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The physical, chemical and biological characteristics of five southern English chalk streams in neighbouring catchments were investigated seasonally over two years. At the catchment scale, the five chalk rivers had very similar physio-chemical properties. Differences between years and between seasons were much greater than those between rivers or within-river longitudinal differences. Elevated inorganic nutrient concentrations, relative to reportedly 'pristine' systems, indicated some degree of catchment water quality deterioration in all five rivers. The effect of physical habitat degradation (channel overwidening and sedimentation) on river biota was investigated at a within-river, reach scale. The increased proportion of fine sediment within the coarse gravel substratum had a marked effect on invertebrate communities. Overwidening, however, was found to have little impact over the two years. Communities showed a high degree of stability between years, and between individual catchments, reflecting the high overall biological stability of these aquifer-fed river systems. Habitat manipulation experiments at the within-reach scale demonstrated the importance of substratum characteristics to macroinvertebrate communities. Invertebrate colonisation of newly exposed substrata over time was quantitatively and qualitatively different for coarse and fine particles - a function of shifting resource utilisation and microhabitat preferences. The relatively long time taken to fully colonise new substrata demonstrated the weak ability of chalk stream invertebrate communities to respond rapidly to changes in habitat, reflecting the stable physical nature of natural chalk streams and the vulnerability of their communities to anthropogenic disturbance.

The aims of this work are to improve the understanding of the way in which a river system approaches equilibrium during and after sediment transporting events and by using experimental data and hypothetical models to gain an insight into mixed grain sized transport and its connection with local bed morphology. Large scale flume experiments were undertaken in a trapezoidal channel where a mixed grain sized river bed is subjected to a variety of imposed sediment loads. The river system was allowed to adjust naturally to the imposed conditions while flow and bed conditions were frequently monitored. Changes to both flow and bed occur at many scales and the superimposition of these changes adds to the complexity of the interpretation of hydraulic and bed data. Three experiments are reported in which the sediment influx differ. One in which no material is added. One in which a feed rate is established equal in magnitude to 50% of the initial transport rate for the equivalent non-fed case. In the third experiment the feed rate is doubled to 100% of the initial transport rate in the degradation experiment. The imposed load is continued for approximately 75% of the duration of the run or until a dynamic equilibrium transport rate is evident within the reach. The river channel is analysed at two distinct scales; grain scale and reach scale. Conclusions about the relative influence of grain and form effects are drawn on the basis of detailed surface texture information and reach scale measurements of the bed surface. A hypothetical model is proposed to show that the transport activity during a degradation experiment can be qualitatively linked to a wave like translation of grain dislodgement through the channel.

During the past decades, the systematic investigation of the morphodynamics of meandering rivers mostly involved the theoreticalanalytical 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 xiii 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 twoparameters perturbation approach. Application of the PyRIS software to several long reaches of freeflowing 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 xiv 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.

The dissertation presented in this manuscript contributes to river science by providing a detailed overview on the state of the art on the interaction between riparian vegetation and hydrogeomorphological processes, by devising a novel model encompassing most of such processes and by proposing a field methodology aimed at providing means for improving the modelling of such interactions. The state of the art is summarized in an extensive review describing riparian vegetation and hydrogeomorphological processes mutual feedbacks. Such review did not simply seek to describe these feedbacks but, compiling from a large array of results from field, laboratory and modelling studies, provides a set of physical thresholds that trigger system changes. Therefore, processes are not only described terms but also explained with a quantitative approach. Processes description provided the conceptual foundation for the development of the novel simulation model while model parameterization was based on the quantitative information collected in the review. Such novel model, encompasses the main relationships entwining riparian woody vegetation and hydrogeomorphological processes and is able of replicating long term riparian landscape dynamics considering disturbance events, environmental stressor and riparian woody vegetation establishment from seeds and large wood. The manuscript presents the model structure and its conceptual validation by means of hydrological scenarios aimed at testing the coherence of the simulation results with expected system behaviour. Examples of such coherences are vegetation growth rate in response to hydrological regime, entrainment and establishment of large wood in an unconfined river system and vegetation effect on erosion and deposition patterns. Analysis of sedimentation patterns from the modelled results suggested that vegetation flow resistance should be modelled with greater detail. These conclusions pointed the dissertation research towards the testing of a novel class of vegetation flow resistance equations, proposed by different authors, able of describing woody vegetation flow resistance on a physical basis. These equations have the advantage of considering flow stage, plants foliation level and species-specific flexibility. However, the use of such equations is limited by the difficulty of measuring the vegetation properties required as equation-inputs. In order to test if these equations could effectively improve sediment dynamics predictions, a field method was formulated and tested. The field method allows to sample vegetation properties that can be used with these novel class of flow resistance equations. In the manuscript, such method is applied and the resulting vegetation properties used in several modelling scenarios. Such scenario proved that hydraulic variables modelled with these novel flow resistance approaches are more realistic and thus that the model developed during the dissertation could benefit from inclusion of such flow resistance equations in its source code.

River flow regime is fundamental in determining lotic fish communities and populations, and especially of salmonid fishes. Quantifying the effects of human induced flow alteration on salmonids is a key question for conservation and water resources management. While qualitative responses to flow alteration are well characterised, a more intractable problem is quantifying responses in a way that is practical for environmental management. Using data drawn from the Environment Agency national database, I fitted generalised linear mixed models (GLMMs) using Bayesian inference to quantify the response of salmonid populations to the effects of impounding rivers, flow loss from rivers due to water abstraction, and the mitigating effects of flow restoration. I showed that in upland rivers downstream of impounded lakes, the magnitude of antecedent summer low flows had an important effect on the late summer abundance of 0+ salmonids Atlantic salmon (Salmo salar) and brown trout (Salmo trutta). In contrast, the abundance of 1+ salmon and brown trout appeared to be largely unresponsive to the same flows. I demonstrated that short-term flow cessation had a negative impact on the abundance of 1+ brown trout in the following spring, but that recovery was rapid with negligible longer-term consequences. I further established that flow restoration in upland streams impacted by water abstraction provided limited short-term benefits to salmonid abundance when compared with changes at control locations. However, while benefits to salmonid abundance were limited, I detected important benefits to the mean growth rates of 0+ and 1+ brown trout from flow restoration. I discuss the implications of my findings for salmonid management and conservation and propose a more evidence-based approach to fishery management based on robust quantitative evidence derived using appropriate statistical models. The current approach to flow management for salmonids requires revision and I recommend an alternative approach based on quantitative evidence.

Reaching agreements over water management on transboundary rivers is a complex yet necessary endeavour to assure that humans can live within the limits of available resources. The myriad of challenges is both physical and social in nature; the uncertainty of water availability due to natural hydrologic variability is often increased by the involvement of multiple management institutions. Jurisdictions of control are typically defined by political borders, and thus they represent distinct geographic domains and interests. Increasing scarcity, driven by rapidly expanding populations and our growing awareness of climatic non-stationary, increases the urgency to find agreements among these institutions. Although the need is significant and growing, a lack of available approaches exist that considers the physical, technical and political dynamics to address these complex challenges. This thesis describes novel analytical methods to engage in the complex political realm of transboundary river management. Building from an engineering systems analysis approach to engage this topic, the main hypotheses of this thesis are: (1) Existing analytical approaches for water resource development are useful but often constrained in a transboundary negotiation context, and (2) cooperation among co-riparian water management institutions can be significantly increased with strategic implementation of analytical tools to jointly manage current and future risks. To test this hypothesis, this thesis presents an analytical approach that (1) examines previous applications of water resource models to identify their perceived contribution to managing transboundary rivers, (2) develops a new modelling framework that engages with transboundary negotiations, and (3) incorporates methods for risk-based decision making to evaluate the benefits, opportunities and trade-offs of cooperation among co-riparian states. A retrospective analysis is conducted on the Colorado and Murray-Darling River Basins to understand lessons learned from recent applications of analytical modelling tools. New methods are then developed and applied to the rapidly changing Eastern Nile River Basin. The ongoing construction of the Grand Ethiopian Renaissance Dam (GERD) and the implications on downstream countries of Sudan and Egypt provides the context and a relevant case for testing the methods and evaluating the hypotheses. Results from this thesis demonstrate the distinct advantages of an early development of system-wide analytical tools within a transboundary context, which is made available to all parties. Conversely, the challenges of reconciling multiple models used by different institutions after full allocation is reached in a basin is a significant barrier to cooperative management. Results also demonstrate the advantages of developing an analytical tool that is sufficiently accurate, transparent and flexible to seek creative solutions, and the need to select an appropriate breadth and depth of model design that conveys its credibility, saliency and legitimacy to support a decision-making process. The appropriate design of tools to consider multiple future hydrologic scenarios can shift a discourse from rigid water allocations to considering the effects of new developments in terms of changes to risks, and to allow stakeholders to decide whether these changes are tolerable when juxtaposed with the benefits that new infrastructure provides. Finally, the results show how risks among multiple stakeholders can be evaluated under expanding uncertainties, and cooperative solutions can be sought to minimise or balance these risks. The application of the proposed methods to the Eastern Nile Basin indicates that solutions are indeed possible that benefit all three countries. A number of cooperative solutions are identified that suggest operational rules for the new and existing infrastructure. These operations can be responsive to variable climatic conditions and thus encourage dynamic cooperation. In this light, the developments in Ethiopia need not be a risk, but can result in substantial benefits to the downstream countries if agreements can be reached. Embedding highly adaptable analytical tools within a negotiation process can help to overcome the challenges faced at this historic point on the Nile River.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第19293号 / 工博第4090号 / 新制||工||1630(附属図書館) / 32295 / 京都大学大学院工学研究科都市社会工学専攻 / (主査)教授 角 哲也, 教授 藤田 正治, 准教授 竹門 康弘 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

This project aims to establish a river park with purification capacity and conservation of soil and water, protecting habitats for plants and animals. Combining local history and culture to form new urban landscape and improve the urban living environment.  Historically, Yangquan had a very favorable ecological environment and was one of the birthplaces of agriculture and culture in Shanxi province. From the 1950s, after a long period of exploration, it was discovered that Yangquan had a large amount of coal resources. Since then Yangquan City has become a coal mining-oriented city. With the development of coal mining industry in recent years, the ecological environment has been deteriorated due to over-exploitation, discharge. The city's most important river, Taohe River, has suffered from declining water volume and fragile water environment, which even led to the loss of self-purification ability of the rivers.  Pollution is not the only issue with the Taohe River, but there are also floods and droughts caused by extreme weather. Therefore, river management is necessary before Yangquan transforms into a livable city. Three strategies, Optimize Water Resource, Anti-Flooding and Diverse Programs, are proposed to solve urban river issues and achieve the aim of living with river.

Floods are major disturbance events for riverine ecosystems, directly and indirectly impacting organisms and their habitat. In this study I investigated the role of riverine floods and flow alteration in regulating aquatic macroinvertebrate population and community structure. I examined this problem using a variety of methods: a meta-analytic review of primary studies from the literature, a mathematical model synthesizing population and flood ecology, a multi-year experimental flood program in an arid-land river, and a field investigation of flood recovery behaviors in a charismatic larval odonate. I found that floods significantly reduced invertebrate abundance in the short term, but had varied effects across particular study sites, microhabitats, and taxonomic groups. I determined that both resistant and resilient capabilities are important to persistence of invertebrate populations after disturbance events, and that these traits may act in a binary fashion. Recovery over time of invertebrate populations may be partially due to "hidden resistance" of spatially displaced individuals in side-channels, benthic substrate, and vegetation or wood. Some invertebrates adapted to flood-prone rivers may possess behavioral adaptations for returning to the main-channel of the river after flood events. This dissertation contributes to riverine disturbance ecology and provides information useful to prediction and management of ecosystem flows in rivers. / Graduation date: 2012