An experimental study on dredge spoil of estuarine sediments in the bay of seine (France): A morphosedimentary assessment

摘要: Studies on the consequences of dredging estuarine morphology and its sedimentary dynamics are common, but impacts dumping dredge spoil in coastal open settings rarely found scientific literature. An experimental study was conducted over period 2012-2013 to monitor physical dredged material dumped at two adjacent sites (one million cubic metres each) inner shelf Bay Seine France (eastern part English Channel, La Manche). As recently reinforced EU Marine Strategy Framework Directive (MSFD), knowledge location intensity human (e.g. marine ecosystems) is critical for effective management conservation. So, methods disposition were tested evaluate environment thus propose recommendations future dumping. The strategy based a Before-After-Control-Impact (BACI) approach, which spatio-temporal variability studied by analysing morphological sedimentological characteristics 28 months, from November 2011 April 2014, also including recovery seafloor after cessation activities. first operation (MASED) carried out regularly 8 months single point generating conical deposit 5 m height, while second (MABIO) lasted 12 involving four steps process. In case, wider area covered, leading formation smaller 2 height. deposits consisted muddy fine sand, whereas this covered with medium sand. result, sand accumulated or near sites, maximum mud (i.e. particles 4 Φ) content 50% compared to<5% before operations. Videos obtained LVB200 Seabotix ROV, highlighted heterogeneity sea floor around areas. Due hydrodynamic forcing (wave climate tidal currents), about 75% volume remained end periods. After ceased, further 5% MABIO 20% MASED, transported area. For latter, spreading observed extending towards south west. To favour long-term exploitation, more dispersive surface recommended MABIO)