Understanding hot-spot problems in catchments: the need for scale-sensitive measures and mechanisms to secure effective solutions for river management and conservation. (Special Issue: Recent developments in classification, assessment and management strategies for freshwater habitats in Britain and Europe.)

摘要

Regulatory progress in controlling point sources of chemical river pollution has progressively thrown the attention of public policy towards anthropogenic physical impacts, many of which are scaled to the catchment via the runoff/sediment system. At the same time, concern over diffuse chemical pollution has reinforced catchment consciousness': land-use and land-management planning and control must be considered to conserve or restore river ecosystem integrity. The scientific, political and legal elements of this scale change are, however, complex and uncertain: 'myths' abound. Landscape-scale consideration of 'pressures' suggests an unequal distribution of regulatory costs and benefits and large uncertainties in the evidence from a 'land-use hydrology' and fluvial geomorphology perspective. 'Hydrological connectivity' brings together a number of knowledge themes about catchment spatial organization which facilitate applying mitigation measures to much smaller areas, helping to offset uncertainty and reduce costs. Instead of blanket 'remedies', more practical use is needed of process evidence from hydrology and fluvial geomorphology; this tends to suggest that hot-spots dominate risks and impacts of factors such as leaching, surface flow generation and silt entrainment. Set in a realistic policy framework, from strategic spatial planning to grant-aided best practice, a 'catchment acupuncture' approach to measures provides a cost-effective contribution to improving ecological status and may also increase resilience to the impacts of climate change. The European Union's Water Framework Directive (WFD) encourages 'joined-up thinking' on this issue but it remains to be seen whether spatial scales, structures and concepts already enshrined in the WFD and the relevant UK national policies for land use and nature conservation can be exploited to permit the much-needed practical uptake of this new riparianism.