Evolution de la flèche Mandji de l'holocène à l'actuel. Analyse et cartographie du risque côtier

Zephirin Menie Ovono 1
1 LETG - Nantes - Littoral, Environnement, Télédétection, Géomatique
LETG - Littoral, Environnement, Télédétection, Géomatique
Abstract : Mandji spit evolution during Holocen period (and in particular Port-Gentil and Cape Lopez sections), was computed using multiple iconographic sources, (maps and historic plans, nautical charts, aerial photos, satellite pictures, situ measurements). This allows analysis of the natural impacts and the anthropogenic actions on this gabonese coast. The long term evolution of the coastline was determined with the use of the C14 datation of paleoenvironments. The medium term evolution is provided by ancient available maps which emphasized spit morphogenesis steps over the period 1660-1886. Concerning the short term, we have used aerial photos registered in 1945, 1957, 1988; two Landsat TM images registered in 1990 and an ETM + Landsat image from 2001. Moreover, a set of nautical charts by Total Gabon from 1962 to 2007 underlines the position of the high-water line during this period. A Geographical Information System (GIS) allowing storage and management of these data is built up to produce statistic and spatial information relative to the dynamics of the shoreline. Coastline mobility was showed and quantified for period 1962-2007. The mains results of this analysis reveal an important erosion of the coast particularly along its urbanized part, which constitutes a real threat for the human installations. Hence, this thesis gives a wide overview of the evolution of Mandji spit and its natural hazards and brings propositions of mitigation over the short, medium and long term.
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Theses
Océan, Atmosphère. Université de Nantes, 2010. Français
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Zephirin Menie Ovono. Evolution de la flèche Mandji de l'holocène à l'actuel. Analyse et cartographie du risque côtier. Océan, Atmosphère. Université de Nantes, 2010. Français. 〈tel-00492018〉

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