Geology, soil and seismic risk

Changes in high-intensity precipitation on the northern Apennines (Italy)

multidisciplinary data over the last 9000 years

Several record-breaking precipitation events have stricken the mountainous area of Emilia-Romagna Region (northern Apennines, Italy) over the last years. As consequence, severe geomorphological processes, like debris avalanches and debris flows, shallow landslides and overbank flooding affected the territory, causing serious damages to man-made structures. The intensity and wide spatial scale of these phenomena led us to investigate their frequency in the past, beyond the instrumental time. A detailed study of recent fossil peat bog and lake deposits can provide useful insights to support a correlations between precipitation intensity and warm climatic phases in antecedent climatic periods, as expected by the increasing air water vapour holding capacity at higher temperatures.
View of the Lake Moo landscape from the southern side

Here we present the results of a field campaign performed in summer 2017 at Lake Moo in the Northern Apennines, a 0.15km2 peat bog located at an altitude of 1130 m a.s.l. During the extreme precipitation event of  13-14 September 2015, several debris flows, generated by small streams, have affected the Lake Moo plain. In accordance with the literature, in such a small drainage basin (area <2 km2), high density flood can be triggered only by high intensity precipitation events (HIP) lasting enough time for water to infiltrate and mobilize large quantities of debris.

The sedimentary succession (ca. 13 m-thick) was studied through the drilling of two cores and one trench. The sedimentary succession, characterized by clusters of coarse-grained alluvial deposits interbedded with organic-rich silty clays and peat layers, was studied combining sedimentological and pollen data with pedological data and radiocarbon dating (AMS 14C).

Observed depositional cycles were correlated with other specific paleoclimatic proxies available in literature for the northern Apennines area. The increase of extreme paleo flood, associated with coarse-grained deposits similar to the ones observed recently correlates well with warm phases with a maximum activity during the Holocene thermal maximum and from the Little Ice Age to the present day.

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last modified 2020-12-23T17:07:51+02:00
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