Adaptive Management of Barriers in European Rivers

Rivers rank among some of the most threatened ecosystems in the world and are the focus of costly restoration programmes that cost billions to taxpayers.

Rivers in Europe are heavily fragmented by barriers such big dams, culverts, and weirs. These barriers provide essential services - drinking water, irrigation, or energy production, but barriers also block and fragment waterways, isolate habitats and weaken wildlife populations. Lateral barriers, including levees and bank walls, can also disconnect rivers from their floodplains.

Under the motto "Let it Flow!" The EU Horizon 2020 project Adaptive Management of Barriers in European Rivers (AMBER) led by Swansea University, researchers took action to help reconnect hundreds of kilometres of river from barriers, improve fish migration and develop tools to help manage European rivers in the future.

AMBER applied adaptive management to the operation of barriers in European rivers to achieve a more effective and efficient restoration of stream connectivity. To do this, AMBER developed tools, models and toolkits that will allow hydropower companies and river managers to maximize benefits and minimize ecological impacts. This will improve energy security, help protect jobs and boost European competitiveness, particularly in rural economies.

The Method

AMBER joined together 20 European partners including academics, conservation foundations (WWF, World Fish Migration Foundation), energy providers (EDF, Sydkraft Hydropower) and policy advisors (European Commission’s Joint Research Centre (JRC)).

The team further engaged with key stakeholder institutions worldwide such as angling associations, environment ministries, fisheries agencies, river trusts and energy providers just to name a few.

AMBER provided the first comprehensive estimate of river fragmentation in Europe based on empirical and modelled barrier densities. A multidisciplinary team of researchers assembled an extensive initial inventory of river barriers 629,955 unique barrier records from 36 European countries and surveyed 2,715 km of 147 rivers to ground truth barrier densities. They also modelled the location and number of missing barriers. 

The AMBER Barrier Atlas now contains approximately 700,000 mapped barrier records, and Swansea University researchers are working with partners to update and improve this inventory. Additional barrier datasets have so far been received from Germany, Austria, Romania, Hungary and Czechia. This work, supported in part by the Danube LifeLines (DLL) project, involves harmonising national inventories, checking locations and possible duplicate records, and identifying barriers not yet represented in the Atlas. The additional datasets will therefore supplement the existing inventory, with the number of genuinely new records confirmed following quality control.

Resource managers need to be able to quantify stream fragmentation, assess barrier impacts and benefits, and make better, informed decisions. The AMBER team developed a set of tools based on existing and future barriers based on what if scenarios.  

Tools included the:

1. AMBER Barrier Atlas: The most comprehensive overview of available information on barriers in Europe, showing approximately 700,000 mapped obstacles. 
2. AMBER Barrier Tracker: The citizen-science app helps people record river barriers and fill gaps in European inventories. Barrier Tracker V2 includes options to report longitudinal barriers and lateral structures such as bank walls, levees and embankments.

Get the app: Android – Barrier Tracker V2  |  iOS – Barrier Tracker. More information: amber.international.

More tools are described in this policy brief.  AMBER has received funding from the European Union's Horizon 2020 Research and Innovation Programme under Grant Agreement 689682.

Impact

Research stemming from AMBER found that there are at least 1.2 million in-stream barriers in Europe (mean density = 0.74 barriers/km), 68% of which are low-head (<2m) structures such as culverts, ramps and fords.  Existing barrier records underestimate true barrier numbers by ~61% but this varies considerably between countries.

All rivers surveyed in Europe have barriers but relatively unfragmented rivers are still found in the Balkans, Scandinavia, the Baltic states, and parts of southern Europe. In the UK, 99% of river basins are fragmented by artificial barriers.

AMBER’s findings helped inform European river-restoration policy, including the EU Biodiversity Strategy for 2030 and its ambition to restore at least 25,000 km of rivers to free-flowing conditions by 2030. The AMBER Barrier Atlas and associated decision-support tools continue to help identify where reconnecting fragmented rivers could deliver substantial ecological benefits.

The project results fed directly into the European Green Deal. The new EU Biodiversity Strategy aims to reconnect at least 25,000 km of Europe’s rivers by 2030 and AMBER’s results contributed to this target. The AMBER Barrier Atlas and decision support tools will now be used to prioritise those rivers where gains in connectivity are most easily achieved and will bring about the greatest benefits.

The project’s positive impact on European rivers include:

• Creating three policy briefs to inform policy makers and directly feed into the European Green Deal.
• Over 30 peer-reviewed publications, including a publication in Nature.
• Freeing 311km of rivers from barriers in Denmark
• Improved fish migration at the Poutès Dam in France using adaptive management strategies
• Contributing to the removal of unused weirs in the UK, Ireland and Demark
• Developing tools to monitor weir removal including:
  • drone based remote sensing
  • fish community surveys using eDNA techniques in the rivers Allier in France, Guadalhorce and Nalón in Spain and the emblematic River Ness catchment in Scotland 
• Creating the Let It Flow magazine to share results, thoughts, and the vision to reconnect rivers
• Delivering the Smart Ways to Improve River Connectivity webinar in June 2020, with 600 participants from all over the world.

Building on AMBER: ongoing research

Mapping lateral barriers. Researchers at Swansea University are extending the work beyond structures that block movement along rivers to barriers that separate river channels from their floodplains. Walkover surveys covering approximately 853 km of rivers in seven watersheds across three countries have identified around 1,700 lateral barriers, including bank walls, levees, embankments and groynes. These field observations are being combined with river-network geometry, sinuosity, valley characteristics and indicators of human pressure to develop and test spatial models that estimate where lateral barriers are likely to occur across Europe. New reporting options in Barrier Tracker V2 will also help collect observations of these previously overlooked structures.

Finding overlooked river–road crossings. A complementary Europe-wide analysis uses digital road and river networks to identify and assess potential crossing structures, including culverts, fords and bridges that may be absent from conventional barrier inventories. Although not all crossings impede movement, some can restrict fish passage and reduce access to cooler upstream habitats during periods of high river temperature. By linking crossing locations and likely passability with the availability of upstream cool-water refugia, this research aims to highlight priority sites for field checks and future connectivity improvements.