The Hull-Gatineau region is largely located on very sensitive 'clays'. A regional mapping of landslide risk areas is hence necessary for the planning of regional development. Many methods have been proposed but are not adequate because they are either too tepid in terms of security (because they do not rake into account sufficient security margins) or too costly in terms of terrain surveys to be applied at the regional scale. The method proposed herein is applicable without having to rely on terrain surveys since solely existing multisource data processed within a geographical information system (GIS) are used. Five main factors, which can be combined for creating situations of landslide risks, were retained and weighted according to their importance. These factors are sensitive to the surficial deposits ('clay') the surface slope (including slope breaks), the slope of the bedrock, the hydrography, and the presence of urban areas. Areas of ancient landslides are also included. The superimposition of these factors permits the addition of the weights of each of the factors that overlap each other, delimiting zones of high, moderate, and low risk. The results show that close to 48% of the Hull-Gatineau region presents risks of landslides, 78% of which present high risk, 19% moderate risk, and 16% low risk. In spite of the use of security margins, in all these areas, precautions must be taken in relation to land development, and local geotechnical studies must be carried out on a case-by-case basis.
