Abstract
Non-invasive techniques such as seismic investigations and high-resolution multibeam sonars immensely improved our understanding of the geomorphology and sediment regimes in both the lacustrine and the marine domain. However, only few studies provide quantifications of basin wide-sediment budgets in lakes. Here, we use the combination of high-resolution bathymetric mapping and seismic reflection data to quantify the sediment budget in an alpine lake. The new bathymetric data of Lake Brienz reveal three distinct geomorphological areas: slopes with intercalated terraces, a flat basin plain, and delta areas with subaquatic channel systems. Quasi-4D seismic reflection data allow sediment budgeting of the lake with a total sediment input of 5.54 × 106 t sediment over 15 years of which three-quarter were deposited in the basin plain. Lake Brienz yields extraordinarily high sedimentation rates of 3.0 cm/yr in the basin plain, much more than in other Swiss lakes. This can be explained by (i) its role as first sedimentary sink in a high-alpine catchment, and by (ii) its morphology with subaquatic channel-complexes allowing an efficient sediment transfer from proximal to distal areas of the lake.
Highlights
Non-invasive techniques such as seismic investigations and high-resolution multibeam sonars immensely improved our understanding of the geomorphology and sediment regimes in both the lacustrine and the marine domain
1 Introduction (Peri-)alpine lakes play a major role as sedimentary sinks and represent important archives for studying past environmental and climatic conditions (Glur et al, 2015; Jenny et al, 2014; Leemann & Niessen, 1994; Lister et al, 1983; Rapuc et al, 2019; Wirth et al, 2011), sediment transport (e.g. Chapron et al, 2002; Arnaud et al, 2016; Silva et al, 2019), and seismotectonic activity
4.1 Bathymetric dataset 4.1.1 General lake morphology High-resolution bathymetric data reveal a large flat basin area bordered by steep lateral flanks along the north-western and southeastern shoreline, respectively (Fig. 2A)
Summary
Non-invasive techniques such as seismic investigations and high-resolution multibeam sonars immensely improved our understanding of the geomorphology and sediment regimes in both the lacustrine and the marine domain. Lake Brienz yields extraordinarily high sedimentation rates of 3.0 cm/yr in the basin plain, much more than in other Swiss lakes This can be explained by (i) its role as first sedimentary sink in a high-alpine catchment, and by (ii) its morphology with subaquatic channel-complexes allowing an efficient sediment transfer from proximal to distal areas of the lake. 22 Page 2 of 17 currents occur often leading to erosion of the substrate (Girardclos et al, 2012; Hizzett et al, 2018) and formation of subaquatic-channel complexes (Corella et al, 2014) Those features, being a small-scale analogue of submarine canyons along continental margins, can be considered as effective conduit transferring high amount of sediments from proximal to distal areas (Corella et al, 2016; Kremer, Corella, et al, 2015).
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