Abstract

Climate change has increased the likelihood of the occurrence of disasters like wildfires, floods, storms, and landslides worldwide in the last years. Weather conditions change continuously and rapidly, and wildfires are occurring repeatedly and diffusing with higher intensity. The burnt catchments are known, in many parts of the world, as one of the main sensitive areas to debris flows characterized by different trigger mechanisms (runoff-initiated and debris slide-initiated debris flow). The large number of studies produced in recent decades has shown how the response of a watershed to precipitation can be extremely variable, depending on several on-site conditions, as well as the characteristics of precipitation duration and intensity. Moreover, the availability of satellite data has significantly improved the ability to identify the areas affected by wildfires, and, even more importantly, to carry out post-fire assessment of burnt areas. Many difficulties have to be faced in attempting to assess landslide risk in burnt areas, which present a higher likelihood of occurrence; in densely populated neighbourhoods, human activities can be the cause of the origin of the fires. The latter is, in fact, one of the main operations used by man to remove vegetation along slopes in an attempt to claim new land for pastures or construction purposes. Regarding the study area, the Camaldoli and Agnano hill (Naples, Italy) fires seem to act as a predisposing factor, while the triggering factor is usually represented by precipitation. Eleven predisposing factors were chosen and estimated according to previous knowledge of the territory and a database consisting of 400 landslides was adopted. The present work aimed to expand the knowledge of the relationship existing between the triggering of landslides and burnt areas through the following phases: (1) Processing of the thematic maps of the burnt areas through band compositions of satellite images; and (2) landslide susceptibility assessment through the application of a new statistical approach (machine learning techniques). The analysis has the scope to support decision makers and local agencies in urban planning and safety monitoring of the environment.

Highlights

  • Landslides are responsible worldwide for significant socioeconomic losses and, historically, have taken on a fundamental position in the list of natural hazards affecting the Italian territory [1,2,3,4]

  • Wildfire maps were created that were defined to the perimeter of around 1 km2 of areas covered by fire in the three periods inspected (1997—0.36 km2, 2001—0.25 km2, and 2019—0.39 km2), covering 45% of the total study area, confirming that these slopes have been frequently affected by fires over the years, increasing the predisposition to instability

  • Two different strategies to exclude highly collinear variables through a gradual procedure were used: The Vifcor and the Vifstep

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Summary

Introduction

Landslides are responsible worldwide for significant socioeconomic losses and, historically, have taken on a fundamental position in the list of natural hazards affecting the Italian territory [1,2,3,4]. Over a few decades, huge neighbourhoods have grown rapidly, reaching a rather high population density of 6000–7000 inhabitants per square kilometer In many cases, these areas are exposed to natural hazards, such as floods and landslides [8,12]. Naples is a city with high territorial “fragility”, as it is characterized by a complex and often chaotic urban fabric that exists in an extremely complex geological and geomorphological context [14]. It is made even more fragile by a multitude of underground artificial cavities as a result of past mining activities. Both areal and linear erosion phenomena have occurred in the burnt sectors of the slope (Figure 1)

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