During the summer field season of the 65 ^th Russian Antarctic Expedition a research aimed at studying the structure of the snowice dams of the Lakes Progress and Discussion (Larsemann Hills, East Antarctica), which are characterized with annual outburst floods, was carried out. Survey was performed using groundpenetrating radar sounding complemented with noncore drilling and analysis of the aerial photo data acquired with unmanned aerial vehicle during the last field seasons. The results show that location of the waterways, which occur during the outbursts of the both lakes, does not change significantly year in year out and fits a linear depression in basement topography under the dam and a following flexure of the ice layer. During the winter period, the opened channels are being filled with snow, and thereby a natural softened zone is being formed. Further outburst flood propagates mainly within this zone. Monitoring survey of the snowice dam of the Progress Lake during the summer period showed that destruction of the dam does not happen rapidly when the outburst takes place, but begins a few weeks before it with gradual filtration within the snow layer.