GIS-Based Flow-R Model for Debris Flow Susceptibility Mapping: A Case Study from Muong Bo, Lao Cai, Vietnam

Abstract

Landslides and debris flows are frequent hazards in Vietnam’s mountainous regions, causing severe socio-economic damage that has intensified under climate change and extreme rainfall conditions.  This study applies the open-source GIS-based Flow-R model to assess debris-flow susceptibility and runout characteristics in Muong Bo Commune, Lao Cai Province, northwestern Vietnam (specifically focusing on the highly vulnerable area around the Nam Cang stream). The methodology involved developing a geospatial database and simulating potential initiation and propagation zones. A major debris-flow event that occurred on 12 September 2023 was used for model calibration and validation. Field validation confirmed the model’s robust capability to simulate flow runout distances based on observed data. Seventy percent of the mapped debris-flow initiation points were used for calibration, and 30% for validation[/RED], and model performance was evaluated using the Area Under the ROC Curve (AUC). The Flow-R model achieved an AUC value of 0.868, indicating good predictive capability[/RED], while 48.5% of observed debris-flow initiation points were correctly predicted. Results demonstrate that Flow-R effectively delineates high-susceptibility source zones and plausible debris-flow runout paths, particularly for medium- to large-scale events. The novelty of this study lies in the first integrated application of Flow-R, combined with systematic field validation in northwestern Vietnam, and the coupling of detailed geological–geomorphological characterization with susceptibility and runout modeling, providing a transferable framework for debris-flow assessment in data-scarce mountainous regions.