Selection, implementation and cost of restorations in lowland streams: A basis for identifying restoration priorities

Abstract

Abstract Restorations have been conducted in Danish lowland streams for almost 30 years to combat the poor physical conditions resulting from decades of channelisation, flood plain drainage and other impacts. Despite this effort, the recently drafted River Basin Management Plans show that physical improvements are still required in more than 7000 km of stream in order to comply with the Water Framework Directive. In this study we used published studies and expert knowledge to describe the restoration approaches most likely to achieve the environmental goals. In addition, we collected information about the economic costs of the different restoration approaches based on Danish experiences. For heavily impacted lowland streams (channelised and deeply incised streams) we described only two different restoration methods, both of which are relatively expensive. For lesser impacted streams (channelised but not deeply incised streams) we described six different options for improving ecological quality, varying significantly in cost. Our analysis showed that the cost may increase dramatically if several remedial actions are required or if land owners are entitled to large monetary compensations. Consequently, stream managers face an important challenge in the future prioritisation of restoration efforts aimed to obtain ecological improvements within tight budgets. The information presented in this paper can help the decision-making of managers.