Characterizing Consecutive Flooding Events after the 2017 Mt. Salto Wildfires (Southern Italy): Hazard and Emergency Management Implications

Giuseppe Esposito,Filiberto Russo,Giovanni Nanni,Stefano Alfano,Gaetano Giannatiempo,Rocco Masi,Antonio Parodi,Martina Lagasio

doi:10.3390/w11122663

Abstract

Every summer, wildfires affect thousands of steep watersheds in Italy, causing the partial or complete destruction of vegetation, and changes in soil hydraulic properties. Such effects alter the hydrologic response of watersheds, increasing post-fire debris and sediment-laden flow hazard. This study characterizes the most relevant predisposing and triggering factors for a sequence of four post-fire flooding events, which, in the late summer-autumn of 2017, affected Montoro village in southern Italy. This research work consists of a fire severity assessment based on multispectral satellite images, characterization of meteorological systems and related flood-triggering rainfall, and provides an overview of the damage that occurred in the repeatedly affected urban area using crowdsourced data. The research findings demonstrate that the analyzed area burned with moderate-high (64.4%) and low severity (35.6%) levels. All the flooding events were triggered by rainfall evaluated as non-extreme, but with relevant peak intensities (I10 and I30), associated with the first convective storms impacting the burned watersheds. The crowdsourced data highlight the fact that roads and buildings on footslopes were inundated by mud and debris transported by rapid flows. The study identifies a clear relationship between wildfires and flooding processes and provides useful information for hazard assessment and emergency management operations.

Highlights

Wildfires represent one of the most widespread hazards in Mediterranean forest ecosystems
Fire severity assessment was carried out by using satellite data acquired by the Sentinel-2
The sequence of post-fire flooding events described in this study highlights that wildfires may Conclusions increase theand susceptibility to erosion processes along steep slopes covered by pyroclastic airfall deposits and andosols, with generation of hyperconcentrated and debris flowsthat downstream

Summary

Introduction

Wildfires represent one of the most widespread hazards in Mediterranean forest ecosystems. The effects of the ongoing climate change promote long-lasting periods of drought and heat waves, with favorable conditions for the ignition and propagation of severe fires [1,2]. Pronounced vegetation and soil moisture reduction during summer droughts can increase the likelihood of high-severity crown fire, especially with high winds [3]. Together with fire residence time (heating duration), vegetation properties, topography, substrate, and climate control the loss or decomposition of aboveground and belowground organic matter [4], meaning that each fire can burn with different severity levels. In order to perform a fire severity assessment, both field and remote sensing approaches can be used. Extensive field observations can be made for accessible and limited burned

Methods

Results

Conclusion