| Description
The River Bure is one of the major rivers flowing through the Norfolk Broads. The sampling site at Horstead Mill (National Grid Ref. 6267 3198) is in its middle reaches, approximately 40km from the source of the river, at the limit of navigation, and at an elevation of less than10m. Here the river is 17-20m wide and up to 4m deep with a predominantly silty substrate. The surrounding catchment is underlain by Quaternary deposits of Norwich crag with chalk at depth and superficial glacial till and outwash deposits. Land use in the catchment is predominantly agricultural, especially arable. Due to problems with eutrophication of the Broads, there has been a programme of phosphate stripping at the major sewage treatment works on the Bure since 1986. Invertebrate monitoring takes place downstream of the Mill where the river is divided into two channels and there is a riffle area of gravel, pebbles and sand and areas of emergent plants (Sparganium erectum, Glyceria sp.) at the margins. Macrophyte and diatom monitoring takes place between 0.5-1km upstream of the Mill at a semi-natural stretch of river away from man-made structures. The substrate is predominantly silty. There is a diverse submerged plant community, including a good cover of Elodea nuttallii. Several marginal and emergent species are also present. |
