Influence of Navigation Channel Alignment on Sedimentation Rate – Consideration for a Sustainable Design

Prediction of sedimentation rate in navigation channel is important and challenging especially in muddy coastal areas. Feasibility of a navigation or access channel relies significantly on the required maintenance dredging. Although the orientation should normally be perpendicular to
the depth contours, variation in local bathymetry and flow
pattern may result in relatively higher sedimentation rate. In this study, feasibility of various channel alignments for Sg. Muar was assessed. A navigation channel was to be dredged to improve the navigational condition for the local fishermen as well as for other river users. Three different navigational channel options and alignments were investigated using numerical model: (1) Alignment 1 - is an L-shaped channel about 6.3 km long, (2) Alignment 2 - an approximately 9 km straight channel; and (3) Alignment 3 - an almost J-shaped channel about 6.6 km long. The outer channel (before the almost 90° bend) of Alignment 1 was aligned almost perpendicular to current flow in the open waters. Modeling results indicated that there was a reasonably significant reduction in current speed within the channel at this location which induced further sedimentation. It was found that relatively much lesser annual sedimentation was predicted for Alignment 2. The average annual rate of sedimentation within the channel was estimated to be about 0.3 to 0.5 m/year. The study revealed that channel alignment has significant influence on the hydrodynamic regime which affect sedimentation/siltation pattern.