1,720,973 research outputs found
30-year response to damming of a Mediterranean river in California, USA
No full textDry Creek is a major tributary of the Russian River in Northern California (USA) that has experienced hydrologic and morphologic alterations after the closure of Warm Springs Dam in 1983. Our objective is to present a detailed diagnosis of the modification of the creek’s flow and sediment regimes, and interpret the alterations regarding the ecomorphologic evolution previously observed in the creek. Statistical analysis of the river’s flow and sediment series indicates that dam operation has had significant impacts on the magnitude and frequency of occurrence of the highest floods, and the magnitude, variability, and duration of low and very low flows. Similarly, sediment concentration and discharge have also experienced major alterations. Loss of habitat complexity for native flora and fauna (especially endangered salmonids), channel incision, and vegetation encroachment are some of the negative trends found for the creek over the last 30 years, since river regulation began. We discuss the present dynamics of the river and propose, on that basis, the improvement of its hydromorphic functioning as part of future large-scale restoration initiatives
Fractal dimension of the hydrographic pattern of three large rivers in the Mediterranean morphoclimatic system: geomorphologic interpretation of Russian (USA), Ebro (Spain) and Volturno (Italy) fluvial geometry
No full textBy applying fractal geometry analysis to the drainage network of three large watercourses in America and Europe, we have calculated for the first time their fractal dimension. The aim is to interpret the geomorphologic characteristics to better understand
the morphoevolutionary processes of these fluvial morphotypes; to identify and discriminate geomorphic phenomena responsible for any difference or convergence of a fractal dimension; to classify hydrographic patterns, and finally to compare the fractal degree with some geomorphic-quantitative indexes. The analyzed catchment of Russian (California, USA), Ebro (Spain), and Volturno (Italy) rivers are situated in Mediterranean-climate regions sensu Ko ̈ppen, but with different geologic context and tectonic styles. Results show fractal dimensions ranging from 1.08 to 1.50. According to the geological setting and geomorphic indexes of these basins, the lower fractal degree indicates a prevailing tectonics, active or not, while the higher degree indicates the stronger erosion processes on inherited landscapes
Hydrogeomorphic features and improvement strategies of some Mediterranean rivers in California, Spain and Italy: a comparison between the Russian, Ebro and Volturno rivers
No full textThe application of an interdisciplinary approach to river management in some fluvial environments is presented. Three large rivers in Mediterranean climate have been studied: Russian River in northern California (drainage area of 3,846 km2), Ebro River in northeastern Spain (85,530 km2) and Volturno River (5,550 km2) in southern Italy. The aim is to compare hydrological and geomorphic features to highlight natural and human-based evolution, considering climatic crises and river basin management in the last decades. Moreover, improvement strategies held in the last years to increase their ecological status and to reduce pressures on hydromorphological attributes are analyzed. These rivers have been facing increasing changes in hydrogeomorphic aspects, mainly due to river damming, coastal retreat and floodplain occupation. These changes have deeply altered the fluvial dynamics, modifying aquatic and riparian habitats and imposing large alterations in their ecomorphological connectivity. However, they are being actively managed nowadays to improve their ecohydrological status: habitat restoration for protected species and amelioration of flow regime in Russian River, improvement of river connectivity and reduction of hydrologic alteration in Ebro River, river banks and mouth recovery to reduce erosion in Volturno River are some of those strategies.
Application of these tools shows that an integrated, adaptive approach suitable for Mediterranean rivers improves their ecological status restoring natural processes
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Fractal dimension of drainage network geometry of some Mediterranean-type river basins in California, Spain and Italy: a geomorphologic key to interpretation
No full textBy applying fractal geometry analysis to the drainage network of the Russian (USA), Ebro (Spain) and Volturno (Italy) Mediterranean-type rivers, 2D-fractal dimensions have been calculated. Preliminary results have been compared with classical geomorphic-quantitative indexes to highlight fluvial dynamics. The average fractal dimension results slightly above unity, suggesting that the basins have experienced concurrent overlay of secondary modeling processes on the primary tectonic ones
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe 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
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe 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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