River infrastructure planning decision support tool

A decision support tool has been developed to optimise environmental and socioeconomic trade-offs associated with river infrastructure (i.e. barriers), including river connectivity, hydropower generation, and shipping and other costs. The model extends previous work by considering (i) multithreaded river sections, essential for estimating river connectivity in the presence of diverted channels for hydropower and shipping, (ii) backwater effects caused by the lowering or raising of artificial in-stream structures, which , in turn, affect hydropower generation potential and transport capacity of shipping vessels, and (iii) the integration of realistic cost functions for estimating the cost of hydropower installation/retrofitting and cross-port shipping of goods by a heterogeneous fleet of vessels. To demonstrate the applicability of the planning tool, a database for the Neckar River in Germany was created. The database contains more than 1000 existing river barriers and more than 4,000km of river and includes detailed information on river flow, hydropower, and waterborne traffic. The planning tool is designed to find the best combination of river infrastructure modification, mitigation, and removal actions in order to optimise three key performance indicators (KPIs): 1) river connectivity based on a generalisation of the well-known Dendritic Connectivity Index, 2) hydropower potential/revenue and 3) total cost, broken down by the cost of structural engineering works, installation and retrofitting of hydropower, and annual shipping. The model focuses specifically on the socioeconomic benefits of hydropower and shipping, as these are the two main human uses of rivers within the Neckar catchment. The model could be readily modified to consider other environmental and socioeconomic factors, which may be important in other planning areas, such as irrigation, water supply, fishing, recreation, and water purification. The planning model has been specially configured to examine ten scenarios for adaptive barrier management. The results show which river infrastructure modification, mitigation, and removal actions could be undertaken to maximise connectivity, maximise hydropower, or minimise total cost subject to defined river connectivity and energy production targets

More than one million barriers fragment Europe’s rivers

Rivers support some of Earth’s richest biodiversity1 and provide essential ecosystem services to society2, but they are often fragmented by barriers to free flow3. In Europe, attempts to quantify river connectivity have been hampered by the absence of a harmonized barrier database. Here we show that there are at least 1.2 million instream barriers in 36 European countries (with a mean density of 0.74 barriers per kilometre), 68 per cent of which are structures less than two metres in height that are often overlooked. Standardized walkover surveys along 2,715 kilometres of stream length for 147 rivers indicate that existing records underestimate barrier numbers by about 61 per cent. The highest barrier densities occur in the heavily modified rivers of central Europe and the lowest barrier densities occur in the most remote, sparsely populated alpine areas. Across Europe, the main predictors of barrier density are agricultural pressure, density of river-road crossings, extent of surface water and elevation. Relatively unfragmented rivers are still found in the Balkans, the Baltic states and parts of Scandinavia and southern Europe, but these require urgent protection from proposed dam developments. Our findings could inform the implementation of the EU Biodiversity Strategy, which aims to reconnect 25,000 kilometres of Europe’s rivers by 2030, but achieving this will require a paradigm shift in river restoration that recognizes the widespread impacts caused by small barriers

More than one million barriers fragment Europe’s rivers

Rivers support some of Earth’s richest biodiversity and provide essential ecosystem services to society, but they are often fragmented by barriers to free flow. In Europe, attempts to quantify river connectivity have been hampered by the absence of a harmonized barrier database. Here we show that there are at least 1.2 million instream barriers in 36 European countries (with a mean density of 0.74 barriers per kilometre), 68 per cent of which are structures less than two metres in height that are often overlooked. Standardized walkover surveys along 2,715 kilometres of stream length for 147 rivers indicate that existing records underestimate barrier numbers by about 61 per cent. The highest barrier densities occur in the heavily modified rivers of central Europe and the lowest barrier densities occur in the most remote, sparsely populated alpine areas. Across Europe, the main predictors of barrier density are agricultural pressure, density of river-road crossings, extent of surface water and elevation. Relatively unfragmented rivers are still found in the Balkans, the Baltic states and parts of Scandinavia and southern Europe, but these require urgent protection from proposed dam developments. Our findings could inform the implementation of the EU Biodiversity Strategy, which aims to reconnect 25,000 kilometres of Europe’s rivers by 2030, but achieving this will require a paradigm shift in river restoration that recognizes the widespread impacts caused by small barriers