Environnement, ville, société

Rivers support some of Earth’s richest biodiversity1 and provide essential ecosystem services to society2, but they are often fragmented by barriers to free flow3. In Europe, attempts to quantify river connectivity have been hampered by the absence of a harmonized barrier database. Here we show that there are at least 1.2 million instream barriers in 36 European countries (with a mean density of 0.74 barriers per kilometre), 68 per cent of which are structures less than two metres in height that are often overlooked. Standardized walkover surveys along 2,715 kilometres of stream length for 147 rivers indicate that existing records underestimate barrier numbers by about 61 per cent. The highest barrier densities occur in the heavily modified rivers of central Europe and the lowest barrier densities occur in the most remote, sparsely populated alpine areas. Across Europe, the main predictors of barrier density are agricultural pressure, density of river-road crossings, extent of surface water and elevation. Relatively unfragmented rivers are still found in the Balkans, the Baltic states and parts of Scandinavia and southern Europe, but these require urgent protection from proposed dam developments. Our findings could inform the implementation of the EU Biodiversity Strategy, which aims to reconnect 25,000 kilometres of Europe’s rivers by 2030, but achieving this will require a paradigm shift in river restoration that recognizes the widespread impacts caused by small barriers. Validated barrier inventories and modelling indicate that Europe’s rivers are fragmented by more than one million barriers, such as dams, weirs and fords, causing major impacts on biodiversity.

1. Large wood forms an important component of woodland river ecosystems. The relationship between large wood and the physical characteristics of river systems varies greatly with changes in the tree species of the marginal woodland, the climatic and hydrological regime, the fluvial geomorphological setting and the river and woodland management context. 2. Research on large wood and fluvial processes over the last 25 years has focussed on three main themes: the effects of wood on flow hydraulics; on the transfer of mineral and organic sediment; and on the geomorphology of river channels. 3. Analogies between wood and mineral sediment transfer processes (supply, mobility and river characteristics that affect retention) are found useful as a framework for synthesising current knowledge on large wood in rivers. 4. An important property of wood is its size when scaled to the size of the river channel. ′Small′ channels are defined as those whose width is less than the majority of wood pieces (e.g. width < median wood piece length). `Medium' channels have widths greater than the size of most wood pieces (e.g. width < upper quartile wood piece length), and `Large' channels are wider than the length of all of the wood pieces delivered to them. 5. A conceptual framework defined here for evaluating the storage and dynamics of wood in rivers ranks the relative importance of hydrological characteristics (flow regime, sediment transport regime), wood characteristics (piece size, buoyancy, morphological complexity) and geomorphological characteristics (channel width, geomorphological style) in `Small', `Medium' and `Large' rivers. 6. Wood pieces are large in comparison with river size in `small' rivers, therefore they tend to remain close to where they are delivered to the river and provide important structures in the stream, controlling rather than responding to the hydrological and sediment transfer characteristics of the river. 7. For `Medium' rivers, the combination of wood length and form becomes critical to the stability of wood within the channel. Wood accumulations form as a result of smaller or more mobile wood pieces accumulating behind key pieces. Wood transport is governed mainly by the flow regime and the buoyancy of the wood. Even quite large wood pieces may require partial burial to give them stability, so enhancing the importance of the sediment transport regime. 8. Wood dynamics in `Large' rivers vary with the geometry of the channel (slope and channel pattern), which controls the delivery, mobility and breakage of wood, and also the characteristics of the riparian zone, from where the greatest volume of wood is introduced. Wood retention depends on the channel pattern and the distribution of flow velocity. A large amount is stored at the channel margins. The greater the contact between the active channel and the forested floodplain and islands, the greater the quantity of wood that is stored.

Abstract In the last two decades river restoration has become increasingly a field of research asking a series of complex questions related not just to science but also to society. Why should we restore ecosystems? Is restoration always beneficial? When is it beneficial? What should be the target reference states? What is success and when can it be evaluated? Our objective is to chronicle and discuss the fundamental concepts of reference versus objective, state versus process‐based actions, nature versus culture and ecosystem integrity versus ecosystem benefits driven restoration. We discuss the dynamic and yet unresolved definition of a reference state. Although the desire to re‐create the past is tempting, science has shown that river systems follow complex trajectories frequently making it impossible to return to a previous state. Therefore, restoration goals are moving away from explicitly defining a reference state because of the difficulty of attaining that reference state. We argue that the reference‐based strategy should be progressively replaced by an objective‐based strategy that reflects the practical limitations of developing sustainable landscapes and the emerging importance of accounting for human services of the target ecosystem. After a decade during which natural processes have been the focus of restoration, it appears that particular processes are not equally valuable everywhere and that regional complexity must be better understood to adjust restoration actions. Copyright © 2009 John Wiley & Sons, Ltd.

BACKGROUND: Comparable global data on health and nutrition of school-aged children and adolescents are scarce. We aimed to estimate age trajectories and time trends in mean height and mean body-mass index (BMI), which measures weight gain beyond what is expected from height gain, for school-aged children and adolescents. METHODS: For this pooled analysis, we used a database of cardiometabolic risk factors collated by the Non-Communicable Disease Risk Factor Collaboration. We applied a Bayesian hierarchical model to estimate trends from 1985 to 2019 in mean height and mean BMI in 1-year age groups for ages 5-19 years. The model allowed for non-linear changes over time in mean height and mean BMI and for non-linear changes with age of children and adolescents, including periods of rapid growth during adolescence. FINDINGS: . In some countries, children aged 5 years started with healthier height or BMI than the global median and, in some cases, as healthy as the best performing countries, but they became progressively less healthy compared with their comparators as they grew older by not growing as tall (eg, boys in Austria and Barbados, and girls in Belgium and Puerto Rico) or gaining too much weight for their height (eg, girls and boys in Kuwait, Bahrain, Fiji, Jamaica, and Mexico; and girls in South Africa and New Zealand). In other countries, growing children overtook the height of their comparators (eg, Latvia, Czech Republic, Morocco, and Iran) or curbed their weight gain (eg, Italy, France, and Croatia) in late childhood and adolescence. When changes in both height and BMI were considered, girls in South Korea, Vietnam, Saudi Arabia, Turkey, and some central Asian countries (eg, Armenia and Azerbaijan), and boys in central and western Europe (eg, Portugal, Denmark, Poland, and Montenegro) had the healthiest changes in anthropometric status over the past 3·5 decades because, compared with children and adolescents in other countries, they had a much larger gain in height than they did in BMI. The unhealthiest changes-gaining too little height, too much weight for their height compared with children in other countries, or both-occurred in many countries in sub-Saharan Africa, New Zealand, and the USA for boys and girls; in Malaysia and some Pacific island nations for boys; and in Mexico for girls. INTERPRETATION: The height and BMI trajectories over age and time of school-aged children and adolescents are highly variable across countries, which indicates heterogeneous nutritional quality and lifelong health advantages and risks. FUNDING: Wellcome Trust, AstraZeneca Young Health Programme, EU.

Diatoms of Europe: Diatoms of the European Inland Waters and Comparable habitats, Vol 6. Eunotia and some related genera (2011) by Horst Lange-Bertalot, Malgorzata Ba¸k & Andrzej Witkowski. Edited ...

Abstract Extensive channel narrowing in southeastern France provides an illustration of geomorphic response to land‐use changes. The study region comprises a range of environments, from large piedmont and intramountain gravel‐bed rivers, to small mountain streams. Field measurements and analysis of historical data demonstrate two distinct periods of channel change. From 1850 to 1950, channel narrowing is interpreted to be the result of a recovery process in response to widespread channel destabilization induced by major floods during the second half of the 19th century. At the time, the largely deforested basins were highly responsive to flooding, whereas the recovery process was accelerated by floodplain and basin‐scale land use changes (afforestation) and torrential control works, which in turn reduced sediment delivery and enabled vegetation development in channels. From 1950 to 1970, channel narrowing accelerated in most of the studied rivers. This recent phenomenon is considered as a human‐induced fluvial adjustment, directly related to forest development on river margins and human abandonment of intensive floodplain land uses. At the same time, long‐profile degradation occurred as a result of long‐term bedload supply decrease. In small mountain streams, channel narrowing is mainly explained by channel incision which seems to progress from upstream where sediment sources are progressively stabilized by afforestation. Copyright © 2002 John Wiley & Sons, Ltd.

Second Edition

This paper surveys the vehicle routing problems met in cities for good distribution. It applies the following methodology. First, it gives an overview of the literature devoted to vehicle route optimization in cities. Then, it classifies and analyses urban logistic flows. As a result, it identifies the principal scientific challenges that need to be addressed: time-dependency, multi-level and multi-trip organization of the distribution, dynamic information. Finally, it focuses on each one of these challenges, analyses the main difficulties they imply and how they are treated in the literature.

Abstract Hydrogeomorphic processes within alluvial river systems create, maintain and degrade riparian habitat. The dynamic interactions between water, sediment, aquatic–terrestrial landforms and biotic elements control the functional processes and biodiversity patterns within the riparian zone and, thus, contribute directly to their ecological integrity and societal value. Numerous researchers from different disciplines publish work on the physical, biological, economic and societal functions of the riparian zone within various physiographic areas. The present paper aims to review the hydrogeomorphic processes of unconfined alluvial channel–floodplain rivers within the temperate zone. These processes and their interactions with the biotic environment provide the basis for understanding the physical as well as the ecological functioning of fluvial hydrosystems. The review focuses mainly on the European context, but major advances in riparian research from other continents are also considered. Rehabilitation and management strategies for the riparian zone are summarized and recommendations for further research conclude this review. Copyright © 2005 John Wiley & Sons, Ltd.

Abstract In many regions and at the planetary scale, human pressures on the environment exceed levels that natural systems can sustain. These pressures are caused by networks of human activities, which often extend across countries and continents due to global trade. This has led to an increasing requirement for methods that enable absolute environmental sustainability assessment (AESA) of anthropogenic systems and which have a basis in life cycle assessment (LCA). Such methods enable the comparison of environmental impacts of products, companies, nations, etc, with an assigned share of environmental carrying capacity for various impact categories. This study is the first systematic review of LCA-based AESA methods and their applications. After developing a framework for LCA-based AESA methods, we identified 45 relevant studies through an initial survey, database searches and citation analysis. We characterized these studies according to their intended application, impact categories, basis of carrying capacity estimates, spatial differentiation of environmental model and principles for assigning carrying capacity. We then characterized all method applications and synthesized their results. Based on this assessment, we present recommendations to practitioners on the selection and use of existing LCA-based AESA methods, as well as ways to perform assessments and communicate results to decision-makers. Furthermore, we identify future research priorities intended to extend coverage of all components of the proposed method framework, improve modeling and increase the applicability of methods.

Nearly 300 million t of phosphogypsum (PG) are produced every year as a byproduct from phosphate fertilizer production worldwide. Approximately 58% of the PG are stacked, 28% are discharged in coastal waters and only 14% are further processed. This critical review provides an overview of the physical-chemical properties of PG produced from sedimentary and magmatic phosphate ore worldwide using various analytical tools. Results from more than 25 years of work on PG at École des Mines de Saint-Étienne are presented and critically discussed. In total PG samples from 67 industrial storage sites around the world and PG samples synthesized under different conditions in the laboratory have been considered. The low radioactivity present in PG (particularly PG produced from sedimentary phosphate rock) was identified as the main challenge to using PG as a raw material in construction. Water-soluble and volatile chemical compounds were identified as the main challenge to environmentally sound PG management. Although PG does (in most cases) not pose an immediate threat to the environment the authors recommend processing all PG instead of storing or disposing it, to eliminate potential long-term risks and utilize a relevant secondary resource.

Future climate changes and the resulting modifications in anthropogenic activities will alter the interactions between rivers and groundwater. The quantification of these hydraulic interactions is absolutely necessary for achieving sustainable water use and requires accurate analytical methodologies. This report proposes an interdisciplinary approach to the quantitative and qualitative characterization of hydraulic interactions between rivers and shallow aquifers, wherein it outlines the advantages of coupling groundwater modeling with biological markers. As a first step, we built independent diagnostic maps of hydrological exchanges at the sector scale on the basis of hydrogeological modeling and biological indicators. In a second step, these maps were compared to provide a quantitative and qualitative understanding of exchanges between groundwater and surface water. This comparison significantly improved the calibration of groundwater models through a better assessment of boundary zones. Our approach enabled us to identify the conditions under which it could be possible to use biological indicators instead of a large set of piezometric measures. The integration of such combined tools in a future decision support system will assist governmental authorities in proposing appropriate long-term water policies for the preservation of groundwater resources, such as for supplying potable water and/or mitigating pollution risks.

ABSTRACT The rivers of the world are undergoing accelerated change in the Anthropocene, and need to be managed at much broader spatial and temporal scales than before. Fluvial remote sensing now offers a technical and methodological framework that can be deployed to monitor the processes at work and to assess the trajectories of rivers in the Anthropocene. In this paper, we review research investigating past, present and future fluvial corridor conditions and processes using remote sensing and we consider emerging challenges facing fluvial and riparian research. We introduce a suite of remote sensing methods designed to diagnose river changes at reach to regional scales. We then focus on identification of channel patterns and acting processes from satellite, airborne or ground acquisitions. These techniques range from grain scales to landform scales, and from real time scales to inter‐annual scales. We discuss how remote sensing data can now be coupled to catchment scale models that simulate sediment transfer within connected river networks. We also consider future opportunities in terms of datasets and other resources which are likely to impact river management and monitoring at the global scale. We conclude with a summary of challenges and prospects for remotely sensed rivers in the Anthropocene. © 2019 John Wiley & Sons, Ltd.

Unmanned Aerial Vehicle (UAV) technology provides potential for very high spatial resolution (<25 cm) mapping of relatively large areas at a user-defined re-survey frequency. In a riparian context, UAV technology provides a mechanism for riparian managers to (a) quantify riparian terrain and vegetation units and (b) identify standing dead wood and canopy mortality. In this study a paraglider UAV was used to survey 174 ha at 6.8–21.8 cm ground resolution. Pixel-based and object-oriented classification approaches were used at the scale of a single image and a channel mosaic. Significant potential was demonstrated: vegetation units were classified with an accuracy of kappa = 0.79 and standing dead wood units were identified with an average accuracy with respect to omission and commission errors of 80% and 65%, respectively. Work across multiple images identified that major constraints currently result from factors such as illumination conditions and sensor movement during flight, which create variations in spatial resolution and radiometry. It is expected that with further methodological refinement and more complex methods of automated radiometric correction UAV technology can provide the flexibility to rapidly produce very high resolution map products to aid riparian management.

Abstract The increasing availability of aerial photography and satellite imagery offers new possibilities for characterizing river morphology. The precision of new very high resolution (VHR) images allows smaller scale objects within river corridors to be studied. High survey frequencies provide increased opportunities for the monitoring of river restoration. Following this evolution in platform technology, a small radio‐controlled motorized vehicle flying at low altitude was used to study both channel water depth and gravel bar geometry. The VHR imagery provided by this equipment allowed both channel bathymetry and a high accuracy photogrammetric digital elevation model (DEM) to be realized. Using case studies from the Ain and the Drôme Rivers in France, the accuracy of the results is presented and the various challenges associated with the new platform are discussed. One significant issue is that due to the low elevation of the survey the coverage of a target area is usually based on several photographs, which leads to variations in illumination conditions that stem from atmospheric changes. The images were processed to minimize this source of error but a number of issues have yet to be resolved. Bathymetric models with R 2 values between 0·59 and 0·90 were created in spite of the lack of channel bed homogeneity at the various sites. The gravel bar was also effectively mapped, and the photogrammetrically predicted DEM provided a 5–10 cm pixel resolution with a vertical precision between 2 and 40 cm according to the position within the image. This paper shows that, despite unstable image acquisition, unmanned radio‐controlled platforms provide significant advantages for the study of river processes, offering a flexible very high resolution data source for both channel bathymetry and gravel bar topography. Copyright © 2007 John Wiley &amp; Sons, Ltd.

The late 2000s have seen the emergence of a new kind of workplace: the coworking space. As of February 2013, 2500 spaces had been identified worldwide. This paper endeavors to situate the phenomenon within the existing theory of the creative, urban economy, and to serve as a platform for discussion and further research. Coworking spaces (CS) are regarded as "serendipity accelerators", designed to host creative people and entrepreneurs who endeavor to break isolation and to find a convivial environment that favors meetings and collaboration. At the beginning of the movement, CS creations were purely private initiatives. The concept has since attracted the interest of media, and CS have been incorporated in larger public programs aimed at the making of the "creative city", which often materializes in the regeneration of decayed industrial neighborhoods. CS are the outcome of the blurring of the frontiers and hybridization processes between technological, economic and social categories. Even if their sustainability and growth potential deserve to be questioned, they are strongly anchored in the workplace landscape of major business cities.

Abstract Human‐induced modifications of the vegetation cover in river basins may cause strong geomorphic responses by disturbing sediment supply, transport and deposition regimes. The response is particularly noticeable in upland regions, where sensitivity to change is enhanced by strong coupling between river channels and hillslopes, as is exemplified by studies undertaken in the East Coast region, North Island, New Zealand, and in the Southern French Prealps. Both regions have been affected by land‐use change during the past 150 years (deforestation and reforestation) that can be chronologically linked to geomorphic change on hillslopes and on valley floors. In this paper we use these studies to draw attention to: (1) the magnitude of the change in sediment production associated with a modification to the vegetation cover; (2) the impact that reforestation has on the sediment production and the channel system; and (3) the relative influence of anthropogenic and climatic forcing on the channel response. Finally, we consider the manner in which land use has been used as a tool to manage sediment production in France and New Zealand. The results obtained in both regions demonstrate the strong effect that the vegetation cover has on hillslope erosion processes, through its impact on the landsliding threshold (in New Zealand) and the total sediment yield (from paired forested and non‐forested catchments in France). Consideration of channel response serves to emphasize the sensitivity of upland regions to land‐use change, and suggests that the successful discrimination between the respective influences of climatic and land‐use change depends, in large part, upon the ability to detect spatial and chronological links (or, conversely, gaps) between causes and effects. Copyright © 2005 John Wiley &amp; Sons, Ltd.

SIMPOP is a knowledge-based simulation system for the description of the evolution of settlement patterns over long time periods. Rules and parameters are introduced into a multiagent systems formalism where each settlement is considered as a separate entity interacting with the others and transforming itself. The rules may allow for the simulation of the ‘urban transition’ from a set of homogeneous, agriculture-oriented, and scattered villages into a complex system of functionally diverse, competing, and hierarchised urban settlements. In this paper we show how several modifications of rules and parameters alter further the spatial and hierarchical structure of the simulated urban system.

Differences in the nature and quantity of sediment filling oxbow lakes have significant implications for the evolution of meandering rivers and the development of floodplains, influencing rates of meander migration and the valley width over which migration takes place. In an effort to identify the controls on the alluviation of oxbow lakes by coarse bed material, this study examined the sedimentary records stored within oxbow lakes of the Sacramento River of California, USA, and found that the volume of gravel in storage correlated negatively with the diversion angle separating flow between the river channel and the entrance into each lake. A method was devised for estimating the original channel bathymetry of the studied lakes and for modelling the hydraulic and sediment-transport effects of the diversion angle within channels recently abandoned by meander cut-off. The diversion angle determines the width of a flow separation within the abandoned-channel entrance, reducing the discharge diverted from the river channel and thus limiting the ability of the abandoned channel to transport bed material. Aggradation rates are faster within entrances to abandoned channels with high diversion angles, resulting in the rapid isolation of lakes that store only a small volume of coarse-grained sediment. Aggradation rates are slower within channel entrances where diversion angles are low, resulting in the slow transitioning of such channels into oxbow lakes with a larger and more extensive accumulation of coarse-grained sediment. These findings compare well with observations in other natural settings and the mechanism which is described for the control of the diversion may explain why some oxbow lakes remain as open-water environments for centuries, whereas others are filled completely within decades of cut-off.

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