Systematic experimental investigations have been performed under uniform flow conditions in a channel whose banks are equipped with large scale rectangular roughness elements. The practical motivation of this project is to see how restoration of banks, such as lateral cavities, has an influence on the transport of fine sediments. The implementation of lateral cavities may affect the sediment and morphological equilibrium of the river since these may trap sediments. This work aims to study the influence of the lateral cavities on the transport of fine sediments in the main channel. A set of laboratory experiments are done which covers a wide range of rectangular cavity configurations and includes aspect ratios (lateral cavity depth divided by cavity length) between 0.2 and 0.8. Key parameters such as the flow discharge and the initial sediment concentration are tested. Surface PIV, sediment samples and turbidity temporal records are collected during the experiments. The trapping efficiency of the cavities and the associated flow patterns are calculated and discussed. The resulting conclusions provide useful information for the future design of river restoration projects.