Jökull - 01.01.2009, Page 28

A. A. Beylich
Table 6. Peak runoff events and fluvial suspended sediment transport in Latnjavagge. – Leysing og aurburður
í Latnjavagge.
Year Runoff Reason Total Percent of Total Percent of SSC max SSC mean Percent of
peak for sediment annual runoff mean annual during during annual mean
runoff yield mechanical during runoff peak peak mechanical
peak during denudation peak (717 mm) denudation
peak
[t km!2] [mm] [mg l!1] [mg l!1] (2.3 t km!2)
2000 1 Snow 1864 72 163 23 43.40 11.44
melt
2 Snow 412 16 211 29 6.75 1.95
melt
3 Rain 113 4 66 9 2.20 1.71 100
2001 1 Snow 2064 91 388 56 16.20 5.32 88
melt
2002 1 Snow 1820 89 334 47 18.23 5.45
melt
2 Rain 49 2 31 4 1.80 1.58 80
2003 1 Snow 1902 88 376 52 23.20 5.06 81
melt
2004 1 Snow 2008 78 352 49 26.05 5.71
melt
2 Rain 7500 293 50 7 365 150 406
2005 1 Snow 2154 80 352 49 27.50 6.12
melt
2 Rain 133 5 39 5 4.50 3.41 98
2006 1 Snow 2102 91 360 50 25.90 5.84 90
melt
2007 1 Snow 1872 90 342 48 21.11 5.47 80
melt
sediment transport and denudation was analysed by
calculating their total yields at the inlet of lake Latn-
jajaure (Table 6). In addition, total runoff as well as
the mean and maximum suspended sediment concen-
trations were analysed. Altogether 13 runoff peaks,
9 snowmelt-generated and 4 rainfall-generated, have
been investigated and quantitatively compared. The
importance of snowmelt generated runoff peaks is
high. In the year 2000, 97% of the total mechan-
ical flux occurred during two snowmelt generated
runoff peaks whereas 78 to 92% of the mean an-
nual suspended sediment yield was transported dur-
ing snowmelt-generated runoff peaks in 2001–2007
(Table 6).
Rainfall-generated runoff peaks thus have a much
smaller quantitative importance for annual sediment
yields in Latnjavagge (Table 6). The quantitative im-
portance of snowmelt generated runoff peaks is very
high in both the Kidisjoki and the Latnjavagge catch-
ments with about 90% of the annual sediment trans-
port. With the exception of rare rainfall events trig-
gering slope processes and direct sediment delivery
to channels, rainfall events have only little quantita-
tive importance for annual suspended sediment trans-
port and sediment yields in both catchments. How-
ever, rainfall generated runoff peaks are of major im-
portance for fluvial sediment transport in Hrafndalur.
Highmechanical weathering rates of rhyolites in com-
bination with limited vegetation cover are main fac-
28 JÖKULL No. 59