Jökull - 01.01.2009, Page 25

Chemical and mechanical fluvial denudation in cold environments
Table 1: Annual runoff and denudation in Hrafndalur (SSC: Suspended Sediment Concentration, TDS: Total
Dissolved Solids). – Ársúrkoma, aurburður og efnahvarfarof í Hrafndal. SSC: Styrkur svifaurs, TDS: Heildar-
magn uppleystra efna.
Year Runoff Mean Yield of Mean Yield of Chemical
weighted suspended weighted dissolved denudation
SSC solids TDS solids
[mm] [mm l−1] [t km−2] [mm l−1] [t km−2] [t km−2]
2002 1779 17.2 30.6 39.7 70.6 35.9
2003 1283 14.0 18.0 41.0 52.6 26.8
2004 1112 10.2 11.4 42.1 46.8 26.1
2005 1285 10.8 13.8 41.8 53.7 29.3
2006 1458 15.8 23.0 40.9 59.6 31.9
2007 1149 12.2 14.0 42.0 48.3 25.5
Annual mean
2002 – 2007 1344 13.4 18.5 41.3 55.3 29.3
Table 2. Annual runoff and denudation in Kidisjoki. – Ársúrkoma, aurburður og efnahvarfarof í Kidisjoki.
Year Runoff Mean Yield of Mean Yield of Chemical
weighted suspended weighted dissolved denudation
SSC solids TDS solids
[mm] [mm l−1] [t km−2] [mm l−1] [t km−2] [t km−2]
2002 340 0.8 0.27 24.9 8.5 3.3
2003 318 0.7 0.22 25.2 8.0 2.9
2004 312 0.7 0.22 25.1 7.8 3.0
2005 341 0.9 0.31 25.4 8.7 3.4
2006 309 0.7 0.22 25.1 7.8 2.8
2007 322 0.8 0.25 25.5 8.2 3.1
Annual mean
2002 – 2007 324 0.8 0.25 25.2 8.2 3.1
transport rates total mechanical denudation dominates
over chemical denudation in Hrafndalur. The denuda-
tion rates in both Kidisjoki and Latnjavagge are lower
than denudation rates in Eastern Iceland (Beylich and
Kneisel, 2009). Variable steepness and vegetation
cover in the three catchments are primary causes of
their different denudation rates. The steepness of
Hrafndalur in combination with rhyolitic bedrock re-
sults in higher mechanical denudation rates compared
with Latnjavagge and Kidisjoki.
The role of snowmelt- and rainfall-generated peak
runoff for annual fluvial sediment transport and
denudation rates
In Hrafndalur runoff peaks occur during snow melt in
spring (April-June), during heavy rainfall (especially
in fall) and during wintry thaws, which are often con-
nected with rainfall. A significant increase of inor-
ganic suspended sediment concentrations was mea-
sured at days with runoff over 40 mm d−1, with these
runoff peaks being caused by heavy rainfall events.
The number of days with daily runoff over 40 mm
varied from 4 to 8 during the period 2002–2007 (Ta-
ble 4). Altogether 80% of the annual suspended sed-
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