Contemporary suspended sediment transfer and accumulation processes in the small proglacial Sætrevatnet sub-catchment, Bødalen, western Norway

Abstract

A combination of different process monitoring, lake sediment coring and sediment analysis methods and techniques was applied in the 17.5km2 Sætrevatnet sub-catchment in the upper Bødalen drainage basin (Nordfjord, western Norway) in order to define hydro-meteorological controls on runoff, suspended sediment transfer and sediment accumulation, and to determine the role of Lake Sætrevatnet within the drainage basin-wide sediment routing system. The proglacial system shows the typical seasonal and weather-depended runoff variations for glacierized drainage basins. Significant suspended sediment transport is associated to summer glacier melt (when 61.9% of the annual suspended sediment yield was recorded in 2010) as well as to single rainfall events (when 19.8% of the annual suspended sediment yield was recorded in 2010). The intensity of atmospheric energy input and the frequency of heavy rainfall events were found to be critical for the rate of suspended sediment transport within the Sætrevatnet sub-catchment. The computed annual suspended sediment yield from the proglacial area was 24.2tkm−2, which is notably lower as compared with a number of other glacierized basins worldwide. Delta accumulations rates from 2009 (4cmyr−1) and 2010 (3cmyr−1) as well as average annual delta advance ranging from 3.8m to 4.6m confirm the calculated high annual lake sedimentation rate of 1.7cmyr−1. Lake Sætrevatnet (0.02km2) currently traps about 80–85% of the sediments delivered from the upstream-located glacial system highlighting the importance of small ephemeral proglacial lakes within larger valley–fjord sediment routing systems.