Deep down between the stone polished phyllite bedrock in Bordalsgjelet canyon, there is a cascading river. In close cooperation with hard polishing stones, the water has carved into the bedrock for thousands of years - and is still doing so today.
The Strandaelvi river is forever protected from the development of hydropower. The Lønaøyane islands – which comprise the delta furthest north in Lake Lønavatnet - are a part of this water system. In 1995 the level of protection for the Lønaøyne islands was strengthened to that of a nature preserve because of the rich birdlife in this wetland.
Mykdal delta had an unusually diverse bird life, right up until 1987. The Myrkdal delta should have been protected, and the plans were prepared. Despite the area's high elevation at 227 m a.s.l., it had a wide variety of bird species compared with other fresh water wetlands in inner Hordaland. Several of the bird species were also unusual for the region. The delta had for example a permanent nesting colony of Eurasian Wigeon, believed to be the only one of its kind in the municipality.
The sediment that was deposited from the river Dyrvo has created the fan-shaped delta Rekvesøyane. The bit of land farthest out toward the water gets periodically flooded, especially during snow melt and after periods of much rain.