy failure and poverty. The present study seeks to find out the impact of population growth and road network expansion on forest cover of Palas valley based on remotely sensed data and employing geospatial techniques. Changes in forest cover were determined by classifying time-series satellite images of Landsat and Sentinel 2 A. The images of October 1980, 2000, 2010 and 2017 were classified into six land cover classes and then the impact of population growth and accessibility on forest cover was analyzed. Furthermore, forest cover and land-use change detection map was prepared using classified images of 1980 and 2017. The data were collected mainly from field visits(ground verification), census reports, Communication and Works Department, Kohistan. Satellite imageries were obtained from the United States Geological Survey's websites and classified in ERDAS imagine 2014 and ESRI ArcGIS 10.2.1 using supervised classification-maximum likelihood algorithm. Result of this study revealed that a substantial reduction in forest cover has taken place mainly in the proximity of human settlements. On the average, during the study period, annually more than 460 hectares of forest area has been converted into other uses.
  • Quantitatively determine the dominant driving factors of the spatial–temporal changes of vegetation NPP in the Hengduan Mountain area during 2000-2015
    CHEN Shu-ting, GUO Bing, ZHANG Rui, ZANG Wen-qian, WEI Cui-xia, WU Hong-wei, YANG Xiao, ZHEN Xiao-yan, LI Xing, ZHANG Da-fu, HAN Bao-min, ZHANG Hai-ling
    2021, 18(02): 427-445.
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    The Hengduan mountain area, located in the upper reaches of the Yangtze River of China, is an important ecological barrier that significantly impacts the climate and ecological environment of the surrounding region and western China as a whole. This paper introduces the gravity center model used to analyze the spatial-temporal variation patterns of vegetation Net Primary Productivity(NPP) from 2000 to 2015, which were determined by the use of MOD17 A3 NPP products. Additionally, the dominant driving factors of the spatial–temporal changes of vegetation NPP of the Hengduan Mountain area were quantitatively determined with a geographical detector over 2000-2015. The results revealed that:(1) From 2000 to 2015, there was an increasing trend of vegetation NPP in the Hengduan mountain area. Throughout the whole study region, the vegetation NPP with a mean value of 611.37 gC·m-2·a-1 indicated a decreasing trend from southeast to northwest in terms of spatial distribution.(2) The gravity centers of vegetation NPP in 2000-2015 were mainly concentrated in Zhongdian County. During the study period, the gravity center of vegetation NPP moved northward, which indicated that the increment and increasing rate of vegetation NPP in the northern parts were greater than that of the southern areas.(3) The vegetation NPP showed a moderately positive correlation with temperature, accumulated temperature(>10°C), and sunshine, while there was an overall negative relationship between NPP and precipitation.(4) The dominant factors and interactive dominant factors changed in different subregions over different segments of the study period. The dominant factors of most sub-regions in Hengduan mountain were natural factors, and the climate change factors played an increasingly greater role over the 16 years of the study period.
  • Mountaineering incidents in France: analysis of search and rescue interventions on a 10-year period(from 2008 to 2018)
    VANPOULLE Maud, LEFEVRE Brice, SOULE Bastien
    2021, 18(02): 446-461.
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    In Europe and especially in France, there is a growing enthusiasm for outdoor sports and recreation. In the meantime, the risk of both severe and frequent injuries associated with active pursuits is acknowledged, especially in mountainous areas. The effectiveness of prevention must rely on detailed knowledge of typical circumstances and scenarios but thorough understanding of the mechanisms of accidentality remains limited by the fragmentation of sources and by mostly heterogeneous methodologies. This paper aims at giving insights on victims' profiles, season, location, and circumstances of mountaineering accidents in the French Alps, through the study of rescue interventions data from 2008 to 2018. Thanks to the analysis of the exhaustive database of search and rescue interventions from the French mountain national police force, and while questioning its limitations, we strive to answer two questions: what are the characteristics of the hazardous situations leading to a rescue intervention in mountaineering? Among these situations, what are the characteristics that tend to make them more harmful?
  • Physical modeling into outflow hydrographs and breach characteristics of homogeneous earthfill dams failure due to overtopping
    KOUZEHGAR Kamran, HASSANZADEH Yousef, ESLAMIAN Saeid, YOUSEFZADEH FARD Mikaeil, BABAEIAN AMINI Alireza
    2021, 18(02): 462-481.
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    The main objective of the present study is to introduce new empirical equations for the determination of breach geometrical dimensions and peak outflow discharge(Q_p). Therefore, a historic failure database of 109 embankments was collected and examined. The most important factors that affect the breach evolution, including grading size, hydraulic, and outflow characteristics are also studied. Some of the parameters used for the determination of Q_p and average breach width(B_(ave)) have a significant effect on the erosion process, but they are less reflected in the technical literature. To study the behavior of noncohesive soils during overtopping, 15 physical tests were performed at the laboratory, and the effects of interfering parameters were investigated. The experimental output hydrograph was used to simulate the hydrographs resulting from the failure of real dams, and recent artificial intelligence techniques along with linear and nonlinear regression models were employed. The area-time analysis of the laboratory hydrographs shows that the soil particle size and the characteristics of reservoir-basin significantly affect the rate of breach formation and outflow discharge. New relationships are introduced, based on the breach characteristics, by a combination of historical and experimental data, as well as case studies conducted on the hypothetical failure of 10 operational dams. The mathematical model is also used to simulate the process of breach evaluation. Based on statistical indices, comparison of the results, and sensitivity analysis, the developed equations can better express the susceptibility of materials to erosion and their application can minimize downstream vulnerabilities.
  • The use of UAVs for landslide disaster risk research and disaster risk management: a literature review
    Ricardo J. GARNICA-PE?A, Irasema ALCáNTARA-AYALA
    2021, 18(02): 482-498.
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    On a global scale, from 2005 to 2019, there were 275 high-magnitude, low-frequency disasters that involved 14,172 fatalities and four million affected people. Similar patterns have taken place during longer periods of time in recent decades. This paper aims to analyse the contribution of the international landslide research community to disaster risk reduction and disaster risk management in reference to the use of Unmanned Aerial Vehicles(UAVs) in a literature review. The first section notes the relevance of disaster risk research contributions for the implementation of initiatives and strategies concerning disaster risk management. The second section highlights background information and current applications of drones in the field of hazards and risk. The methodology, which included a systematic peer review of journals in the ISI Web of Science and SCOPUS, was presented in the third section, where the results include analyses of the considered data. This study concludes that most current scholarly efforts remain rooted in hazards and post-disaster evaluation and response. Future landslide disaster risk research should be transdisciplinary in order to strengthen participation of the various relevant stakeholders in contributing to integrated disaster risk management at local, subnational, national, regional and global levels.
  • Distribution, failure risk and reinforcement necessity of check-dams on the Loess Plateau: a review
    GUO Wen-zhao, WANG Wen-Long, XU Qiang, HU Jian-jun, ZHU Li-li
    2021, 18(02): 499-509.
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    Check-dams are the most important measure to control the soil and water loss in highly erodible catchments on the Chinese Loess Plateau. Based on the data of check-dams from 1950 to 2014, our study roundly analyzed the regional distribution, function and the problems of check-dams on the Loess Plateau. A total of 17,094 check-dams with a storage capacity of over 100,000 m~3 and an average density of 0.027 counts km~(-2) were installed on the Loess Plateau. Check-dams' densities varied greatly in the Qinghai Province, Gansu Province, Ningxia Hui Autonomous Region, Inner Mongolia Autonomous Region, Shaanxi Province, Shanxi Province and Henan Province. The highest density of check-dams reached 0.088 counts km~(-2) in Shaanxi Province, whereas the lowest density of check-dams was only 0.005 counts km~(-2) in Qinghai Province. However, after decades of operation, 3025 large check-dams and 2257 medium check dams are dangerous and have security risks, which are seriously threatening downstream safety. The dangerous rate of checkdams is high. Specifically, the check-dams in Shanxi and Qinghai Province have the highest dangerous rates, with both exceeding 53%. Therefore, there is an urgent need for carrying out reinforcement of the dangerous check-dams. The results are helpful to policymakers to extend and develop check-dams.
  • Coulomb stress and gravity changes associated with the 2016 Mw 7.8 Kaikoura Earthquake, New Zealand: Application for aftershock triggering and fault interaction process analysis
    HASSAN Abubakr, HUANG Ding-fa, JIANG Zhong-shan, ZHANG Lu-peng
    2021, 18(02): 510-527.
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    The Kaikoura earthquake on November 14, 2016 is one of the largest and most complex earthquakes in New Zealand since 1947. Despite the fact that it has ruptured about 12 separate faults, triggered 2132 aftershocks within one week of the mainshock and induced considerable stress changes, few studies have been conducted to comprensively investigate the characteristics. The current study examines the horizontal and vertical displacements as well as the stress and gravity changes, aftershock distributions and also find out whether these changes affect the surrounding regions along the complex fault systems. The study covers the entire area affected by the Kaikoura event, which includes the northern part of the South Island and the southern part of the North Island. The dislocation theory was employed to evaluate the coseismic slip model on the multiple faults. The displacement results revealed that the maximum horizontal displacement is about 6 m and the vertical about 2 m, which are reasonably consistent with earlier study findings. Besides, the stress and gravity changes are quite complicated and inhomogeneous as evidenced by our coseismic model, demonstrating the complexity of the Kaikoura earthquake as well. Almost all the aftershocks are distributed in places where the stress and gravity change are found to be significant. In order to investigate the stability of our stress change models, we applied different friction coefficients and receiver fault parameters. The results justify the friction coefficient(?=0.4) and the receiver fault parameters(230°, 70°, 150°) are suitable to define good stress change estimates. According to the stress change results at 15 km depth, the northern parts of the mainshock region, Hundalee fault, Humps fault and Jordan thrust areas together with the Wellington area are closer to failure and situated in a seismic risk zone. The multidimensional analysis adopted in this paper is helpful for making decisions and applications of stress and gravity change models in assessing seismic hazards.
  • Land use suitability analysis for town development planning in Nanjing hilly areas: A case study of Tangshan new town, China
    YANG Yang, TANG Xiao-lan, LI Zhe-hui
    2021, 18(02): 528-540.
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    Land use suitability analysis plays an important role in sustainable land use and solving environmental problems caused by rapid urban development. A land use suitability mapping approach for town development planning in hilly areas was constructed based on two multi-criteria evaluation methods: Weighted Linear Combination(WLC) and Ordered Weighted Averaging(OWA), to comparatively evaluate and map land use suitability of Tangshan new town in Nanjing, China. Fourteen evaluation factors related to topographic, environmental, socio-economics and historical sites data were used as suitability criteria. The analytic hierarchy process(AHP) method and GIS techniques were integrated into the evaluation models to create the land use suitability map for town development planning. The results of WLC approach showed that 11.4% of the total area is highly suitable while the 48.6% is unsuitable. The results of WLC and OWA approach showed the distribution of degree of land use suitability is almost the same. The areas located at the southern and eastern flat regions are highly suitable for land use, whereas the areas close to the mountain forests, steep slopes, waters, and hot springs, have lower suitability for land use. Sensitivity analysis indicated that the suitability results of the two proposed methods are robust. Indirect validation was achieved by mutual comparison of suitability maps derived from the WLC and OWA methods. It demonstrated that the overall agreement is 90.81% and kappa coefficient is 0.81, indicating that both methods provide very similar spatial suitability distributions. By overlaying the resultant map with the previous master plan map of Tangshan new town, the overlay map once again indicated a satisfactory ecological fit between the two maps. At last, several recommendations are proposed aiming at improving the long-term town development plan for Tangshan new town.
  • Effect of freeze-thaw cycles on soil engineering properties of reservoir bank slopes at the northern foot of Tianshan Mountain
    QIN Zi-peng, LAI Yuan-ming, TIAN Yan, ZHANG Ming-yi
    2021, 18(02): 541-557.
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    The instability of soil bank slopes induced by freeze-thaw cycles at the northern foot of Tianshan Mountain is very common. The failure not only caused a large amount of soil erosion, but also led to serious reservoir sedimentation and water quality degradation, which exerted a lot of adverse effects on agricultural production in the local irrigation areas. Based on field investigations on dozens of irrigation reservoirs there, laboratory tests were carried out to quantitatively analyze the freeze-thaw effect on the soil engineering characteristics to reveal the facilitation on the bank slope instability. The results show that the softening characteristics of the stressstrain curves gradually weaken, the effective cohesions decline exponentially, the seepage coefficients enlarge, and the thermal conductivities decrease after 7 freeze-thaw cycles. The freeze-thaw effect on the specimens with low confining pressures, low dry densities and high water contents is more significant. The water migration and the phase transition between water and ice result in the variations of the soil internal microstructures, which is the main factor affecting the soil engineering characteristics. Sufficient water supply and the alternation of positive and negative temperatures at the reservoir bank slopes in cold regions make the water migration and phase transition in the soil very intensely. It is easy to form a large number of pores and micro cracks in the soil freezing and thawing areas. The volume changes of the soil and the water migration are difficult to reach a dynamic balance in the open system. Long-term freeze-thaw cycles will bring out the fragmentation of the soil particles, resulting in that the micro cracks on the soil surfaces are developing continuously. The soil of the bank slopes will fall or collapse when these cracks penetrate, which often happens in winter there.
  • Spatial correlation between groundwater seepage faces and fault zone in high bedrock channel: method and application
    Yaser NIKPEYMAN, Mohsen EHTESHAMI-MOINABADi
    2021, 18(02): 558-566.
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    The groundwater may recharge the surface water bodies through seepage faces and springs. The spatial correlation between the fault zones and the groundwater seepage faces results in deep understanding of the hydrogeologic regime, especially where there is no monitoring boreholes. Locating these recharging zones by conventional methods is a challenging task; particularly in areas where(1) there is no hydrogeologic monitoring boreholes or reliable data,(2) private pumps withdraw the stream, and(3) intense canopy limits the use of drones and satellite images. This paper aims to study the relationship between the fault zones and occurrence of the groundwater seepage faces by using the high resolution handheld thermal imaging cameras as a tool to locate the seepage faces along a small river in the Damavand County, north of Iran. The correlation between the structural geology features and occurrence of the groundwater seepage faces revealed that the stream in the study area is being recharged by the groundwater at extensive fault zones. Additionally, this study suggests that the handheld thermal imaging cameras are a useful robust tools to evaluate the surface-groundwater interaction. However, it is essential to use the field structural geologic and hydrogeologic observations to interpret the thermal images.