High Steep Slopes Research Articles

Evaluation of sites for the reestablishment of the American chestnut (Castanea dentata) in northeast Georgia, USA

The American chestnut (Castanea dentata, hereafter called chestnut), a valuable tree species that was once common in the last century in the eastern USA, is currently nearly extinct due to blight. Many efforts have been made to develop blight-resilient seedlings of this species, and an associated challenge is to identify the most suitable sites for its restoration. Our objectives were to identify the suitable sites for planting blight-resistant chestnut seedlings and the environmental parameters associated with the suitability assessment. Furthermore, we considered land ownership due to practical planning and management implications. Our study area is located in northeast Georgia, USA. We used global sensitivity and uncertainty analysis to select four environmental factors, as criteria in multi-criteria decision analysis, to create suitability maps for chestnut reestablishment. The results indicate that chestnut is sensitive to elevation, precipitation during the driest month (PDM), normalized difference of water index (NDWI), ground slope, and topographic aspect. Soil attributes did not play a significant role in determining the site suitability. Deciduous forests were the most suitable sites for chestnut reestablishment, while over 99% of the suitable sites fall within the federal lands. The occurrence of chestnut may be expected to increase in areas with high elevations and steep slopes. This study identifies the most critical environmental variables in northern Georgia for assuring a successful reestablishment of chestnut with the new blight-resistant strains of this species. It also identifies silvicultural prescriptions that may help landowners with the reestablishment process and its success.

Farmers’ diagnosis of current soil erosion status and control within two contrasting agro-ecological zones of Rwanda

Rwanda, the land of thousand hills, hosts a large diversity in environmental conditions, regionally classified into agro-ecological zones (AEZs). This paper aimed to explore the current perceptions of farmers on soil erosion processes, soil erosion control (SEC) and their impacts on the adopted farming systems within two watersheds from contrasting AEZs, i.e. Murehe in the Eastern plateau and Tangata in the Buberuka highlands, using participatory survey data from 300 households collected during face-to-face interviews in 2017. Both zones differed in socio-economic environment, the short distance to the capital favouring higher education levels in Murehe, while the production of cash crops in the well aroused and more fertile, yet also more steeply sloping Tangata watershed offered higher incomes. Despite these differences, adoption of SEC measures proved uniform across both zones reflecting strong but seemingly low-differentiated governmental supported action. Diversity in available erosion control measures within both zones was large, but dominated by combined structural and vegetative measures. Most farmers relied on government support for the installation of bench terraces, but adopted also other SEC such as progressive terracing and agroforestry. SEC adoption furthermore changed the agricultural systems heading to crop rotation, contour tillage and combined application of (in)organic fertilizers, albeit mainly fostered through subsidies. Despite these efforts, SEC seemed to be only partly effective in the highlands where erosion continued to have multiple high impact consequences affecting the entire landscape. High rainfall amounts and steep slopes were held responsible. The potential contribution of land management to erosion was generally less recognized, except for the tillage practices. Erosion was considered most prominent in the mid-season periods on Acrisols located at vulnerable landscape positions. These research results might question the effectiveness of the adopted control practices in particular AEZs. However, it can also pinpoint to the need of a much more integrated watershed management approach. The long-standing exposure of the surveyed population to diverse erosion control measures offers a unique insight that can be useful for other tropical highland countries.

Multistep rocky slope stability analysis based on unmanned aerial vehicle photogrammetry

High-steep slope information collection and multistep rocky slope stability analysis play an important role in slope engineering. However, traditional on-site investigations suffer from terrain restrictions and data omissions. This paper presents a block identification method based on UAV (unnamed aerial vehicle) photogrammetry and its computer implementation. An SfM (structure from motion) method is introduced and a 3D reconstruction software-PhotoScan was used to build the DEM (digital elevation model) of the rock mass for real-time monitoring. Then, an RANSAC (random sample consensus) shape detection algorithm was used to search the structural planes in the point cloud model. A computer program GeoSMA-3D (geotechnical structure and model analysis-3D) has been developed to implement engineering applications and a case study was carried out which confirmed the efficiency of the method in dealing with complex surface modeling and multistep rocky slope stability analysis.

New prospects on high on-current and steep subthreshold slope for innovative Tunnel FET architectures

We propose three innovative SOI Tunnel FET architectures to solve the recurrent issue of low ION and degraded subthreshold slope measured on TFETs. These are evaluated and compared with a standard TFET structure (with lateral tunneling) using the Sentaurus TCAD tool. Extending the source (anode) at the bottom of the body region generates vertical band-to-band tunneling. Moreover, reducing the vertical distance between the extension and the gate oxide (Lrt) yields a very steep slope and higher ION compared to a device with only lateral tunneling, but only for gate lengths longer than 100 nm. Using an ultrahigh boron dopant concentration (1021 cm−3) thin layer at the bottom for extremely small body thickness (TSi < 7 nm), increases ION even for small gate lengths (LG < 100 nm). The implementation of an embedded tip in the source enhances the maximum electric field at the source/channel junction, but the impact on the performance is limited because the tunneling area is not increased. Therefore, this architecture provides a performance similar to a standard TFET. TCAD simulations using SiGe with different germanium concentrations (30% and 50%) and pure germanium, instead of silicon, show an increase of the interband tunneling current when using an ultrahigh dopant concentration thin boron layer for small gate lengths (LG < 50 nm). The reduction of the tunneling current using a relatively thick channel (11–7 nm) can be compensated by using a higher germanium concentration to reduce the energy bandgap. However, this will increase the density of defects causing a TAT tunneling instead of interband tunneling, jeopardizing the possibility of achieving a subthreshold swing below 60 mV/dec.

Unusual Roles of Discharge, Slope and SOC in DOC Transport in Small Mountainous Rivers, Taiwan

Riverine dissolved organic carbon (DOC), responsible for riverine productivity, is rarely documented in subtropical small mountainous rivers (SMRs) where high rainfall and steep slopes are the main features. This study investigated the DOC export at eight sites in three Taiwan SMRs to characterize the dynamics and controlling factors of DOC transport. Results showed that the mean DOC concentration of ~0.78 mg L−1 is much lower than the global average of ~5.29 mg L−1. However, the mean DOC yield, ~22.51 kg-C ha−1 yr−1, is higher than the global average of 14.4–19.3 kg-C ha−1 yr−1. Comparing with worldwide rivers from literature, the annual discharge, slope, and SOC (soil organic carbon) are controlling factors as expected, though they influence in different ways. SOC stock likely regulated by elevation-dependent biomes dominate the DOC supply, while slope restrains the DOC generation due to shallow soil depth and fast runoff velocity. However, the abundant discharge flushing this persistent low supply leads to a large DOC export in the SMRs. Furthermore, the DOC dynamics during typhoon periods showed a clockwise hysteresis, suggesting that the DOC is mainly from the riparian zone or downslope area during the rising limb of the hydrograph. This study elucidates the DOC transport in SMRs and provides an atypical yet significant piece of understanding on DOC transport in a global context.

Seepage Characteristics and Its Control Mechanism of Rock Mass in High-Steep Slopes

In Southwest China large-scale hydropower projects, the hydraulic conductivity and fracture aperture within the rock mass of a reservoir bank slope has dramatically undergone a time series of evolution during dam abutment excavation, reservoir impounding and fluctuation operation, and discharge atomization. Accordingly, seepage control measures by hydro-structures such as drainage or water insulation curtains should be guided by scientific foundation with a dynamic process covering life-cycle performance. In this paper, the up-to-date status of studying the evolution mechanism of seepage characteristics relating to fractured rock hydraulics from experimental samples to the engineering scale of the rock mass is reviewed for the first time. Then, the experimental findings and improved practice method on nonlinear seepage flow under intensive pressure drives are introduced. Finally, the scientific progress made in fractured rock seepage control theory and optimization of the design technology of high-steep slope engineering is outlined. The undertaken studies summarized herewith are expected to contribute to laying a foundation to guide the further development of effective geophysical means and integrated monitoring systems in hydropower station construction fields.

The CAMELS-CL dataset: catchment attributes and meteorology for large sample studies – Chile dataset

Abstract. We introduce the first catchment dataset for large sample studies in Chile. This dataset includes 516 catchments; it covers particularly wide latitude (17.8 to 55.0∘ S) and elevation (0 to 6993 m a.s.l.) ranges, and it relies on multiple data sources (including ground data, remote-sensed products and reanalyses) to characterise the hydroclimatic conditions and landscape of a region where in situ measurements are scarce. For each catchment, the dataset provides boundaries, daily streamflow records and basin-averaged daily time series of precipitation (from one national and three global datasets), maximum, minimum and mean temperatures, potential evapotranspiration (PET; from two datasets), and snow water equivalent. We calculated hydro-climatological indices using these time series, and leveraged diverse data sources to extract topographic, geological and land cover features. Relying on publicly available reservoirs and water rights data for the country, we estimated the degree of anthropic intervention within the catchments. To facilitate the use of this dataset and promote common standards in large sample studies, we computed most catchment attributes introduced by Addor et al. (2017) in their Catchment Attributes and MEteorology for Large-sample Studies (CAMELS) dataset, and added several others. We used the dataset presented here (named CAMELS-CL) to characterise regional variations in hydroclimatic conditions over Chile and to explore how basin behaviour is influenced by catchment attributes and water extractions. Further, CAMELS-CL enabled us to analyse biases and uncertainties in basin-wide precipitation and PET. The characterisation of catchment water balances revealed large discrepancies between precipitation products in arid regions and a systematic precipitation underestimation in headwater mountain catchments (high elevations and steep slopes) over humid regions. We evaluated PET products based on ground data and found a fairly good performance of both products in humid regions (r&gt;0.91) and lower correlation (r&lt;0.76) in hyper-arid regions. Further, the satellite-based PET showed a consistent overestimation of observation-based PET. Finally, we explored local anomalies in catchment response by analysing the relationship between hydrological signatures and an attribute characterising the level of anthropic interventions. We showed that larger anthropic interventions are correlated with lower than normal annual flows, runoff ratios, elasticity of runoff with respect to precipitation, and flashiness of runoff, especially in arid catchments. CAMELS-CL provides unprecedented information on catchments in a region largely underrepresented in large sample studies. This effort is part of an international initiative to create multi-national large sample datasets freely available for the community. CAMELS-CL can be visualised from http://camels.cr2.cl and downloaded from https://doi.pangaea.de/10.1594/PANGAEA.894885.

Assessment of Pluvial Floods Potential on the Rivers of the Republic of Moldova

Abstract Present study is dedicated to assessment and mapping of generation and propagation potential of flash flood and river floods on the rivers of the Republic of Moldova. Main methods applied in the research are Flash Flood Potential Index (FFPI) and Flooding Potential Index (FPI). Additionally, a new index for estimation of flood propagation potential (FPPI) is proposed in order to evaluate impact of main factors (natural and human) on propagation of flood wave through the floodplain of small and medium-sized rivers of Moldova. In total, assessment of FFPI an FPI was performed for 789 elementary river basins (basin area less than 200 km2) and also was considered for 983 elementary territorial-administrative units (communes). Estimation of FPPI was made for 50 main small and medium sized rivers of Moldova. All index parameters (7 for FFPI, 6 for FPI and 12 for FPPI) were integrated, analyzed and combined in GIS environment. As a results, it was found that the FFPI is average for mostly all basins and communes but is characterized by significant differences in spatial representation on local level. FPI is high in basins and communes situated in the floodplains of large and medium sized rivers, in flood-prone areas, and is low in those with high altitudes and steep slopes (Codri and Nistru heights). Flood propagation potential was estimated with average values for 56% of total number of rivers, high for 34% and very high for 6%. The results can be used for future estimation of flood generation and flood wave propagation processes and for improvement and optimization of flood management practices and strategies on rivers weakly studied from hydrology point of view.

Morphometric analysis of Vaitarna and Ulhas river basins, Maharashtra, India: using geospatial techniques

Drainage network quantification with respect to the climate, tectonics, lithology and geomorphology provides significant evidence of the drainage development, hydro-geomorphic and denudation characteristics of an area. The present study was carried out by using Shuttle Radar Topographic Mission DEM to study the drainage morphometry and its influence on the hydrological characteristics of Vaitarna and Ulhas basins in Maharashtra, India. Results of the morphometric analysis reveal that the catchment of Vaitarna and Ulhas can be described as of 6th and 7th order drainage basins, encompassing an area of 3795 and 4733 km2, respectively. Additionally, Vaitarna basin is characterised by relatively higher mean bifurcation ratio as compared to the Ulhas basin, indicative of higher structural control and steeper gradient in Vaitarna basin. Lower drainage density and stream frequency affirm availability of permeable sub-surface material and homogeneous lithological characteristics in both basins. The shape parameters show both basins are semicircular with dendritic and sub-dendritic drainage pattern. The relief parameters of Vaitarna and Ulhas suggest both of these basins are characterised by very high relief and steep slope. GIS-based analysis of all these morphometric parameters indicates the drainage development of the study area progressed well beyond maturity stage and lithology have a major impact on the drainage development in Vaitarna and Ulhas basins.

Hybrid P-Channel/N-Substrate Poly-Si Nanosheet Junctionless Field-Effect Transistors With Trench and Gate-All-Around Structure

This paper demonstrates the gate-all-around P/N hybrid nanosheet p-channel junctionless field-effect transistors (GAA NS-JLFET) with trench and raised source and drain structure. The GAA NS-JLFET exhibits the superior electrical properties, including high field-effect mobility (18.9 cm2/Vs), high on/off current ratio (>5 × 106), steep subthreshold slope (136 mV/dec.), and low DILB (60 mV/V). The high mobility and steep subthreshold slope of this GAA NS-JLFET indicates that the conducting hole filled the whole thin nanosheet channel. This GAA NS-JLFET is simple to fabricate and highly favorable for use in advanced system-on-panel and three-dimensional stacked ICs applications.

Analisis Stabilitas Lereng pada Longsor Desa Caok, Purworejo, Jawa Tengah

Longsor telah terjadi pada tanggal 19 Juni 2016 di dusun Caok, Kabupaten Purworejo, Jawa Tengah. Desa Caok masuk dalam wilayah pegunungan Menoreh. Lereng pada lokasi longsor tersebut mayoritas memiliki kemiringan lebih dari 200. Sebelum longsor, terjadi hujan dengan curah hujan mencapai 325 mm/hari. Hal tersebut mengindikasikan bahwa longsor terutama terjadi karena dipicu proses infiltrasi air tanah akibat intensitas hujan yang tinggi, serta lereng yang curam. Dalam penelitian ini dilakukan analisis stabilitas lereng dengan program Plaxis dan Geo-Slope berdasar muka air tanah kemiringan lereng, dan sifat parameter tanah. Data tersebut selanjutnya diolah dengan program Plaxis dan Geo-slope untuk mengetahui stabilitas lereng dan deformasi yang akan terjadi. Batas nilai aman suatu lereng adalah 1,25 (Bowless 1984), tanpa ada gempa. Dari hasil pemodelan Geo-Slope didapatkan angka keamanan 1,162. Pemodelan dengan program Plaxis 0,9522 dengan potensi perpindahan maksimal 205m. Kedua hasil angka keamanan mengindikasikan bahwa lokasi penelitian rawan terjadi longsoran.

Assessment of soil erosion vulnerability in the heavily populated and ecologically fragile communities in Motozintla de Mendoza, Chiapas, Mexico

Abstract. Variability in physical rates and local knowledge of soil erosion was assessed across six rural communities in the Sierra Madre del Sur, Chiapas, Mexico. The average erosion rate estimated using the RUSLE model is 274 t ha−1 yr−1, with the estimated erosion rates ranging from 28 to 717 t ha−1 yr−1. These very high erosion rates are associated with high rainfall erosivity (17 000 MJ mm ha−1 h−1 yr−1) and steep slopes (mean slope = 67 %). Many of the highest soil erosion rates are found in communities that are dominated by forestland, but where most of the tree cover has been removed. Conversely, lower erosion rates are often found where corn is cultivated for most of the year. According to the results of the soil erosion KAP (knowledge, attitude and practices) survey, awareness of the concept of soil erosion was reasonably high in all of the communities, but awareness of the causes of erosion was considerably lower. More than half of respondents believed that reforestation is a viable option for reducing soil erosion, but only a third of respondents were currently implementing reforestation practices. Another third of the respondents indicated that they were not following any soil conservation practices. Respondents indicated that adoption of government reforestation efforts have been hindered by the need to clear their land to sell forest products or cultivate corn. Respondents also mentioned the difficulties involved with obtaining favorable tree stocks for reforestation. The KAP results were used to assess the overall level of motivation to solve soil erosion problems by compiling negative responses. The relationship between the magnitude of the soil erosion problem and the capacity to reduce soil erosion is inconsistent across the communities. One community, Barrio Vicente Guerrero, had the highest average negative response rate and the second highest soil erosion rate, indicating that this community is particularly vulnerable.

Community managed forests dominate the catchment sediment cascade in the mid-hills of Nepal: A compound-specific stable isotope analysis

Soil erosion by water is critical for soil, lake and reservoir degradation in the mid-hills of Nepal. Identification of the nature and relative contribution of sediment sources in rivers is important to mitigate water erosion within catchments and siltation problems in lakes and reservoirs. We estimated the relative contribution of land uses (i.e. sources) to suspended and streambed sediments in the Chitlang catchment using stable carbon isotope signature (δ13C) of long-chain fatty acids as a tracer input for MixSIAR, a Bayesian mixing model used to apportion sediment sources. Our findings reveal that the relative contribution of land uses varied between suspended and streambed sediment, but did not change over the monsoon period. Significant over- or under-prediction of source contributions could occur due to overlapping source tracer values, if source groups are classified on a catchment-wide basis. Therefore, we applied a novel deconvolutional framework of MixSIAR (D-MixSIAR) to improve source apportionment of suspended sediment collected at tributary confluences (i.e. sub-catchment level) and at the outlet of the entire catchment. The results indicated that the mixed forest was the dominant (41 ± 13%) contributor of sediment followed by broadleaf forest (15 ± 8%) at the catchment outlet during the pre-wet season, suggesting that forest disturbance as well as high rainfall and steep slopes interact for high sediment generation within the study catchment. Unpaved rural road tracks located on flat and steep slopes (11 ± 8 and 9 ± 7% respectively) almost equally contributed to the sediment. Importantly, agricultural terraces (upland and lowland) had minimal contribution (each <7%) confirming that proper terrace management and traditional irrigation systems played an important role in mitigating sediment generation and delivery. Source contributions had a small temporal, but large spatial, variation in the sediment cascade of Chitlang stream. D-MixSIAR provided significant improvement regarding spatially explicit sediment source apportionment within the entire catchment system. This information is essential to prioritize implementation measures to control erosion in community managed forests to reduce sediment loadings to Kulekhani hydropower reservoir. In conclusion, using compound-specific stable isotope (CSSI) tracers for sediment fingerprinting in combination with a deconvolutional Bayesian mixing model offers a versatile approach to deal with the large tracer variability within catchment land uses and thus to successfully apportion multiple sediment sources.

On the initiation, movement and deposition of a large landslide in Maoxian County, China

At 5 am 24th June 2017, a catastrophic landslide hit Xinmo Village, Maoxian County, Sichuan Province, China. The slide mass rushed down from an altitude of 3400m and traveled 2700 m in a high velocity. The 13 million m3 deposition buried the whole village and caused about 100 deaths. The source area of the landslide is located in a high steep slope, average slope angle is 40o and maximal angle is 65o. The strata are interbedded Triassic Zagunao Formation metamorphic sandstone and slate with the dip slope angle of 45°. Based on high-resolution satellite remote sensing image, UAV image, DEM data, and field investigation, failure mechanism, travel features, and deposit characteristics were analyzed. The results showed that this landslide was influenced by Songpinggou Fault zone. According to the topography before the failure, the landslide is located in the back scarp of an antecedent landslide induced by Diexi Earthquake in 1933. The bedding slope provided potential rupture surface. Historical seismic activities and long-term gravitational deformation caused rock mass accumulated damages. Weathering and precipitation weakened the rock mass and finally induced shearing and tension failure. A huge block detached from the top rock slope, pushed the past landslide deposits in the middle part, rushed out of the slope bottom in a high velocity and buried the Xinmo Village. The rapid movement entrained and brought the soil into the Songping Gully which recoiled with and bounced back from the opposite mountain.

V shaped gully method for controlling rockfall on high-steep slopes in China

Large, deep open-pit mining projects lead to rockfall, which becomes an engineering hazard second only to slope stability. The V shaped gully (V-gully) method introduced here was shown to have a significant effect on preventing rockfall through reduction of kinetic energy and rainfall discharge. The method, where a gravel cushion was laid on the V-gully surface, was applied in a typical open-pit mine. A drain dyke should be set at the bottom of the V-gully to discharge rainfall effectively. The slope stability analysis under different drainage rates was calculated by Modified Sarma (MSARMA) software. Slope stability, engineering activities and weathering condition of slope were taken into account to identify the rockfall prone areas. RocFall numerical software was used to calculate the effect of various angle V-gullies on the movements of various rockfall. A striking reduction in kinetic energy of rockfall was achieved, and the effects of V-gully protective measures were studied. Then, a system for controlling rockfall effectively and economically was designed for a particular slope according to the field situation. The effectiveness and reasonableness of design were evaluated through numerical simulations and field testing. This paper provides a theoretical and practical basis for a novel rockfall prevention technique on the high-steep slopes in similar engineering projects.

Combined methodology for three-dimensional slope stability analysis coupled with time effect: a case study in Germany

High-steep slopes in open pit mines are much more likely to collapse due to mining operations. Challenges such as data acquisition, precise numerical models and adaptable methodologies have impeded more reliable results of slope stability analysis based on the current methods. Within this context, this paper proposes a combined methodology using light detection and ranging technology to capture high-resolution slope geometry, three-dimensional geological and geotechnical modeling technologies for creating high-quality numerical simulation models and finite-element slope stability analyses combined with a new automatic strength reduction technique to analyze complex geotechnical problems. At the end, the methodology introduces a time series analysis to improve the reliability of the calculated factor of safety. A case study in the deepest open pit mine in Hambach, Germany, was conducted to test and demonstrate the effectiveness and applicability of the proposed methodology.

Assessing soil loss using GIS based RUSLE methodology. Case of the Bou Namoussa watershed – North-East of Algeria

AbstractThis study aims to estimating annual soil erosion rate and its spatial distribution in the Bou Namoussa water-shed located in the North-East of Algeria by applying the revised universal soil loss equation (RUSLE) within a Geographical Information System environment (GIS). The application of the RUSLE model in different natural environments and on every scale takes into account five key factors namely: the rainfall erosivity, the soil erodibility, the steepness and length of slopes, the vegetation cover and the conservation support practices. Each of these factors was generated in GIS as a raster layer, their combination, resulted in the development of a soil loss map indicating an average erosion rate of 7.8 t·ha−1·y−1. The obtained soil loss map was classified into four erosion severity classes; low, moderate, high and very high severity representing respectively 40, 30.48, 22.59 and 6.89% of the total surface. The areas, showing moderate, high and very high erosion rates which represent more than half of the basin area were found generally located in regions having high erodibility soils, steep slopes and low vegetation cover. These areas should be considered as priorities in future erosion control programs in order to decrease the siltation rate in the Cheffia reservoir.

Unidirectional threshold switching in Ag/Si-based electrochemical metallization cells for high-density bipolar RRAM applications

We herein present a novel unidirectional threshold selector for cross-point bipolar RRAM array. The proposed Ag/amorphous Si based threshold selector showed excellent threshold characteristics in positive field, such as high selectivity (~ 105), steep slope (< 5 mV/decade) and low off-state current (< 300 pA). Meanwhile, the selector exhibited rectifying characteristics in the high resistance state as well and the rectification ratio was as high as 103 at ± 1.5 V. Nevertheless, due to the high reverse current about 9 mA at − 3 V, this unidirectional threshold selector can be used as a selection element for bipolar-type RRAM. By integrating a bipolar RRAM device with the selector, experiments showed that the undesired sneak was significantly suppressed, indicating its potentiality for high-density integrated nonvolatile memory applications.

Assessment of landslide-triggering factors and occurrence using morphometric parameters in Geyraz Basin, Tokat, Northern Turkey

The Geyraz Stream is one of the tributaries of the Yesilirmak River, located within the southern of Middle Black Sea section, and enters the main river at Tokat city centre. Geyraz is a basin that has experienced numerous landslide events. In this study, morphometric parameters of areas prone to landslide occurrence were investigated and computed in GIS. These parameters included the Dissection Index, hypsometric integral, drainage density, Stream Power Index, and Compound Topographic Index, first and second orders. In addition, rocks, slopes and frequencies of first- and second-order streams in subbasins were considered and their correlations were examined. The moderate (15–20%) and high slope (20–25%) values with primarily clayey rocks (schist and flysch) correspond to high Di and Hi values, a maximum number of first- and second-order streams, and high landslide occurrence, while very steep slopes lead to low Di values and a low density of landslides. Results show that former landslides occurred in areas with Di values of 0.1–0.15, moderately steep and steep slopes, a maximum number of first- and second-order streams, high stream frequency on clayey rocks (schist and flysch), CTI values of 60–100, and SPI values of 75–85. In other words, landslide events are triggered by higher drainage frequency on primarily clayey rocks, intense fluvial incision and medium–high steep slopes. The location of agricultural land in the landslide area, reflecting lack of vegetation cover, is another landslide-triggering factor. Thus, the study area was ranked in six different classes and risk was rated as very low, low, medium, medium to high, high and very high. Determination of areas prone to landslide occurrence and their triggering factors is important for regional planning with respect to basin management and hazard prevention.

Accurate coastal DEM generation by merging ASTER GDEM and ICESat/GLAS data over Mertz Glacier, Antarctica

Mertz Glacier (MG) calved in February 2010 and a 70-years' calving cycle of MG was reported recently because of the shallow Mertz Bank. To better investigate the calving process, a high accurate surface Digital Elevation Model (DEM) with accurate date marker over MG is urgently required for numerical modeling, especially over the ice tongue. However it is quite challenging to generate an accurate DEM over high relief and steep slope regions. To solve this problem, a new method for accurate coastal DEM production by merging ASTER GDEM and ICESat/GLAS data is designed, which can effectively discriminate accurate elevation data from ASTER GDEM. Then, a DEM corresponding to the end of 2002 over MG is generated, which has an accuracy of 0.99±17.50m. This DEM is several times better in accuracy than the original ASTER GDEM (accuracy: −8.17±54.31m) and two new characteristics of ASTER GDEM have been found through analysis. First, ASTER GDEM has elevation bias (varying from −23m to 28m), spatially correlated to ASTER ground tracks, which was most probably caused by uncertainty of attitude measurements of ASTER. Second, ASTER GDEM grids with stacking number ≥4 can be effectively adjusted by ground control points so as to improve elevation accuracy. Additionally, this DEM has the best accuracy by comparing with other DEMs (RAMP DEM: 47.71±91.61m, ICESat/GLAS DEM: −1.01±30.33, Bamber DEM: −1.07±33.04m, Bedmap-2 DEM: 9.19±48.34m, and Cryosat-2 DEM: −5.42±32.02m). The high performance of our DEM in accuracy indicates that our method is effective and has a potential to be widely used to improve existing ASTER GDEM along Antarctic coast.