Highly concentrated suspensions are present in many natural environments. When the concentration becomes large enough, particles start to interfere with each other and their settling velocity reduces. This is called hindered settling. As a result of the reduced settling velocity, particles remain in the water column for a longer time and the light penetration through the water column is reduced. This affects primary production, which stands at the base of the food chain. This research deals with the hindered settling of suspensions of mud and mud-sand mixtures. A combination of laboratory experiments, mathematical theories and modelling was used to come to a better understanding and prediction of the settling velocity of the different fractions within these suspensions and the interaction between the fractions. The combination of techniques proved to be successful. This research has increased the understanding on the behaviour of highly concentrated mud and mud-sand mixtures. As a result, questions that relate to increased turbidity levels and environmental impact might be answered better.