The elevated bluffs of the Bergisches Land region that extend along both sides of the Wupper receive a great deal of precipitation, yet are made up of a relatively water-impermeable bedrock formation of graywake and argillaceous shale. Thus, the water here flows to the Wupper in numerous brooks and streams. Where the springs rise in the forest, steep-sided V-shaped valleys – known locally as “Siefen” – form around them. With their open seeps, water-beaded, mossy rocks and side-springs, they are often structurally very rich, which supports the diversity of the animal and plant species living in the brook. The cool forest streams between Müngsten and Burg thus nurture, for example, fire salamander larvae. The often extensive miltwort growth along gently flowing stretches of water is characteristic of this biome.