Practical use of dredge plume source terms
CEDA Dredging Days 2015 - Innovative Dredging Solutions for Ports, Rotterdam
Van Eekelen EMM, van Wiechen JJJ and van Koningsveld M - Van Oord Dredging and Marine Contractors, the Netherlands
Abstract: Estimations of suspended sediment spreading are important for Environmental Impact Assessments (EIAs) for dredging and port construction works. Modelling outcomes rely on predictions of local (hydrodynamic) conditions, as well as on estimated suspended sediment sources that are used as model input. Becker et al. (2015) introduced a generic method for source term estimation based on the ‘source term fractions’ concept. Source term fractions relate the suspended fine sediment that is available for dispersion, to the amount of fine sediment that is present in the soil and the way it is dredged. The method is particularly useful for rapid (initial) assessments. As more detailed information becomes available initial estimates may gradually be specified further. This paper briefly describes the ‘source term fraction’ concept and a suggested method for its application. Next, a fictive, but realistic practical example illustrates its use in the various phases of project realization: from the Planning and Design phase, where it can be applied for initial assessments for EIA purposes as well as for the more detailed designs for tendering, to the Construction phase, where it can be applied during execution and monitoring. As the project progresses key aspects of the assessment, such as the characteristics of the soil and the effect of different work methods, can be estimated with greater detail. We show that the estimation and validation of ‘source term fractions’ is a key element of the adaptive management of suspended sediment spreading.
Key words: dredge plume, suspended sediment spread, Environmental Impact Assessment, modelling, source terms