L’érosion côtière en Guyane

Abstract

Coastal erosion in french Guiana Modem shoreline changes in French Guiana are very active, linked to the Amazon Dispersal System : approximately 250 million m3 of fine grained sediments are transported annually by the currents and the waves along the Guianas coastline. As the result, a specific sedimentation pattern with alternating sectors of deposition (mudbanks and mudflats, with coastal progradation) and erosion (interbank zones, with erosion of the mangrove forest and of the siliclastic shorelines) characterizes the foreshore/shoreface area. Mudbanks and mudflats migrate slowly to the NW. On account of this dynamic, shoreline is continually changing. Our paper focused on modem coastal erosion within some interbank areas representing seasonal, interannual and decade time scales, owing to field studies and Remote Sensing data (SPOT-1 and LANDSAT MSS and TM) ; the results reveal that these areas (in Kourou-Sinnamary and Mana) are being extensively eroded despite the considerable amazonian supply. Such conclusion is important, furthermore coastal erosion in French Guiana was (and still is) considered as a minor event, coastal silting and correlated mangrove development being uphold as consistent barriers against shoreline retreat... To minimize coastal erosion is however a mistake : most significant has been the retreat of mangroves, of the cheniers' coasts, of the coastal swamps and even the mechanical erosion of peat. One of the most striking exemples is presently the zone of Mana (near the Maroni River mouth) where a sharply indented shoreline indicates a maximum of coastal erosion.