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Reconstruction and simulation of an extreme flood event in the Lago Maggiore catchment in 1868

Type of publication Peer-reviewed
Publikationsform Original article (peer-reviewed)
Author Stucki Peter, Bandhauer Moritz, Heikkilä Ulla, Rössler Ole, Zappa Massimiliano, Pfister Lucas, Salvisberg Melanie, Froidevaux Paul, Martius Olivia, Panziera Luca, Brönnimann Stefan,
Project Swiss Early Instrumental Measurements for Studying Decadal Climate Variability (CHIMES)
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Original article (peer-reviewed)

Journal Natural Hazards and Earth System Sciences
Volume (Issue) 18(10)
Page(s) 2717 - 2739
Title of proceedings Natural Hazards and Earth System Sciences
DOI 10.5194/nhess-18-2717-2018

Open Access

URL http://doi.org/10.5194/nhess-18-2717-2018
Type of Open Access Publisher (Gold Open Access)

Abstract

Abstract. Heavy precipitation on the south side of the central Alps produced a catastrophic flood in October 1868. We assess the damage and societal impacts, as well as the atmospheric and hydrological drivers using documentary evidence, observations and novel numerical weather and runoff simulations. The greatest damage was concentrated close to the Alpine divide and Lago Maggiore. An atmospheric reanalysis emphasizes the repeated occurrence of streamers of high potential vorticity as precursors of heavy precipitation. Dynamical downscaling indicates high freezing levels (4000 m a.s.l.), extreme precipitation rates (max. 270 mm 24 h −1 ) and weather dynamics that agree well with observed precipitation and damage, and with existing concepts of forced low-level convergence, mid-level uplift and iterative northeastward propagation of convective cells. Simulated and observed peak levels of Lago Maggiore differ by 2 m, possibly because the exact cross section of the lake outflow is unknown. The extreme response of Lago Maggiore cannot be attributed to low forest cover. Nevertheless, such a paradigm was adopted by policy makers following the 1868 flood, and used to implement nationwide afforestation policies and hydraulic structures. These findings illustrate the potential of high-resolution, hydrometeorological models – strongly supported by historical methods – to shed new light on weather events and their socio-economic implications in the 19th century.
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