Bio-morphodynamics of evolving river meander bends from remote sensing, field observations and mathematical modelling

Interactions between fluvial processes and vegetation along the natural channel margins have been shown to be fundamental in determining meandering rivers development. By colonizing exposed sediments, riparian trees increase erosion resistance and stabilize fluvial sediment transport through their root systems, while during a flood event the above-ground biomass interacts with the water flow inducing sediment deposition and altering scour patterns. In turn river dynamics and hydrology influence vegetative biomass growth, affecting the spatial distribution of vegetation. These bio-morphological dynamics have been observed to direct control accretion and degradation rates of the meander bend. In particular, vegetation encroachments within the point bar (i.e. colonizing species and strand wood), initiate pioneeristic landforms that, when evolving, determine the lateral shifting of the margin that separates active channel from river floodplain and thus inner bank aggradation (bar push). This diminishes the portion of the morphologically active channel cross-section, influencing the erosion of the cutting bank and promoting channel widen- ing (bank pull ). As a result of the cyclical occurrence of these erosional and depositional processes, meandering rivers floodplain show a typical ridge and swale pattern characterized by the presence of complex morphological structures, namely, benches, scrolls and chutes within the new-created floodplain. Moreover, difference in migration rate between the two banks have been observed to induce local temporal variations in channel width that affect river channel morphodynamics and its overall planform through their influence on the local flow field and channel bed morphology. Despite enormous advances in field and laboratory techniques and modelling development of the last decades, little is known about the relation between floodplain patterns and their controlling bio-morphological interactions that determine the bank accretion process. This knowledge gap has so far limited the development of physically-based models for the evolution of meandering rivers able to describe the lateral migration of banklines separately. Most existing meander migration models are indeed based on the hypothesis of constant channel width. Starting from this knowledge gap, the present doctoral research has aimed to provide more insight in the mutual interactions among flow, sediment transport and riparian vegetation dynamics in advancing banks of meandering rivers. In order to achieve its aims, the research has been designed as an integration of remote sensing and in-situ field observations with a mathematical modelling approach to i) provide a quantitative description of vegetation and floodplain channel topography patterns in advancing meanders bend and to ii) explore the key control factors and their role in generating the observed patterns. The structure of the present PhD work is based on four main elements. First, two types of airborne historical data (air photographs and Lidar survey) have been investigated, in order to quantify the effects of spatial-temporal evolution of vegetation pattern on meander morphology and to provide evidence for the influence of vegetation within the topography of the present floodplain. Such remote sensing analysis has highlighted a strong correspondence between riparian canopy structure and geomorphological patterns within the floodplain area: this has clearly shown the need to interpret the final river morphology as the result of a two-way interaction between riparian vegetation dynamics and river processes. Second, field measurments have been conducted on a dynamic meander bend of the lower reach of the Tagliamento River, Italy, with the initial aim of checking the outcomes of the remote sensing analysis through ground data. The outcomes of the field measurements have further supported the results, providing ground evidence on the relations between vegetation and topographic patterns within the transition zone that is intermediate between the active channel bed and the vegetated portion of the accreting floodplain. The influence of vegetation on inner bank morphology has also been interpreted in the light of the expected time scales of inundation and geomorphic dynamics that characterize the advancing process of the inner bank. The combined analysis of both remotely sensed data and field measurements associated with the historical hydrological dataset have allowed to quantitatively characterize the biophysical characteristics of the buffer zone, close to the river edge, where the accretion processes take place. The third research element has foreseen the development of a biophysically-based, simplified bio-morphodynamic model for the lateral migration of a meander bend that took advantage of the empirical knowledge gained in the analysis of field data. The model links a minimalist approach that includes biophysically-based relationships to describe the interaction between riparian vegetation and river hydromorphodynamic processes, and employs a non linear mathematical model to describe the morphodynamics of meander channel bed. Model application has allowed to reproduce the spatial oscillations of vegetation biomass density and ground morphology observed in the previous analyses. Overall, the model allows to understand the role of the main controlling factors for the ground and vegetation patterns that characterize the advancing river bank and to investigate the temporal dynamics of the morphologically active channel width, providing insights into the bank pull and bar push phenomena. The fourth and concluding element of the present PhD research is a analytical investigation of the fundamental role of unsteadiness on the morphodynamic response of the river channel. Results obtained in the previous elements have clearly showed the tendency of a meander bend to develop temporal oscillations of the active channel width during its evolution, but no predictive analytical tool was previously available to investigate the channel bed response to such non-stationary planform dynamics. A non linear model has therefore been proposed to investigate the effect of active channel width unsteadiness on channel bed morphology. The basic case of free bar instability in a straight channel has been used in this first investigation, which has shown the tendency of channel widening to increase river bed instability compared to the steady case, in qualitative agreement with experimental observations. Overall, the research conducted within the present Doctoral Thesis represents a step forward in understanding the bio-morphodynamics of meandering rivers that can help the development of a complete bio-morphodynamic model for meandering rivers evolution, able to provide support for sustainable river management

Bio-morphodynamics of evolving river meander bends from remote sensing, field observations and mathematical modelling

Interactions between fluvial processes and vegetation along the natural channel margins have been shown to be fundamental in determining meandering rivers development. By colonizing exposed sediments, riparian trees increase erosion resistance and stabilize fluvial sediment transport through their root systems, while during a flood event the above-ground biomass interacts with the water flow inducing sediment deposition and altering scour patterns. In turn river dynamics and hydrology influence vegetative biomass growth, affecting the spatial distribution of vegetation. These bio-morphological dynamics have been observed to direct control accretion and degradation rates of the meander bend. In particular, vegetation encroachments within the point bar (i.e. colonizing species and strand wood), initiate pioneeristic landforms that, when evolving, determine the lateral shifting of the margin that separates active channel from river floodplain and thus inner bank aggradation (bar push). This diminishes the portion of the morphologically active channel cross-section, influencing the erosion of the cutting bank and promoting channel widen- ing (bank pull ). As a result of the cyclical occurrence of these erosional and depositional processes, meandering rivers floodplain show a typical ridge and swale pattern characterized by the presence of complex morphological structures, namely, benches, scrolls and chutes within the new-created floodplain. Moreover, difference in migration rate between the two banks have been observed to induce local temporal variations in channel width that affect river channel morphodynamics and its overall planform through their influence on the local flow field and channel bed morphology. Despite enormous advances in field and laboratory techniques and modelling development of the last decades, little is known about the relation between floodplain patterns and their controlling bio-morphological interactions that determine the bank accretion process. This knowledge gap has so far limited the development of physically-based models for the evolution of meandering rivers able to describe the lateral migration of banklines separately. Most existing meander migration models are indeed based on the hypothesis of constant channel width. Starting from this knowledge gap, the present doctoral research has aimed to provide more insight in the mutual interactions among flow, sediment transport and riparian vegetation dynamics in advancing banks of meandering rivers. In order to achieve its aims, the research has been designed as an integration of remote sensing and in-situ field observations with a mathematical modelling approach to i) provide a quantitative description of vegetation and floodplain channel topography patterns in advancing meanders bend and to ii) explore the key control factors and their role in generating the observed patterns. The structure of the present PhD work is based on four main elements. First, two types of airborne historical data (air photographs and Lidar survey) have been investigated, in order to quantify the effects of spatial-temporal evolution of vegetation pattern on meander morphology and to provide evidence for the influence of vegetation within the topography of the present floodplain. Such remote sensing analysis has highlighted a strong correspondence between riparian canopy structure and geomorphological patterns within the floodplain area: this has clearly shown the need to interpret the final river morphology as the result of a two-way interaction between riparian vegetation dynamics and river processes. Second, field measurments have been conducted on a dynamic meander bend of the lower reach of the Tagliamento River, Italy, with the initial aim of checking the outcomes of the remote sensing analysis through ground data. The outcomes of the field measurements have further supported the results, providing ground evidence on the relations between vegetation and topographic patterns within the transition zone that is intermediate between the active channel bed and the vegetated portion of the accreting floodplain. The influence of vegetation on inner bank morphology has also been interpreted in the light of the expected time scales of inundation and geomorphic dynamics that characterize the advancing process of the inner bank. The combined analysis of both remotely sensed data and field measurements associated with the historical hydrological dataset have allowed to quantitatively characterize the biophysical characteristics of the buffer zone, close to the river edge, where the accretion processes take place. The third research element has foreseen the development of a biophysically-based, simplified bio-morphodynamic model for the lateral migration of a meander bend that took advantage of the empirical knowledge gained in the analysis of field data. The model links a minimalist approach that includes biophysically-based relationships to describe the interaction between riparian vegetation and river hydromorphodynamic processes, and employs a non linear mathematical model to describe the morphodynamics of meander channel bed. Model application has allowed to reproduce the spatial oscillations of vegetation biomass density and ground morphology observed in the previous analyses. Overall, the model allows to understand the role of the main controlling factors for the ground and vegetation patterns that characterize the advancing river bank and to investigate the temporal dynamics of the morphologically active channel width, providing insights into the bank pull and bar push phenomena. The fourth and concluding element of the present PhD research is a analytical investigation of the fundamental role of unsteadiness on the morphodynamic response of the river channel. Results obtained in the previous elements have clearly showed the tendency of a meander bend to develop temporal oscillations of the active channel width during its evolution, but no predictive analytical tool was previously available to investigate the channel bed response to such non-stationary planform dynamics. A non linear model has therefore been proposed to investigate the effect of active channel width unsteadiness on channel bed morphology. The basic case of free bar instability in a straight channel has been used in this first investigation, which has shown the tendency of channel widening to increase river bed instability compared to the steady case, in qualitative agreement with experimental observations. Overall, the research conducted within the present Doctoral Thesis represents a step forward in understanding the bio-morphodynamics of meandering rivers that can help the development of a complete bio-morphodynamic model for meandering rivers evolution, able to provide support for sustainable river management

Return period of vegetation uprooting by flow

Fluvial environments are dynamic systems whose evolution and management are strongly affected by the resilience of riparian vegetation to uprooting by flow. Similarly to other natural phenomena, the interactions between flow, sediment and vegetation uprooting is governed by both the magnitude and duration of hydrological events. In this work, we analytically derive the link between probabilities of plant uprooting by flow and the return time of corresponding hydrologic erosion events. This physically-based analysis allows to define the key parameters involved in the plant uprooting dynamics, and to link the uprooting probability of riparian vegetation to plant biomechanical characteristics, hydrological regime and sediment parameters. For example, we show how the rooting depth changes the return time of critical hydrologic event uprooting plants with different probabilities. The model also shows the difference between magnitude driven and duration driven flow uprooting events. The proposed approach is eventually validated against data from field measurements and numerical simulations of pioneer woody species for two flood events with different return period. Our approach demonstrates the strong interrelations between the hydrological river regime and vegetation properties and suggests that such interactions may be key for species recruitment and consequent ecosystem shifts when hydrological regime is altered by either human or climate changing scenarios

UTILIZAÇÃO DE DIFERENTES HIDROCOLOIDES PARA MELHORAR A QUALIDADE SENSORIAL DE PRODUTOS CÁRNEOS

O aumento da demanda de carne de frango faz com que as indústrias do mundo todo invistam em tecnologias capazes de agregar valor aos novos produtos. A presente pesquisa teve o objetivo de avaliar a influência de diferentes hidrocoloides sobre as características de pH, retenção de água e composição centesimal da carne de frango. Para que os hidrocoloides fossem injetados na carne foi preparada uma salmoura contendo água, sal, tripolifosfato de sódio e dextrose. Os tratamentos foram realizados por meio da incorporação dos hidrocoloides na salmoura nas concentrações de 0,2%, 0,5% e 1%. Os resultados mostraram que houve uma diminuição no teor de lipídeos quando utilizado o hidrocoloide pectina, o qual apresenta um maior teor de proteína, então, pode-se dizer que o uso do hidrocoloide pectina agregou valor ao peito de frango, reduzindo o teor de lipídeos e aumentando o teor de proteína. Em relação ao pH, não apresentaram diferença significativa entre si (p>0,05) e os resultados de retenção de água mostraram que o padrão foi o que apresentou um maior percentual de perda de água por exudação 30%, seguido da pectina, 25%, carragena, 20%, e o peito de frango, com proteína de soro de leite, foi o que apresentou menor perda de água por exaudação de 5%. Portanto, concluiu-se que a aplicação dos hidrocoloides em peito de frango proporciona uma série de vantagens tecnológicas, sem prejuízos às principais características sensoriais, com vantagens econômicas, propondo a permissão legal da utilização desses hidrocoloides.Palavras-chave: Hidrocoloides. Peito de frango. Análise sensorial. Composição centesimal

Biomorphodynamics of river banks in vegetated channels with self-formed width

Laboratory and field studies investigating the mutual interaction betweenriparian vegetation dynamics and river morphodynamics have revealed thatriparian vegetation may play an important role in the evolution of channelbeds and river banks. In order to disentangle this still debated question,field and modeling techniques have helped to explore and better understandthe time and spatial scales of such processes. Simple morphodynamic modelsfor river evolution have typically used a constant discharge to describein-channel processes and basic relationships for river bank dynamics. In orderto overcome these limits we propose a longitudinally integrated dynamicalmodel that describes the bank pull - bar push mechanisms in channelswith symmetric cross section. Different hydrographs (constant, periodic andstochastic discharge) are applied to investigate channel width and vegetationbiomass evolution trajectories and equilibrium values. Results show theinterplay of riparian vegetation and water flow in controlling channel widthevolution and the trajectories of channel adjustment to flow perturbations.These results also highlight the limit of adopting a constant discharge whendescribing mutual flow and vegetation processes affecting channel evolution.In addition, under stochastic forcing, the model shows the existence of arange of flood frequencies for which the cooperation between the hydrologictime scales and that characterizing vegetation colonization induces a regularpattern in channel width time variations (coherence resonance). Finally,model application to real case studies confirm the possibility to use the modelto interpret long-term river evolutionary trajectories in realistic applications.Keywords: bio-morphodynamic model, dynamical system, bank deposition,vegetation colonization, channel width temporal adjustments, stochasticwater discharg

Which factors influence the extent of indoor transmission of SARS-COV-2? A rapid evidence review

Background: It is well established that SARS-CoV-2 is readily transmitted in indoor environments; however questions remain about the relative importance of different transmission mechanisms, the risks associated with non-clinical indoor environments and activities and the role of ventilation and plumbing systems in mitigating or amplifying transmission. This rapid evidence review identifies and integrates evidence from three distinct disciplines: epidemiology, microbiology and fluid dynamics. Objectives: This review addresses the following research questions: 1. What evidence is there for aerosolised transmission? 2. What evidence is there for faecal-oral transmission? 3. What evidence is there regarding the role of ventilation systems in indoor transmission? 4. What evidence is there regarding the role of plumbing systems in indoor transmission? 5. What evidence is there regarding transmission via different indoor surfaces (materials and specific objects)? 6. What evidence is there for the transmission in indoor residential settings? 7. What evidence is there for transmission in indoor workplace settings? 8. What evidence is there for transmission in other indoor settings (social, community, leisure, religious, public transport)? 9. Do particular activities convey greater risk (e.g. shouting, singing, eating together, sharing bedrooms)? 10. What evidence is there for the appropriate length of distancing between people? Data sources: Searches were conducted in PubMed, medRxiv, arXiv, Scopus, WHO COVID-19 database, Compendex & Inspec. Eligibility criteria: We included studies reporting data on any indoor setting except schools, any indoor activities and any potential means of transmission. Additional screening criteria were modified slightly for the three study disciplines. Title and abstract and full text screening was conducted by a single reviewer, with rejections assessed by a second reviewer. Data extraction, quality appraisal and data synthesis: We used Joanna Briggs Institute and Critical Appraisal Skills Programme tools for evaluating epidemiological studies and developed bespoke tools for the evaluation of study types not covered by these instruments. Data extraction was limited to a minimum set of items, given the rapid nature of this review. Data extraction and quality assessment were conducted by a single reviewer. We conducted a meta-analysis of secondary attack rates in household transmission. Otherwise, data were synthesised narratively. Results and conclusion: Literature searches yielded a total of 1573 unique articles. After screening and quality assessment, fifty-eight articles were retained for analysis. Experimental evidence from fluid mechanics and microbiological studies demonstrates that aerosolised transmission is theoretically possible; however, we found no conclusive epidemiological evidence of this occurring. The evidence suggests that ventilation systems have the potential to decrease virus transmission near the source through dilution but to increase transmission further away from the source through dispersal. There is compelling evidence that, if infectious virus is present in faeces, defective plumbing systems can amplify transmission within high-rise buildings. However, although viral RNA can be detected in stool samples, we found no evidence for the detection of live infectious virus in faeces, nor did we find any examples of faecal-oral transmission. Laboratory studies suggest that the virus survives for longer on smooth surfaces and at lower temperatures. Environmental sampling studies have recovered small amounts of viral RNA from a wide range of frequently touched objects and surfaces; however, we did not find any such studies which had successfully cultured live virus from collected samples and epidemiological studies are inconclusive on the extent of fomite transmission. We found many examples of transmission in settings characterised by close and prolonged indoor contact, such as households (pooled secondary attack rate 11%, 95 % confidence interval 9, 13), communal residential settings, workplaces and religious gatherings. There were insufficient data to evaluate the transmission risks associated with specific activities; however workplace challenges related to poverty, such as continuing to work whilst ill, especially when attendance is incentivised, warrant further attention. Finally, the physical properties of droplets generated by coughing, speaking and breathing are well characterised and reinforce the importance of maintaining 2 metres social distance to reduce droplet transmission

Universidade engajada: Resgatando PMES na crise da Covid-19

The economic effects of isolation policies resulting from the COVID-19 pandemic have led small andmedium-sized enterprises (SMEs) to look for alternatives to survive. Within this crisis scenario, an engaged university has an important role to play in a regional context in addressing not only health issues, but also any resultant social and economic problems. An engaged university needs to take actions that go beyond its traditional missions of education and research - it has to deliver knowledge to society. This paper analyzes a university-community project in Brazil to identify the necessary elements that help promote a regionally-engaged university: the SOS-PME Advisory Network project, which was originally designed to assist SMEsduring the crisis. As a result, we identified elements necessary for promoting the university’s third mission - social engagement by way of a university-community project: an engaged team, multidisciplinarity, project management, agility, alliances, a communication strategy, institutional support, and reputation.Los efectos económicos de las políticas de aislamiento de la pandemia de COVID-19 han llevado a las pequeñas y medianas empresas (PYMEs) a buscar alternativas para sobrevivir. En un escenario de crisis, una universidad comprometida desempeña un papel importante para abordar, no solo los problemas de salud, sino también los problemas sociales y económicos en un contexto regional. En este artículo, se analiza un proyecto universidad-comunidad con la intención de señalar los elementos necesarios para promover una universidad regional comprometida: la Red de Asesoramiento SOS-PME, originalmente diseñado para apoyar a las PYMEs durante la crisis. Una universidad comprometida necesita llevar adelante acciones más allá de sus misiones tradicionales de educación e investigación; debe transferir conocimiento a la sociedad. Como resultado, identificamos cuáles son los elementos necesarios para promover la tercera misión de una universidad con compromiso social: equipo comprometido, gestión de proyectos, agilidad, alianzas, multidisciplinariedad, estrategia de comunicación y apoyo, y reputación de la institución.Efeitos econômicos das políticas de isolamento da pandemia da Covid-19 levaram pequenas e médiasempresas (PMEs) a buscar alternativas para sobreviver. Em cenários de crise, uma universidade engajada tem um papel importante ao abordar não apenas questões de saúde, mas também problemassociais e econômicos em contextos regionais. Neste artigo, um projeto de universidade-comunidade éanalisado com o intuito de apontar os elementos necessários para promover uma universidade regional engajada: a Rede de Assessoria SOS-PME, originalmente projetada para apoiar PMEs durante a crise. Uma universidade engajada entrega conhecimento para a sociedade, além de educação e pesquisa. Como resultado, identificam-se elementos para promover a terceira missão da universidade engajada – engajamento social: equipe engajada, multidisciplinaridade, gerenciamento de projetos, agilidade,alianças, estratégia de comunicação, e suporte e reputação da instituição

Universidade engajada: Resgatando PMES na crise da Covid-19

Efeitos econômicos das políticas de isolamento da pandemia da Covid-19 levaram pequenas e médias empresas (PMEs) a buscar alternativas para sobreviver. Em cenários de crise, uma universidade engajada tem um papel importante ao abordar não apenas questões de saúde, mas também problemas sociais e econômicos em contextos regionais. Neste artigo, um projeto de universidade-comunidade é analisado com o intuito de apontar os elementos necessários para promover uma universidade regional engajada: a Rede de Assessoria SOS-PME, originalmente projetada para apoiar PMEs durante a crise. Uma universidade engajada entrega conhecimento para a sociedade, além de educação e pesquisa. Como resultado, identificam-se elementos para promover a terceira missão da universidade engajada – engajamento social: equipe engajada, multidisciplinaridade, gerenciamento de projetos, agilidade, alianças, estratégia de comunicação, e suporte e reputação da instituição