Vegetation grown on rip-rap lining or grasscretes along channelized rivers in Hong Kong is regularly mowed by the Drainage Services Department (DSD). Aiming at revealing the optimal mowing frequency and intensity for biodiversity conservation, we carried out a manipulative experiment in which the vegetation grown on grasscretes were mowed at various frequencies and intensity. We perform biodiversity surveys to record usage of the different experimental plots by birds, reptiles, amphibians and macroinvertebrates. The results will be useful in suggesting the optimal mowing scheme to maintain biodiversity along channelized rivers in Hong Kong and beyond.