Sediment deposition in a small lowland stream - Management implications

Fine sediment deposition is a widespread phenomenon encountered in rivers a nd streams as a result of both natural and anthropogenic activities. The Li ttle Stour (Kent, UK) has a history of low-flow problems owing to drought a nd groundwater abstraction. Fine sediment deposits were mapped at two sites on the falling limb of the hydrograph at monthly intervals between May and September, 1995. The sampling period coincided with one of the driest peri ods in England since records began in the 17th century. The area of the cha nnel bed covered by fine sediments increased from approximately 10 to 20% a t the upstream site and from 20 to 40% at the downstream site during the st udy period. The benthic macroinvertebrate communities from different substr ate mesohabitats were distinct, with riffle taxa (i.e. Agapetus fuscipes an d Simuliidae) confined to areas of clean gravel. This suggests that an expa nsion of fine sediment deposits may result in impoverishment of the communi ty. The implications of these findings are discussed with particular refere nce to the timing of management activities within lowland streams. Copyrigh t (C) 1999 John Wiley & Sons, Ltd.