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Details are given of a combined physical and numerical model study of sediment transport processes in a square harbour caused by tidal motion. The effects on bed level changes due to tidal currents and the configuration of the harbour entrance were investigated. A lightweight material called Cation Resin was used in this study to represent bed sediments in the laboratory experiments. This material enabled the erosion and deposition processes to be exaggerated within the model harbour, in which the magnitude of the flow velocities was relatively small. An unstructured mesh generation technique, namely a quad-tree grid, was incorporated into an existing two-dimensional depth-integrated numerical model to predict the transport of water quality constituents and sediment particle fluxes. The numerical model was further refined to include the prediction of bed level changes. Detailed comparisons between the numerical model predictions and the laboratory data were undertaken. It was found that the numerical model predictions and the laboratory measurements were in good agreement. It was also concluded that Cation Resin was an appropriate material to use for physical modelling of sediment transport processes in laboratory model studies.

One of the main factors in determining pipe diameter to design of potable water supplying systems is the flow velocity. The design flow velocity cannot be chosen above a certain value since higher velocities cause deterioration of cement mortar lining, additional management costs and destructive water impact. The flow velocity limits noted in the literature are given in a specific range (0,5-3,0 m/sec). However, the mentioned velocity limits can be increased up to a certain value in systems without pumping by decreasing the pipe diameter. Better quality of cement mortar used in the interior lining of the pipes help to increase capacity and thus the cost of the project can be reduced. In this study, an experimental pipeline model was set up from ductile pipes with cement mortar lining in which high velocities were aimed and a series of experiments were conducted. Experimental set up was composed of ductile pipes with four different diameters (Ø200-300-400-450 mm) and water was recycled from a reservoir to the pipe system and back to the reservoir by pumps. The measured thicknesses from the pipes were compared and the changes on the cement mortar lining were observed.

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