A Case Study of Silt Screen Performance
Type:
Presented during:
WODCON XIX: "Dredging makes the World a better place" - 2010, Beijing, China
Authors:
Thu-Trang Vu , Soon-Keat Tan
Abstract: One of the most critical environmental issues associated with dredging projects is the large amount of sediment released during the dredging operation. The sediment entrained into the water column, in the form of suspended sediment, may disperse and cause serious environmental problems such as aesthetics and impacts on the well-being of certain aquatic ecosystems. To mitigate the problems of uncontrolled sediment dispersion in dredging projects, several management and engineering mitigation measures could be deployed. One of the popular engineering measures is to use a silt screen, which is also known as silt barrier, silt barricade, turbidity curtain, etc. This paper presents a case study of a silt screen deployment in association with a dredging and reclamation project. The silt screen was to contain and prevent suspended sediment from migrating into a nearby sensitive habitat area and was deployed in an open configuration, such that the screen was laid out normal to the flow direction. In this paper, the adopted approach in layout design and selection of the silt screen during the three stages: (1) design stage, (2) deployment stage, and (3) monitoring stage – are presented. Furthermore, the observed behaviour of suspended sediment and the environmental flow field in the presence of the silt screen are also documented.
The effects of the silt screen on velocity profiles and suspended sediment concentration distribution were analyzed and presented, based on the instantaneous velocity and suspended sediment concentration profiles collected on both sides of the screen, using an acoustic backscatter via an Acoustic Doppler Current Profiler mounted on board a survey vessel. The efficiency of the silt screen was analyzed with respect to the change in suspended sediment concentration and the change in sediment flux across the silt screen.
Keywords: silt screen, silt screen efficiency, suspended sediment concentration profile, Acoustic Doppler Current Profiler, open configuration.