Over a century ago a sparsely populated landscape of water meadows was transformed into an industrial conurbation, and the untamed river Emscher, in the Ruhr area, turned into a man-made system of open waste waterways. Due to subsidence caused by mining, it was impossible to build an underground sewer system. Therefore, the Emscher and its tributaries were regulated and used to transport the wastewater together with rainwater on the surface. This made the Emscher simply a great open wastewater channel.