A prototype harbour design toolbox has been developed, with a Graphical User Interface, incorporating simple model instruments to rapidly assess the impact of a harbour construction on a coastal environment, such as expected siltation rates and impact on the coastline evolution. The toolbox can be useful for different stakeholders, particularly in the early phases of a harbour development project, to explore order of magnitude impacts, relevant design parameters and dominant processes. This paper will set out the current status of the harbour design toolbox and investigate the benefits of use for specific stakeholders. The ambition is to further extend the harbour design toolbox towards an integral coastal design tool, facilitating the implementation of other type of interventions and linking to other disciplines such as marine ecology and navigation. It is intended that the integral coastal design tool will facilitate a multi-disciplinary approach to aid in the feasibility, design, construction or maintenance phase of coastal development project.

A study of siltation processes was undertaken for the harbour of Harlingen in the Netherlands, to investigate their relative importance for potential sedimentation. Three distinct harbour siltation processes were studied: tidal filling and emptying, horizontal eddy circulation in the harbour mouth and density driven vertical circulation. The Harlingen case, with its complex harbour geometry, seemed a promising candidate for a very early pilot application of D-Flow Flexible Mesh, a new hydrodynamic simulation code. Objective of this paper therefore was to investigate its performance, flexibility and efficiency by means of a qualitative comparison with an existing calibrated Delft3D curvilinear model. It was found that the flexible mesh allows for a more precise distribution of high resolution grid cells and capturing of complex geometries using a local triangular network. Moreover, the accuracy of the model was in line with existing Delft3D results. The tide and density driven current were found to be the main contributors to the siltation in Harlingen. Concluding, the applied research method combined with the Flexible Mesh approach look like a promising tool to help identify possible mitigating measures against harbour siltation problems.

The Morphological Acceleration Factor (MORFAC) approach for morphodynamic upscaling enables the simulation of long term coastal evolution. However the general validity of the MORFAC concept for coastal applications has not yet been comprehensively investigated. Furthermore, a robust and objective method for the a priori determination of the highest MORFAC that is suitable for a given simulation (i.e. critical MORFAC) does not currently exist. This paper presents some initial results of an ongoing, long-term study that attempts to rigorously and methodically investigate the limitations and strengths of the MORFAC approach. Based on the results of a numerical modelling exercise using the morphodynamic model Delft3D, the main dependencies and sensitivities of the MORFAC approach are investigated. Also, a criterion is proposed for the a priori determination of the critical MORFAC, based on the CFL condition for bed form migration.

The Guyana coastal system is characterized by very thick deposits of Amazon mud and high mud concentrations in its coastal waters. The mud deposits can be quite soft and may liquefy under incoming waves. Subsequently, the liquefied mud damps the incoming waves effectively. This paper presents a simple model to predict wave attenuation over soft (fluid) mud beds. This model is based on the two-layer approach by Gade [Gade, H.G., 1958, Effects of a non-rigid, impermeable bottom on plane surface waves in shallow water, Journal of Marine Research, 16 (2) 61-82.] which is implemented in the standard version of the state-of-the-art wave-prediction model SWAN. Input to the mud wave damping module consists of the extension, thickness, density and viscosity of the liquefied (fluid) mud layer. The model is validated against small-scale wave attenuation measurements carried out in a laboratory wave flume. The model predictions agree favourably with the experimental data. Next, the model is applied to predict wave height and wave attenuation in the Guyana coastal system. Extension and thickness of the liquefiable layer could be assessed from dual-frequency echo soundings. In the absence of field data, the density of the liquefied mud layer is obtained from literature, whereas the value of the mud's viscosity had to be established by trial and error - the selected value, though, is in the range of literature values. The model predicts significant wave attenuation. The computed changes in wave energy spectrum agree qualitatively with measurements in Surinam, whereas the decrease in significant wave height agrees more or less with historic observations along the Guyana coast.