1,721,034 research outputs found
The flash flood of October 2011 in the Magra river (Italy): Results of Post-Event documentation
No full textA method for the assessment and analysis of the hydromorphological condition of Italian streams: The Morphological Quality Index (MQI)
Full text linkA new index has been developed for the hydromorphological assessment of Italian rivers. The method was designed to comply with the EU Water Framework Directive requirements, but its use can be extended to other applications in river management. The evaluation of stream morphological quality is preceded by a phase of river segmentation, consisting of an initial division of the network into river reaches with homogeneous morphological characteristics. The evaluation procedure consists of a set of 28 indicators, which were defined to assess longitudinal and lateral continuity, channel pattern, cross section configuration, bed structure and substrate, and vegetation in the riparian corridor. These characteristics are analyzed in terms of geomorphological functionality, artificiality, and channel adjustments. Indicators, classes, and the scoring system were defined based on expert judgement. The scoring system leads to the definition of the Morphological Quality Index (MQI). Application of the method to 102 river reaches covering a wide range of physical conditions and human pressures of Italian streams enabled the testing of the overall methodology and the refinement of the indicators and scores. Limitations, strengths, and the applicability of the method are also discussed in the paper
Geomorphometric assessment of spatial sediment connectivity in small Alpine catchments
No full textComplex and rugged topography induces large variations in erosion and sediment delivery in the headwaters of alpine catchments. An effective connection of hillslopes with the channel network results in highly efficient sediment transfer processes, such as debris flows. In contrast, morphological conditions producing decoupling of hillslopes from channels (e.g. glacial cirques) may exclude large areas of the catchment from sediment delivery to its lower parts. Moreover, an efficient connection between hillslopes and channel network does not always ensure an effective downstream transfer of sediment. Low-slope channel reaches (e.g. in hanging valleys) cause sediment deposition, which often results in changes of the sediment transport processes, typically from debris flow to streamflow with low bedload and suspended load rates. The availability of high-resolution digital terrain models, such as those derived from aerial LiDAR, improves our capability to quantify the topographic controls on sediment connectivity. A geomorphometric index, based on the approach by Borselli et al. (2008), was developed and applied to assess spatial sediment connectivity in two small catchments of the Italian Alps featuring contrasting morphological characteristics. The results of the geomorphometric analysis were checked against field evidences, showing good performance and thus potential usefulness of the index
Ruolo della vegetazione riparia nella stabilizzazione degli alvei di corsi d’acqua montani = The role of riparian vegetation in streambed stabilitation
No full textLa vegetazione riparia può influenzare significativamente la capacità dei corsi
d’acqua di convogliare la portata liquida e solida e condizionarne l’assetto fluviomorfologico.
Le piante presenti sul contorno bagnato, infatti, favoriscono la deposizione
del materiale solido e con il loro apparato radicale stabilizzano tali depositi. Per valutare
gli effetti della vegetazione riparia sul consolidamento dei sedimenti e sulla morfologia,
sono state effettuate misure di densità e resistenza meccanica degli apparati
radicali, in cinque trincee scavate lungo il rio Mareit/Mareta in provincia di Bozen/
Bolzano, dove nel 2010 è stato effettuato uno dei più significativi interventi di riqualificazione
fluviale. Quattro trincee sono state scavate su isole fluviali vegetate, mentre
una sulla sponda sinistra del torrente. Sono state anche effettuate analisi sullo sviluppo
dei raggruppamenti vegetali pre- e post- intervento di riqualificazione, per poter poi
estendere i risultati a scala di tratto, attraverso la differenza tra quote di DEM (DoD)
ottenuti con LiDAR aereo e fotogrammetria “Structure from Motion” (SfM). I risultati
ottenuti dall’analisi dei raggruppamenti vegetali mostrano una loro riduzione nel tempo
dovuta all’unione di più raggruppamenti, mentre l’area complessivamente coperta
dalle piante è cresciuta di quasi il 300%. I risultati relativi al rinforzo radicale, mostrano
che esso, espresso in termini di coesione aggiuntiva, varia fra 5 e 30 kPa, con significative
variazioni di andamento con la profondità passando da specie più pioniere a specie
che vi succedono. Mentre nelle situazioni in cui prevalgono i salici si ha un rinforzo
meno spiccato rispetto all’ontano, ma più regolare lungo il profilo verticale e si mantiene
apprezzabile anche in profondità, viceversa, dove prevale l’ontano il rinforzo è
più marcato ma localizzato in superficie. In generale, si evidenzia l’importanza della
vegetazione nella stabilizzazione dei sedimenti ed una dipendenza dalla successione
ecologica che si instaura. Tali risultati forniscono un contributo anche di carattere
quantitativo utile ad una migliore comprensione della dinamica morfologica dei corsi
d’acqua montani, utile anche nell’ambito degli interventi di riqualificazione fluviale.Instream and riparian vegetation may significantly affect flow discharge and
sediment transport in channels with rigid and flexible vegetation, under emergent
and submerged conditions. Riparian plants, in fact, increase flow resistance inducing sediment deposition.. whereas the root systems stabilize the deposited sediments. In order to estimate the effects of the vegetation root system on sediment retention and stream morpholoiD" we measured roots density and strength in five points of Mareit/ Mareta river in Bozen/Bolzano Province, where one of the largest river restoration intervention was carried out. Four trenches were excavated on a vegetated island and one trench on the vegetated left bank of the channel. Samples of roots were tested for tensile strength and root reinforcement was calculated. Moreover, an analysis of veg etation patch difference between pre- and post-restoration was performed in order to extend the effect of root reinforcement at a reach scale. Increased surface occupancy of riparian vegetation and vertical growth was estimated by calculating difference of DEM (DoD) produced with airbome LiDAR and Structure from Motion (SfM) photo grammetry. Results from vegetation patches analysis, show that the number of patch es decreased from pre-restoration and post-restoration as result of vegetation patches merging, whereas the total covered area increase of almost 300%. The minimum size of the patches decreased between pre- and post-restoration proving a recruitment of totally new small patches located in some little island in the middle of the channel, while the maximum patch surface increased in post-restoration conditions as result of merging patches. Results from root reinforcement analysis show that roots can exert an additional cohesion from 5 to 30 kPa underlining the importance to consider the effect of the vegetation in stabilizing the bed and the consequence on morphology dynamics in gravel-bed rivers
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
Riparian forest structure in a morphologically altered gravel-bed river
No full textThe pattern of riparian vegetation in gravel bed rivers depends on the climate, hydrological regime, and the morphological settings of the river. Also, the marked spatial variability of density, height, species diversity, age, and rates of growth reflects the very complex nature of bed colonization, the strong influence of sequences and magnitude of floods, and the feedbacks between morphology, vegetation and hydraulics. Furthermore, a wide array of human impacts acting at either the basin or river network scales can influence substantially the morphodynamics and thus the characteristics, types and distribution of vegetation within the river corridor. The aim of the work is to analyze the relationship between the vegetation structure and the morphological characteristics of two sub-reaches of the Piave river which suffered intense and multiple human impacts especially due to dam building and in-channel gravel mining. The Piave river shows a complex pattern of vegetation distribution along the cross- sections, with no clear relationship between the elevation and the “maturity” of plant communities as a result of a recent tendency of active channel widening after a long period of channel narrowing
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
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