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Abstract: This paper analyses with the help of tree-ring studies the recurrence of extreme snow avalanches in a path situated in the upper Bødalen valley and originating from an outlet glacier of the Jostedalsbreen ice cap. By analysing tree-ring patterns of 91 trees, four extreme snow-avalanche events, extending over the entire valley floor and up to a distance of 800m from the foot of the slope, are clearly highlighted during the 20th century and at the beginning of the 21st century. Return periods of 15 to 20years for the most extreme events are extracted from the analyses, and recurrence intervals of 10 to 15years for avalanches presenting distinct deposition lobes uphill of the distal torrent. Results obtained by tree-ring analyses are successfully compared with available documents at different spatial and temporal scales. Rock-face snow-avalanche occurrences in the area, of small to medium size, are associated with heavy wintry precipitation combined with strong winds. However this normal situation is not valid for extreme snow avalanches crossing the path investigated in the paper, which result from the outlet glacier located in the starting zone; this glacier commands spatial and inter-annual variations of snow accumulation in the departure zone. [Copyright &y& Elsevier]

Sediment load delivered by rivers is an important terrestrial factor in the evolution and productivity of coastal ecosystems and coastal morphology. As the strongest interannual climate signal, the El Niño Southern Oscillation (ENSO) is closely related to variations in the hydrological cycle at global and regional scales. However, the influence of ENSO on temporal variations in sediment discharge is poorly understood. In this paper, we examine periodic variations in sediment discharge to the South China Sea from the Pearl River since the 1950s using wavelet transform analysis (WT). Furthermore, we apply cross wavelet spectrum (XWT) and wavelet coherence (WTC) to investigate the linkages between ENSO and sediment variability. The WT results revealed that periodic oscillations in sediment discharge in the Pearl River occurred annually (1 yr) before the 2000s, interannually (2–8 yr) from 1960–2002, and decadally (10–16 yr) from 1975–1995. These periodic variations in the sediment load series had common spectrum power with the water discharge and precipitation series, indicating an important climatic control. The XWT and WTC results revealed significant impacts of ENSO on precipitation, water discharge and sediment load at interannual time scales of 2–4.6 yr from 1960–2002 with a shift of patterns of ENSO on sediment variability after the 1970s. In addition, an in-phase relation between sediment discharge and ENSO at time scales of 10–16 yr from 1975–1995 was detected, indicating that variations at decadal scales could be related to other climatic teleconnections such as the Pacific Decadal Oscillation. Compared with the spectrum structures of periodic variations in precipitation and water discharge and their relationship with ENSO, there was a loss of energy in the sediment load at annual time scales after 2002 that can be attributed to dam construction in the river basin. Our study provides perspectives on the connections between ENSO and sediment variability at different time scales, which is of practical and scientific importance for forecasting global hydrological processes and for river management. [ABSTRACT FROM AUTHOR]

Talus slopes beside glaciers are among the best objects to research on climate change. In the Tatra Mountains, the highest mountains of central Europe, no glaciers remain, only glacierets and permafrost. For that reasona complex investigation of talus slopes was conducted there in the years 2009–2010. This paper presents the results of GPR and lichenometric measurements of the talus slopes in six glacial cirques located in the High and Western Tatras. The thickness and internal structure of talus slopes were identified along with the variability and conditions of their development. Maximum thickness of the talus slopes ranges from 20 to 35 m, reaching higher values in the High Tatras. The diversity of the thickness of the talus slopes within the Tatras is mostly explained by differences in the relief conditioned by lithology. The diverse altitudinal locations of the talus slopes, and the exposure and inclinations are not reflected in the size and thickness. The thickness of the studied slopes depends primarily on the activity of the processes supplying rock material and on the size and shape of the sediment supply area. The results of the lichenometric testing together with the analysis of the long-term precipitation data imply a several hundred-year-long deterioration of the climate during the Little Ice Age, which is reflected in the increased activity of morphogenetic processes on the talus slopes across the whole massif of the Tatras. In the last 200 years, the talus slopes of the Tatras were most active in three periods: at the end of the Little Ice Age, in the 1930s and 1940s, and in the early 1970s. [ABSTRACT FROM AUTHOR]

The beginning of the 1770s in the Czech Lands is well documented for its meteorological extremes and their social impacts. However, the effects of these extremes on geomorphic systems and on landslide occurrence and activity in particular have been minimally studied. In this paper, we use a complex set of written and iconographic documentary data to reconstruct the landslide calamity in North Bohemia, with a detailed case study of the Kozí vrch Hill landslide. The landslide calamity of 1770 is the oldest known landslide calamity in this region, including 14 documented events; and its reconstruction may therefore provide important data on landslide frequency, triggers, and impacts during the adverse weather patterns in the last part of the Little Ice Age (LIA). We focus on a case study of the Kozí vrch Hill landslide, and we use the documentary evidence and field techniques to reconstruct its location, extent, topography, kinematics, and triggers. Based on precipitation indices and weather descriptions, the extremely wet and rainy preceding year and the 1769/1770 winter were the major triggering factors that resulted in water saturation of Neogene volcaniclastics underlying the basalt lava flows and their subsequent collapse. Furthermore, we analyse the post-landslide terrain transformation and land use patterns during the 240 years following the landslide to illustrate the persistence of particular landslide features. We conclude that the major transformations, which obscured most of the landslide features, occurred in only the last 50–60 years. Finally, we discuss the role of documentary data and the current methodological advances in their use for the reconstruction of landslide frequency and impacts during the LIA. [ABSTRACT FROM AUTHOR]

Landslide inventories are critical to support investigations of where and when landslides have happened and may occur in the future; however, there is surprisingly little information on the historical occurrence of landslides at the global scale. This paper presents a new publicly available global landslide catalog (GLC), which is based on media reports, online databases, and other sources. This database is currently available at http://ojo-streamer.herokuapp.com/ . The 5741 points in the GLC provide a foundation for evaluating spatial and temporal trends in landslide activity from 2007 to 2013. Globally, landslides were reported most frequently from July to September. Most events occurred in Asia, North America and Southeast Asia. In contrast, fewer than 5% of the fatalities were reported in North America, suggesting a significant amount of under-reporting in other regions as well as potential discrepancies between developing and developed regions. Reported landslide events were also compared to satellite-based precipitation estimates from the Tropical Rainfall Measuring Mission (TRMM) to evaluate the co-occurrence of extreme precipitation and landslide activity. Of the 3550 points considered in a subset of the GLC, approximately 60% of the reported landslides have daily precipitation exceeding the 95th percentile of precipitation calculated over a 14-year TRMM record for the same location. This study also investigated how the recurrence interval of extreme precipitation corresponded to some of the most catastrophic landslide events. In spite of several reporting and cataloging biases, spatial and temporal analysis of the GLC suggests that it is a valuable database for characterizing global patterns of landslide occurrence and evaluating relationships with extreme precipitation at regional and global scales. [ABSTRACT FROM AUTHOR]

Zero-order drainage basins, and their constituent hillslopes, are the fundamental geomorphic unit comprising much of Earth's uplands. The convergent topography of these landscapes generates spatially variable substrate and moisture content, facilitating biological diversity and influencing how the landscape filters precipitation and sequesters atmospheric carbon dioxide. In light of these significant ecosystem services, refining our understanding of how these functions are affected by landscape evolution, weather variability, and long-term climate change is imperative. In this paper we introduce the Landscape Evolution Observatory (LEO): a large-scale controllable infrastructure consisting of three replicated artificial landscapes (each 330 m 2 surface area) within the climate-controlled Biosphere 2 facility in Arizona, USA. At LEO, experimental manipulation of rainfall, air temperature, relative humidity, and wind speed are possible at unprecedented scale. The Landscape Evolution Observatory was designed as a community resource to advance understanding of how topography, physical and chemical properties of soil, and biological communities coevolve, and how this coevolution affects water, carbon, and energy cycles at multiple spatial scales. With well-defined boundary conditions and an extensive network of sensors and samplers, LEO enables an iterative scientific approach that includes numerical model development and virtual experimentation, physical experimentation, data analysis, and model refinement. We plan to engage the broader scientific community through public dissemination of data from LEO, collaborative experimental design, and community-based model development. [ABSTRACT FROM AUTHOR]

The Matiali fan is a coarse-grained, small alluvial fan in the eastern Himalayan foothills. It co-exists side by side with the large Tista megafan and other Quaternary fluvial deposits, and has been affected by a number of young thrust faults. It is generally believed that tectonics is the main control in the deposition of these proximal fan–terrace systems. In this paper, geomorphologic and sedimentologic study of the Matiali fan and associated river terraces are combined with five OSL dates from these deposits to understand the succession of events and the forcing mechanism that shaped the geomorphology in the study area during late Quaternary time. Two aggradational terraces (T1 and T2; T2 > T1) occur within the river valleys incised on the Matiali fan. Three E–W scarps cross the fan surface, and they represent the steeper limb of the asymmetric fault-propagation folds formed over blind thrusts. These folds have deformed the fan (T3) and T2 terrace sediments, but the youngest T1 terrace deposits have remained undeformed. Sedimentological studies indicate continuous gradation from the coarsening-upwards mass-flow megagravel in the proximal part to the traction transported finer sheetflood gravels in the distal part, implying a continuous sedimentation history across the fan, uninterrupted by any evidence of syn-depositional tectonic movement. Poorly consolidated sandy gravels of the terraces indicate deposition through braided fluvial processes during a later period of sediment aggradation that filled up the incised river valleys. Previously published 14 C dates indicate that deposition of the Matiali fan started around 34 ka coinciding with a period of the intensified Indian summer monsoon of MIS-3. It is suggested that the fan was abandoned and river valleys incised during the LGM between 24 and 18 ka when the discharge decreased substantially. Increased rainfall and sediment supply, with their inherent fluctuations, during wetter periods of MIS-2 and MIS-1 since 12 ka probably resulted in the aggradation of T2 and T1 as shown by our OSL dates. OSL dates from the top of deformed T2 and base of undeformed T1 indicate that the Chalsa fold formed between ~ 11 and ~ 6 ka. Succession of geomorphic and deformational events reconstructed from this study and available age data indicate that the Matiali fan and terrace aggradation coincides with periods of increased monsoonal precipitation, whereas tectonic movements along blind thrusts of Chalsa and Matiali took place later, deforming the fan and older terrace deposits. The evidence unequivocally indicates, contrary to the prevalent notion of tectonic control of geomorphic features in the proximal mountain-front setting, that the deposition of the fan–terrace system was primarily controlled by the fluctuation of the Asian summer monsoon rather than Himalayan tectonics. [ABSTRACT FROM AUTHOR]

Abstract: The paper examines the potential of dendrogeomorphic analyses to deliver a one-year resolution chronology of snow-avalanche winters in Northern Iceland, at the scale of a colluvial cone covered with European White Birch trees and shrubs (Betula pubescens Ehrh.). Reconstruction of the avalanche history is performed using tree-ring analyses. Determination of the most reliable growth disturbance (class 1 of growth eccentricity) and applying a tempering index value with threshold 10% of trees responding in the same year and at least two trees affected, avalanche-activity years are highlighted, resulting in 52 avalanche winters. Amongst those, 5 winters have activity index over 40%, indicating major years. Calculation of frequency of similar growth disturbances at each tree provides a return period ranging from 4.2 to 19years. Inferred spatial extent of snow-avalanche events induces flow-like snow avalanches with limited extent around the tree-less parts of the cone with a return period under 6years; the cone is totally covered and the distal tree-limit over-passed with a return period of 15–20years. [Copyright &y& Elsevier]

Abstract: Following construction of the Three Gorges Dam, many farmers resettled in surrounding mountain areas and cultivated marginal lands, which are mostly on steep slopes with soil of poor structure. In general, high soil loss rates occur during intense storms. Therefore, soil erosion is a major environmental problem in the Three Gorges area (TGA) of China. Understanding and quantifying sediment load is important for sustainable agriculture and the environment in this region. This paper analyzes the relationships between rainfall, runoff, and sediment transport in the Wangjiaqiao watershed. Strong seasonal and monthly variability in sediment load was found. Sediment was strongly transported during summer months, a period when frequent flood events of high magnitude and intensity occurred. Analysis of the relationships between precipitation, discharge and sediment transport at an individual event scale showed significant correlations between total precipitation, peak discharge, total water yield, maximum 30min rainfall intensity, and sediment-related variables. Stepwise multiple regression analysis revealed that rainfall amount is the major cause of runoff, while events producing a large discharge in a short time play an important role in inducing severe soil erosion. During 40 flood events, three different types of hysteretic loops were observed: clockwise (28 events, 70%), figure-eight (5 events, 12.5%), and complex (7 events, 17.5%). The results of this study confirm the complex and heterogeneous nature of sediment response in the Wangjiaqiao watershed. [Copyright &y& Elsevier]

Abstract: Sierra de Gredos, a mountain range in Central Spain, is prone to the occurrence of shallow landslides, which can transform into sediment laden flows as demonstrated by geomorphologic evidence. The analyses of these complex processes require reliable design tools for predicting thresholds of triggering precipitation in order to assess the susceptibility characteristics. In the Sierra de Gredos there is a lack of knowledge concerning how weathering mantle properties vary spatially, and what effects these spatial patterns have on infiltration, surface runoff and shallow subsurface flow. In this context, this paper is focused on the hydrogeomorphic characterization of a shallow landslide that occurred on December 17, 1997. The Generalized Quasi-Dynamic Model (GQDM) was implemented to approach the critical rainfall intensity set for different durations and to establish the intensity–duration (ID) threshold. To this purpose, field and laboratory methods, such as: Seismic Refraction Tomography (SRT), Time Domain Reflectometry (TDR), and geotechnical tests were applied. The use of these field investigations and their combination with the GQDM have allowed us to provide a detailed description of the behavior of the catchment, and reproduce the pattern of instability generated by an intense storm which triggered the 1997 shallow landslide. Furthermore, this threshold can be used as a predictive tool for hazard prevention. [Copyright &y& Elsevier]

Abstract: The empirical rainfall intensity and duration (I–D) threshold for the initiation of shallow landslide is newly defined for Japan where heavy rainfalls frequently occur during the East Asian summer monsoon season. The rainfall causes sediment-related disasters annually. This paper presents an examination of 1174 rainfall-induced shallow landslides that occurred during 2006–2008. Their I–D conditions were analyzed objectively from rainfall data (Radar-Raingauge Analyzed Precipitation) to derive the I–D threshold using the quantile-regression method: I =2.18 D −0.26, where I is measured in millimeters per hour and D in hours, as measured from the beginning of rainfall to the landslide occurrence. Rainfall events are separated by the absence of rainfall for 24h. We then established a rescaled I–D threshold by dividing the rainfall intensity by the mean annual precipitation (MAP), as I MAP =0.0007 D −0.21, where I MAP is the rescaled average per-hour rainfall intensity. These thresholds were defined by the second percentile regression line for D of 3–537h. The new thresholds are considerably lower than those previously reported for the world, humid subtropical regions, the Asian monsoon region, and Japan. The result suggests that Japan is highly prone to rainfall-induced shallow landslides because of its high-relief topography, geologic conditions, human interference, and rainfall characteristics during the East Asian summer monsoon season. [Copyright &y& Elsevier]

Abstract: Transgressive dunefields are present along the entire stretch of the Rio Grande do Sul (RS) coast, from Rondinha to Mostardas. These dunefields change their morphology and size along the coast and through time. The aim of this paper is to describe the spatial and temporal variations of the dunefields and analyze the main agents that control these variations. The dunefields at the northern littoral are narrow (1300 to 1400m wide) due to the local higher precipitation, lower wind drift potential (DP) and smaller sand supply. Southwards, the dunefields increase their width (reaching 6900m), as the precipitation decreases and the wind DP and the sand supply increase in the area. The RS dunefields have changed through time. Since 1948, the dunefields have experienced increases in the deflation area, in the vegetation cover and in the moist areas. These processes of dunefield stabilization are probably the result of the historical increase in precipitation and decrease in wind DP. As the northern dunefields are smaller, they have less sand, thus they were more susceptible to stabilization processes. In the southern dunefields, the larger amount of sand and the ongoing coastline erosion have retarded the stabilization processes. [Copyright &y& Elsevier]