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1st July 2016

A review of techniques for the monitoring of fine sediments: discussion document to inform workshop

iMAGE OF FRESHWATER MUSSEL; Cover photograph courtesy of: Susan Cooksley, James Hutton Institute

Fine sediments (particles <2mm) in rivers and streams generally result from land management activities such as forestry, agriculture or development. Their ecological effects can be highly damaging (Owenes et al., 2005). In suspension, fine particles interfere with biological processes (e.g. reduced sunlight penetration impairs plant growth) and behaviours (e.g. restricting the ability to find prey). When deposited, fine sediments can smother the riverbed and restrict the infiltration of oxygen-rich free-flowing water. They also introduce organic matter and nutrients, which can increase biochemical oxygen demand (BOD) and promote eutrophication. Once present in a river system, fine sediments have the potential to cause a long-term cycle of environmental damage due to repeated mobilisation and resettlement.

Fine sediment is thought to be one of the principal pressures affecting the Freshwater pearl mussel (FPM) in Scotland - detrimental effects include prevention of feeding, damage to gills/feeding structures, and degradation of inter-gravel habitat (CEN, 2016). However, as there is no agreed method for monitoring and regulating fine sediment in UK rivers, it is difficult to assess the extent of problems that may be affecting FPM sites and to target remedial measures effectively. Therefore, there is a desire to establish a monitoring programme in Scotland.