Research highlights

Lütschine fan delta response to climate variability and land use during the last 2400 years.

The Late Holocene depositional and vegetation history of the Lütschine fan delta records important environmental changes. The sedimentological findings showed a general agreement between geochemical and pollen cycles and δ14C anomalies from 2400 to 850 yr cal. BP and could be interpreted as natural response to climate forcing (Figure 7). Furthermore, the coarse-grained layers, deposited during paleofloods about 100, 700, 1100, 1528, and 1831 yr AD, correlate with positive radiocarbon anomalies, suggesting that aggradation in the Lütschine fan delta during the focused period was triggered by solar forcing. According to our pollen data and the traced correlations, the Lütschine river floods occurred during cold and wet periods. The return interval of recorded flooding events during the last 2400 years varies between 300 and 600 years. With regard to the last millennium, anthropogenic impacts, such as woodland clearance for grazing and agriculture and river diversion, have changed the sedimentary and geomorphic pattern on the Lütschine fan delta, reducing wetland environments (Figure 7).

Correlation between geochemistry, pollen proxies, lithology and geomorphology of the Lütschine fan delta according to Schulte et al. (2006)

Figure 7: Correlation between geochemistry, pollen proxies, lithology and geomorphology of the Lütschine fan delta according to Schulte et al. (2006). The inverse relationship between SiO2, Al2O3 and CaO contents, determined by X-ray fluorescence, stresses a lithological control of the geochemistry of the profile IN-2 samples. Variations result predominately from the deposition of siliciclastic sediments (upper reach) and carbonate rich fine sediments (lower reach) and pedogenic processes in the peat horizons. The deposition of coarse-grained flood layer and shifts (arrows) of Lütschine channel results from exceptional flood event during the last 2400 years.

Relevant publications

Schulte, L. et al. 2019.

Integration of multi-archive datasets towards the development of a four-dimensional paleoflood model in alpine catchments.

Global and Planetary Change 180, 66-88.

Peña, J.C.; Schulte, L., 2020.

Simulated and reconstructed atmospheric variability and their relation with large Pre-industrial summer floods in the Hasli-Aare catchment (Swiss Alps) since 1300 CE.

Global and Planetary Change 190, 103191.

Schulte, L. et al., 2019.

Pluridisciplinary analysis and multi-archive reconstruction of paleofloods: societal demand, challenges and progress.

Global and Planetary Change 177, 225-238.

Blöschl, G. et al. 2020.

Current European flood-rich period exceptional compared with past 500 years.

Nature 583, 560–566 (2020).

Sánchez-García et al. 2019.

500-year flood history in the arid environments of south-eastern Spain. The case of the Almanzora River.

Global and Planetary Change, 102987.

Schulte, L. et al. 2015.

A 2600-year history of floods in the Bernese Alps, Switzerland: frequencies, mechanisms and climate forcing.

Hydrology and Earth System Sciences 19, 3047-3072.

Peña, J.C. et al. 2015.

Influence of solar forcing, climate variability and atmospheric circulation patterns on summer floods in Switzerland.

Hydrology and Earth System Sciences 19, 3807-3827.

Universitat de BarcelonaICREA - Institució Catalana de Recerca i Estudis AvançatsUniversität BernServei Meteorològic de CatalunyaGobierno de España - Ministerio de Educación y CienciaAlexander von Humboldt Foundation