AbstractForestry is generally considered to be a land use giving low sediment yields. However, in Britain most forestry is on land that requires extensive drainage, and it was found that the drainage of a small upland catchment resulted in sediment yields over the following five years equivalent to nearly half a century's load at pre‐drainage rates. Subsequent sediment yields did not decline to pre‐drainage levels, but remained about four times higher, as a result of erosion of the dra