Publication Date:
2020-02-18
Description:
Lake sediments are increasingly explored as reliable paleoflood archives. In addition to
established flood proxies including detrital layer thickness, chemical composition, and grain
size, we explore stable oxygen and carbon isotope data as paleoflood proxies for lakes in
catchments with carbonate bedrock geology. In a case study from Lake Mondsee (Austria),
we integrate high-resolution sediment trapping at a proximal and a distal location and stable
isotope analyses of varved lake sediments to investigate flood-triggered detrital sediment flux.
First, we demonstrate a relation between runoff, detrital sediment flux, and isotope values in
the sediment trap record covering the period 2011–2013 CE including 22 events with daily
(hourly) peak runoff ranging from 10 (24) m3 s−1 to 79 (110) m3 s−1. The three- to ten-fold
lower flood-triggered detrital sediment deposition in the distal trap is well reflected by attenuated
peaks in the stable isotope values of trapped sediments. Next, we show that all nine
flood-triggered detrital layers deposited in a sediment record from 1988 to 2013 have elevated
isotope values compared with endogenic calcite. In addition, even two runoff events that did
not cause the deposition of visible detrital layers are distinguished by higher isotope values.
Empirical thresholds in the isotope data allow estimation of magnitudes of the majority of
floods, although in some cases flood magnitudes are overestimated because local effects can
result in too-high isotope values. Hence we present a proof of concept for stable isotopes as
reliable tool for reconstructing flood frequency and, although with some limitations, even
for flood magnitudes.
Repository Name:
EPIC Alfred Wegener Institut
Type:
Article
,
isiRev
Format:
application/pdf
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