ABSTRACT
Forest drainage is used to change the hydrological conditions in the soil into a state favorable for forest growth. The erosion and sedimentation problems caused by ditching have been recognized throughout the 60 year history of forest drainage in Finland. By the beginning of the 1970s practical forest ditching recommendations and textbooks started to mention the role of environmental protection structures such as sedimentation ponds. Sedimentation ponds are excavated to retain sediment from large drainage basins. Their effective functioning presupposes a sufficent reduction in the water flow rate for the waterborne solid matter to sediment on the bottom of the pond. The efficiency of sedimentation ponds to retain solid material has been monitored for a considerable period of time in peat production areas in Ireland. The efficiency of sedimentation ponds in six forestry board districts was investigated during summer 1988. The variation in the sediment accumulation of the sedimentation ponds was investigated by means of regression analysis.
