1,720,967 research outputs found
Sediment Sampling and Analysis in Rönne å at Ängelholm
No full textThis report presents the results of sediment sampling in Rönne å (river) at Ängelholm, located in the north-western part of Scania, which is the southern-most province in Sweden. The sampling and subsequent grain-size analysis were performed primarily to verify hypotheses about main mechanisms controlling local scour at a number of sites where scour holes had been observed in the river during detailed bathymetric surveys. Thus, this study is expected (1) to complement the results from the bathymetric survey where bottom erosion (local scour) was detected in order to establish the main causes of the erosion, and (2) to subsequently employ the information on bottom sediment (grain size) conditions into an existing hydrodynamic model, improving model predictability regarding scour. Sampling were performed at 8 locations encompassing in total 19 samples that represented parts of the Rönneå river bottom experiencing scour in the city of Ängelholm, covering a stretch from the river mouth to about 8 km upstream. These locations comprised bottom areas with pronounced scour holes due to the presence of bends, bridges, and hard bottom. The samples were subjected to analysis, including sieving and visual inspection and classification, depending on the material composition. A few samples consisted mainly of cohesive material and they have not been analysed yet.Overall, the sampling and related analysis verified the hypotheses about the mechanisms governing the evolution of the scour holes at the investigated locations. The main causes of the scour were bend scour (locations SH1, SH4, SH9, SH10, and, SH12; see figure 1), bridge scour (SH8), and hard bottom scour (SH5 and SH6). However, at SH8, SH9, and SH10, hard bottom also contributed to the scour. The sediment parameters determined in the grain-size analysis will be useful for calculating the development and equilibrium properties of the scour holes using appropriate formulas from the literature. For the samples where grain-size analysis could be carried out the median grain size approximately varied between 0.6 mm and 15 mm, but larger-sized substrate (e.g., gravel) was observed in the field at hard bottom locations, where no samples could be retrieved by the applied sampling technique
Assessing the Combined Risk of Fire and Flood on a National Scale for Sweden
Get PDFFloods and wildfires are two critical hazards that impose substantial direct and indirect costs to society, including the resource needs of rescue services. Their occurrence is strongly linked to meteorological conditions, playing a fundamental role in hazard development and assessment. These hazards are notably distinguishable due to opposing weather requirements, wet conditions for floods and dry conditions for wildfires. However, certain regions are exposed to the convergence of these hazards simultaneously or in temporal proximity, demanding different levels of resources and mitigation strategies. Consequently, there is a vital need for a comprehensive combined risk assessment to enhance the effectiveness of rescue services to face such risks. This study presents an analysis for the combined risk of wildfires and floods on a national scale in Sweden over an 11-year period based on daily values on the Fire Weather Index (FWI) and river flow data, taken as proxies for the occurrence of fire and flood, respectively. The present study employed different methods to assess the joint occurrence of fire and floods including simultaneous plots of FWI and flow timeseries, scatter plots with risk categorization, and index plots combining standardized FWI and flow, offering both qualitative and quantitative insights into combined risk assessment
Compound effects of sea level and flow on river-induced flooding in coastal areas of southern Sweden
Get PDFStudy region: Rönne River, Säve River, and Höje River, Sweden. Study focus: River-induced flooding in coastal areas results from a multitude of drivers interacting in complex ways. The primary drivers are sea level (SL) and river flow (Q) that often exhibit coherent behavior to be considered in flood risk management. To describe and quantify the compound effects of SL and Q on flooding, a methodology was developed involving hydraulic simulations with long time series of data yielding statistical properties of output quantities such as river water level and flooded areas. Dominance analysis was conducted to quantify the relative influence of SL and Q on river water level along reaches. Also, simplified, empirically based equations were derived to predict the river water level at any location based on SL and Q. New hydrological insights for the region: The long-term simulations revealed that the relative influence of SL and Q on the river water level changes significantly from the coast to upstream. For example, at the Rönne River, influence of SL decreases from 90 % to 20 % between 1 km and 11 km from the coast. Meanwhile, influence of Q increases from 10 % to 80 % over the same distance. The simplified equations derived to predict the water level can be used by stakeholders to forecast flood events or in risk assessment where many alternatives need to be considered
Impact of extreme flows on bridges : A case study from Lagan river, Ljungby
Get PDFFlowing water impacts bridges over rivers primarily in two ways: (1) hydrodynamic forces that directly impact the structure and (2) scouring at piers and abutments, including contraction scour. The design prin-ciples for bridges in Sweden, including both impacting forces and local scour, are relatively simplistic. The purpose of this paper is to examine the impact of extreme river flows on bridges, particularly in circumstances beyond the design flow, using as a case study Ljungby Municipality. Although the study was made with focus on Swedish conditions, the work is to a large extent based on international literature and experiences. First, an overview of the literature on the impacts of extreme river flows on bridges was conducted. This was followed by a numerical study using the HEC RAS (1D – steady flow) hydraulic model to simulate the impact of extreme flows on bridges in Ljungby. This resulted in inundation and flood hazard maps for the study area, besides the determination of overflowed bridges. A 100-year event resulted in the overflowing of the Ljungsätersbron. During the 200-year event, Ljungsätersbron and Söderbron overflowed. Also, abut-ment scour analyses were performed for all bridges. Overall, the modeling approach provided a satisfactory estimation of the potential threats posed by scouring at bridges abutments during extreme flow conditions
Assessing the Combined Risk of Fire and Flood on a National Scale for Sweden [Elektronisk resurs]
No full textFloods and wildfires are two critical hazards that impose substantial direct and indirect costs to society, including the resource needs of rescue services. Their occurrence is strongly linked to meteorological conditions, playing a fundamental role in hazard development and assessment. These hazards are notably distinguishable due to opposing weather requirements, wet conditions for floods and dry conditions for wildfires. However, certain regions are exposed to the convergence of these hazards simultaneously or in temporal proximity, demanding different levels of resources and mitigation strategies. Consequently, there is a vital need for a comprehensive combined risk assessment to enhance the effectiveness of rescue services to face such risks. This study presents an analysis for the combined risk of wildfires and floods on a national scale in Sweden over an 11-year period based on daily values on the Fire Weather Index (FWI) and river flow data, taken as proxies for the occurrence of fire and flood, respectively. The present study employed different methods to assess the joint occurrence of fire and floods including simultaneous plots of FWI and flow time series, scatter plots with risk categorization, and index plots combining standardized FWI and flow, offering both qualitative and quantitative insights into combined risk assessment
Bridge Scour : Basic Mechanisms and Predictive Formulas
Get PDFThis report aims at presenting basic knowledge on bridge scour and the processes governing its evolution as well as summarizing the most common formulas used to calculate scour depth at bridges. Design procedures concerning bridge scour in several different countries are also discussed, including United States, Australia, and the United Kingdom. The situation in Sweden with regard to bridge scour is briefly reviewed and several case studies are presented where marked scour holes have been detected at bridges. Two cases of bridge failures in Sweden are included where local scour was the main reason for the collapse.Bridge scour is typically separated into pier, abutment, and contraction scour, where each mechanism is controlled by different physics and governing parameters. Each type of bridge scour is discussed separately in the report with sections on basic mechanisms, governing parameters, common predictive formulas, and concluding remarks.The report also includes a brief summary on the expected influence of climate change on bridge scour. Larger and more intense rainfalls in the future imply larger flows in the rivers with increased bridge scour as a result.The report deals only with scour induced by bridges; other types of scour, such as general scour due to longitudinal transport gradients in the river, scour related to secondary flows in river bends, or scour downstream hard bottom, are not discussed. Most of the formulas included to estimate bridge scour are valid for friction material and only a few examples are given that are applicable to cohesive sediment, mainly related to recommended design procedures from different countries. Also, the objective of bridge scour analysis is often to estimate the maximum scour depth, occurring at equilibrium conditions under a certain flow, implying that most of the formulas are valid for such conditions
Compound effects of sea level and flow on river-induced flooding in coastal areas of southern Sweden [Elektronisk resurs]
No full textStudy region: Rönne River, Säve River, and Höje River, Sweden. Study focus: River-induced flooding in coastal areas results from a multitude of drivers interacting in complex ways. The primary drivers are sea level (SL) and river flow (Q) that often exhibit coherent behavior to be considered in flood risk management. To describe and quantify the compound effects of SL and Q on flooding, a methodology was developed involving hydraulic simulations with long time series of data yielding statistical properties of output quantities such as river water level and flooded areas. Dominance analysis was conducted to quantify the relative influence of SL and Q on river water level along reaches. Also, simplified, empirically based equations were derived to predict the river water level at any location based on SL and Q. New hydrological insights for the region: The long-term simulations revealed that the relative influence of SL and Q on the river water level changes significantly from the coast to upstream. For example, at the Rönne River, influence of SL decreases from 90 % to 20 % between 1 km and 11 km from the coast. Meanwhile, influence of Q increases from 10 % to 80 % over the same distance. The simplified equations derived to predict the water level can be used by stakeholders to forecast flood events or in risk assessment where many alternatives need to be considered
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
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