Development of methodology and methods for mitigating damages caused by landslides at basin scale (Bolaman micro basin, Ordu)

The aim of this study is to develop methodologies and methods to reduce damages caused by landslides at the basin scale. These developed methodologies were tested in the Bolaman Stream Micro Basin, which is situated in the south-east of Fatsa district of Ordu province in the Central Black Sea Region of Türkiye and covers an area of almost 1339 km2, and is highly active in terms of landslide development. As part of a doctoral thesis, the methodology and methods for reducing damages caused by landslides at the basin scale have been developed. Initially, the landslide inventory map of the basin was produced, and landslide susceptibility maps were generated using logistic regression and random forest methods, considering the development of landslides, the factors that cause them, and triggering mechanisms. In the stage of producing the landslide hazard map of the study region, the susceptibility map generated by the random forest method was utilized. In the hazard assessment, rainfall factors were used as a triggering factors, and the data was analyzed using Generalized Extreme Value distribution. Also, the areal susceptibility parameter used in the hazard analysis was calculated according to the Pearson 5 probability density function considering the size-frequency relationships of landslides. Then, elements at risk were identified by empirically calculating the relationships between landslide area-volume and volume-run out and by scoring their vulnerability levels according to expert opinion. The study area's risk maps were created using two distinct methods. The first approach produced 15 risk maps of varying sizes and years by multiplying hazard and vulnerability maps. The second method employed the Mamdani Fuzzy Logic approach to produce the regional risk map by incorporating landslide susceptibility, vulnerability, and run-out distance maps. Finally, practical, eco-friendly, and cost-effective remediation technics were proposed to the areas with high risk levels on basin basis by considering the risk maps produced.