Studies of the impact of forests on peak flows and baseflows: A European perspective

Most of the scientific studies of forest impacts on stream flows have been conducted in North America. Many were primarily concerned with felling effects. These have generally found forests to be associated with reducing both peak and low flows. Their results, however, may not necessarily be directly applicable to European forests due to differences in tree species, forest management, catchment physiography and climate. Forests are a major land cover in Europe, and there are plans to promote and further expand the area of European forests. The recent droughts and floods in different parts of Europe have heightened interest in the role of forests on river flow regimes, particularly flood peak and dry weather baseflows. This paper presents the hydrological results from 28 basins across Europe sampling a wide range of forest types, climate conditions and ground conditions. The aim was to determine if forestry can have significant impacts on stream flows and to identify particularly critical situations. The findings highlighted coniferous plantations on poorly drained soils in NW Europe and eucalyptus in Southern Europe as the situations where the most marked changes to flows are likely to occur. In contrast, other forest types, and changes in forest cover at a regional scale will be likely to have a relatively small effect on peak and low flows.