We investigate crevasse initiation by analyzing the artificial drainage of a water-filled cavity at Tête Rousse Glacier (Mont Blanc, France). Using a numerical model, we compute stress fields in response to water level variations in the cavity and compare them to observed crevasse patterns. Results show that a non-linear viscous rheology and a maximum principal stress criterion (with a stress threshold of 100–130 kPa) best predict crevasse occurrence.