River Deltas of the Inner Sognefjord (Inner Sogn Region): Consequences of Anthropogenic Change

Abstract

This study investigates ten river deltas for anthropogenic environmental change in the Inner Sogn Region, Western Norway, using aerial photographs of the 1960s and the 2010s. In addition, it presents qualitative interviews made with two experts, focusing on the development of bird and fish populations in the observed river deltas. These river deltas are the Årøy Delta near Sogndal, the Lærdal Delta at Lærdal, the Sogndalsfjøra Delta at Sogndal, the Gaupne Delta at Gaupne, the Gudvangen Delta at Gudvangen, the Skjolden Delta at Skjolden the Årdalstangen Delta at Årdalstangen, the Bøyaøyra Delta near Fjærland, the Vetlefjordøyra Delta at Vetlefjorden and the Flåm Delta at Flåm. The observed river deltas are habitats for fish and bird populations. The deltas are used as resting places, feeding grounds, nesting areas and for nursery. All the observed river deltas are influenced by human activity. Two of these river deltas have changed from >50% natural to <25% cultivated over the past 50 years. One river delta has changed from >50% natural to >25% cultivated. Four out of the ten observed river deltas have changed from >50% natural to >>50% urban. Three river deltas changed from >50% urban to >>50% urban. The natural delta area of six out of ten river deltas decreased by more than 50% between the 1960s and the 2010s due to land fillings, road buildings and harbor constructions. These results suggest that the progressing destruction of the natural river delta environment had a declining effect on the fish and bird population of the region. To reduce the potential for future conflicts, it is suggested that river delta management uses the historic development of the river deltas as an additional tool when deciding on future delta change.