ABSTRACT The erosion affecting the coast of Port-Bouet (Abidjan, Ivory Coast) is a major threat a... more ABSTRACT The erosion affecting the coast of Port-Bouet (Abidjan, Ivory Coast) is a major threat and concern to the economic infrastructure of the Ivorian Refining Company (SIR), the Felix Houphouet Boigny airport international and homes along the coast. In recent years, in order to better understand this scientific accumulation-erosion budget phenomenon, CURAT (Centre Universitaire de Recherche et d’Application en Télédétection) undertook studies both in situ and from a mapping approach to assess the rate of coastal retreat on the sandy coasts of the Ivory Coast. In this study, the study changes in the morphology of the coastal area of Abidjan, the economic capital of Côte d’Ivoire, was derived from the use of the software Digital Shoreline Analysis System (DSAS) to process vertical aerial photographs, and Corona and HRG panchromatic SPOT-5 imagery to estimate the displacement of shorelines by photointerpretation. The mid-secular evolution of the coastline (beach dune contact) has been analysed over 42 years (1967-2009). We discuss the role of the destabilising developments and crises on the erosive dynamics of the coastline in the Bay of Port-Bouet, which seek a new equilibrium position by readapting its shore relative to the longshore drift. As a result, a new up drift zone has developed, resulting in a general enhancement of the concavity of the bay of Port-Bouet.
Recent changes in climate have led to an increased exposure of glacial archaeological artefacts d... more Recent changes in climate have led to an increased exposure of glacial archaeological artefacts due to the melting of glaciers and ice patches. Here we calculated Least Cost Paths (LCPs) between archaeologically significant locations in Switzerland and Italy using a Least Cost Path Analysis (LCPA) method in which cost rasters were first calibrated at a study site near Haut-Val de Réchy, Switzerland to develop a prehistoric cost raster. Tools were used to calculate the LCPs based on DEM-derived slope using Tobler's anisotropic hiking function and landcover. Our results have since provided a focus for prehistoric glacial archaeological prospection in the Pennine Alps of central Europe, as well as led to the discovery of an artefact from the Bronze Age (~2,800 years BP). This methodology could be used as an example for identifying additional sites of prehistoric glacial archaeological remains around the world. More information about that project: www.glacialarchaeology.com
Ce précis est le troisième volume de la série en télédétection. Le premier traite des Principes e... more Ce précis est le troisième volume de la série en télédétection. Le premier traite des Principes et Méthodes alors que le deuxième, ouvrage collectif, présente les Applications thématiques de la télédétection. Ce volume présente les traitements d'image selon une structure relativement conventionnelle et logique: les séquences de traitements permettant la transformation des données de télédétection originales en une information géographique dont le contenu exprime des thématiques exploitables. Ainsi chaque chapitre se rapporte à des traitements liés aux fonctions de base du traitement numérique d'image.
ABSTRACT Die Hochgebirgs-Kryosphäre, insbesondere Schnee, Permafrost und Gletscher, spielt in Bez... more ABSTRACT Die Hochgebirgs-Kryosphäre, insbesondere Schnee, Permafrost und Gletscher, spielt in Bezug auf die Auswirkungen eines sich ändernden Klimas auf die Gebirgsökosysteme eine Schlüsselrolle aufgrund (i) ihrer starken Sensitivität infolge von Temperaturen nahe dem Schmelzpunkt, (ii) ihrer Funktion als (Haupt-) Steuerungsgrösse des hydrologischen Abflusses und (iii) des Einflusses von Veränderungen bezüglich der saisonalen Schneedecke, da diese Boden-Atmosphäre Wechselwirkungen auf verschiedene Weise stark beeinflusst. Um den Einfluss des Klimawandels auf die Kryosphäre und die damit verbundenen Auswirkungen für die Gesellschaft verlässlich bestimmen zu können, ist ein besseres Verständnis der für die Wechselwirkungen zwischen alpiner Kryosphäre und Atmosphäre relevanten Prozesse auf verschiedenen räumlichen und zeitlichen Skalen vonnöten. Da Veränderungen der Kryosphäre im Hochgebirge mit geomorphologischen Prozessen gekoppelt sind, können diese zu Naturgefahren aufgrund aktueller und zukünftiger Klimaänderungen führen. Temperaturabhängige Prozesse (z.B. Phasenübergänge von Wasser, Deformation von Eis sowie Eis/ Fels-Gemischen, Vorrat an Schnee/Eis, Permafrostdegradation) beeinflussen die physikalischen Faktoren, die den Sedimenttransport steuern (z.B. Gletscher, Blockgletscher, Murgänge), das hydrologische System sowie die Stabilität steiler Hänge. Aktuelle Forschungen an der Universität Freiburg im Bereich der alpinen Kryosphäre und Geomorphologie beschäftigen sich insbesondere mit der Entwicklung neuer Mess- und Modelliermethoden, um periglaziale und glaziale Systeme in Gebirgsregionen zu untersuchen und langfristig zu beobachten. Dies beinhaltet prozess-basierte Modellstudien, Monitoringstrategien sowie Impact-Studien in Bezug auf Hydrologie und Naturgefahren. In diesem Beitrag wird das Potential dieser neuen Modellier-, Mess- und Auswertungsmethoden für die Grundlagenforschung und ihrer Anwendung in den Gebirgsregionen der Schweiz vorgestellt. The high-mountain cryosphere, in particular snow, permafrost and glaciers, plays a key role regarding climate change impacts on mountain ecosystems because of (i) its high climate sensitivity due to the proximity to the melting point, (ii) its major controlling function on hydrological runoff, and (iii) particularly because of the influence of seasonal snow on ground-atmosphere processes. In order to reliably assess the influence of climatic changes on the cryosphere and consequently their impacts on society, more detailed knowledge of the relevant processes that determine the interactions between the alpine cryosphere and the atmosphere on different spatial and temporal scales is required. As cryospheric changes in high mountains are strongly coupled to geomorphic processes these may result in dramatic changes in response to ongoing and future climatic evolution. Temperature dependent mechanisms (e.g. phase change of water, deformation of ice and ice/rock mixture, storage of snow/ice, permafrost degradation) will affect the physical factors controlling the transfer of sediment (e.g. glaciers, rock glaciers, debris flows), the hydrological system and the stability of steep slopes. Research in alpine cryosphere and geomorphology at the University of Fribourg particularly focuses on the development of new measurement and modelling techniques to investigate and monitor mountain periglacial and glacial systems, including process-based modelling studies, monitoring strategies, and analyses of the impact on hydrology and natural hazards. In this contribution, the potential of these new modelling, measurement and analysis techniques for fundamental and applied research on mountain regions in Switzerland is presented.
Astronomical research at present requires that a telescope with an aperture diameter of between 5... more Astronomical research at present requires that a telescope with an aperture diameter of between 50 and 100 metres be constructed within the next 10 years or so. Selection of an ideal site for this telescope is dependent on many parameters, especially local climatological and meteorological variables. A GIS-based interface and database is currently being built for this task at the University of Fribourg, Switzerland. The interface will combine a fully comprehensive climatological database (e.g. ECWMF and NCEP/NCAR Reanalysis data) complete with GIS tools (e.g. IDRISI software and PHP web server language) in order to aid the decision making process. The interaction between air-flow and topography is also of critical importance, as unfavourable air-flow can signifîcantly perturb astronomical observations (e.g. Beniston et al, 2002). This problem is addressed by the inclusion of an Upwind Roughness Index (URI), which is based on a combination of the upwind topography and wind frequency ...
Certain aspects of the specification of the land cover characteristics for use in high-resolution... more Certain aspects of the specification of the land cover characteristics for use in high-resolution regional climate models (RCMs) are considered in this paper. We demonstrate the importance of specifying the appropriate surface characteristics at high horizontal resolution and discuss their impacts on the simulated surface prognostic variables, on the surface energy flux as well as on the surface winds in
ABSTRACT The erosion affecting the coast of Port-Bouet (Abidjan, Ivory Coast) is a major threat a... more ABSTRACT The erosion affecting the coast of Port-Bouet (Abidjan, Ivory Coast) is a major threat and concern to the economic infrastructure of the Ivorian Refining Company (SIR), the Felix Houphouet Boigny airport international and homes along the coast. In recent years, in order to better understand this scientific accumulation-erosion budget phenomenon, CURAT (Centre Universitaire de Recherche et d’Application en Télédétection) undertook studies both in situ and from a mapping approach to assess the rate of coastal retreat on the sandy coasts of the Ivory Coast. In this study, the study changes in the morphology of the coastal area of Abidjan, the economic capital of Côte d’Ivoire, was derived from the use of the software Digital Shoreline Analysis System (DSAS) to process vertical aerial photographs, and Corona and HRG panchromatic SPOT-5 imagery to estimate the displacement of shorelines by photointerpretation. The mid-secular evolution of the coastline (beach dune contact) has been analysed over 42 years (1967-2009). We discuss the role of the destabilising developments and crises on the erosive dynamics of the coastline in the Bay of Port-Bouet, which seek a new equilibrium position by readapting its shore relative to the longshore drift. As a result, a new up drift zone has developed, resulting in a general enhancement of the concavity of the bay of Port-Bouet.
Recent changes in climate have led to an increased exposure of glacial archaeological artefacts d... more Recent changes in climate have led to an increased exposure of glacial archaeological artefacts due to the melting of glaciers and ice patches. Here we calculated Least Cost Paths (LCPs) between archaeologically significant locations in Switzerland and Italy using a Least Cost Path Analysis (LCPA) method in which cost rasters were first calibrated at a study site near Haut-Val de Réchy, Switzerland to develop a prehistoric cost raster. Tools were used to calculate the LCPs based on DEM-derived slope using Tobler's anisotropic hiking function and landcover. Our results have since provided a focus for prehistoric glacial archaeological prospection in the Pennine Alps of central Europe, as well as led to the discovery of an artefact from the Bronze Age (~2,800 years BP). This methodology could be used as an example for identifying additional sites of prehistoric glacial archaeological remains around the world. More information about that project: www.glacialarchaeology.com
Ce précis est le troisième volume de la série en télédétection. Le premier traite des Principes e... more Ce précis est le troisième volume de la série en télédétection. Le premier traite des Principes et Méthodes alors que le deuxième, ouvrage collectif, présente les Applications thématiques de la télédétection. Ce volume présente les traitements d'image selon une structure relativement conventionnelle et logique: les séquences de traitements permettant la transformation des données de télédétection originales en une information géographique dont le contenu exprime des thématiques exploitables. Ainsi chaque chapitre se rapporte à des traitements liés aux fonctions de base du traitement numérique d'image.
ABSTRACT Die Hochgebirgs-Kryosphäre, insbesondere Schnee, Permafrost und Gletscher, spielt in Bez... more ABSTRACT Die Hochgebirgs-Kryosphäre, insbesondere Schnee, Permafrost und Gletscher, spielt in Bezug auf die Auswirkungen eines sich ändernden Klimas auf die Gebirgsökosysteme eine Schlüsselrolle aufgrund (i) ihrer starken Sensitivität infolge von Temperaturen nahe dem Schmelzpunkt, (ii) ihrer Funktion als (Haupt-) Steuerungsgrösse des hydrologischen Abflusses und (iii) des Einflusses von Veränderungen bezüglich der saisonalen Schneedecke, da diese Boden-Atmosphäre Wechselwirkungen auf verschiedene Weise stark beeinflusst. Um den Einfluss des Klimawandels auf die Kryosphäre und die damit verbundenen Auswirkungen für die Gesellschaft verlässlich bestimmen zu können, ist ein besseres Verständnis der für die Wechselwirkungen zwischen alpiner Kryosphäre und Atmosphäre relevanten Prozesse auf verschiedenen räumlichen und zeitlichen Skalen vonnöten. Da Veränderungen der Kryosphäre im Hochgebirge mit geomorphologischen Prozessen gekoppelt sind, können diese zu Naturgefahren aufgrund aktueller und zukünftiger Klimaänderungen führen. Temperaturabhängige Prozesse (z.B. Phasenübergänge von Wasser, Deformation von Eis sowie Eis/ Fels-Gemischen, Vorrat an Schnee/Eis, Permafrostdegradation) beeinflussen die physikalischen Faktoren, die den Sedimenttransport steuern (z.B. Gletscher, Blockgletscher, Murgänge), das hydrologische System sowie die Stabilität steiler Hänge. Aktuelle Forschungen an der Universität Freiburg im Bereich der alpinen Kryosphäre und Geomorphologie beschäftigen sich insbesondere mit der Entwicklung neuer Mess- und Modelliermethoden, um periglaziale und glaziale Systeme in Gebirgsregionen zu untersuchen und langfristig zu beobachten. Dies beinhaltet prozess-basierte Modellstudien, Monitoringstrategien sowie Impact-Studien in Bezug auf Hydrologie und Naturgefahren. In diesem Beitrag wird das Potential dieser neuen Modellier-, Mess- und Auswertungsmethoden für die Grundlagenforschung und ihrer Anwendung in den Gebirgsregionen der Schweiz vorgestellt. The high-mountain cryosphere, in particular snow, permafrost and glaciers, plays a key role regarding climate change impacts on mountain ecosystems because of (i) its high climate sensitivity due to the proximity to the melting point, (ii) its major controlling function on hydrological runoff, and (iii) particularly because of the influence of seasonal snow on ground-atmosphere processes. In order to reliably assess the influence of climatic changes on the cryosphere and consequently their impacts on society, more detailed knowledge of the relevant processes that determine the interactions between the alpine cryosphere and the atmosphere on different spatial and temporal scales is required. As cryospheric changes in high mountains are strongly coupled to geomorphic processes these may result in dramatic changes in response to ongoing and future climatic evolution. Temperature dependent mechanisms (e.g. phase change of water, deformation of ice and ice/rock mixture, storage of snow/ice, permafrost degradation) will affect the physical factors controlling the transfer of sediment (e.g. glaciers, rock glaciers, debris flows), the hydrological system and the stability of steep slopes. Research in alpine cryosphere and geomorphology at the University of Fribourg particularly focuses on the development of new measurement and modelling techniques to investigate and monitor mountain periglacial and glacial systems, including process-based modelling studies, monitoring strategies, and analyses of the impact on hydrology and natural hazards. In this contribution, the potential of these new modelling, measurement and analysis techniques for fundamental and applied research on mountain regions in Switzerland is presented.
Astronomical research at present requires that a telescope with an aperture diameter of between 5... more Astronomical research at present requires that a telescope with an aperture diameter of between 50 and 100 metres be constructed within the next 10 years or so. Selection of an ideal site for this telescope is dependent on many parameters, especially local climatological and meteorological variables. A GIS-based interface and database is currently being built for this task at the University of Fribourg, Switzerland. The interface will combine a fully comprehensive climatological database (e.g. ECWMF and NCEP/NCAR Reanalysis data) complete with GIS tools (e.g. IDRISI software and PHP web server language) in order to aid the decision making process. The interaction between air-flow and topography is also of critical importance, as unfavourable air-flow can signifîcantly perturb astronomical observations (e.g. Beniston et al, 2002). This problem is addressed by the inclusion of an Upwind Roughness Index (URI), which is based on a combination of the upwind topography and wind frequency ...
Certain aspects of the specification of the land cover characteristics for use in high-resolution... more Certain aspects of the specification of the land cover characteristics for use in high-resolution regional climate models (RCMs) are considered in this paper. We demonstrate the importance of specifying the appropriate surface characteristics at high horizontal resolution and discuss their impacts on the simulated surface prognostic variables, on the surface energy flux as well as on the surface winds in
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Papers by Claude Collet