How to explain avalanche dynamics to children and... their parents

International audienceSnow avalanches threaten mountain communities worldwide: avalanches affect not only snow sport tourists but people can also be caught in inhabited areas and on roads, as reminded by the extraordinary winter of 1998/99 in the Alps. It means that we have to increase local population awareness of avalanche hazard, risk assessment and mitigation. In this case, it is interesting to focus not only on avalanche release, as it is generally done for snow sport tourists but also on avalanche dynamics and interaction with structures. In the laboratory, powder avalanches are often modeled by density currents (salt water in pure water) and dense avalanches are modeled by granular avalanches. Similitude requirements are fulfilled to estimate real pressure, velocity, run-out distance from the small-scale model. But even if small-scale models are used in the laboratory, their dimensions are too large to be removed from the lab to exhibition halls, schools or meeting rooms. With water, salt, grains, aquarium and wood panels it is still possible to reproduce laboratory experiments physically based at a smaller scale to explain qualitatively the dynamics of powder and dense avalanches and to show the effectiveness or ineffectiveness of protective measures such as dams and retarding mounds. Examples of such experiments and devices, which can be reproduced everywhere, will be described in this paper, offering the children a unique opportunity to release the avalanche by their own and to play with grains and water. Such an initiative is thus always a success