AbstractsEarth & Environmental Science

By its very nature dredging is an environmental impact, since dredging includes the excavation and/or relocation of sediment in a river, sea or estuary. One of the environmental impacts related to dredging is increased suspended sediment concentration (SSC) levels, forming plumes of sediment. These so called dredge plumes originate from spillage of dredged material. Especially the fine sediment can stay in suspension on long time and spatial scales. Environmental Impact Assessments (EIAs) are conducted prior to the project's start to assess impact of dredging activities. One of the concerns of an EIA is to determine dredge induced rise of SSC levels. Forecast modelling is often applied to simulate dredge plumes in order to verify SSC and sedimentation levels. However, due to large uncertainties about the project, input parameters and ambient parameters, forecast modelling of dredge plumes is often challenging. In this study the most important parameters involved in far-field dredge plume dispersion were identified. Furthermore, by means of a numerical model experiment the influence of these parameters on far-field plume results was tested. Subsequently, the model was compared to data from several measurement campaigns concerning dredge plumes. This helped to verify the applicability of the model and made comparison possible between the comparison model output and experimental results. Recommendations were developed, supporting more informed selection of modelling techniques and model input regarding forecast modelling far-field plume dispersion. All recommendations use the requested output as starting point, based on both parameter (concentration or flux) and plume age.