Shoreline erosion and aeolian deposition along a recently formed hydro-electric reservoir, Blöndulón, Iceland

Erosion and deposition processes have been active along the shores of the Blöndulón hydro-electric reservoir in the Icelandic highlands since its formation nearly two decades ago. In this study, bluff development and distribution of aeolian material along the shores of the reservoir is related to erosive forces and source materials. The 57 km2 reservoir was formed in the glacial river Blanda in 1991 and enlarged in 1996. Bluff erosion and aeolian deposition has been monitored since 1997. Field observations, meteorological data, GIS analyses and calculations of wave power were used to measure and describe erosive processes along the new shoreline. Wave-induced bluff erosion was most rapid during the first years after impoundment and was most active at sites with glacial till substrate, high cumulative wave power, and long fetches along the dominant wind direction. In recent years, relatively high erosion rates have continued at bluffs of fluvioglacial material under low cumulative wave power. The fluvioglacial material has low resistance to wave activity, creating unstable bluffs, whereas bluffs made of glacial till are more stable. Aeolian sandy sediment, mainly volcanic tephra eroded from soils, has been deposited at sites open towards dry strong winds during low water levels in inlets of low wave energy. Slope and aspect against wind direction restricted the sediment distribution to 212 000 m2 (21 ha) of the heathland along the reservoir. By 2008 a volume of ~ 11 000 m3 had accumulated. The continued redistribution of aeolian sediments and processes of bluff erosion were controlled by the water level fluctuations in the reservoir.