Sediment production by landslides in Hong Kong: Two case studies

Abstract

Landslide studies in Hong Kong are increasingly providing budgets of active debris through the landslide scar and, in some cases, into the stream system. These data are reviewed and two case studies of landslide debris entering the fluvial system are reported. In the first case study, two small landslides of 50 m 3 and 7 m 3 volume occurred above a stream sediment monitoring station, in 2001 and 2003 respectively. While almost all of the debris remained on the slope, both events resulted in increased stream sediment transport in the stream. In the second case study, debris from a 1600 m 3 landslide formed a delta of approximately 200 m upon entering a reservoir. Sediment budgets from the landslides illustrate the role of mass movement in the production of sediment and the coupling of the hillslope and fluvial systems. They provide information on the nature of material delivered to the drainage system and evidence of the selective transport of materials. Possible influences on the controls on sediment production by landslides are also discussed.