Alpine glacier retreat due to global warming generates major landscape changes in high mountain environments. New lakes can potentially form in Glaciers Bed Overdeepenings (GBOs). Those new water bodies, sometimes located near potentially instable slopes or behind unstable moraine dams, can increase outburst flood hazards, generating risks for valley floors. Such GLOF events (Glacial Lake Outbrust Floods) can result from displacement waves triggered by rock fall into lakes and/or sudden dam breaching. Those events can travel far down to low altitude areas and turning into high magnitude debris flows. Beyond the threats, those lakes can also represent opportunities for tourism, hydropower production or fresh water supply.