1,720,965 research outputs found
On the influence of river Basin morphology and climate on hydrogeomorphic floodplain delineations
No full textElevation-based hydrogeomorphic models are widely used to parsimoniously delineate floodplains with limited input data using topographic gradients to distinguish floodplain areas from hillslopes. Hydrogeomorphic models generally use scaling laws to assess flood flow depths as a function of contributing drainage areas. Floodplains are consequently mapped as those areas underlying maximum flood levels. Recent scientific literature has demonstrated that hydrogeomorphic models consistently perform from regional to global scale, validating geomorphic floodplain delineations in diverse morphological and hydroclimatic river settings. Nevertheless, the relationship between model fidelity, basin morphology, and basin hydroclimatic conditions is still unclear. Specifically, further investigations on the applicability of scaling laws in semi-arid and low-gradient basins is needed. In this work we investigated how climatic variability and basin slope can influence the parameterization of the abovementioned scaling laws in support of hydrogeomorphic floodplain modeling. Eleven basins in the west-central United States were selected as case studies. This research demonstrated that sub-basins slope and annual rainfall are the most influential morphometric and climatic parameters on scaling law regressions. Specifically, we found that scaling relationships are inconsistent in defining semi-arid basin floodplains (average annual rainfall lower than 570 mm) with low-gradient valley slopes (lower than 5%)
Investigating hydrogeomorphic floodplain mapping performance with varying DTM resolution and stream order
No full textHydrogeomorphic models allow parsimonious, fast and effective floodplain extent mapping using topographic data as the main input. Hydrogeomorphic approaches enforce the principle that floodplains are well-distinguished and unique landscape features within river corridors. We investigated the sensitivity of a hydrogeomorphic floodplain delineation algorithm, based on a hydrological power law, relating flow depth to contributing area, digital terrain model (DTM) resolution and river network hierarchy. In addition, we compared the results to other common floodplain mapping methods using standard flood-hazard maps as a reference. Taking the Arno River Basin, Italy, as a case study, our results show a dependency between the optimal power law parameters and DTM resolution, with larger parameter values required to reach optimal consistency with flood-hazard maps as DTM resolution increased. Floodplain mapping performance was also found to depend on stream order. We further tested the model consistency at a larger scale to evaluate its performance with respect to inundation maps in Hungary, Italy, Spain and the UK. Our study suggests that pre-defined power law parameters can be assumed, considering DTM resolution and stream order, supporting the use of the presented hydrogeomorphic model for large-scale floodplain mapping in ungauged basins where reference flood-hazard maps are not available
Understanding the Large-Scale Influence of Levees on Floodplain Connectivity Using a Hydrogeomorphic Approach
No full textThe widespread construction of levees has reduced river–floodplain connectivity and altered associated fluvial processes in many river systems. Despite the recognition that levees can alter floodplain connectivity, few studies have examined the role of levees in reducing floodplain areas at large watershed scales. This paper explores the application of a hydrogeomorphic floodplain inundation model in the Wabash Basin, located in the Midwestern United States, to assess changes in floodplain area in levee-protected areas. We evaluate 10- and 30-m topographic resolutions and spatially examine the influence of levees on floodplain area in relation to river network attributes. Generally, floodplains in levee-protected areas were influenced by topographic resolution, stream order, and elevation details of levees found in topography datasets. We show, when compared to Federal Emergency Management Agency maps, our approach underpredicts floodplain area when using 10-m resolution topography data but only slightly overpredicts when using 30-m resolution data. After removing details of levees from topography data, we found changes in floodplain area varied spatially, but basin-aggregate results changed little compared to topography datasets that contain levees, though larger floodplain areas were produced in some regions where levees were removed. This work contributes to a growing research emphasis on using hydrogeomorphic floodplain models to understand floodplain disconnectivity
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
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
Hydrologic scaling for hydrogeomorphic floodplain mapping: Insights into human-induced floodplain disconnectivity
No full textHydrogeomorphic approaches for floodplain modelling are valuable tools for water resource and flood hazard management and mapping, especially as the global availability and accuracy of terrain data increases. Digital terrain models implicitly contain information about floodplain landscape morphology that was produced by hydrologic processes over long time periods, as well as recent anthropogenic modifications to floodplain features and processes. The increased availability of terrain data and distributed hydrologic datasets provide an opportunity to develop hydrogeomorphic floodplain delineation models that can quickly be applied at large spatial scales. This research investigates the performance of a hydrogeomorphic floodplain model in two large urbanized and gauged river basins in the United States, the Susquehanna and the Wabash basins. The models were calibrated by a hydrologic data scaling technique, implemented through regression analyses of USGS peak flow data to estimate floodplain flow levels across multiple spatial scales. Floodplain model performance was assessed through comparison with 100-year Federal Emergency Management Agency flood hazard maps. Results show that the hydrogeomorphic floodplain maps are generally consistent with standard flood maps, even when significantly and systematically varying scaling parameters within physically feasible ranges, with major differences that are likely due to infrastructure (levees, bridges, etc.) in highly urbanized areas and other locations where the geomorphic signature of fluvial processes has been altered. This study demonstrates the value of geomorphic information for large-scale floodplain mapping and the potential use of hydrogeomorphic models for evaluating human-made impacts to floodplain ecosystems and patterns of disconnectivity in urbanized catchments
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