Pathways of runoff and sediment transfer in small agricultural catchments

Simultaneous field monitoring of runoff and suspended sediment loads from a 30 ha. artificially-drained. mixed-agricultural catchment in Herefordshire. UK indicates field drains are the dominant pathway for the transfer 017 runoff and sediment to the stream. Surface runoff pathways draining 6.2% of the catchment area transported around 1% of the catchment sediment load, while subsurface runoff in field drains draining, 26.5% of the catchment transported around 24% of the sediment load. The explanations offered here for the dominance of drain flow-the spatial limitation Of surface runoff generation and low hillslope-stream connectivity Of surface runoff compared With subsurface runoff-are also likely to apply to other artificially-drained lowland agricultural catchments in the UK. These catchments are usually oil poorly-drained soils. and land management call have a considerable effect oil the operation Of runoff pathways and the transfer of sediment from hillslope to stream. As a result, subsurface inputs may also dominate sediment transfers in other underdrained catchments. The focus oil sediment and pollutant losses via surface runoff pathways means that pollution inputs from subsurface, preferential pathways have been Unfairly neglected, and it may be more important to FOCUS Oil subsurface sediment and sediment-associated pollution inputs for mitigation rather than inputs from surface pathways. Copyright (C) 2009 John Wiley & Sons, Ltd.