Communicating Hydrological Hazard-Prone Areas in Italy With Geospatial Probability Maps

2021

Sci Rep

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Rainfall erosivity drives damaging hydrological events with significant environmental and socio-economic impacts. This study presents the world’s hitherto longest time-series of annual rainfall erosivity (725–2019 CE), one from the Tiber River Basin (TRB), a fluvial valley in central Italy in which the city of Rome is located. A historical perspective of erosive floods in the TRB is provided employing a rainfall erosivity model based on documentary data, calibrated against a sample (1923–1964) of actual measurement data. Estimates show a notable rainfall erosivity, and increasing variability, during the Little Ice Age (here, ~ 1250–1849), especially after c. 1495. During the sixteenth century, erosive forcing peaked at > 3500 MJ mm hm–2 h–1 yr–1 in 1590, with values > 2500 MJ mm hm–2 h–1 yr–1 in 1519 and 1566. Rainfall erosivity continued into the Current Warm Period (since ~ 1850), reaching a maximum of ~ 3000 MJ mm hm–2 h–1 yr–1 in the 1940s. More recently, erosive forcing has attenuated, though remains critically high (e.g., 2087 and 2008 MJ mm hm–2 h–1 yr–1 in 1992 and 2005, respectively). Comparison of the results with sediment production (1934–1973) confirms the model’s ability to predict geomorphological effects in the TRB, and reflects the role of North Atlantic circulation dynamics in central Italian river basins.

Section: Resultsmentioning

confidence: 99%

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

Diodato¹,

2021

Sci Rep

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“…We have analyzed the erosivity density (ED, MJ hm −2 h −1 ), which measures the erosivity per rainfall unit and is a better indicator of the erosive hazard than rainfall erosivity (Glur et al, 2013;Diodato et al, 2019a). We addressed this issue by examining the estimated ED time-series since 1891, as it is only from this year that high-quality, well-documented, and homogeneous annual rainfall records are available for the ARB.…”

Section: )mentioning

confidence: 99%

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

Diodato¹,

2021

Front. Earth Sci.

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Rainfall erosivity causes considerable environmental damage by driving soil loss. However, the long-term evolution of erosive forcing (over centennial to millennial time-scales) remains essentially unknown. Using a rainfall erosivity model (REMARB), this study simulates the variability of rainfall erosivity in Arno River Basin (ARB), Italy, a Mediterranean fluvial basin, for the period 1000–2019 CE resulting in the world’s longest time-series of erosivity. The annual estimates show a noticeable and increasing variability of rainfall erosivity during the Little Ice Age (∼1250–1849), especially after c. 1490, until the end of 18th century. During this cold period, erosive forcing reached ∼1600 MJ mm hm−2 h−1 yr−1 once every four years, and ∼3000 MJ mm hm−2 h−1 yr−1 once every 20 years. The extremes of rainfall erosivity (the 98th percentile) followed a similar increasing trend, with an acceleration of the hydrological hazard (erosivity per unit of rainfall) during the 20th century. The comparison of REMARB output with the sediment yield of the basin (1951–2010) confirmed the model’s ability to predict geomorphological effects in the ARB. Thus, our methodology could be applied to simulate erosivity in environmentally similar basins. A relationship has been identified between the Atlantic Multidecadal Variation and erosivity patterns, suggesting a role of North Atlantic circulation dynamics on the hydrology of central Italy’s fluvial basins.

“…In the absence of such detailed rainfall information, rainfall variability and its linkage to atmospheric pressure systems can be inferred from meteorological observations available for the Mediterranean region over the twentieth century 24 and even earlier back to mid-seventeenth century on a restricted regional basis 25 , but also from time-series of millennium-long hydrological extremes derived from documentary sources 26 . Long series derived from documentary data can help linking local and regional hydrological extremes to impacts 27 , assess climatic forcing features 28 , and recognise the climatic variability in hazard-exposed areas 29 , 30 . Their analysis supports that climate can vary in response to natural processes such as those governing the occurrence of erosive rainfall and, thus, help us to understand present-day hydrological dynamics and improve projections of future changes 31 .…”

Section: Introductionmentioning

confidence: 99%

Fingerprint of climate change in precipitation aggressiveness across the central Mediterranean (Italian) area

Diodato¹,

2020

Sci Rep

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Rainfall erosivity and its derivative, erosivity density (ED, i.e., the erosivity per unit of rain), is a main driver of considerable environmental damages and economic losses worldwide. This study is the first to investigate the interannual variability, and return periods, of both rainfall erosivity and ED over the Mediterranean for the period 1680–2019. By capturing the relationship between seasonal rainfall, its variability, and recorded hydrological extremes in documentary data consistent with a sample (1981–2015) of detailed Revised Universal Soil Loss Erosion-based data, we show a noticeable decreasing trend of rainfall erosivity since about 1838. However, the 30-year return period of ED values indicates a positive long-term trend, in tandem with the resurgence of very wet days (> 95th percentile) and the erosive activity of rains during the past two decades. A possible fingerprint of recent warming is the occurrence of prolonged wet spells in apparently more erratic and unexpected ways.