In recent years there has been increasing concern about the environmental effects of dredging in coastal waters, often performed in relation to large infrastructure projects. Of particular concern is the increased turbidity caused by resuspension of bottom sediment and spillage from dredging. In close cooperation with Argoss, NLR and the end user Van Oord NV, the RESTSCOD project was set up with the aim of demonstrating a new method for synoptic monitoring of turbidity, represented by Total Suspended Solids (TSS).
The method aims to optimise information from dredging operations, satellite remote-sensing data, water quality modelling of sediment transport and in situ data using new data-model integration (DMI) techniques. Using hindcast model simulations in combination with archived optical remote sensing and in situ data, the background TSS levels are modelled. Separately, the extent and concentration of dredging/disposal plumes is modelled using the Delft3D particle tracking model with a Graphical User Interface.
Using existing in-situ data, remote sensing reflectance images and flow and spreading models from the Penny¿s Bay area in Hong Kong where extensive dredging operations took place in 2002, the individual data sources were assessed on information content and the DMI methodology was further developed. An important part of this was the creation of the Graphical User Interface ¿ a new software module that checks, interprets and processes the operational dredging data from the field into consistent and comprehensive information suited for modelling the plume spreading characteristics. This interpretation tool was specified, developed and tested in close cooperation with dredging staff. Together with the industrial partners in the project, the prototype experiment was evaluated in terms of its generic applicability.
By means of DMI the three sources of data (in situ, remote sensing and model data) can be integrated in a structured way to obtain an optimal information product suited to the end user's needs. The preoperational Dredging Information System can presently be used in two ways:
1. During the tendering phases of dredging projects: assessment of initial effects caused by dredging and translation into the design of optimum execution methods that satisfy the environmental criteria and which are cost-effective (a so-called forecasting system);
2. Hindcasting of the turbidity field when information is required about a site after dredging works have been completed (a hindcasting system).
A proposed follow-up project will focus on extension into an operational near real-time system for carrying out compliance monitoring during the dredging operations (a nowcasting system). |
