Improve efficiency of morphological rehabilitation of gold mined streams: An adaptive approach in French Guiana.

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Melun Gabriel, Le Bihan Mikaël, De Billy Véronique, Gallay Marjorie, Rhoné Mathieu

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Alluvial gold mining began on the Guiana shield in the middle of the 19th century. During the three last decades, a particular socio-economic context led to ongoing gold-rush in French Guiana, as well as in all of its border countries (Brazil, Surinam) and more widely in the Amazon region. By deforesting, destroying bed channels, washing soils and polluting rivers and alluvial floodplains (mercury and high suspended load), gold mining is one of the main anthropogenic pressures and causes major environmental disturbances on physical habitat and associated biota. In French Guiana, the National Forestry Office (ONF) has recently estimated that 30,000 ha of rainforest as well as 3,300 km of watercourses were directly affected by gold mining. If illegal small-scale mines are massively involved in those impacts, authorized mining exploitations (width stream < 7.5 m) also contribute to a significant environmental degradation. Within this context, our study aims to help legal operators to achieve a morphological rehabilitation of mining sites after exploitation in order to reduce anthropogenic impacts of gold mining. For that, we first develop a step-by-step method – from bed channel reconstruction to revegetalisation of sites – to recover functional efficiency of fluvial patterns. Then, this method is implemented directly on mining sites and a scientific monitoring partnership is currently carried out to finely describe morphological adjustments of the streams after rehabilitation works. This adaptive management approach will allow to measure the effectiveness of rehabilitation, and the possibility and ways to adjust actions in this tropical environment.

Resource Type:
Conference Presentation, SER2021

Pre-approved for CECs under SER's CERP program