Bravard J.-P.,CNRS Environment City Society
BSGLg | Year: 2016
Sediment continuity along the river continuum has recently become a topical subject in Europe, together with ecological continuity. In reality it is an old subject, dating back to the 19th century, an era of sediment overloading in river channels resulting from the intense erosion of slopes caused by an aggressive climate. This paper shows how, in the Rhône watershed: 1) the first hydro-development schemes were adapted to excessive load by allowing food and coarse bed load passage; 2) large retention dams were erected in the 1930s in order to optimize the energy potential, but with a risk of intense sediment trapping; 3) gravel harvesting has partially made it possible to control sediment input and to conserve reservoir capacity; 4) the Rhône River diversion dams (1899-1986) were erected within a context of a marked decrease of bed load input into the river from tributaries and constraints related to their technology, to such an extent that sediment continuity was considerably fragmented.
Riquier J.,University Lumiere Lyon 2 |
Piegay H.,CNRS Environment City Society |
Sulc Michalkova M.,Masaryk University |
Sulc Michalkova M.,Comenius University
Freshwater Biology | Year: 2015
Over the past few decades, numerous floodplain restoration projects have attempted to re-establish complex and diverse river floodplains. They often aim to restore lateral connectivity (i.e. interactions between the main river channel and floodplain channels) and rejuvenate floodplain habitats which are no longer maintained or created by fluvial processes. Nonetheless, results of these experiences in terms of hydromorphological conditions and adjustments are rarely shared. The Rhône River is a large, highly regulated system where lateral connectivity has been greatly reduced. We investigated habitat dynamics (using sedimentological indicators as proxies) in 18 floodplain channels that were restored between 1999 and 2006. Environmental data (bathymetry and grain size of surficial fine sediments) were acquired on 3-5 surveys for each channel covering 6-12 years after restoration. In addition, a pre-restoration survey was made in 12 of the 18 channels. Using pressure sensors in the floodplain channels and rating curves in the main channel, we quantified the upstream overflow frequency and magnitude (i.e. maximum shear stress) in the channels and tested how these variables explain observed sedimentological patterns. Between-channel diversity accounted for 81% of the sedimentological variability observed after restoration. Time-averaged sedimentological conditions were robust and well predicted from overflow frequency and magnitude. Similarly, an indirect index of lateral connectivity used by hydrobiologists was also predictable from overflow frequency and magnitude. The remaining 19% of the sedimentological variability was attributed to temporal variation within channels and was mainly related to changes in longitudinal grain size gradient. This emphasises that grain size patterns are periodically reworked as a result of the flooding regime (backflow versus overflow) without significantly affecting average grain sizes. However, trajectories of grain size changes were stochastic and not always related to the hydrological regime. Accordingly, the partial pre-restoration data suggest that post-restoration sedimentological conditions were often similar to those observed before restoration, except in a few channels where major restoration works were performed. Our results quantify how changes in upstream overflow frequency and magnitude can modify physical conditions in the floodplain channels. They can be used to design habitats that are infrequent or missing at the floodplain scale. These results also suggest that changes in upstream plug morphology are a primary habitat driver. Such changes could be more frequently implemented in the Rhône and elsewhere to maximise the diversity of physical conditions in floodplains. © 2015 John Wiley & Sons Ltd.
Heritier S.,CNRS Environment City Society
Canadian Geographer | Year: 2011
Canadian national parks are well-known for protecting natural areas dedicated to 'the benefit and the enjoyment of the Canadian people'. The history of national parks illustrates the evolution of a concept of nature from functional conservation, such as tourism, to an environmental conception, based on ecosystem protection and biodiversity preservation. Banff, Waterton Lakes and Wood Buffalo National Parks in Alberta, and Kootenay National Park in British Columbia (four of the fourteen parks established before 1930, the year the National Parks Act was passed) have been chosen for this study in order to understand how national parks have dealt with local communities since the beginning of the national park movement, and how these relationships have changed during the last forty years. Inclusion of local communities and collaborative management processes have been well developed in northern Canadian parks since the mid-eighties. These practices have been considered successful in this region, but the situation is very different in the southern parks, especially those that were created before 1930. However, things have changed since Aboriginal culture and rights have been recognized in judgements rendered by the Supreme Court of Canada and by the Canadian Constitution. In the four parks chosen for this study, involvement of local communities and the development of their participation have been slow. Round tables and participation in the creation of interpretation sites and exhibits of Aboriginal history can be considered a step toward further cooperation. ©/ Canadian Association of Geographers / L'Association canadienne des géographes.
Rees Catalan A.K.,CNRS Environment City Society
Environmental Development | Year: 2015
The Monarch Butterfly Biosphere Reserve is located in central Mexico at the state border of Michoacán and Mexico, is the primary wintering area for the monarch butterfly (Danaus plexippus) and an important water aquifer for Toluca and Mexico City valley. Since the reserve's expansion in 2000, several efforts have been made to integrate nature preservation and social development. Therefore, the main objective of this paper is to analyse the territorial dynamics generated by the participation mechanisms that have been implemented in this region. Mexican environmental law only allows the National Commission of Protected Areas to make final decisions, thus, true participative management, defined as effective citizen power, including in the decision-making processes between citizens and institutions, is not legally recognized in the country. However, some mechanisms exist to enhance participation. The Monarch Fund, which pays for environmental services, has helped to improve acceptance of the protected area, even though opportunity costs are not fully covered. In the process of establishing leadership, NGOs play a central role as valid intermediaries between institutional and local resident stakeholders, working for increased social participation. However, strengthening social participation is limited by the characteristics of Mexican social organizations, ejidos and comunidades, in which three social classes exist with different rights pertaining to each category. Nevertheless, micro-regional councils and the consultative council make a long-term relationship between stakeholders possible; every inhabitant, regardless of social status, can take part in the process. These elements led us to state that participation is not exemplary but is quite promising. © 2015 Elsevier B.V.
Renard F.,CNRS Environment City Society
Theoretical and Applied Climatology | Year: 2016
The Greater Lyon area is strongly built up, grouping 58 communes and a population of 1.3 million in approximately 500 km2. The flood risk is high as the territory is crossed by two large watercourses and by streams with torrential flow. Floods may also occur in case of runoff after heavy rain or because of a rise in the groundwater level. The whole territory can therefore be affected, and it is necessary to possess in-depth knowledge of the depths, causes and consequences of rainfall to achieve better management of precipitation in urban areas and to reduce flood risk. This study is thus focused on the effects of topography and land cover on the occurrence, intensity and area of intense rainfall cells. They are identified by local radar meteorology (C-band) combined with a processing algorithm running in a geographic information system (GIS) which identified 109,979 weighted mean centres of them in a sample composed of the five most intense rainfall events from 2001 to 2005. First, analysis of spatial distribution at an overall scale is performed, completed by study at a more detailed scale. The results show that the distribution of high-intensity rainfall cells is spread in cluster form. Subsequently, comparison of intense rainfall cells with the topography shows that cell density is closely linked with land slope but that, above all, urbanised zones feature nearly twice as many rainfall cells as farm land or forest, with more intense intensity. © 2016 Springer-Verlag Wien
Alber A.,CNRS Environment City Society |
Piegay H.,CNRS Environment City Society
Geomorphology | Year: 2011
Network-scale heterogeneity in fluvial forms and processes has been analyzed for decades through the field-based characterization of a reduced number of sites. Spatially continuous data sets are increasingly available at a national scale (e.g., digital elevation models or aerial orthophotographs) and open up new possibilities to investigate spatial structures in stream networks. The paper introduces a GIS methodological framework to support and automate the large-scale characterization of the fluvial system based on spatial disaggregation and aggregation procedures. The spatial disaggregation consists in the longitudinal discretisation of geographical objects into relatively high resolution spatial units to characterize fluvial features continuously along stream networks. Because rivers are heterogeneous and hierarchically organized, the spatial aggregation aims to delineate statistically pattern or process-based spatial units to answer questions at appropriate scales. The paper develops the GIS implementation of the disaggregation and aggregation procedures for characterizing stream networks in a geomorphic perspective. We illustrate the approach on the Rhône network, focusing on the characterization of three geographical objects commonly used in classification schemes: the streamline, the valley bottom, and the active channel (the latter on a limited area). The spatial aggregation is automated using the threshold test of Pettitt (1979) to detect change points in univariate data series and delineate homogeneous spatial units throughout the stream network. We provide three simple application examples to illustrate the potentialities of the spatial aggregation to investigate spatial heterogeneity in stream networks. Finally, insights, limitations and future challenging issues emerging from the application of the methodological framework are discussed. © 2010 Elsevier B.V.
Toone J.,Loughborough University |
Rice S.P.,Loughborough University |
Piegay H.,CNRS Environment City Society
Geomorphology | Year: 2014
The rehabilitation of degraded river channels is often guided by assumptions of continuity, yet in response to spatial and temporal variations in controlling conditions rivers typically display discontinuous response in space and time. This study examines the development of a 5. km reach of the DrÔme River, S.E. France, characterised by alternating alluvial and bedrock zones that are separated by abrupt downstream transitions. This reach is representative of the DrÔme River as a whole, and other rivers in the European Alps where braided channel planforms have been replaced by more complex, discontinuous morphologies. The primary aims are to understand how this spatial complexity has developed on the DrÔme; evaluate how temporal channel changes have been affected by local factors, particularly bedrock exposures, and by long-term, catchment-scale changes in sediment supply and the flood activity; and consider the implications of this discontinuous geomorphology for reach management. The development of geomorphological zonation is examined by documenting sequential changes in channel planform between seven periods, using aerial photography (1948-2006) and by analysing change in bed elevation from profiles surveyed in 1928, 2003 and 2005. Between 1948 and 2001 bedrock exposed in the channel bed and along the floodplain margins defined discontinuities in sediment connectivity that were largely responsible for the configuration of channel zones. The impact of floods on this system was not proportional to flood magnitude. A modest flood in 1978 was an important event that, by incision and avulsion at key locations, defined a pattern of zonation that persisted until the end of the study in 2006. During the final 5. years of the study, alluvial zones that previously responded to large floods by widening underwent narrowing, despite the occurrence of a large flood, and led to an overall reduction in width variance. This resulted from progressive incision beneath and disconnection from formerly active channel areas, in response to long-term, catchment-scale reductions in sediment supply and flood frequency. In 2006 the pattern of zonation remains distinct, disguising this recent change in channel response and underlining the need for long-term and sequential perspectives of channel development to fully understand the processes in operation; contemporary snapshots of channel form may be misleading. Understanding interactions between inherent channel complexity and prevailing flow and sediment conditions, and how this shapes channel response to individual floods, is essential when interpreting future trajectories of channel change and likely response to management intervention. © 2012 Elsevier B.V.
Verdeil E.,CNRS Environment City Society
Urban Studies | Year: 2014
Metropolitan authorities and local business elites are often seen as major players in the energy transition in the city. Such energy transitions are mostly conceived of as low carbon technologies, which permit the retrofitting of urban infrastructure and the rebundling of metabolic circuits. This article contests these views by highlighting the major role of non-urban energy sector institutions and actors. By examining the connections between technology, space and energy politics, and by using a relational understanding of the urban, this article explores the case of Amman's energy transition. The growth of consumption coupled with new energy practices face a problematic supply because of shifts in regional geopolitics. This situation has prompted energy transition policies, among which are a green growth programme and the building of a nuclear power plant at the edge of the city. The article analyses the socio-political assemblages that shape those policies and unravels the competing interests at stake. It demonstrates the political and highly unruly nature of energy transitions. © 2013 Urban Studies Journal Limited.
Jean-Francois B.,CNRS Environment City Society
Geomorphology | Year: 2011
On a landscape scale, the location of archaeological sites strongly influences their potential for preservation. The recent progress made in the acquired knowledge of the Rhône River basin palaeodynamics, occurring simultaneously to the development of intensive rescue archaeological surveys on fluvial plains, provides information on the burying and post-depositional processes of archaeological records for all of the Holocene cultural phases. Even if the lowlands have traditionally been seen as having lower population densities and are dominated by Late Holocene sediments, the systematic exploration of the soil archives has revealed that the archaeological potential was concentrated in the lower alluvial plains and the Alpine foothill river fans. The taphonomic corrections and correlative predictive model carried out under GIS have changed our perception of the settlement history of the northwestern Mediterranean region. They put in doubt some initial settlement patterns, some chronocultural hiatuses, based on preconceived models of land use, especially for the First Neolithic and the Protohistoric periods. © 2011 Elsevier B.V.
Gonzalez-Feliu J.,CNRS Environment City Society
ILS 2016 - 6th International Conference on Information Systems, Logistics and Supply Chain | Year: 2016
This paper presents a general framework to assess urban rail logistics suitability via a socio-economic cost benefit analysis. Firstly, we propose an overview on the basic notions of CBA and SCBA. Secondly, we identify and present the main types of costs and benefits or railway urban logistics services and the related final delivery services using low emission road vehicles to serve customers where the rail systems cannot. Thirdly, as an example of application, we propose to assess a scenario of deployment of a freight tramway in Paris, in a possible configuration. The results show the potential of those approaches but also show that it is important to contextualize them and inform the different users about their real capacities.