Reduced complexity debris flow/flood hazard assessment at the southwestern slope of Mt. Omo, L’Aquila municipality, central Italy

In recent decades, the increasing number and severity of wildfires have become a major concern in many regions of the world. Besides having direct consequences for forests, crops, and settlements, wildfires can have significant effects on the catchment’s hydrology, altering their response to rainfal...

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Bibliographic Details
Published in:Landslides 2024, Vol.21 (1), p.183-195
Main Authors: Guerriero, Luigi, Francioni, Mirko, Calcaterra, Domenico, Di Martire, Diego, Palumbo, Simone, Zito, Claudia, Sciarra, Nicola
Format: Article
Language:English
Subjects:
Agriculture
Alluvial deposits
Alluvial fans
Analysis
Aquatic reptiles
Availability
Catchment area
Catchments
Civil Engineering
Complexity
Debris flow
Detritus
Earth and Environmental Science
Earth Sciences
Flood hazards
Flooding
Floods
Geography
Hazard assessment
Headwaters
Hydrodynamics
Hydrology
Modelling
Municipalities
Natural Hazards
Precipitation
Probability theory
Rainfall
Runoff
Sediment
Shallow water
Shallow water equations
Slopes
Surface runoff
Technical Note
Two dimensional analysis
Two dimensional models
Wildfires
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Summary:In recent decades, the increasing number and severity of wildfires have become a major concern in many regions of the world. Besides having direct consequences for forests, crops, and settlements, wildfires can have significant effects on the catchment’s hydrology, altering their response to rainfall and promoting enhanced runoff and erosion. Increased runoff in burnt areas can result in catastrophic damage and loss of life from destructive debris flows and floods. Although observed in many regions of the world, post-wildfire debris flows/floods seem to prevail in the western USA and southern Europe. In Italy, post-wildfire debris flows/floods have been observed in a number of sectors of the Apennine range, and a total of 113 events occurred between 2001 and 2021 in the Campania region. A recent event occurred on August 24, 2020, in the Fosso delle Pescine catchment, on the southwestern slope of Mt. Omo in the L’Aquila municipality, hit by a severe wildfire at the beginning of the month. The consequences of the event on people and properties indicate the need for an evaluation of debris flow/flood hazard in both pre- and post-wildfire conditions. The analysis of these events may often be complex, requiring time and many input data. In this context, a simplified method of analysis which accounts for event initiation and propagation through a shallow water equation-based approach would represent a new and innovative solution for fast and preliminary debris flow/flood analyses. In this research, a reduced complexity analysis based on probability analysis of rainfall and 2D hydrodynamic modeling was carried out by estimating (i) wildfire extent and severity, (ii) sediment characteristics and availability, (iii) potential runoff induced by rainfall, and (iv) inundation by debris flow/flood. A debris flow/flood hazard model was developed on the basis of multiple return periods (10, 50, 100, and 300 years) for debris flow inundation scenarios derived by non-Newtonian 2D hydrodynamic modeling of debris flow hydrograph and qualitatively validated on the basis of the extent of alluvial fan deposits. Potential drawbacks of the model are related to the possible overestimation of surface runoff, related to the consideration of the whole catchment contributing area, and the limited volumetric sediment budget available at the headwater, which might not sustain a high return period event generation. A debris flow/flood event might originate from rainfall concentrated at t
ISSN:1612-510X
1612-5118
DOI:10.1007/s10346-023-02143-2