The Art of Screening: Effectiveness of Silt Screens
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Type:
Presented during:
WODCON XX: "The Art of Dredging" - 2013, Brussels, Belgium
Authors:
Radermacher M, Van der Goot, F, Rijks D, De Wit L
Abstract: One of the potential environmental issues associated with dredging in the marine environment is the increase of suspended sediment concentrations (SSC) by generation and dispersion of sediment plumes. This can be mitigated by source control or the installation of containment barriers like silt screens. This paper focuses on hanging silt screens and describes:
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The decision process for deployment of hanging silt screens
Decisions on the necessity of environmental mitigation measures and subsequently on the viability of silt screen deployment should be made using a receptor-based approach. This starts with the identification of (ecological) receptors and related impact levels, understanding the local environment, checking compatibility with work methods and determining cost and schedule impacts. -
Effectiveness of hanging silt screens
Local hydrodynamic and morphological circumstances determine the effectiveness of silt screens. Results of extensive numerical modeling tests (3D and 2DH) supported by hands-on experiences from dredging projects are used to describe the effect of hanging silt screens on the distribution of SSC in the water under different conditions. Results show that when deploying silt screens it is important to realize that silt screens are flexible curtains; they do not block the flow. Therefore suspended sediments generated at a dredging project will always pass the hanging screen vertically and/or horizontally. Silt screens can only reduce the distribution of SSC by settling if local hydrodynamic conditions are favourable. -
Adaptive management strategies as an alternative for silt screens
When local conditions are not optimal for deployment of silt screens, alternative mitigation measures can be used such as adaptive monitoring strategies, to manage SSC around dredging projects.
Keywords: silt screens, environment, mitigation, turbidity