Influence of Tributary Widening on Confluence Morphodynamics

In alpine regions of Europe, river training works were typically the reason for the transformation of wide and braided rivers into linear river systems with a lack of structural diversity, i.e. gravel banks, islands, woody debris, riffles or pools. These interventions considerably impoverished river ecosystems. From the end of the 20th century, "river rehabilitation" has been a concept commonly used by environmental professionals and river management authorities. The rehabilitation purpose is to recover the vital space required for the rivers that were degraded by human interventions and to link the sustainable use of rivers and wetlands with human well-being. Furthermore the flood safety has to be adapted to the higher hydrological risk resulting from increased urbanization. A good understanding of the flow dynamics, sediment transport patterns and of the development of the bed morphology is essential to successfully accomplish river rehabilitation projects. Alpine confluences are typically characterized by steep gravel-bed streams carrying large sediment loads, which often connect asymmetrically at large angles with the main river. Such zones present important challenges, not only for flood protection but also for rehabilitation works. Current knowledge of river channel confluences, mainly based on lowland confluences is not applicable to alpine conditions. The morphodynamics of confluences have been experimentally investigated with special attention to the potential of local tributary widening in the framework of confluence rehabilitation projects. Local widening of the tributary in the confluence zone aims to increase the heterogeneity in sediment substrate, flow depth and flow velocity, which is favourable for in-stream habitat (e.g. aquatic invertebrates, fish, and vegetation) and for the connectivity between the main river and the tributary. Zones of quiescent water (flow stagnation or flow recirculation zones) may play an important role as refuges during flood events. Moreover, a local tributary widening can create a riparian zone which favours the diversity of plants and animals (e.g. birds, mammals, insects, amphibians). Obviously, river rehabilitation by means of local tributary widening is only feasible if it has negligible adverse effects on the flood safety of the confluence zones. The experimental set-up and the test configurations are based on the analysis of the Upper Rhone River, in Switzerland, which can be considered as representative of regulated alpine river confluences. Systematic laboratory experiments were performed in a confluence flume where the main channel is 8.5 m long and 0.50 m wide. A 4.9 m long and 0.15 m wide tributary channel is connected at an angle of 90°. Three discharge scenarios were tested for four different geometrical configurations: a reference case (without widening) and three different tributary widenings: the "Small" configuration, (Bw = 0.30 m and Lw = 0.45 m, the "Medium" configuration (Bw = 0.45 m and Lw = 0.45 m) and the "Large" configuration (Bw = 0.45 m and Lw = 0.60 m). Each experiment was conducted under steady flow conditions in the main and tributary channels and with a steady supply of poorly sorted sediments (d50 = 0.82 mm and d90 = 5.7 mm) at the tributary. There is no sediment transport in the main channel upstream of the confluence. All experiments were conducted until the equilibrium conditions were reached. The duration of the tests varied between 22 and 24 hours. Measurements of the three-dimensional velocity field, turbulence, bed material grain size distribution and morphology as well as observations of the sediment transport in the confluence flume for the reference case revealed that the hydro-morpho-sedimentary processes occurring in alpine confluences differ fundamentally from existing conceptual models of confluence morphodynamics. Therefore, a conceptual model for the main hydraulic and morphological processes occurring in confluences with characteristics similar to those found in alpine environments is proposed. Bed morphology in alpine confluences is characterized by the presence of a significant deposition bar downstream of the confluence. Differences between the water depths in the tributary and in the main channel induce the formation of large bed discordance between the confluent channels. Moreover, no considerable scour hole is observed. Regarding the flow, the tributary momentum input, associated with the presence of the deposition bar resulted in a considerable mass redistribution in the confluence zone as the main flow is deviated towards the outer bank. The main channel flow is hardly hindered by the tributary in the lower part of the water column, giving rise to a two-layer flow structure at the tributary mouth. The two-layer flow plays an important role in dampening the formation of a flow recirculation zone downstream of the confluence. The deposition bar downstream from the confluence reduces the flow area and causes flow acceleration. The sediment supplied by the tributary is mainly sorted and transported on the face of the deposition bar. The sediment transport capacity is further increased by the three-dimensionality of the flow. It is characterized by maximum velocities occurring near the bed and by a considerable increase in turbulent kinetic energy generated in the shear layer at the interface of the flows originating from the main channel and the tributary. Laboratory experiments revealed that the local widening of tributaries creates a pronounced heterogeneity in the sediment substrate, flow velocities and flow depths, without having any adverse effects on flood safety in the confluence zone. Although the local tributary widening allows a reduction in the confluence angle, it locally amplifies the hydro-morpho-sedimentary processes in the confluence zone. This is due to the reduction of the effective flow area in the local tributary widening, resulting in locally increased tributary velocities and momentum flux. This reduction of the effective flow area occurs due to a general rise of the bed elevation and by a lateral constriction of the flow induced by a zone of flow stagnation at the upstream confluence corner. Flow coming from the tributary remains in the upper part of the water column in the main river and it is considerably more directed outwards than flow in the lower part of the water column coming from the main channel. The increased tributary velocities lead to increased bed discordance and a higher tributary penetration in the confluence zone. Despite the different morphodynamic responses at the widened zones depending on the geometry and the discharge ratio, the local tributary widening always enhance the variability of flow depths, bed constitution and flow velocities without causing adverse effects on the morphodynamics of the tributary and main channels in equilibrium conditions. Furthermore, the lateral freedom obtained by the local widening associated to the different combinations of the main and tributary discharge events further allows the formation of different bed forms, which contributes to the improvement the lateral connectivity of regulated networks. Therefore, local tributary widening can be considered as an efficient solution for increasing the ecological potential of fluvial systems without reducing the conveyance capacity of a given network

Morphodynamic changes in a channel confluence due to local tributary widening

The morphodynamic changes in a confluence zone due to local tributary widening were experimentally investigated in a set-up representative of regulated piedmont confluences. A reference configuration with a constant tributary width of 0.15 m is compared to a configuration where the tributary is widened to 0.30 m over its last 0.45 m. The main channel is 0.5 m wide and the confluence angle is 90°. Comparison is made for a discharge ratio Qt/Qm = 0.11. Tests were run until equilibrium with a constant solid discharge of poorly-sorted material from the tributary. The paper presents detailed data on the morphology and on the three-dimensional flow velocity field at the confluence zone. Results revealed that the local widening of the tributary creates a pronounced heterogeneity in the flow velocities and flow depths, without having any adverse effects on flood safety in the confluence zone. Although the local tributary widening allows a reduction in the confluence angle, it locally amplifies the hydro-morpho-sedimentary processes in the confluence zone

Evidência de associação entre uso precoce de álcool e risco de problemas futuros

OBJECTIVES: To investigate the relationship between age of onset, alcohol consumption patterns and related problems. METHOD: In 2004, one self-administered questionnaire was completed by 1,990 students from the 5th to 11th grades of schools in Paulínia-SP. Data collection was conducted at the classroom without the presence of the teacher. The participation in the study was voluntary and anonymous. RESULTS: Prevalence of lifetime alcohol use was 62.2%. The mean age of first use of alcohol was 12.35 (sd = 2.72) and ranged between 5 and 19 years of age. In 78% of the cases, the first use occurred before the age of 15, and more than 22% of the students reported having tried alcohol before 10 years of age. There were significant differences regarding current pattern of use: those who started earlier consumed more drinks per occasion (p = 0.013) and had more drunkenness episodes in the last 30 days (p = 0.05). A relationship between the age of first alcohol use and the use of tobacco (p = 0.017) and other drugs (p = 0.047) was observed. CONCLUSIONS: Adolescents first use alcohol in early ages, what impacts the current consumption patterns. This study emphasizes the need of actions regarding public alcohol policies in Brazil in order to prevent or delay the initiation of alcohol use and its related problems.OBJETIVOS: Investigar a relação entre idade de início de uso de álcool, padrão de consumo e problemas relacionados. MÉTODO: Em 2004, um questionário de autopreenchimento foi respondido por 1.990 alunos de 5ª série do ensino fundamental a 3ª série do ensino médio do município de Paulínia-SP. A coleta de dados foi realizada em sala de aula, sem a presença do professor. A participação no estudo era voluntária e anônima. RESULTADOS: A prevalência de uso de álcool na vida foi de 62,2%. A média de idade de primeiro uso de álcool foi de 12,35 (sd = 2,72), variando entre 5 e 19 anos. Em 78% dos casos, o primeiro uso de álcool ocorreu antes dos 15 anos, sendo que mais de 22% dos adolescentes relataram que experimentaram bebida alcoólica antes dos 10 anos. Houve diferenças significantes para padrão de consumo atual: aqueles que começaram mais cedo consumiram mais doses por ocasião (p = 0,013) e tiveram mais episódios de embriaguez nos últimos 30 dias (p = 0,05). Houve associação entre a idade de experimentação do álcool e o uso de tabaco (p = 0,017) e outras drogas (p = 0,047). CONCLUSÕES: Jovens experimentam álcool em idade precoce e isto tem impacto no padrão de consumo atual. Esse artigo enfatiza a necessidade de ações imediatas em relação às políticas públicas do álcool no Brasil para prevenir ou adiar o início do consumo de álcool e problemas relacionados.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Universidade Federal de São Paulo (UNIFESP) Department of Psychiatry Unidade de Pesquisa em Álcool e DrogasUNIFESP, Department of Psychiatry Unidade de Pesquisa em Álcool e DrogasSciEL

Einmündungen ökologisch aufwerten

Werden im Rahmen von Flussrenaturierungen EinmUndungen aufgeweitet, bilden sich im MUndungsbereich reichhaltige morphologische Strukturen. Mit solchen okologischen Aufwertungen verbessert sich die Vernetzung der Seitengewasser mit dem Hauptgewasser

Morphodynamic changes in a natural river confluence due to a hydropower modified flow regime

River channel confluences form important morphological components of any river system. This article presents the results of an investigation on a natural river confluence in Switzerland. The aim of the field work performed at the confluence of the Sarine (main channel) and Gerine (tributary) Rivers near Fribourg (CH) is to analyze the interaction between morphological processes on the confluence and hydropower-affected hydrology of the main River. Important morphological changes have been observed over the last years, especially the deflection of the Sarine River and erosion of the left bank opposite of the tributary. Numerical calculations have shown that currently the minimal discharge of the Sarine River which transports the sediments annually deposited at the confluence is attained on average once each 2 years. Before the construction of the Rossens Dam, the minimum discharge was reached every year. This lack of yearly floods with sediment mobilization can explain the morphological changes occurred at the confluence since the construction of the dam

Discussion of "Three-dimensional numerical study of flow structure in channel confluences"

The Discussers would like to congratulate the Authors for their interesting work concerning the flow characteristics in channel confluences, performed by means of three-dimensional numerical simulations considering rectangular crosssections with smooth bed. The model is validated with reasonable agreement with experimental data. The investigation of several geometries (angles and channels widths) and hydraulic conditions (discharge ratios and Froude Numbers) contributes to increase the knowledge on the hydrodynamics in channel confluences

Flow and sediment dynamics in bed discordant channel confluences

Confluences between small steep tributaries with dominant supply of poorly sorted sediment and larger main channels with dominant flow supply, which are characterized by a pronounced bed discordance, have not yet been considered in the literature. The hydro-morpho-sedimentary processes in such confluences are not well described by existing conceptual models of confluence dynamics. Examples of such confluences on the Upper Rhone River, Switzerland, served as prototype for the reported laboratory experiments. Based on detailed measurements of the morphology, the sediment size, the sediment transport, and the three-dimensional flow field in a laboratory experiment, Leite Ribeiro, et al. (submitted) have proposed a conceptual model for the hydro-morpho-sedimentary processes in the investigated type of confluences. According to this model, the pronounced bed discordance is essentially due to the difference between the low flow depth in the steep tributary and the higher flow depth in the main channel. The tributary flow penetrates into the main channel mainly in the upper part of the water column. Due to the bed discordance, the main-channel flow is hardly hindered by the tributary in the lower part of the water column, giving rise to a two-layer flow structure at the tributary mouth. In confluences with dominant sediment supply from the tributary, the development of a deposition bar downstream of the confluence reduces the flow area and causes a flow acceleration that contributes to the required increase in sediment transport capacity. The sediment supplied by the tributary is mainly sorted and transported on the sloping face of the depositional bar. The sediment transport capacity is further increased by the three-dimensionality of the flow, which is characterized by maximum velocities occurring near the bed. The present paper reports data on the morphology and flow visualizations for two additional hydrological scenario, characterized by different flow ratios, but an identical sediment supply in the tributary. An increase in the ratio of tributary discharge to main-channel discharge led to an attenuation of the morphological features in the confluence zone: (i) the bed discordance was less pronounced; (ii) the tributary penetration was reduced; (iii) the volume of sediment accumulated in the depositional bar just downstream of the confluence decreased. Leite Ribeiro et al. „s (submitted) conceptual model is able to explain these morphological adaptations, which lends credit to the robustness of their model

Identification of putative new Escherichia coli flagellar antigens from human origin using serology, PCR-RFlP and DNA sequencing methods

Escherichia coli has been isolated frequently, showing flagellar antigens that are not recognized by any of the 53 antisera, provided by the most important reference center of E. coli, The International Escherichia and Klebsiella Center (WHO) of the Statens Serum Institute, Copenhagen, Denmark. The objective of this study was to characterize flagellar antigens of E. coli that express non-typeable H antigens. The methods used were serology, PCR-RFLP and DNA sequencing. This characterization was performed by gene amplification of the fliC (flagellin protein) by polymerase chain reaction in all 53 standards E.coli strains for the H antigens and 20 E. coli strains for which the H antigen was untypeable. The amplicons were digested by restriction enzymes, and different restriction enzyme profiles were observed. Anti-sera were produced in rabbits, for the non-typeable strains, and agglutination tests were carried out. In conclusion,the results showed that although non-typeable and typable H antigens strains had similar flagellar antigens, the two types of strains were distinct in terms of nucleotide sequence, and did not phenotypically react with the standard antiserum, as expected. Thirteen strains had been characterized as likely putative new H antigen using PCR-RFLP techniques, DNA sequencing and/or serology.14415

A new damage model for composite laminates

Aircraft composite structures must have high stiffness and strength with low weight, which can guarantee the increase of the pay-load for airplanes without losing airworthiness. However, the mechanical behavior of composite laminates is very complex due the inherent anisotropy and heterogeneity. Many researchers have developed different failure progressive analyses and damage models in order to predict the complex failure mechanisms. This work presents a damage model and progressive failure analysis that requires simple experimental tests and that achieves good accuracy. Firstly, the paper explains damage initiation and propagation criteria and a procedure to identify the material parameters. In the second stage, the model was implemented as a UMAT (User Material Subroutine), which is linked to finite element software, ABAQUS (TM), in order to predict the composite structures behavior. Afterwards, some case studies, mainly off-axis coupons under tensile or compression loads, with different types of stacking sequence were analyzed using the proposed material model. Finally, the computational results were compared to the experimental results, verifying the capability of the damage model in order to predict the composite structure behavior. (C) 2011 Elsevier Ltd. All rights reserved.KU Leuven Arenberg doctoral schoolKU Leuven Arenberg doctoral schoolCAPESCAPESSao Paulo Research Foundation (FAPESP) [2009/00544-5]Sao Paulo Research Foundation (FAPESP)AFOSRAFOSRUSArmyUS-Army [FA9550-10-1-0011

Estilos gerenciais e eficácia administrativa na produção de café

The objective of this article was to analyze the managerial styles in coffee farmers of two regions in Minas Gerais State, Brazil (Sul and Zona da Mata), and the difficulties which can be compromising the administrative effectiveness. Primary data were collected from forms applied to 56 coffee farmers, in the harvest period 2003/2004. To analyze the relation between the dominant managerial styles and the reached economic and technical performances in the activity, the analysis of simple correlation was used (coefficient of Pearson). Regressions were estimated to indicate as the situational variables had intervened in the styles. Among the main results it is important to point out that the producers, in general, presented as dominant managerial style 9,9, which represents the versatile and intent manager to the changes of the environment. The situational variables intervened, significantly, in the managerial styles in both regions, of differentiated form. Also positive correlations between the dominant managerial styles were observed and the physical production and total gross income in the production of coffee in the Zone of Mata region. This can be an indication that the versatile style is related to a good economic and technical performance in the activity. The results of this research can be considered reference to reach managerial effectiveness in the production of coffee in the studied regions.Managerial styles, Managerial effectiveness, Managerial grid, Coffee production, Crop Production/Industries,