1,720,957 research outputs found
Sediment export from an Alpine proglacial area under a changing climate: Budgets, rates, and geomorphological processes
No full textProglacial areas in the European Alps and other high-elevation mountains are currently undergoing rapid change due to global warming. Because of rising temperatures, glaciers and glacier forefields are subjected to increased melting and associated sediment export. This observation is increasingly important with respect to high-elevation geomorphological and ecological dynamics, emerging natural hazards and mitigation efforts, and hydropower plant management. It is therefore crucial to analyze the factors and feedback mechanisms governing sediment production, transport, and deposition in these rapidly changing areas.
In this study, we investigated the sediment dynamics of a proglacial area located in the Eastern Italian Alps over the period 1969-2021 with the aims of: i) identifying the areas of sediment production; ii) quantifying volumes and rates of bedload sediment transport; and iii) determining the relative contribution of glacial export and fluvial erosion to the total sediment budget. We found that i) apart from glaciers, moraines and fluvial channels have been the most important sediment sources, albeit with substantial differences in terms of connectivity and thus supply rates; ii) the volumes and rates of sediment erosion varied by one order of magnitude (between tens and hundreds of mm per year), and were generally higher along the channel network; and iii) for a relatively shorter time interval between 2005 and 2021, the relative contribution of glacial bedload input with respect to the total sediment budget ranged between 34 % and 37 %, whereas 45 % to 59 % was derived from lateral fluvial erosion. Only a relatively small sediment volume was generated by net channel bed incision. These results imply that most of the sediment released from the proglacial area of the Sulden glacier is progressively transferred to the downstream sector of the channel network, with volumes that range between 931 and 1017 tons yr(-1) km(-2). These values are in the typical range of sediment export volumes from glaciated basins and highlight the high dynamicity of this region of the Alps. In general, our results confirm the complexity - in terms of spatial and temporal variability - of Alpine proglacial systems and highlight the need to systematically study these areas on a wide spatial and temporal scale, since the information provided by single locations or individual sectors of the sediment cascade, may not be adequate for understanding the dynamics acting in the entire proglacial regions
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Scale dependency in modeling nivo-glacial hydrological systems: the case of the Arolla basin, Switzerland
No full textHydrological modeling in alpine catchments poses unique challenges due to the complex interplay of meteorological, topographical, geological, and glaciological drivers with streamflow generation. A significant issue arises from the limited availability of streamflow data due to the scarcity of high-elevation gauging stations. Consequently, there is a pressing need to assess whether streamflow models that are calibrated with moderate-elevation streamflow data can be effectively transferred to higher-elevation catchments, notwithstanding differences in the relative importance of different streamflow-generation processes. Here, we investigate the spatial transferability of calibrated temperature-index melt model parameters within a semi-lumped modeling framework. We focus on evaluating the melt model transferability from the main catchment to nested and neighboring subcatchments in the Arolla valley, southwestern Swiss Alps. We use the Hydrobricks modeling framework to simulate streamflow, implementing three variants of a temperature-index snow and ice melt model (the classical degree-day model, the aspect-related model, and the Hock temperature-index model). Through an analysis of streamflow simulations, benchmark metrics consisting of resampled and bootstrapped discharge time series, and model performance metrics, we demonstrate that robust parameter transferability and accurate streamflow simulation are possible across diverse spatial scales. This finding is conditional upon the melt model applied, with melt models using more spatial information leading to convergence of the model parameters until we observe overparameterization. We conclude that simple semi-lumped models can be used to extend hydrological simulations to ungauged catchments in alpine regions and improve high-elevation water resource management and planning efforts, especially in the context of climate change
Multi-temporal sediment budgeting by geomorphic change detection in an instrumented debris flow basin
No full textRepeated topographic surveys enable the creation of multi-temporal Digital Elevation Models (DEMs) and allow the derivation of DEM of Difference (DoD) that permits assessing geomorphic changes and estimates area and volume of changes through time. This study analysed three high-resolution DEMs (1 m resolution) in order to assess topographic changes within a debris-flow catchment, the Gadria basin, located in Vinschgau-Venosta valley, South Tyrol, Italy. DEMs were acquired via airborne Light Detection and Ranging (LiDAR) surveys in 2011, 2018 and 2020 and thus the sediment budget in between those intervals was analysed via DoD. Sediment budgeting was performed at the basin-scale and in a selected Sediment Contributing Area (SCA). Volume estimates from the DoD analyses were compared to volume computed through data collected by monitoring sensors located at the outlet of the catchment. The main aim was to test DoD techniques and identify the most active areas within the catchment in the investigated period. Additionally, a highly active area in the headwaters of the catchment was surveyed by photogrammetry (0.20 m resolution) and analysed with Structure from Motion (SfM) technique. The suitability for sediment budget analyses was assessed for both methods. Results show that DoD analyses within SCA can provide accurate data, whereas caution must be paid when performing analyses at the catchment scale since several issues such as the different vegetation filtering techniques adopted to build DEMs, may cause large erroneous erosion and deposition changes not reflecting actual geomorphic processes. The high accuracy of SfM analyses and ease of acquisition of photogrammetric surveys result in a powerful tool for geomorphic change detection. This makes frequent mapping of highly active areas and tracking sediment motion possible. However, this approach is not suitable for surveying large areas, like an entire basin. For such purpose, the construction of DoD via LiDAR data is more appropriate. Even though the theory behind DoD construction can seem trivial, this is most often not the case in practical applications. This study shows that multiple sources of inaccuracies can lead to serious errors in the sediment budget calculation in every step of the DoD derivation. For accurate results, the impact of each error must be minimised, resulting in a time-consuming but necessary task.by Felix PitscheiderRiassunto in italienischer SpracheMasterarbeit University of Innsbruck 2021Masterarbeit Free University of Bozen-Bolzano 202
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Multi-temporal sediment budgeting by geomorphic change detection in an instrumented debris flow basin
No full textRepeated topographic surveys enable the creation of multi-temporal Digital Elevation Models (DEMs) and allow the derivation of DEM of Difference (DoD) that permits assessing geomorphic changes and estimates area and volume of changes through time. This study analysed three high-resolution DEMs (1 m resolution) in order to assess topographic changes within a debris-flow catchment, the Gadria basin, located in Vinschgau-Venosta valley, South Tyrol, Italy. DEMs were acquired via airborne Light Detection and Ranging (LiDAR) surveys in 2011, 2018 and 2020 and thus the sediment budget in between those intervals was analysed via DoD. Sediment budgeting was performed at the basin-scale and in a selected Sediment Contributing Area (SCA). Volume estimates from the DoD analyses were compared to volume computed through data collected by monitoring sensors located at the outlet of the catchment. The main aim was to test DoD techniques and identify the most active areas within the catchment in the investigated period. Additionally, a highly active area in the headwaters of the catchment was surveyed by photogrammetry (0.20 m resolution) and analysed with Structure from Motion (SfM) technique. The suitability for sediment budget analyses was assessed for both methods. Results show that DoD analyses within SCA can provide accurate data, whereas caution must be paid when performing analyses at the catchment scale since several issues such as the different vegetation filtering techniques adopted to build DEMs, may cause large erroneous erosion and deposition changes not reflecting actual geomorphic processes. The high accuracy of SfM analyses and ease of acquisition of photogrammetric surveys result in a powerful tool for geomorphic change detection. This makes frequent mapping of highly active areas and tracking sediment motion possible. However, this approach is not suitable for surveying large areas, like an entire basin. For such purpose, the construction of DoD via LiDAR data is more appropriate. Even though the theory behind DoD construction can seem trivial, this is most often not the case in practical applications. This study shows that multiple sources of inaccuracies can lead to serious errors in the sediment budget calculation in every step of the DoD derivation. For accurate results, the impact of each error must be minimised, resulting in a time-consuming but necessary task.by Felix PitscheiderRiassunto in italienischer SpracheMasterarbeit University of Innsbruck 2021Masterarbeit Free University of Bozen-Bolzano 202
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