Soil erosion by water is a major environmental threat to the sustainability and productive capacity of agriculture in many tropical and sub-tropical regions of the world. In temperate regions, meanwhile, the ‘off-site’ transport of sediment and pollutants into nearby water courses and the ‘muddy flooding’ of properties and infrastructure pose a much greater threat.

This paper explores how environmental policy is implemented and enacted through the management of technical and institutional knowledge at the local level. We use the conservation of the freshwater pearl mussel in the River Esk, North Yorkshire, UK, as an empirical case study to examine the interaction that takes place between professionals from different institutional and disciplinary backgrounds as they come together to work on a common problem. We focus on two aspects: the way in which an institutional context was created; and the interaction between the professionals involved.

The spatio-temporal variation underlies and complicates studies related to earth surface processes. Subsequent to our previous studies reporting the temporal invariability of sediment concentration, this study further reports the spatial invariability of sediment concentration or the flow–sediment relationship in the hilly part of the Chinese Loess Plateau. The dense channel network dissects this area into numerous sub-watersheds, which are composed of entire slopes (a combination of the hill slope and the valley side slope).