Multi-Hazard Risk Mapping in Mountainous Microcatchments: Integrated Avalanche–Flood Simulations with RAMMS and HEC-RAS

Climate change is intensifying the frequency and severity of extreme events such as avalanches and floods, particularly in mountainous regions where these hazards may develop concurrently and interactively. Despite growing recognition of the need for integrated risk management, most previous studies have assessed avalanche and flood hazards in isolation. This study presents a microcatchment-scale, physically based multi-hazard modeling framework that combines the RAMMS and HEC-RAS models to assess compound avalanche–flood risks in the Lediz Microcatchment (Bingöl Province, Türkiye), a representative high-risk mountainous basin. Avalanche simulations were performed using RAMMS with validated release areas and flow dynamics, while flood hazards were modeled using 2D HEC-RAS simulations calibrated against historical events and stakeholder observations. Results revealed substantial spatial overlap between high to very high avalanche risk zones and extreme flood hazard areas, particularly affecting settlements such as Dereköy, Şehittepe, Şin, Balgöze, Işıklı, and Palacık. Zones exceeding 15 m/s in avalanche velocity, 100 kPa in dynamic pressure, and HR > 2.5 in flood hazard rating indicate severe structural and socio-economic vulnerability. The findings underscore the critical need to integrate multi-hazard analysis into spatial planning and disaster risk reduction policies, with a particular focus on vulnerable rural landscapes. This study provides a scalable and adaptable modeling framework for identifying compound hazard hotspots, offering novel insights for risk-informed land-use planning and resilience-based disaster management in climate-sensitive mountainous environments.