Context:
Following the project to update the ‘’Plan for the Prevention of Natural Risks’’ in the communes of ‘’Magland’’ and ‘’Arâches’’ (French Alps), the ski resort of Flaine asked Engineerisk to present an in-depth counter-analysis of avalanches flows on a specific area where the proposed zoning appeared to be particularly pessimistic and penalizing for future projects.

Work provided by Engineerisk:

• - Historical study and analysis of each avalanche paths allowing to highlight a consequent evolution of the topography (linked to the creation of several ski slopes) and its major influence on the new flows conditions compared with the known/current ones.
• - Errors detection in the transcrip of the avalanche footprint indicated on the avalanche map by comparison with the different historical testimonies and pictures
• - Numerical modeling according to the different return periods (from 30 to 300 years) to prove that avalanche flows are now widely deviated by earthworks
• - Results interpretation in a ‘’Plan for the Prevention of Natural Risks’’ context compared with the initial zoning and proposing of new and better justified flows limits that reveals areas of development that had been unfairly classified as ‘’high risk’’ area
• - In parallel, development of a whole methodology to take into account the influence of existing buildings on downstream risk level