During the latter half of the 1900s the big natural river deltas on Westland disappeared. Until the 1980s there was still a small, but significant remnant of the original river delta from the Etneelva river, but today most of this, too, is industrial land.
When the Etne water system was protected in 1994, preservation of the cultural landscape in Stordalen Valley was a a main objective. This is a valley with an exceptional abundance of Different types of plants and animals. In the grey alder forest in Stordalen there are more bird species than in most other places, in fact, denser than one tends to find in a tropical rainforest.