Hydrology and Earth System Sciences www.hydrol-earth-syst-sci.net 1027-5606 1607-7938 1 3 1997 10.5194/hess-1-483-1997 http://www.hydrol-earth-syst-sci.net/1/483/1997/ http://www.hydrol-earth-syst-sci.net/1/483/1997/hess-1-483-1997.html http://www.hydrol-earth-syst-sci.net/1/483/1997/hess-1-483-1997.pdf 483 497 0000-00-00 Dynamics of river sediments in forested headwater streams: Plynlimon G. J. L. Leeks S. D. Marks Institute of Hydrology, Maclean Building, Crowmarsh Gifford, Wallingford, Oxon, OX10 8BB Long term studies of fluvial sediment processes in the Plynlimon catchments have contributed to the assessment and quantification of plantation forestry impacts in British upland catchments, at all stages of the forest cycle. The results from the Plynlimon studies are placed in the context of the observed impacts of particular forest practices and studies of forestry effects on sediment transport elsewhere in the world. The effects associated with drain excavation, ploughing, track construction, ground and channel disruption are outlined for both bedload and, particularly, for suspended load. <br>Finally, recent data on sediment yields from 1995 to 1997 at Plynlimon are reported and discussed in the light of longer-term sediment yield estimates. This paper also provides background information relevant to other sediment process studies which use data from the main Plynlimon sediment monitoring network.