With the aid of the Canadian Space Agency and the Canadian geospatial industry (Ærde, HCL, Strata 360), CARTEL is working in close collaboration with the Mekong River Commission (MRC) and the Cambodian Red Cross to establish a Flood Emergency Response System in Cambodia. Earth Observation (EO) and Geomatics generally insists on spatial distribution and the accessibility of the health centres, food warehouses, flood safe areas as well as the spatial distribution of the disease according to the changing factors of the physical environment and planning and the management of public health in order to improve quality of the decision-making process. The strategy is centered on the analysis of the needs for the managers of the Mekong River Commission and of the Cambodian Red Cross. It also focuses on the questions and data relating to the follow-up in space and time of the flood events and its effects on the local communities. This study takes into account the three dimensions of security: vulnerability, preparedness, response. The methodology includes the following stages: (1) analysis of the needs of the Mekong River Basin managers such as health, transportation, safe areas, infrastructures at risk, food security; (2) design of the diagram of the emergency response system including the identification and the conception of georeference data and spatial analysis functionalities; (3) design and development of a database and metadata; (4) development of vulnerability maps by using multi-date EO imagery (RADARSAT-1, aerial photography, high resolution optical imagery) combined with the historical and topographic data.