River restoration: basics

In short: River restoration refers to measures that return artificially altered rivers to a more natural state, improving ecosystems and flood protection. Many European rivers were heavily straightened and constrained in the 19th and 20th centuries.

In more detail: Straightened rivers drain faster, which prevents flooding at one location in the short term but often worsens flood risk downstream.

In detail

• Removing bank reinforcements: Removing concrete and stone reinforcements lets the river move more naturally and form its own structures.
• Meanders and floodplain forests: Restoring natural river bends and adjacent floodplain forests provides valuable habitat for numerous plant and animal species.
• Flood protection: Restored river sections can absorb and retain more water during flooding, relieving pressure on settlements downstream.
• Fish passage: Removing cross-structures or installing fish ladders restores the natural migration of fish species.
• Self-purification capacity: Naturally structured rivers with gravel banks and shallow zones filter and clean water more effectively than channelised sections.
• Economic aspects: Restoration projects are often cheaper than permanently maintaining flood walls along straightened rivers.
• Long-term process: The full ecological recovery of a restored river section can take decades depending on its starting condition (hochwasser-und-starkregen-vorsorge, artensterben-und-biodiversitaet).