Redesign of the Tutong River Training Walls

Abstract

The Tutong River entrance located on the central part of the Brunei coastline is causing navigational problems due to the existence of a sandbar obstructing the majority of the channel’s opening. Training walls are constructed on both sides of the river entrance to direct and confine the river flow. The existing western training wall is damaged and the eastern one is filled to capacity by the westward littoral drift of sand. The sand is now bypassing the eastern training wall and causing the sandbar formation. The area down drift of the river entrance has suffered erosion due to the interruption of sediment supply from the eastern area up-drift of the entrance. The Water Research Laboratory (WRL) of the University of New South Wales has provided specialist advice in the redesign of the Tutong River training walls to provide a better stabilization of the river mouth. In order to determine the location and length of the new training walls, several studies were completed. Wave modelling, littoral drift modelling and a sand bypassing model was implemented to determine the seaward extent and sand bypassing of the new walls. Hydrodynamic modelling was used to test several entrance configurations and dredging scenarios. Physical modelling was used to determine sizing of materials for the training walls and layout optimisation. This paper will discuss the existing training wall issues and the modelling used by the WRL to help configure the new training wall configuration.