Accéder directement au contenu Accéder directement à la navigation
Article dans une revue

Pluri-decadal impact of mining activities on coastline mobility of estuaries of New Caledonia

Abstract : The coastline mobility at decadal timescales is relatively easy to monitor. However, it results from numerous factors acting at global scale (climate change and sea level rise induced), at regional scale (vertical movements linked to tectonic or isostasy ...) or at local scale (sediment transport, sedimentary supply from continent, anthropogenic actions etc.). The present study aims at analysing the relative impact of sedimentary supply by the rivers versus the effect of sea level rise and other processes over the last 5 decades on some representative coastal stretches of New Caledonia (South Pacific Ocean). Ten coastal estuarine stretches of the main island of New Caledonia have shown erosion rates ranging from -2m/y to accretion rates up to 4m/y over the last 50 years. During this time, the climate component of sea level rise has been evaluated around 0,5mm/y in Nouméa and can be considered identical at the scale of the island. Thus, it cannot be considered as the driving factor of coastline changes Vertical movements affecting the New Caledonia are suspected to be different between the western and the eastern part of the island. Vertical movements of the western coast are negative (around -2.5mm/y in Nouméa) to inexistent while the eastern coast is visibly affected by a higher subsidence as indicated by morphological indicators (ria morphologies, lack of coastal plain, dissymmetry of the lagoon bathymetry). Nevertheless, in areas with homogeneous vertical movement, the coastal stretches studied show various evolution rates (from erosion to accretion). This indicates that the vertical movements are not the predominant forcing factor of the coastline changes. The analysis of accreting estuarine coastal areas shows that this evolution is linked to the sedimentary supply of the rivers. On New Caledonia Island, the creation of bare soils by the nickel mining during the last 50 years has increased the erosion processes on the watersheds and the solid discharge of the rivers. The study shows that there is a strong correlation between the percentage of the surface of bare soils (up to 3.7 % of the watershed surface) generated by nickel mining and the coastline evolution rate (from -2m/y to +4m/y) around the estuaries of each watershed. In poorly anthropogenised estuaries of New Caledonia, an indirect anthropogenic activity (mining) on watersheds is thus suspected to have been the major forcing factor of recent coastal changes, while other parameters like sea level rise and vertical movements seems to be negligible.
Type de document :
Article dans une revue
Liste complète des métadonnées

https://hal-brgm.archives-ouvertes.fr/hal-00752365
Contributeur : Manuel Garcin <>
Soumis le : jeudi 15 novembre 2012 - 15:14:17
Dernière modification le : mardi 31 mars 2020 - 09:20:03

Identifiants

Collections

Citation

Manuel Garcin, Audrey Baills, Gonéri Le Cozannet, Thomas Bulteau, Anne-Laure Auboin, et al.. Pluri-decadal impact of mining activities on coastline mobility of estuaries of New Caledonia. Journal of Coastal Research, Coastal Education and Research Foundation, 2013, 65 (Special Issue), pp. 494-499. ⟨10.2112/SI65-084.1⟩. ⟨hal-00752365⟩

Partager

Métriques

Consultations de la notice

388