Modeling and Classification of Alluvial Fans with DEMs and Machine Learning Methods: A Case Study of Slovenian Torrential Fans

Matej Babič,Jošt Sodnik,Dušan Petrovič,Marko Komac,Božo Soldo,Matjaž Mikoš,Michele Calì,Miha Kovačič,Olena Chernieva

doi:10.3390/rs13091711

Abstract

Alluvial (torrential) fans, especially those created from debris-flow activity, often endanger built environments and human life. It is well known that these kinds of territories where human activities are favored are characterized by increasing instability and related hydrological risk; therefore, treating the problem of its assessment and management is becoming strongly relevant. The aim of this study was to analyze and model the geomorphological aspects and the physical processes of alluvial fans in relation to the environmental characteristics of the territory for classification and prediction purposes. The main geomorphometric parameters capable of describing complex properties, such as relative fan position depending on the neighborhood, which can affect their formation or shape, or properties delineating specific parts of fans, were identified and evaluated through digital elevation model (DEM) data. Five machine learning (ML) methods, including a hybrid Euler graph ML method, were compared to analyze the geomorphometric parameters and physical characteristics of alluvial fans. The results obtained in 14 case studies of Slovenian torrential fans, validated with data of the empirical model proposed by Bertrand et al. (2013), confirm the validity of the developed method and the possibility to identify alluvial fans that can be considered as debris-flow prone.

Highlights

Alluvial fans are a typical form of sedimentary deposits growing at the outlets of steeper drainage areas such as torrential watersheds [1]
Summing up the present study proposed a replicable procedure based on digital elevation model (DEM) and machine learning (ML) methods to analyze morphological parameters and physical characteristics of alluvial fans and predict hazardous torrential fans
− P7 (FANSlope_avg): the average slope of the fan following the flow direction in degrees. These gathered parameters were capable of describing more complex properties, such as relative fan position depending on the neighborhood that could affect their formation or shape, or properties describing a specific part of a fan in a special way

Summary

Introduction

Alluvial (torrential) fans are a typical form of sedimentary deposits growing at the outlets of steeper drainage areas such as torrential watersheds [1]. Torrential fans are a sediment body of intermixing layers of coarse and poorly sorted debris (rocks, stones, gravel, or sand), generally having a cone-like shape. A fan’s conical shape is formed due to the rapid decrease in flow velocity and, due to the lower transport capacity to transfer debris material. According to their formation, we can distinguish between the debris flows resulting from torrential outbreaks (torrential debris flows) and those that are developed on slopes from landslides (slope debris flows).

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Conclusion