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The southern Apuan Alps (Italy) are prone to rainfall-induced landslides. A first attempt to calculate rainfall thresholds was made in 2006 using non-statistical and repeatable methods for the 1975–2002 period. This research aims to update, validate, and compare the results of that attempt through different statistical approaches. Furthermore, a new dataset of rainfall and landslides from 2008 to 2016 was collected and analyzed by reconstructing the rainfall events via an automatic procedure. To obtain the rainfall thresholds in terms of the duration–intensity relationship, we applied three different statistical methods for the first time in this area: logistic regression (LR), quantile regression (QR), and least-squares linear fit (LSQ). The updated rainfall thresholds, obtained through statistical methods and related to the 1975–2002 dataset, resulted in little difference from the ones obtained with non-statistical methods and have similar efficiency values among themselves. The best one is provided by the LR, with a landslide probability of 0.55 (efficiency of 89.8%). The new rainfall thresholds, calculated by applying the three statistical methods on the dataset from 2008–2016, are similar to the 1975–2002 ones, except for the LR threshold, which exhibits a higher slope. This result confirms the validity of the thresholds obtained with the old database. [ABSTRACT FROM AUTHOR]

Acid mine drainages (AMD) have adversely affected the southern Apuan Alps (northern Tuscany, Italy). The study particularly focuses on the Baccatoio stream, which receives AMD from the abandoned Pollone and M. Arsiccio mines. The mine waters have an average pH of 2.2 and contain potentially toxic elements (PTE) at concentrations that exceed the Italian regulatory threshold for Al, Fe, Mn, Cu, Zn, As, Ni, Co, Cd, Sb, Pb, and Tl. The AMD flow directly into the stream, severely contaminating it. Downstream of the mined areas, the pH increases and most PTE (especially Fe, Al, As, and Pb) are readily scavenged from the stream waters by precipitation and/or adsorption. However, Tl, which peak at 1000 µg/L in the AMD, behaves almost conservatively along the stream flow path, undergoing only dilution, and remains at or above the concentration of concern of 4 µg/L almost to the coastline, before sharply decreasing to 0.5 µg/L where seawater is encountered. Since the stream water was locally used for irrigation, these observations may have important environmental and public health consequences in such a densely populated area. [ABSTRACT FROM AUTHOR]