Major disasters of geological origin regularly occur in the Lake Kivu area (Burundi, East DR Congo, Rwanda). Within the framework of GeoRisCA project focusing on multi-risk assessment, the research was initiated in partnership with local institutions in charge of disaster management and risk prevention, which are highly concerned by the susceptibility of population and assets to suffer from damages. Following literature review and in-depth discussions with local partners highlighting some divergence regarding vulnerability definition, a primarily objective is to contextualize this concept and develop a regional definition. The Delphi method is used for this approach: it is an interactive communication technique composed by two rounds of targeted questions submitted to a panel of experts (local, international). The experts inputs lead us to a specific definition on which the vulnerability assessment is constructed. Indeed, proxy variables are then identified in order to measure exposure to perturbations and adaptive capacity of the systems through an household field survey. Our partnership with local institutions and scientists has been at the roots of the project. It has highlighted the need and the will to conduct the vulnerability assessment together, in order to develop the most appropriate tools for risk prevention support.