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Assessing the historical residual flood-risk evolution over large floodable areas: dependence of the results on the 2D hydrodynamic numerical model
Full text linkThis study investigates the evolution of the flood risk along the middle-lower reach of the River Po (length ~350 km,
Northern Italy). The analysis starts from the common perception that, due to a combination of different causes, the flood
risk is dramatically increasing in Europe and in other areas of the world, which is supported by the steadily increasing
economic flood losses recorded worldwide. We refer in particular to the residual flood-risk and we consider an inundation
scenario simulated by means of a simplified quasi-two-dimensional (quasi-2D) hydrodynamic model that reproduces the
hydraulic behavior of a large floodable area outside the main embankment system of the Po river (named “C-Buffer”) for
an exceptional flood event with a 500-year return period; then we perform a detailed flood risk assessment for different
land-use scenarios and population dynamics that have been observed for the C-Buffer over the last five decades. The
detailed flood-risk assessment refers separately to four hydraulic compartments located within the C-Buffer, which
according to the study inundation scenario are flooded during the exceptional event. In particular, the analyses use flooddamage
curves proposed in the literature coupled with a reproduction of the inundation dynamics simulated by two fully
two-dimensional (2D) hydrodynamic models based on 2D shallow water Saint-Venant equations: Hec-Ras 5.0 and
Telemac-2D. The former model has been recently released and enables users to perform combined one-dimensional (1D)
and 2D unsteady-flow simulations (i.e. combining 1D reaches and storage areas with 2D flow areas schematized with
finite-volume method), while the latter is a widely employed and well known 2D finite-element scheme. The comparison
enabled us to assess how recent land-use changes affected the residual risk in the study area and, indirectly, to quantify
the dependence of flood-risk assessments on the considered 2D model, i.e. Telemac-2D and the new Hec-Ras 5.0
Effetti della subsidenza antropica sulle dinamiche di inondazione: il caso studio di Ravenna
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Evolution of flood risk over large areas: Quantitative assessment for the Po river
Full text linkThe worldwide increase of damages produced by floods during the last decades strengthens the common perception that flood risk is dramatically increasing due to a combination of different causes, among which climate change is often described as the major driver. Nevertheless, the scientific community is increasingly aware of the role of the anthropogenic pressures (e.g. steady expansion of urban and industrial areas in dyke-protected floodplains) that may strongly impact the flood risk in a given area by increasing potential flood damages and losses (i.e. so called "levee effect"). The scientific literature on quantitative assessments of the "levee-effect" or robust methodological tools for performing such assessments is still sparse. We refer to the dyke-protected floodplains of the middle and lower portion of River Po (Northern Italy), a broad geographical area (~46,000km2) with two specific research questions in mind: (i) has the flood risk increased over the last half century? And, if so, (ii) what are the main drivers of this change? First, we assess the flood-hazard evolution by analyzing three long series of daily streamflow available at different gauging stations. Secondly, we quantitatively assess the temporal variability of the flood exposure and risk by looking at the evolution in time of anthropogenic pressures (i.e. land-use and demographic dynamics observed from 1950s). To this aim, we propose graphical tools (i.e. Hypsometric Vulnerability Curves - HVCs) that are suitable for assessing vulnerability to floods over large geographical areas. Our study highlights the absence of statistically significant trends in annual statistics of the observed streamflow series and a stable population density within the dike-protected flood-prone area. Nevertheless, the proposed flood-vulnerability indexes show a significant increase of the exposure to floods in residential settlements, which has doubled since the 1950s
Effects of anthropogenic land-subsidence on inundation dynamics: the case study of Ravenna, Italy
Full text linkCan differential land-subsidence significantly alter
river flooding dynamics, and thus flood risk in flood prone areas? Many
studies show how the lowering of the coastal areas is closely related to an
increase in the flood-hazard due to more important tidal flooding and see
level rise. The literature on the relationship between differential
land-subsidence and possible alterations to riverine flood-hazard of inland
areas is still sparse, although several geographical areas characterized by
significant land-subsidence rates during the last 50 years experienced
intensification in both inundation magnitude and frequency. We investigate
the possible impact of a significant differential ground lowering on flood
hazard over a 77 km2 area around the city of Ravenna, in Italy. The
rate of land-subsidence in the study area, naturally in the order of a few
mm year−1, dramatically increased up to 110 mm year−1 after World War II,
primarily due to groundwater pumping and gas production platforms. The
result was a cumulative drop that locally exceeds 1.5 m. Using a recent
digital elevation model (res. 5 m) and literature data on land-subsidence,
we constructed a ground elevation model over the study area in 1897 and we
characterized either the current and the historical DEM with or without road
embankments and land-reclamation channels in their current configuration. We
then considered these four different topographic models and a
two-dimensional hydrodynamic model to simulate and compare the inundation
dynamics associated with a levee failure scenario along embankment system of
the river Montone, which flows eastward in the southern portion of the study
area. For each topographic model, we quantified the flood hazard in terms of
maximum water depth (h) and we compared the actual effects on flood-hazard
dynamics of differential land-subsidence relative to those associated with
other man-made topographic alterations, which resulted to be much more
significant
Is anthropogenic land subsidence a possible driver of riverine flood-hazard dynamics? A case study in Ravenna, Italy
Full text linkWe investigate possible changes in flood hazard over a 77-km2 area around the city of Ravenna. The subsidence rate in the area, naturally a few mm year−1, increased dramatically after World War II because of groundwater and natural gas extraction, exceeding 110 mm year−1 and resulting in cumulative drops larger than 1.5 m. The Montone–Ronco river system flows in the southern portion of the area, which is protected against frequent flooding by levees. We performed two-dimensional simulations of inundation events associated with levee breaching by considering four different terrain configurations: current topography and a reconstruction of ground elevations before anthropogenic land subsidence, both neglecting and representing the main linear infrastructures (e.g. roads, artificial channels). Results show that flood-hazard changes due to anthropogenic land subsidence (e.g. significant changes in computed water depth and velocity) are observed over less than 10% of the study area and are definitely less important than those resulting from construction of the linear infrastructures
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
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