One of the most extensive river restoration efforts is currently taking place in one of the most populated areas in Europe. The Emscher restoration is a large-scale restoration project in the “Ruhr Metropolitan Area” in the federal state of Northrhine-Westphalia, Western Germany. This area is one of the densest urban agglomerations in Europe.
In a 30-year project that started in 1990, the Emscher River and its tributaries are re-converted from highly modified open wastewater channels with concrete beds into near natural stream systems. For this, an underground sewer network of 423 km length is constructed to separate waste and river water. Subsequently, the concrete shells are removed, the channelization reversed, stream profiles widened, and secondary floodplains created. This intergenerational project is worldwide unique in its spatial and temporal scale and associated with the immense costs of approx. 5.3 billion Euro.
Further information here.