Évolution naturelle et anthropisation du linéaire côtier de l’île de Wallis : une prise de conscience de l’impact environnemental des extractions de sables de plage

Résumé En

As a response to both demographic expansion and changes concerning new ways of life, the increasing demand in beach sands and gravels induced coastal erosion process and other marine pollutions. In the first part of the text are presented some aspects of the human and physical original context of Wallis Islands. The second part explains the way actually chosen by Wallisian people to explore one of the different possibilities of substitution. This way prioritises the talks between scientific analysis and native Authorities in order to create a protected area on the near shore of Uvea, under the control of the French state administration. The first step of environnemental studies was a coastal geological expertise ordered to make an estimation of the erosion at Uvea. This expertise conclude that the determinant parameters are recently anthropogenic factors. For researching substitute to uncontrolled beach extraction sands, a marine geophysics survey was made in 2000 with aim to evaluate the thickness of marine sand in the lagoon and to show if extraction of marine granulates was possible without harmful impact on coastal sedimentary dynamics. Three superficial horizons were identified in the substrate structure. If the thickness of the upper layer appears very sufficient to satisfy the demand in sand flor numerous years, the technical survey (“étude d’impact”) will define the extraction conditions, if this way of substitution was agreed by Wallisian community.