Journal of Mountain Science

Floods are one of the most common natural hazards occurring all around the world. However, the knowledge of the origins of a food and its possible magnitude in a given region remains unclear yet. This lack of understanding is particularly acute in mountainous regions with large degrees in Sichuan Province, China, where runoff is seldom measured. The nature of streamflow in a region is related to the time and spatial distribution of rainfall quantity and watershed geomorphology. The geomorphologic characteristics are the channel network and surrounding landscape which transform the rainfall input into an output hydrograph at the outlet of the watershed. With the given geomorphologic properties of the watershed, theoretically the hydrological response function can be determined hydraulically without using any recorded data of past rainfall or runoff events. In this study, a kinematic-wave-based geomorphologic instantaneous unit hydrograph (KW-GIUH) model was adopted and verified to estimate runoff in ungauged areas. Two mountain watersheds, the Yingjing River watershed and Tianquan River watershed in Sichuan were selected as study sites. The geomorphologic factors of the two watersheds were obtained by using a digital elevation model (DEM) based on the topographic database obtained from the Shuttle Radar Topography Mission of US’s NASA. The tests of the model on the two watersheds were performed both at gauged and ungauged sites. Comparison between the simulated and observed hydrographs for a number of rainstorms at the gauged sites indicated the potential of the KW-GIUH model as a useful tool for runoff analysis in these regions. Moreover, to simulate possible concentrated rainstorms that could result in serious flooding in these areas, synthetic rainfall hyetographs were adopted as input to the KW-GIUH model to obtain the flow hydrographs at two ungauged sites for different return period conditions. Hydroeconomic analysis can be performed in the future to select the optimum design return period for determining the flood control work.

Landslide hazard susceptibility evaluation takes on critical significance in early warning and disaster prevention and reduction. In order to solve the problems of poor effectiveness of landslide data and complex calculation of weights for multiple evaluation factors in the existing landslide susceptibility evaluation models, in this study, a method of landslide hazard susceptibility evaluation is proposed by combining SBAS-InSAR (Small Baseline Subsets-Interferometric Synthetic Aperture Radar) and SSA-BP (Sparrow Search Algorithm-Back Propagation) neural network algorithm. The SBAS-InSAR technology is adopted to identify potential landslide hazards in the study area, update the cataloging data of landslide hazards, and 11 evaluation factors are chosen for constructing the SSA-BP model for training and validation. Baihetan Reservoir area is selected as a case study for validation. As indicated by the results, the application of SBAS-InSAR technology, combined with both ascending and descending orbit data, effectively addresses the incomplete identification of landslide hazards caused by geometric distortion of single orbit SAR data (e.g., shadow, overlay, and perspective contraction) in deep canyon areas, thereby enabling the acquisition of up-to-date landslide hazard data. Moreover, in comparison to the conventional BP (Back Propagation) algorithm, the accuracy of the model constructed by the SSA-BP algorithm exhibits a significant increase, with mean squared error and mean absolute error reduced by 0.0142 and 0.0607, respectively. Additionally, during the process of susceptibility evaluation, the SSA-BP model effectively circumvents the issue of considerable manual interventions in calculating the weight of evaluation factors. The area under the curve of this model reaches 0.909, surpassing BP (0.835), random forest (0.792), and the information value method (0.699). The risk of landslide occurrence in the Baihetan Reservoir area is positively correlated with slope, surface temperature, and deformation rate, while it is negatively correlated with fault distance and normalized difference vegetation index. Geological lithology exerts minimal influence on the occurrence of landslides, with the risk being low in forest land and high in grassland. The method proposed in this study provides a useful reference for disaster prevention and mitigation departments to perform landslide hazard susceptibility evaluations in deep canyon areas under complex geological conditions.

The value-chain approach (VCA) was used for exploring how a niche crop, namely large cardamom (Amomum subulatum Roxb.), can be developed sustainably to increase incomes and enhance rural livelihoods in the mountains. Large cardamom is a high-value, agro-climatically suitable, and non-perishable spice crop grown in the Himalayan region. Originating in Sikkim, the crop is important to the local economy and is sold in both domestic and international markets; however, its production in India has been declining significantly in recent years. Using VCA and participatory methods of data collection the study helped elicit value chain actors’ perspectives on various reasons for the decline as well as potential strategies to improve the cardamom value chain. The results present the multiple environmental and climatic (e.g. water stress), social (e.g. women participation) and institutional (e.g. lack of trust between actors) challenges and corresponding upgrading strategies. Through participatory multi-criteria analysis (MCA), the strategies were prioritized based on the overall preferences of multiple stakeholders. The analysis considered eight criteria and 25 options, or strategies, and found that that marketability and profitability were the most important criteria, and increasing cardamom production, the most important option trait. Stakeholder discussions along with sensitivity analysis also showed how these options could be implemented and revealed how criteria preferences can change with expert inputs. This combination of VCA and MCA, because it supports participatory decision-making and balances multiple dimensions of sustainable development, can be effectively deployed in planning for agricultural development in the mountains.

Land use and land cover (LULC) in Nepal has undergone constant change over the past few decades due to major changes caused by anthropogenic and natural factors and their impacts on the national and regional environment and climate. This comprehensive review of past and present studies of land use and land cover change (LUCC) in Nepal concentrates on cropland, grassland, forest, snow/glacier cover and urban areas. While most small area studies have gathered data from different sources and research over a short period, across large areas most historical studies have been based on aerial photographs such as the Land Resource Mapping Project in 1986. The recent trend in studies in Nepal is to focus on new concepts and techniques to analyze LULC status on the basis of satellite imagery, with the help of geographic information system and remote sensing tools. Studies based on historical documents, and historical and recent spatial data on LULC, have clearly shown an increase in cropland areas in Nepal, and present results indicating different rates and magnitudes. A decrease in forest and snow/glacier coverage is reported in most studies. Little information is available on grassland and urban areas from past research. The unprecedented rate of urbanization in Nepal has led to significant urban land changes over the past 30 years. Meanwhile, long term historical LUCC research in Nepal is required for extensive work on spatially explicit reconstructions on the basis of historical and primary data collection, including LULC archives and drivers for future change.

Rừng Andean ở phía Bắc Ecuador được biết đến với mức độ đa dạng thực vật cao tương đối so với diện tích mà chúng chiếm lĩnh. Thông thường, những rừng này phát triển trên những sườn dốc dẫn đến sự biến đổi môi trường sống mạnh mẽ trong khoảng cách ngắn. Những gradient môi trường sống cực đoan này khiến hệ sinh thái rừng Andean trở thành một phòng thí nghiệm tự nhiên lý tưởng để hiểu tác động của độ cao lên tính đa dạng, cấu trúc và thành phần của cộng đồng rừng. Chúng tôi đã thiết lập 31 ô (50 m × 5 m) chia thành hai transect độ cao trong rừng mây của Khu bảo tồn Siempre Verde ở chân phía Tây của dãy Andes ở phía Bắc Ecuador. Tất cả các cây và dương xỉ cây có đường kính ở độ cao ngực (dbh) ≥ 5 cm đã được đo và xác định. Chúng tôi đã xem xét những thay đổi trong thành phần, cấu trúc và tính đa dạng của cộng đồng dọc theo và giữa các transect độ cao và ba vùng độ cao: thấp (2437–2700 m), giữa (2756–3052 m) và cao (3163–3334 m). Chúng tôi phát hiện bốn xu hướng chính liên quan đến gradient độ cao tại địa điểm này: (1) thành phần cộng đồng khác nhau giữa hai transect và giữa ba vùng độ cao theo N-MDS, ANOSIM, và tỷ lệ % các loài chia sẻ, với một số loài có phân bố hạn chế; (2) các chỉ số của cấu trúc cộng đồng cho thấy mối quan hệ ngược chiều với độ cao, tùy thuộc vào transect, với mối quan hệ duy nhất có ý nghĩa (tiêu cực) được tìm thấy giữa diện tích mặt cắt ngang và độ cao trong transect đường mòn mở; (3) đa dạng alpha, nói chung, đạt đỉnh ở độ cao trung bình; và (4) đa dạng beta đã tăng lên một cách nhất quán theo khoảng cách giữa các ô dọc theo độ cao. Sự phức tạp của những thay đổi trong thành phần cộng đồng, cấu trúc và đa dạng alpha dọc theo độ cao có thể liên quan đến tính không đồng nhất của môi trường ở quy mô địa phương, chẳng hạn như địa hình, thành phần đất và ngay cả tác động của con người, hoặc do hạn chế phát tán và cần được nghiên cứu thêm. Những thay đổi trong thành phần cộng đồng và tính đa dạng beta tương đối cao được phát hiện tại địa điểm này minh họa cho sự phức tạp sinh học của rừng núi, củng cố những lập luận từ các nghiên cứu khác về tầm quan trọng của việc bảo tồn chúng.

An experiment was performed to study the influence of polymer binders on the physical properties, and stability against a simulated rainfall, of a slope consisting of engineering spoil. Results showed that low polymer binder concentrations (≤500 g/m3) could enhance the air permeability and moisture -retaining capacity of the engineering spoil; however, adding more polymer binder made the hardness of the engineering spoil increase and then decline. With the increase of polymer binder concentrations, the surface (0–5 cm) permeability of the engineering spoil decreased but the permeability of the lower layers (5–10 cm) increased. Polymer binders might reduce runoff and sediment, but the effect becomes weaker with the increase of rainfall. The results of this study have significance for engineering practices. Further experiments are needed to study the effects of binders under other conditions, such as natural rainfall, different slopes, different rock types, different degrees and spoil weathering and different added material, and the chemical interaction between soil and polymer binders.

This paper describes model tests of single piles subjected to vertical cyclic compressive loading for three kinds of topography: sloping ground, level ground, and inclined bedrock. Comprehensive dynamic responses involving cyclic effects and vibration behaviours are studied under various load combinations of dynamic amplitude, mean load, frequency and number of cycles. Test results show that permanent settlement can generally be predicted with a quadratic function or power function of cycles. Sloping ground topography produces more pronounced settlement than level ground under the same load condition. For vibration behaviour, displacement amplitude is weakly affected by the number of cycles, while load amplitude significantly influences dynamic responses. Test results also reveal that increasing load amplitude intensifies nonlinearity and topography effects. The strain distribution in a pile and soil stress at the pile tip are displayed to investigate the vibration mechanism accounting for sloping ground effects. Furthermore, the dynamic characteristics among three kinds of topography in the elastic stage are studied using a three-dimensional finite method. Numerical results are validated by comparing with experimental results for base inclination topography. An inclined soil profile boundary causes non-axisymmetric resultant deformation, though a small difference in vertical displacement is observed.

Decades of commercial planting and other anthropogenic processes are posing a threat to the riparian landscapes of the Cauvery river basin, which supports a high floral diversity. Despite this, the habitats in the upstream sections of the River Cauvery are still intact, as they are located in sacred groves. To understand the dynamism of riparian forests exposed to anthropogenic pressures, the upstream stretch of Cauvery extending from Kushalanagara to Talacauvery (∼102 km) was categorized into two landscapes: agro ecosystem and sacred (i.e. preserved). The tree species were sampled using belt transects at 5 km intervals and the regeneration status of endemic species assessed using quadrats. A total of 128 species belonging to 47 families, and representing 1,590 individuals, was observed. Amongst them, 65% of unique species were exclusive to sacred landscapes. A rarefaction plot confirmed higher species richness for the sacred compared to the agro ecosystem landscapes, and diversity indices with more evenness in distribution were evident in sacred landscapes. A significant loss of endemic tree species in the agro ecosystem landscapes was found. Overall, this study demonstrates that an intense biotic pressure in terms of plantations and other anthropogenic activities have altered the species composition of the riparian zone in non-sacred areas. A permanent policy implication is required for the conservation of riparian buffers to avoid further ecosystem degradation and loss of biodiversity.

Global climate change during the twentieth century had a significant impact on the glaciers that resulted in creation of new lakes and expansion of existing ones, and ultimately an increase in the number of glacial lake outburst floods (GLOFs) in the Himalayan region. This study reports variation of the end-moraine dammed lakes in the high altitude Hindukush-Karakoram-Himalaya (HKH) region of Pakistan to evaluate future floods hazard under changing climate in this region. An integrated temporal remote sensing and Geographic information system (GIS) based approach using satellite images of Landsat-7 and 8 was adopted to detect 482 endmoraine dammed lakes out of which 339 lakes (>0.02 km2) were selected for temporal change analysis during the 2001-2013 period. The findings of the study revealed a net expansion in the end-moraine dammed lakes area in the Karakoram (about 7.7%) and in the Himalayas (4.6%), while there was a net shrinkage of about 1.5% in the lakes area in the Hindukush range during this period. The percentage increase in the lakes’ area was highest above 4500 m asl in the Hindukush, within 3500-4000 m asl in the Himalayas and below 3500 m asl in the Karakoram range. The overall positive change in the lakes’ area appears to prevail in various altitudinal ranges of the region. The heterogeneous areal changes in the endmoraine dammed lakes might be attributed to different climate regimes and glacial hydrodynamics in the three HKH ranges. A periodic monitoring of the glacial lakes and their associated glaciers is essential for developing effective hazard assessment and risk reduction strategies for this high altitude Himalayan region.