Abstract. To prepare for the potential impact of climate change and related hazards, many countries have implemented integrated river basin management programs. This has led to significant challenges for local authorities to improve their understanding of how the vulnerability factors are linked to losses in climatic disaster. This article aims to examine whether highly vulnerable areas experience significantly more damage at the river basin levels due to weather extreme events, and investigates the vulnerability and hazard impact factors determine losses in a disaster. Using three river basins in southern Taiwan that were seriously affected by Typhoon Morakot in 2009 as case studies, a novel methodology is proposed that combines a geographical information system (GIS) and a multicriteria decision analysis (MCDA) to evaluate and map composite vulnerability to climatic hazards across river basins. The linkages between the hazard impacts, vulnerability factors and disaster losses are then tested using a disaster damage model (DDM). The results of the vulnerability assessments demonstrate that almost all of the most vulnerable areas are situated in the regions of the middle, and upper reaches and some coastlines of the river basins. The losses and casualties due to typhoon are significantly affected by local vulnerability contexts and hazard impact factors. Finally, policy implications to minimize vulnerability and risk and for integrated river basin governance are suggested.