Determination of Settling Velocity for Cohesive Sediments Using a Settling Column Experiment—Case Study: Ca Mau, Vietnam

The settling velocity (Ws) is a fundamental parameter in sediment dynamics, particularly in the coastal zones as estuarine and mangrove ecosystems, where various physical processes interact to influence sediment transport and deposition. Determining settling velocity is essential for understanding and predicting sediment transport, erosion–deposition processes in coastal environments. This study aims to determine the settling velocity and examines how sediment concentration affects settling velocity, using empirical models. The study applies these methods to compute the settling velocity of fine sediments in Ca Mau, Vietnam, which were collected in the Song Doc area (Western) in August 2014 and Rach Goc area (Eastern) in August 2015. The particle size analysis results indicate that the sediment samples from Western Ca Mau are coarser than those from Eastern Ca Mau, with sand ratios of 42.78% and 7.08% at the outer station, and 19.09% and 4.39% at the mangroves, respectively. The results also show that the average settling velocity of the sediment samples from Western Ca Mau is higher than that of the samples from Eastern Ca Mau. Specifically, the settling velocity in Western Ca Mau is 2.80 × 10−4 m s–1 at the outer station and 1.68 × 10−4 m s–1 at the mangroves. Meanwhile, in Eastern Ca Mau, the settling velocity of the sediment samples is 1.99 × 10−4 m s–1 at the outer station and 1.42 × 10−4 m s–1 at the mudflat-mangrove. Hence, it can be seen that the settling velocity of cohesive sediments corresponds well with the sediment’s particle size.