Understanding and predicting the effects of width variability and the controls on width adjustment in rivers has a key role in developing management approaches able to account for the physical, ecological and socio-economical dimensions of a river system. Width adaptation in a river occurs due to erosion and accretion of banks, within various geomorphic, environmental and anthropogenic contexts, which set the most relevant factors controlling the morphological dynamics of the river corridor. In turn, changes in channel width imply alterations of the river channel morphodynamics at a variety of space and time scales, implying, for instance, modifications of important controlling parameters, like the width-to-depth ratio, which is closely related to the planform morphology of alluvial rivers. Width adaptation bears crucial implications for river management: on one hand, channel widening may result in loss of valuable land and in the increase of the damage risk of infrastructures in surrounding areas, which are often subjected to increasing pressures related to human settlements and economic activities. On the other hand, several approaches to river restoration are based on the concept of “giving more room to the river”, and thus allow the banks to erode and widen, to increase morphological and physical habitat diversity. In view of these implications, the prediction of width adaptation, understanding of its main causes and controlling factors, and quantification of the riverbed morphodynamic response to width variability is of crucial importance to support effective river management. The practical and engineering interest on stable cross-sections of alluvial channels has attracted a considerable amount of scientific research since late 19th century. Much of the research has focused in developing width prediction tools mostly based on empirical approaches and methods based on extremal hypothesis and to lesser extent on mechanistic methods. In the past two decades, research has advanced in developing numerical models including geotechnical as well as fluvial processes to simulate bank failure mechanism more accurately. Despite significant development on the width predictors, research in controls on width evolution of river channels cannot still be considered a fully settled issue. The study of the morphodynamic response of the riverbed to width variability in space and time is somehow more recent, and has focussed on the dynamics of large-scale bedforms (river bars) that produce a variety of riverbed configurations and planform morphologies. The effect of spatial width variability on river bars has mainly been based on assessing the role of such planform forcing effects to the bed topography, both in case of straight and meandering river channels. The amplitude of width variability has been related to fundamental questions as those behind the transition between single- and multi-thread river morphologies, and most studies consider regular spatial variations of the channel width. Research on the response of channel bed to spatial width variability has mostly consisted of modelling and theoretical approaches, which point out the limit cases of a purely “free” system response, associated with morphodynamic instability, an of purely “forced” bedform pattern by spatial planform non-homogeneity. The large spectrum of mixed configurations between those two theoretical limits has been so far seldom investigated, despite its strong relevance for real river systems. The limits of what can actually be considered a “planform forcing” effect, or has instead a too small variability have never been clarified, a well as its role on the resulting channel morphodynamics. For instance, the effects of small amplitude width variations on straight channels, which may be due to imperfect bank lines or protrusion due to vegetations, on morphodynamics of river bed has been neglected so far. This study has two main scientific goals. The first goal is to quantitatively investigate the role of potentially controlling factors on the width evolution of bedload-dominated straight river channels, including the initial channel width, the flow regime and the sediment supply regime. The major question driving the research is whether a river would attain the same width independently of the initial conditions and whether this would be true for all types of discharge regimes of water and sediment supply. The study is carried out using both laboratory experiments (Chapter 3), analytical model (Chapter 4) and numerical model (Chapter 5) tested with reference to real river data. Integrating the results of the experiments with those of analytical and numerical models allows deriving a more robust and complete understanding of the processes involved, including transient width evolution, time scales to morphodynamic equilibrium, equilibrium conditions and role of each controlling factor. In Chapter 3 a set of controlled laboratory experiments have been performed to study channel adjustments in a movable-bed, erodible-bank channel under different flow and sediment regimes and different initial widths. The long-term width evolution is observed to be independent of initial channel width under uniform formative discharge without upstream sediment supply. Width evolution rate is observed to depend on the initial channel width when the sediment is supplied from upstream with the narrowest initial channel evolving at the highest widening rate and resulting into the widest channel. A physics based analytical model of channel adjustment (Chapter 4) has been applied to some of the experiments described in Chapter 3. Furthermore, in Chapter 5 a field scale numerical model was setup using the flow and topographic data of gravel bed reach of Upper Severn River near Abermule (UK). The trend of width evolution computed by analytical model is also qualitatively in agreement with the observations in the experiments. The results of numerical modeling have further supported the observations in the experiments which reinforce the findings in agreement with laws of physics. The second goal of the present PhD research is to analyze the morphodynamic response of the riverbed to small-scale spatial variability of the channel width, focusing on alternate bars. The main question driving the investigation (Chapter 6) is to which extent small-amplitude, irregular width variations in space affect the morphodynamics of river bars, the fundamental riverbed patterns at the scale of the channel width. The key theoretical question behind this investigation is to which extent “small amplitude” width variations can be considered as a planform forcing, for the channel bed morphodynamic response, and whether it is possible to establish a threshold amplitude below which they may act as a near bank-roughness element. The study is based on hydraulic conditions typical of bedload-dominated piedmont streams, often having flows with Froude numbers around 1 or higher at bar-forming or channel-forming conditions. The study is developed through a numerical modeling approach. Because of the considered hydraulic conditions (close to critical-Froude number) first, a comparison is made between one semi-coupled numerical morphodynamic model, expected to be most suitable for sub critical flows, and one fully-coupled numerical morphodynamic model which can handle Froude-critical flows to assess the potential shortcomings of applying a semi-coupled model under close-to-critial Froude conditions. Such test, (Appendix B) supports the use of both models, and the semi-coupled model is eventually preferred for the advantages in computational speed. Such model is used for the numerical investigations performed in Chapter 6 and to some extent also in Chapter 5. The comparison is based on the reproduction of alternate bars morphodynamics observed in existing sets of flume experiments with fixed banks and super-critical flow conditions. The results of numerical modeling have shown that the small width variations have accelerated the development of the steady bars suppressing the free bar instability. Further investigations reveal that the effects of small width variations to a certain extent can be captured by parameterizing them in the form of increased roughness close to the banks or as small obstructions along the banks.

Increasing energy demand driven by rapid population and economic growth, the need for climate change mitigation, and the depletion of fossil fuels is stimulating the search for renewable, climate neutral energy sources. Hydropower provides an efficient, low maintenance and flexible form of energy, which can provide ancillary benefits such as flood control, water storage and job creation. Yet, the construction of dams for hydropower production has been recognised by scientists as one of the major threats to the ecological integrity of river systems. For instance, the fragmentation of river systems alters the flow, thermal, and sediment regimes of rivers, and restricts the free movement of aquatic organisms. Disruption to the natural flow regime results in the degradation of physical habitat features which generate acoustic stimuli that are relevant to organisms. In addition, initial flooding of terrestrial habitats results in the rapid decay of organic matter, which releases greenhouse gases (GHG) into the atmosphere. Conservation and management of river systems therefore requires a greater understanding of the processes and mechanisms which underpin the ecohydrological impacts of hydropower. In this context, this doctoral thesis aims to investigate: (i), the ramifications of a global boom in hydropower construction, (ii) the prediction of GHG emissions from hydropower reservoirs, and (iii) the temporal and spatial changes in underwater river soundscapes affected by hydropower. Researchers have investigated the social, economic and ecological consequences of reservoir construction for decades. However, the lack of coordinated, georeferenced databases has hindered catchment decision making, and limited the development of regional and global research in particular. In Chapter 1, the primary objectives were to create a high resolution, georeferenced database of hydropower dams under construction or planned to assess the dimension and spatial distribution of hydropower developments, their density relative to available catchment water resources and the future impact on river fragmentation. Data were collected on hydropower schemes under construction or planned with a capacity of 1 MW or above, from government and non-government databases, grey literature and news reports. Spatial analyses were conducted in a geographical information system (GIS) on the extent of global development, impact per water availability and potential consequences for existing status of river fragmentation. The relative contribution of hydropower reservoirs to the global GHG budget, particularly in sub-tropical and tropical regions, remains the subject of intense critical debate. The initial objective of the second study was therefore, to identify principal parameters and underlying processes that drive GHG emissions from reservoirs. The second step was to review global reservoir emission measurements and their source pathways in hydropower systems. Meteorological and landscape derived parameters were then correlated with the GHG measurements in order to assess if and which selected parameters might explain variations in GHG emission data. Similarly, existing empirical models were applied to the measured data to assess their suitability in predictive modelling. Finally, a newly developed process based model (FAQ-DNDC v1.0) was used to simulate ‘net’ CO2 emissions from a newly flooded tropical reservoir and compared to the measured results. The final study (Chapter 3) examined the influence of hydropower systems on the underwater acoustic properties of river habitats. Using recently developed acoustic sensors in addition to traditional hydrophones, the study characterised the temporal and spatial changes in river soundscapes affected by hydropeaking, compared their frequency composition to unaffected river soundscapes, and critically appraised the ecological implications. The results of Chapter 1 indicate that we are now experiencing an unprecedented growth in global hydropower construction. Over 3,700 dams are planned or under construction, primarily in Africa, South America and East Asia. The expansion in dam building will reduce the number of free flowing rivers on a global scale by approximately 21%. The results of Chapter 2 show that variation in measured emissions due to the inherent heterogeneity of the underlying processes, in addition to methodological limitations, impede the prediction of GHG emissions. Source pathways of CO2 are similar for the majority of systems, however, pathways of CH4 emissions are highly variable and dependent on local operating conditions and the configuration of the given hydropower system. A newly developed process based model (FAQ-DNDC v1.0) shows that a mechanistic approach may provide the basis for the ‘net’ assessment of future hydropower reservoirs. Chapter 3 reveals that distinct river soundscapes undergo changes which are highly correlated to hydropower operations, and thus rapid sub-daily changes occur at timescales not often found in natural systems. These changes occur mostly in low frequency bands, which are within the range of highest acoustic sensitivity for fish. In pool habitats affected by hydropeaking, sound pressure levels in the lower frequencies (~0.0315 kHz) may increase by up to 30 decibels. Similarly, sound pressure levels of riffles increase by up to 16 decibels in the low to mid frequencies (~0.250 kHz). Overall, the findings of this thesis have a number of implications for river catchment management. Hydropower construction is taking place in some of the most ecologically sensitive areas of the globe, thus, this research provides a timely contribution to: (i) Provide a foundation for future research at catchment, regional and global scales. For instance, systematic conservation based planning is required to designate ‘no go’ areas to promote the long-term survival of biodiversity. Strategic positioning of future dams or reconfiguration of existing hydropower systems may reduce the combined impacts on biodiversity and GHG emissions without losing power capacity. (ii) Assess driving parameters of GHG emissions, critically appraise current predictive GHG emission models and use a process based approach to simulate ‘net’ emissions from a sub-tropical reservoir. Future reservoirs will sequester, mineralise and emit an increasing quantity of carbon to the atmosphere, and subsequently, will take a greater role in the global GHG budget. This research concludes that, in some cases empirical models may not be suitable for making robust estimations of future GHG’s from hydropower reservoirs. Combining the underlying carbon cycling processes within a process-based model allows the estimation of ‘net’ CO2 emissions from hydropower reservoirs. This approach may be integrated by catchment planners into the future lifecycle assessment of hydropower reservoirs. (iii) Characterise acoustic changes in underwater sound in rivers affected by hydropeaking. The findings emphasise that flow regulation by hydropower results in rapid changes to the amplitude and frequency spectrum of the riverine acoustic environment. These changes persist for longer periods than other forms of anthropogenic sound and may have implications for the whole biota. Thus, future studies should focus on measuring the behavioural and physiological impact on riverine organisms in order to develop guidelines for hydropower licensing.

Looking over a tidal wetland, the tidal network characterised by its intricate system of bifurcating, blind-ended tidal courses clearly stands out from the overall landscape. This tidal landform exerts a fundamental control on the morphology and ecology within the tidal environment. With today’s recognition of the ecological, economical and societal values provided by tidal wetlands, which has been notably reflected in the development of restoration management strategies across Europe and USA, there is a need to fully understand the nature and development of tidal networks as well as their relationships with associated landforms and biotic components (e.g. vegetation), to eventually guarantee the success of current and future restoration practices. Accordingly, this research aims to bring further insights into the bio-physical controls on the geomorphology of tidal networks. To this end, a combination of remote sensing, modelling and field activities was employed. A geo-spatial analysis was performed at Queen Mary, University of London (UK), to address the variability of tidal network patterns. A series of network scale morphometric variables was extracted using airborne LiDAR data among selected tidal networks across the UK depicting different planview morphologies, and supplemented with the collection of corresponding marsh scale environmental variables from published sources. Multivariate statistics were then performed to characterise the variability of tidal network patterns and identify the inherent environmental controls. The analysis has revealed that every network type can be characterised based upon measures of network size and complexity, with each network pattern depicting proper morphometric aspects. Particularly, the stream Strahler order and the median depth of the network main channel have the highest discriminating weight on the patterns investigated. High correlation between the latter variable and network main channel width has revealed that linear, linear-dendritic and dendritic networks followed a transitional gradient in their aspect ratio approximated by a power law and thus are seen to depict similar erosional processes. To the contrary, meandering networks clearly depart from this relationship, and show particular segregation in their aspect ratios with respect to dendritic networks. Globally, differentiation on network morphometric properties has been linked to environmental conditions specific to the marsh physiographic setting within which a tidal network develops. Conceptually, tidal networks seem to adapt to marsh environmental conditions by adopting suitable morphologies to drain their tidal basin effectively.An eco-geomorphic modelling framework was developed at University of Trento (Italy), to address tidal network morphological development. In line with current theories as well as modelling advances and challenges in the field of tidal network ontogeny, emphasis was thus placed on the investigation of tidal channel formation and evolution in progressive marsh accretional context. Under these environmental conditions, tidal network development can be ascribed to the combination of two channel-forming processes: channel initiation results from bottom incisions in regions where topographic depressions occur; channel elaboration results from differential deposition, contributing to the deepening of the tidal channels relative to the adjacent marsh platform. Further evolutionary stages including channel reduction proceed from the horizontal progradation of the marsh platform which may lead eventually to channel infilling. Moreover, both qualitative and quantitative results allude to an acceleration of the morphological development of the synthetic tidal networks with increasing sediment supply. These different observations thus emphasise the prevalence of depositional processes in shaping tidal channels. In a second stage, the investigation was extended to the role of the initial tidal flat morphology as an inherent control on tidal network development, by considering different scenarios of topographic perturbations, which has revealed its legacy on tidal network morphological features. Modelling experiments have also acknowledged salt marsh macrophytes as a potential control on network evolution depending on their biomass distribution within the tidal frame. However, tidal channel morphodynamcis appears to be sensitive to the way biomass growth is mathematically parameterised in the model. In view of the current challenges in transcribing mathematically such a dynamic process and the relevance of bio-physical interactions in driving salt marsh and tidal network evolution, a field survey was conducted in a temperate salt marsh in the Netherlands, as part of the mobility to UNESCO-IHE (Netherlands) in partnership with University of Antwerp (Belgium), to assess vegetation distribution and productivity in the tidal frame. Particularly, emphasis was placed on extending investigations on the possible presence of relationships involving vegetation properties in different climatic and ecological conditions from those characterising these previously documented relationships. Regression analysis has revealed that biomass growth can be expressed as a linear function of marsh relative elevation, providing therefore direct empirical validation for corresponding assumptions reported in the literature and used in the present modelling framework; surprisingly, that increase did not correlate with an increase in species richness and diversity. Analysis of likely associations between vegetation morphometrics and total standing biomass yielded only a single linear relationship linking the latter variable to stem height. In truth, these observations may bear reconsiderations on the global validity of the assumptions used in the formulation of some eco-geomorphic processes which are applied in the study and prediction of wetland resiliency facing climate change.

Braided rivers are complex, fascinating fluvial pattern, which represent the natural state of many gravel and sand bed rivers. Both natural and human causes may force a change in the boundary conditions, and consequently impact the river functionality. Detailed knowledge on the consequent morphological response is important in order to define management strategies which combine different needs, from protection of human activities and infrastructures to preservation of the ecological and biological richness. During the last decades, research has made significant advance to the description of this complex system, thanks to flume investigations, development of new survey techniques and, to a lesser extent, numerical and analytical solutions of mathematical models (e.g. Ashmore_2013). Despite that, many relevant questions, concerning the braided morphodynamics at different spatial and temporal scales (from the unit process scale, to the reach scale, and eventually to the catchment scale) remain unanswered. For example, quantitative analysis of the morphological response to varying external controls still requires investigation and needs the definition of suitable, stage-independent braiding indicators. In addition, the morphodynamics of the fundamental processes, such as bifurcations, also needs further analysis of the driving mechanisms. General aim of the present study is to develop new methods to exploit, in an integrated way, the potential of the new possibilities offered by advanced monitoring techniques, laboratory models, numerical schemes and analytical solutions. The final goal is to fill some gaps in the present knowledge, which could ultimately provide scientific support to river management policies. We adopted analytical perturbation approaches to solve the two-dimensional shallow water model; we performed laboratory simulations on a large, mobile-bed flume; we analysed existing topographic measurements from LiDAR and Terrestrial Laser scanning Devices; and we simulated numerically the river hydrodynamics. Within each of the six, independent, research chapters, we interconnected results from the different approaches and methodologies, in order to take advantage of their potential. Summarising, the more relevant and novel outcomes of the present work can be listed as follows: 1) We explored the morphological changes during a sequence of flood events in a natural braided river (Rees River, NZ)and we proposed a morphological method to assess the sediment transport rate. In particular we propose a semi-automatic method for estimating the particles path-length (Ashmore and Church, 1998) on the basis of the size of the deposition patches, which can be identified on the basis of DEM of differences. Comparison with results of numerical simulation confirmed that such an approach can reproduce the response of the bedload rate to floods of different duration and magnitude. 2) We developed a new indicator of the reach-scale morphology and, on the basis of existing laboratory experiments, we explored its dependence, under regime conditions, to the controlling factors: slope, discharge, confinement width, grain size. In spite of its synthetic nature, this simple indicator embeds the information needed to estimate the variability of the Shield stress throughout the braided network, and consequently enables to assess the transport-rate and its variation with the driving discharge. 3) We investigated, through flume experiments, the effect of the flow unsteadiness on the sediment transport in a braided river. This is possible only by following a statistical approach based on multiple repetitions of the same flow hydrograph. Results revealed that for confined network an hysteresis of the bedload response occurs, which leads to higher sediment transport during increasing flow, whereas relatively unconfined networks always show quasi-equilibrium transport rates. 4) A second set of laboratory experiments provided information on the morphodynamics of a braided network subject to variations of the sediment supply. We proposed a simple diffusive model to quantify the evolution of the one-dimensional bed elevation profile. Such simple approach, albeit having a limited range of practical applications, represents the first attempt to quantify this process and enables to study the relevant temporal and spatial scales of the phenomenon. 5) We solved analytically the two-dimensional morphodynamic model for a gravel-bed river bifurcation. This furnishes a rigorous proof to the idea proposed by Bertoldi and Tubino (2007) to interpret the morphological response of bifurcation in light of the theory of the morphodynamic influence. The analytical approach enables to investigate the fundamental mechanics which leads to balance, and unbalance, configurations and, from a more practical point of view, allows for a better prediction of the instability point than the existing 1D models (e.g. Bolla Pittaluga et al., 2003).

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.

During the past decades, the systematic investigation of the morphodynamics of meandering rivers mostly involved the theoretical-analytical methodology. The development of analytical models enabled the definition of equilibrium conditions, stability and evolution of river meanders and to investigate the interaction between planform and bedform processes and mechanisms. In recent years the new branch of remote sensing applied to river morphodynamics has been constantly developing simultaneously to the rapid increase of computational and satellite resources. The remote sensing analysis is nowadays employed in a wide range fields in geophysics; for this reason, the past years have seen the prolific development of numerous algorithms for remote sensing analysis. However, remote sensing of meandering river morphodynamics has not been consistently integrated with morphodynamic modelling so far. There is a lack of sophisticated algorithms for the extraction of extensive morphodynamic information from the available remotely sensed data; this gap prevented researchers from seeking systematic validation of analytical models to define their range of applicability, and to exploit their potential for improved insight on observations in real world meandering rivers. The evolutionary dynamics of the channel width, at local and bend scale, as well as the dynamics of bars in meandering rivers represent two major unsettled issues in our present understanding of river meandering dynamics. In this thesis I first provide a systematic methodology for the automated extraction of meandering river morphodynamic information from multitemporal, multispectral remotely sensed data, coded in the PyRIS software. Moreover, I develop an analytical model to investigate the long-term planform evolution of periodic sequences of meander bends incorporating spatio-temporal variations of channel curvature, width and slope. A first model component predicts the temporal evolution of the channel width and slope based on a novel treatment of the sediment continuity at the reach scale. A second model component is a fully analytical, evolutionary model of periodic meanders with spatially and temporally oscillating width accounting for nonlinear feedbacks in flow and sediment transport by means of a two-parameters perturbation approach. Application of the PyRIS software to several long reaches of free-flowing meandering rivers allows me to develop a consistent set of observations on the temporal and spatial evolution of channel width and curvature with unprecedented level of detail. Furthermore, model outcomes indicate that meander-averaged width and slope invariably decrease during meander development, and that the temporal adjustment of the hydraulic geometry is controlled by the ratio between the evolutionary timescales of planform and riverbed, quantified from the analyzed meandering rivers dataset. The nonlinear perturbation model indicates that width and curvature co-evolve according to a hysteretic behavior in time and predicts that the meander belt width dramatically decreases when the meander resonance threshold is crossed. The modelling approach predicts wider-at-bend meanders when the bank pull is dominant with respect to bar push, which in turn promotes meander bends that are wider at inflections. Analytical modeling and remote sensing analysis are mostly integrated through a statistical approach; bend-scale evolutionary analysis of planform descriptors such as channel width, width oscillations and curvature in large pristine meandering rivers exhibit good agreement with the outcomes of the proposed analytical models. Finally, the integration between analytical modeling and remote sensing analysis allows me to identify the key processes controlling the interaction between migrating sediment bars and planform-driven steady point bars. The conditions for the formation of migrating bars in meandering rivers are mostly related to the production of sediment supply by the basin, contrarily to the widespread idea that meandering rivers exhibiting migrating bars typically display lower values of the channel curvature.

A erosão hídrica é uma das maiores causas de depauperamento dos solos no Brasil e no mundo. Neste cenário, o objetivo deste trabalho foi aplicar a Análise Empírica da Fragilidade Ambiental, para classificar a vulnerabilidade ambiental à erosão hídrica da sub-bacia hidrográfica do rio Mandu, no sul de Minas Gerais. Isto, considerando os componentes ambientais: usos do solo, relevo, solos e clima, em ordem decrescente de importância, estabelecida pelo Processo Analítico Hierárquico (AHP), que interferiu no resultado final e é recomendado na aplicação deste método. Desta forma, ficou estabelecido que na maior parte da sub-bacia os usos do solo estão inadequados. Nesta, 33,67% da área deveriam ser de preservação permanente e os locais utilizáveis, precisariam ser manejados adequadamente, principalmente as pastagens. Assim 52,91% teria baixa vulnerabilidade. Também, a eliminação dos solos expostos e o rearranjo dos locais com agricultura temporária contribuiriam muito com a atenuação dos impactos ambientais e acabariam com as áreas de vulnerabilidade ambiental muito forte e forte. / Water erosion is one the greatest cause of depletion of soils in Brazil and worldwide. Therefore, the aim of this work was to apply the Empirical Analysis of Environmental Fragility, to classify environmental vulnerability to erosion of the Mandu river watershed, southern Minas Gerais State. This, considering the environmental components: land use, relief, soils and climate, in descending order of priority established by Analytical Hierarchy Process (AHP), which interfered with the final outcome and is recommended when applying this method. In this way, it was established that most of the watershed land uses are inadequate. In this, 33,67% of the area should be permanent preservation and the usable sites, need to be properly managed, mainly pastures. So 52,91% would have low vulnerability. Also, the exposed soil elimination and the rearrangements in locals with temporary agriculture contribute much with attenuation of environmental impacts and phase out areas with very strong and strong vulnerability. / Programa Institucional de Bolsas de Pós-Graduação - PIB-PÓS

Submitted by Liliane Ferreira (ljuvencia30@gmail.com) on 2018-04-23T11:10:57Z No. of bitstreams: 2 Dissertação - Gabriel Cristóbal Valenzuela Saavedra - 2018.pdf: 4929181 bytes, checksum: 32d6c5535f93ba6a8920d6f67beb26e8 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2018-04-23T11:57:24Z (GMT) No. of bitstreams: 2 Dissertação - Gabriel Cristóbal Valenzuela Saavedra - 2018.pdf: 4929181 bytes, checksum: 32d6c5535f93ba6a8920d6f67beb26e8 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2018-04-23T11:57:24Z (GMT). No. of bitstreams: 2 Dissertação - Gabriel Cristóbal Valenzuela Saavedra - 2018.pdf: 4929181 bytes, checksum: 32d6c5535f93ba6a8920d6f67beb26e8 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2018-03-28 / Outro / El presente estudio tiene como finalidad encontrar un camino metodológico para modelar la dispersión de contaminantes atmosféricos provenientes de fuentes de emisión fija, a través de materiales baratos y simples. El camino insto de la revisión teórica de los principales conceptos de la contaminación atmosférica y la calidad del aire, así conocer cuales factores determinan áreas vulnerables a la contaminación atmosférica. Se usó una fuente de emisión fija de una industria alimentaria para mostrar un análisis de lo que sería un estudio de impacto ambiental de las emisiones producto de la operación normal de la fábrica para el año 2012, sin la intención de evaluar, si no, para mostrar cómo se aplica el modelo en un caso práctico. De esta forma, colocar en disposición una metodología que pueda ser usada en estudios que ayuden a la toma de decisión para la planificación en la introducción de nuevas fuentes de emisión o la alteración de las antiguas. Como resultado, se consiguen imágenes donde es fácilmente reconocible el área de susceptibilidad de las emisiones provenientes de la fuente fija, las que son interpretadas para aclarar que podría pasar frente a los diversos escenarios posibles. / O presente estudo teve como objetivo encontrar o caminho metodológico para modelar a dispersão de poluentes atmosféricos provenientes de fontes de emissão fixa, através de materiais baratos e simples. O percurso instou da revisão teórica e dos principais conceptos da poluição e qualidade do ar para saber quais são os fatores que determinam áreas vulneráveis à poluição atmosférica. Usou-se uma fonte de emissão atmosférica fixa de uma indústria alimentar para mostrar um analises do que seria um estudo de impacto das emissões produto da operação normal da fábrica para o ano 2012, sem a intenção de avaliar a indústria, mas para mostrar como se aplica o modelo de dispersão em casos práticos. Dessa forma, disponibilizar uma metodologia que possa ser usada em estudos que ajudem a tomar decisões de planejamento para a colocação de novas fontes de emissão ou a alteração das antigas. Como resultado, se consegue imagens onde é facilmente reconhecível a área de susceptibilidade das emissões provenientes da fonte fixa, as quais são interpretadas para esclarecer o que poderia acontecer frente aos diversos cenários possíveis.

FundaÃÃo Cearense de Apoio ao Desenvolvimento Cientifico e TecnolÃgico / As bacias hidrogrÃficas sÃo Ãreas de relevÃncia significativa para estudos geogrÃficos por testemunharem as dinÃmicas, atuais e pretÃritas, da paisagem, por abrigarem vasta biodiversidade e por serem Ãreas preferencialmente de desenvolvimento das sociedades, contribuindo para atividades socioeconÃmicas e culturais. Devido a estas potencialidades, os usos feitos, em alguns casos, nÃo condizem com a capacidade de suporte, resultando em problemas ambientais. A desertificaÃÃo à a degradaÃÃo da qualidade dos recursos naturais e das condiÃÃes socioeconÃmicas nas terras secas. Esse processo de degradaÃÃo tem nÃveis de atuaÃÃo. As Ãreas do territÃrio brasileiro que possuem maiores nÃveis de degradaÃÃo sÃo denominadas de NÃcleos de DesertificaÃÃo. A presente pesquisa foi desenvolvida na sub-bacia hidrogrÃfica do riacho do Urubu-Mucuim que possui uma Ãrea de 310, 771kmÂ, no municÃpio de Arneiroz, localizado na porÃÃo sudoeste do Estado do CearÃ, no NÃcleo de DesertificaÃÃo dos SertÃes dos Inhamuns, tendo o objetivo de analisar a atuaÃÃo da desertificaÃÃo sobre esta sub-bacia. A metodologia utilizada foi a dos Sistemas Ambientais com a aplicaÃÃo dos Indicadores GeobiofÃsicos, que contribuÃram para entender o nÃvel de desertificaÃÃo existente. Para subsidiar esta anÃlise, tambÃm foram utilizadas como tÃcnicas o trabalho de campo, a aplicaÃÃo de entrevistas e a Cartografia, que contribuÃram na confecÃÃo dos mapas que possuem escalas de 1:100.000 e 1:150.000, as imagens de satÃlites utilizadas para o mapeamento foram Landsat 8 e Rapideye. A Ãrea estudada està susceptÃvel a atuaÃÃo da desertificaÃÃo, pode-se perceber que as caracterÃsticas geoambientais e os intensos usos feitos pelas comunidades contribuem com o quadro degradaÃÃo. PorÃm em algumas Ãreas os programas assistencialistas atenuam os processos de degradaÃÃo ambiental, havendo a necessidade de polÃticas de uso racional dos recursos naturais para mitigar e conviver com a problemÃtica da desertificaÃÃo. / Watersheds are areas of significant relevance to geographical studies by witnessing the dynamic, current and previous, landscape, for harboring vast biodiversity and areas are preferably development of societies, contributing to socioeconomic and cultural activities. Because of this potential, the uses made, in some cases, not consistent with the ability to support, resulting in environmental problems. Desertification is the degradation of the quality of natural resources and socioeconomic conditions in dry lands. This degradation process has performance levels. The areas of Brazil that have higher levels of degradation are called Nuclei of Desertification. This research was developed in the sub-basin of the Urubu-Mucuim stream which has an area of 310, 771km in the municipality of Arneiroz, located in the southwestern portion of the state of CearÃ, in Nuclei of Desertification SertÃes dos Inhamuns, with the aim of analyzing the performance of desertification on this sub-basin. The methodology used was the Environmental Systems with the application of Geobiofisicos indicators that helped to understand the level of existing desertification. To support this analysis, it was also used as technical field work, the application of interviews and Cartography, which contributed to the production of maps that have scales of 1: 100,000 and 1: 150,000, the satellite images used for mapping were Landsat 8 and RapidEye. The study area is likely the work of desertification; one can see that the geo-environmental characteristics and heavy duty applications made by communities contribute to the framework of degradation. However in some areas the welfare programs mitigate the environmental degradation processes, and there is thus a need for rational use of natural resources policies to mitigate and live with the problem of desertification.

Submitted by Erika Demachki (erikademachki@gmail.com) on 2014-09-24T17:16:18Z No. of bitstreams: 2 Pereira, Priscilla Régia de Catro-Dissertação-2012.pdf: 2626898 bytes, checksum: baaf0f0ed6ece423e7ba9eaf6bd32575 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Approved for entry into archive by Jaqueline Silva (jtas29@gmail.com) on 2014-09-24T19:01:19Z (GMT) No. of bitstreams: 2 Pereira, Priscilla Régia de Catro-Dissertação-2012.pdf: 2626898 bytes, checksum: baaf0f0ed6ece423e7ba9eaf6bd32575 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Made available in DSpace on 2014-09-24T19:01:19Z (GMT). No. of bitstreams: 2 Pereira, Priscilla Régia de Catro-Dissertação-2012.pdf: 2626898 bytes, checksum: baaf0f0ed6ece423e7ba9eaf6bd32575 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) Previous issue date: 2012-08-24 / Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq / The difficulty on teaching-learning of Cartography is already a proven fact, by the multiples scientific works developed in the area. However we noticed that face of these difficulties, there was a featured point: The math’s influence on learning of some primordial contents of Cartography (World-Time, Geographic Coordinates and Scale). Understanding how actually this influence occurred was the guiding principle of the search. Lots of inquiries surround this problem. Why the students - as much of Basic Education as Superior - show so much difficulty on learning these contents of own Cartography which are present on Geography? In which time of the process of learning this problem occurs? What occurs on math teaching that make the students to acquire a certain aversion for this area of knowledge? Why the teachers of Basic Education face difficulties to teach that contents? Is the way those contents have been given a significant factor in the genesis of the problem? Are there methods that can minimize this difficulty faced by Teachers and Students? To answer these questions we proposed as general objective the investigation of the causes of the difficulties of teaching-learning of the contents of Cartography, linked to Math (Scale, World-Time and Geographic Coordinates) in the 6º year of Basic Education. And we define the following specific objectives: Identify the main difficulties faced by the teachers of Geography from Public Schools of the 6º year of Basic Education in Anápolis (GO) on teaching the contents of Cartography with Math basis; verify the causes of the limited learning of these contents by the students of 6º year of Basic Education from Public Schools of Anápolis (GO); to diagnose e evaluate the present contents of Cartography in the didactic books of Geography adopted by the scholar unities that were part of the search and show action proposes to alleviate the problems that generate the limitation on learning the contents of Cartography with Math basis. To meet all the proposed objectives, we used the following methodologies: bibliographic searching, interviews, application of questionnaires, systematic observation of classes, analysis of didactic books and application of a course. We concluded that there is in fact a difficulty on teaching-learning of the cartographic contents linked to Math and this difficulty is linked not only to the unpreparedness of teachers of Geography with Cartography and Mathematics contents but also in the limited basis of the students related to Math which is associated to work developed in classroom in past years that reflect on Cartography. Lastly we accomplished the aim of the work: inquires to the real causes of the problem, opening the ways for methods that can alleviate them, like the application of courses to the teachers like a way of professional improvement. / A dificuldade havida no processo de ensino-aprendizagem da Cartografia já é um fato comprovado mediante os vários trabalhos desenvolvidos na área. Porém notamos que, em face dessas dificuldades, havia um ponto que se destacava: a influência da Matemática no aprendizado de alguns conteúdos primordiais da Cartografia (fuso horário, coordenadas geográficas e escala). Entender como, de fato, essa influência ocorria foi o princípio norteador da pesquisa. Muitos questionamentos rondam esse problema. Por que os alunos — tanto da Educação Básica quanto do Ensino Superior — demonstram tanta dificuldade na aprendizagem desses conteúdos próprios da Cartografia presentes na Geografia? Em que momento do processo de ensino esse problema sucede? O que ocorre no ensino da Matemática que leva os alunos a adquirirem certa aversão a tal área do conhecimento? Por que os professores da Educação Básica enfrentam dificuldades em ensinar tais conteúdos? A forma como esses conteúdos têm sido ministrados é um fator relevante na gênese do problema? Existem métodos que possam minimizar a dificuldade enfrentada por professores e alunos? Para que esses questionamentos fossem respondidos, propusemos como objetivo geral a investigação das causas das dificuldades de ensino-aprendizagem dos conteúdos de Cartografia, ligados à Matemática (escala, fuso horário e coordenadas geográficas), no 6º ano do Ensino Fundamental. E definimos os seguintes objetivos específicos: identificar as principais dificuldades enfrentadas pelos professores de Geografia de escolas públicas do 6º ano, da rede pública de Anápolis (GO), em ensinar os conteúdos de Cartografia com base matemática; verificar as causas da deficiente aprendizagem desses conteúdos pelos alunos do 6º ano das escolas públicas de Anápolis; diagnosticar e avaliar os conteúdos de Cartografia presentes nos livros didáticos de Geografia adotados pelas unidades escolares participantes da pesquisa e apresentar proposta de ações para minorar os problemas que acarretam a deficiência na aprendizagem dos conteúdos de Cartografia com bases matemáticas. A fim de que fossem cumpridos todos os objetivos propostos, utilizamos das seguintes metodologias: levantamento bibliográfico, entrevistas, aplicação de questionários, observação sistemática de aulas, análise de livros didáticos e aplicação de um curso. Conclui-se que, com efeito, há uma dificuldade no ensino-aprendizagem dos conteúdos cartográficos ligados à Matemática e que ela está ligada não somente ao despreparo dos professores de Geografia quanto à Cartografia e à Matemática, mas também à falta de base dos alunos em relação à Matemática, o que está associado ao trabalho desenvolvido em sala de aula nos anos anteriores e que acaba refletindo na Cartografia. Por fim, cumprimos o intuito do trabalho: inquirirem-se as reais causas do problema, abrindo caminhos para métodos que possam abrandá-lo, como a aplicação de cursos aos professores como forma de aprimoramento profissional.