Abstract The lignite workings in the former German Democratic Republic have left mang residual holes of sometimes colossal scale. The artificial or natural flooding of these 50- 70 in deep holes causes serious stability problems in sand slopes, and already fatalities have been reported as a result of the sudden initiation of flow slides. The paper describes the soll mechanics of the flow slides, which endanger the edge of the holes, and the measures taken to stabilise the slopes.