Projects / Programmes
Recognition of potentially hazardous torrential fans uasing geomorphometric methods and simulating fan formation.
| Code |
Science |
Field |
Subfield |
| 2.20.00 |
Engineering sciences and technologies |
Hydrology |
|
| Code |
Science |
Field |
| P510 |
Natural sciences and mathematics |
Physical geography, geomorphology, pedology, cartography, climatology |
| Code |
Science |
Field |
| 2.07 |
Engineering and Technology |
Environmental engineering
|
geomorphology, digital terrain model, alluvial fans, debris flows, simulations, laboratory experiments, soil mechanics, rhreological properties
Researchers (13)
Organisations (2)
Abstract
The project will focus on the determination of the shapes of alluvial (torrential) fans, especially detecting those that are shaped by debris flows. It will focus on the use of geomorphometric methods, and therefore the digital elevation model (DEM) and the digital surface model (DSM). We assume that on the basis of good knowledge of shapes, textures, and other characteristics of alluvial fan surfaces (presented with characteristic spatial variables) it is possible to identify significant differences between fans formed by the debris flows in their catchment areas, and other torrential fans that have a lower risk of a sedimentary event that could endanger the built environment and human life. The identified alluvial fans that will be evaluated as dangerous and with a potential for debris flows in their catchment area will be checked by using a mathematical model to simulate the triggering and movement of debris flows from their source areas to the deposition zone (i.e. fans), and compared to the existing forms of fans.
Rainfall, earthquakes, reckless excavation/construction use of material, and inappropriate land use have a decisive impact on the processes of slope mass movements. Among the various types, we will focus on alluvial fans and debris flows in their catchment areas. Debris flows are, beside rock falls, the most destructive type of slope processes, because they cannot be easily predicted in terms of the time of triggering, place of action, their severity (magnitude), high-flow velocities, and their capability to move over large distances.
The main goal of the research project is the automatic determination and classification of fans, with an emphasis on their potential for the development of debris flows in their catchment areas. The basic hypothesis is that by using a high-resolution DEM or DSM, and the characteristic spatial variables, it is possible to distinguish between the fans caused by debris flows and the alluvial fans where debris flows are not expected and where only common torrential processes take place. Moreover, it is assumed that with such an approach the potentially dangerous fans can be distinguished from the more stable ones. In connection with the latter it is also assumed that we can identify potential areas of landslide occurrence.
The originality of the proposed project stems from the comparison of two completely different methodological approaches, i.e. the geomorphometrical analyses and the simulations of fan formation on the basis of mathematical modelling to simulate the triggering and movement of debris flows. The originality of the results is particularly manifested in the following: (1) high quality in determining the type of fans, even individual parts of fans; (2) accuracy – the resolution of the survey results of up to 1 m (completely different 'dimensions' in the modelling, as other applications reach a maximum resolution of 5–10 m); (3) a geomorphometric approach by combining geographic information systems, remote sensing, and image processing methods; (4) innovative indicators based on determining specific areas and eliminating atypical areas on the basis of a precise definition of the different types of fans in relation to debris and torrential flows; (5) taking into consideration the characteristics of fan surroundings; (6) taking into account various quality parameters of the input data, i.e. in this case DTMs and DSMs, in order to set the model parameters; (7) the sensitivity analysis.
When producing the hazard map of debris flows we can integrate new elements, such as automatic determination of torrential fans, laboratory analysis of the rheological properties of soils, and testing different 2D models of debris flows triggering and movement, as typical types of mass movement on the slopes. The proposed project is a decisive step in this direction. The methodological approach, methods, and quality of the expected results will set an example for other parts of the world.
Significance for science
The main goal of the research project is the automatic determination and classification of fans, with an emphasis on their potential for the development of debris flows in their catchment areas. The basic hypothesis is that by using a high-resolution DEM or DSM, and the characteristic spatial variables (indicators), it is possible to distinguish between the fans caused by debris flows and the alluvial fans where debris flows are not expected and where only common torrential processes take place. Moreover, it is assumed that with such an approach the potentially dangerous fans can be distinguished from the more stable ones. In connection with the latter it is also assumed that we can identify potential areas of landslide occurrence.
Fans are common features in mountainous areas. Unstable slopes of valleys are often covered with fans. Their geomorphological shape mostly depends on their poorly distributed material. This, together with other factors, defines the angle of inclination of the deposited material. Fan areas (debris, scree) are frequently overgrown, which can increase the inclination of the fans and thus their instability. Less active, often populated fans in lower-lying valleys have slightly different properties than those located high in the mountains. It is expected that by using remote sensing tools, and specifically image processing and geomorphometry tools (while using terrain and surface models), it is possible to classify different types of fans, especially due to our good experience with their determination on Mars (Podobnikar & Székely, 2015), where our knowledge of field conditions is obviously very limited.
The automatic identification of fans as well as classification of their shapes using the geomorphometric analysis is a step further from the procedures such as the Melton number, which is calculated based on the characteristics of the catchment area. This approach includes the development of several innovative methods of using DTMs as well as remote sensing techniques. Despite the fact that the classical (manual) detection of surface characteristics will remain important in the future, adequately collected and prepared databases consisting of high-quality spatial data allow for the highest possible degree of fast and automated techniques for numerical spatial analyses. We will compare the classically (manually) mapped fans with those determined automatically, and thus evaluate the quality and usefulness of this methodology. Such comparison is a rarity, but essential to establish the credibility of the emerging automated geomorphometry field.
The proposed project will contribute to the development of the young geomorphometry domain as well as geoinformatics for the needs of water management, geology, civil engineering and, generally, geomorphology as a method used in various spatially oriented disciplines.
Significance for the country
In 2002 Slovenia passed the Waters Act (ZV1), defining that the government shall determine risk areas for floods, erosion, landslides and slope slides, as well as avalanches. In 2007, the Rules on the Methodology to Define Flood Risk Areas and Erosion Areas Connected to Floods and Classification of Plots into Risk Classes were adopted, which prescribe the methodology for the definition of flood and erosion risk classes; however, it does not include debris flows. The definition of risks due to debris flow events in Slovenia has come to a standstill halfway through. The proposed research project upgrades the research achievements of the project group and directs them towards the use of modern remote sensing tools for debris flow modelling as part of debris flow hazard assessment. In doing so, the following questions are pursued: where can debris flows be triggered (place of origin), how large can they be (magnitude), what are their material properties (rheology), and where do they act (place of action)? When searching for the answers to the questions asked, one should distinguish between torrential and slope debris flows and deal with them separately. High-quality topographic data are an important part of this. The proposed research project will be directly useful for the development of a methodology for the determination of debris flow risk areas, i.e. a methodology that in Slovenia is still not developed even though it is defined in the Waters Act.
A debris flow susceptibility model in the scale of 1:250,000 was made for the area of Slovenia. The model is intended to a spatial prediction of the areas where debris flows may appear/be triggered and of the debris flow transport areas. It represents a general overview of risk areas in Slovenia. It also serves as the base for further detailed investigations and analyses. According to the model, very high susceptibility to debris flows exists at about 4% of the surface of Slovenia, while high susceptibility is at about 11% of its surface (mainly Alpine areas and mountainous NW and N parts of Slovenia). The proposed project will help to develop a debris flow hazard map of Slovenia.
When producing the hazard map of debris flows we can integrate new elements, such as automatic detection of torrential fans, laboratory analysis of the rheological properties of soils, and testing different 2D models of debris flows triggering and movement, as typical types of mass movement on the slopes. The proposed project is a decisive step in this direction. The methodological approach, methods, and quality of the expected results will set an example for other parts of the world.
Most important scientific results
Interim report,
final report
Most important socioeconomically and culturally relevant results
Interim report,
final report
