Sustainable methods for peak flow control in boreal headwaters affected by peatland drainage

摘要

Peatland drainage for forestry,agriculture and peat harvesting has affected our nation's valuable headwaters.While silvicultural drainages in particular have resulted in a remarkable increase of forest resources,also negative environmental effects are evident,including changes in runoffs,eutrophication,erosion,siltation and changes in stream bed conditions.Since 60 % of Finnish peatlands have been drained for forestry,the amount of the streams and watersheds in need of partial restoration is extensive.Traditional methods for controlling sediment loads in maintenance of ditch networks have been sedimentation ponds,overland flow fields,wetlands,ditch blockings etc.However,these protection measures appear inefficient during peak flow periods,when the majority of the suspended solid loads are generated.Sustainable methods for erosion and transport control would be to integrate peak flow control and water protection.This includes controlled flooding in peatland ditches and flood plains.Effective watershed management contains also restoration of previously disturbed headwater stream channel networks.The effects of these methods on stream flow or sediment transport locally or at catchment scale are currently studied.The oral presentation will present methods,research and preliminary results projects from Northern and Central Finland.