International audienceThe purpose of this study is to propose a methodological essay for defining evolutionary trajectories of channel planforms and to examine the channel change in the middle Garonne River (southwest France) over a 130-year period. The study focuses on a reach of ~90 km situated downstream from the city of Toulouse. A set of four historical maps (1868, 1940s, 1970s, and 2000s) is used to build a geomorphometric diachronic database. Data processing through mixed multiple factor analysis (MFAmix) and hierarchical cluster analysis (HCA) allows distinction between four homogeneous zones within the study reach, depending on their evolutionary trajectories. Channel behavior in the upstream and median zones evolved as of the beginning of the study period (narrowing of the fluvial area, colonization by vegetation, and removal of alluvial bars), likely owing to punctual anthropogenic actions. The downstream zone is characterized by stabilization of the channel and alluvial bar removal over the second half of the twentieth century, coinciding with the campaign undertaken by French local authorities between 1960 and 1984 to protect river banks. The role of ACCEPTED MANUSCRIPT climate transition between the Little Ice Age (LIA) and the onset of the Global Warming period (GW) is also discussed. Results generally are consistent with the chronology established for most European rivers

Article history: Available online xxx a b s t r a c t This paper discusses the evolution of the Tech river lower plain, (western Mediterranean) from the Late Middle Ages, using geomorphological, archaeological and historical data. Geoarchaeological data was obtained from coring and trenching near a buried village and chapel. Radiocarbon and archaeological dating are used to reconstitute sedimentation rates and major flood event chronology. Additional data about channel avulsion are provided by historical data. Increases in sedimentation rate, flooding plain enlargement and repeated avulsion are identified between the last 13th to 15th century AD. This attests to a shift from low water-level regime (LWR) to flood dominated regime (FDR). Climatic or anthropogenic causes of this change are discussed on the basis of regional synthesis. On the western Mediterranean scale, 1250/1350 AD seems to be a wetter phase, associated with the progressive onset of the Early Little Ice Age phase from 1330 to 1450 AD.

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Géohistoire des risques et des patrimoines naturels fluviaux Construction géohistorique du « sauvage » de la Garonne toulousaine : quelle part de naturalité dans les paysages fluviaux ? (1 ère partie) Geohistorical construction of the "wild" of the middle valley of the Garonne (near of Toulouse

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OATAO is an open access repository that collects the work of Toulouse researchers and makes it freely available over the web where possible. This is an author-deposited version published in : http://oatao.univ-toulouse.fr/ Eprints ID : 17924To link to this article :

Résumé : La ville de Toulouse en France s'est installée sur les berges de la Garonne. L'évolution de l'urbanisation de la ville témoigne des relations ambivalentes qu'elle entretien avec le fleuve : fléau à combattre, contre lequel on aménage des digues, mais aussi ressource recherchée pour laquelle on crée des moulins, des ports… La géohistoire des aménagements fluviaux face à l'urbanisation révèle le développement et la juxtaposition des artéfacts sur le fleuve. Les paysages fluviaux urbains de Toulouse sont le résultat d'une lente construction temporelle. L'objectif de ce travail est de définir ces différentes temporalités, qui ont produit les paysages fluviaux actuels. Ces derniers font l'objet de projets de valorisation et leur mise en place permettra de changer les regards en mettant la Garonne au centre et au coeur de la ville. Most-Clés :Toulouse, Garonne, urbanisation, aménagements fluviaux, ressource, inondation, géohistoire, rapport ville/fleuve, temporalités, paysages fluviaux. Abstract:The city of Toulouse in France settled on the banks of the Garonne. The evolution of the urbanization of the city reflects the ambivalent relationship with the river: scourge to fight against dams which is landscape, but also sought to resource which is created mills, ports ... The GEOGRAPHICALIA (2013), 63-64, 177-203 177 Recibido: 22-01-13. Aceptado: 8-10-13. historical geography of river developments facing urbanization reveals the development and juxtaposition of artifacts on the river. Urban river landscapes Toulouse are the result of a slow time construction. The objective of this work is to define these different temporalities that produced the current river landscapes. These are the subject of development projects and their implementation will change the looks by putting the Garonne in the center and heart of the city.