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Master Thesis

Analyse historique des changements fluviaux de la Thio et de la Tôdré (Nouvelle-Calédonie)

Abstract : Opencast mining of nickel in New Caledonia is really damaging for mountain ranges which become highly susceptible to erosion. Erosion on these mining sites, which are located in upland catchments, and extraction practices carried out until the 1970s (dumping of exploitation wastes) lead to significant production of materials, as fine and coarse sediments, transferred from the creeks to the lagoon. These substantial contributions in sediments thus disrupt the dynamic and morphology of these rivers: they increase the bed load in rivers with massive aggradation and active channel widening. This study brings elements of understanding on the dynamics of these mine impacted rivers by analysing the historical and spatial evolution of the active channels. Archive aerial photographs from 1943 to 1989 were orthorectified or georectified and active channels were digitized at each date and their widths extracted. The Thio basin shows a progressive decrease in sediment supply, as active channels show significant narrowing. But it turns out that the study of the active channels can not alone explain these river dynamics that are highly dependent on hydrometeorological forcing and sediment sources connected to the stream network. The results presented in this report will be complemented by other studies planned in the project, and all these data will conduct to a more comprehensive study on the functioning of rivers of New Caledonia impacted by mining activity.
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Master Thesis
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Perrine Drain. Analyse historique des changements fluviaux de la Thio et de la Tôdré (Nouvelle-Calédonie). Sciences de l'ingénieur [physics]. 2016. ⟨dumas-01687006⟩

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