Historical predictability of rainfall erosivity: a reconstruction for monitoring extremes over Northern Italy (1500–2019)

Abstract

Erosive storms constitute a major natural hazard. They are frequently a source of erosional processes impacting the natural landscape with considerable economic consequences. Understanding the aggressiveness of storms (or rainfall erosivity) is essential for the awareness of environmental hazards as well as for knowledge of how to potentially control them. Reconstructing historical changes in rainfall erosivity is challenging as it requires continuous time-series of short-term rainfall events. Here, we present the first homogeneous environmental (1500–2019 CE) record, with the annual resolution, of storm aggressiveness for the Po River region, northern Italy, which is to date also the longest such time-series of erosivity in the world. To generate the annual erosivity time-series, we developed a model consistent with a sample (for 1981–2015 CE) of detailed Revised Universal Soil Loss Erosion-based data obtained for the study region. The modelled data show a noticeable descending trend in rainfall erosivity together with a limited inter-annual variability until ~1708, followed by a slowly increasing erosivity trend. This trend has continued until the present day, along with a larger inter-annual variability, likely associated with an increased occurrence of short-term, cyclone-related, extreme rainfall events. These findings call for the need of strengthening the environmental support capacity of the Po River landscape and beyond in the face of predicted future changing erosive storm patterns.

Reconstruction of erosivity density in northwest Italy since 1701

“…Acquaotta et al (2019) also confirmed an upward erosivity trend for the period 1981-2015 in much of northern Italy. This increasing trend, together with increased inter-annual variability, is in fact a continuous process of precipitation intensification in Northern Italy, which began in the 1700s, likely associated with an increase in the frequency of extreme short-term rainfall events (Diodato et al 2020b). This means that northern Italy has been exposed to a progressively increasing inter-annual variability in rainfall erosivity, resulting in an increased hazardous landscape stress.…”

“…Long-term reconstructions of rainfall erosivity can help to disentangle the role of anthropogenic climate change and the natural variability of the climate system in heavy rainfall events and floods (Diodato et al 2020a(Diodato et al , 2020b. The latter, through atmospheric-oceanic teleconnection patterns such as El Niño Southern Oscillation (ENSO), the North Atlantic Oscillation (NAO), the Atlantic Multidecadal Oscillation (AMO) and the Pacific Decadal Oscillation (PDO), can drive the frequency and intensity of regional rainfall events worldwide (Wetter et al 2011, Willems 2013, Gómara et al 2018, Diakhaté et al 2019).…”

A millennium-long climate history of erosive storms across the Tiber River Basin, Italy, from 725 to 2019 CE

“…2 d, black squared). Recently published studies on the relationship between hydrological extremes and climate change 34 , including rainfall erosivity 35 – 37 , indicate a new focus of environmental science about the history of extreme hydroclimatic events. Indeed, there are studies regarding the relationship between erosive forcing and climate in the central Mediterranean region 38 – 44 , indicating renewed attention to environment–climate interactions in historical and ecological research in support of reconstruction of extreme rainfall events (including rainfall erosivity) and planning decisions, especially in agriculture.…”

“…In this way, modelling rainfall erosivity requires exploring mechanisms inherited from past hydrological extremes like storms and floods 45 , using parsimonious models to overcome the limitations imposed by detailed models, which required detailed data and cannot be applied to historical periods 46 . In particular, low-resolution historical documentary records of extreme weather events can be adopted to help predict rainfall erosivity when satisfactory instrumental data are not available 37 . However, the floods of the Roman period, and earlier times, are almost all dated on an annual time-scale.…”

Climate Patterns in the World’s Longest History of Storm-Erosivity: The Arno River Basin, Italy, 1000–2019 CE

“…Damaging hydrological events triggered by either short and intense storms, or longer duration rainfall (e.g., Diodato et al, 2020b;Duulatov et al, 2021), cause sustained erosive forcing and considerable soil losses in many parts of the world (Wuepper et al, 2020). They may increase in frequency and/or severity with changes in the climate system associated with global warming (Easterling et al, 2000;Morera et al, 2017;Harris et al, 2018;Rineau et al, 2019;Wei et al, 2020).…”