Aggradations are very important for the developing and dying-out of lakes. The aggradations of floods and debris flows are common environmental problems in fault lakes in southwestern China. Investigating the background of the basin of Goose Foot River, the effect of human activities on Lake Qionghai, Sichuan Province, China, and the underwater topography maps of 1988 and 2003 were analyzed. In the past 30 years, turbidity currents were formed by debris flows and floods of Goose Foot River and took huge sediment into Lake Qionghai. The sediment not only pushed the coastline of Lake Qionghai at Goose Foot River fan into lake, but also deposited in the lake to the opposite bank. Debris flows took much more sediment into Lake Qionghai than the soil erosion did in the same basin. There is an underwater levee on the underwater fan. The underwater levee is 2 km in length, 200 m (at south coast) to 600 m (at north coast) in width and the average 2 m in height. The maximum height of sediment deposition at underwater levee is 8. 29 m, or 0. 55 m for every year. There is a channel on the slope of the underwater fan of Goose Foot River mouth eroded by turbidity currents. The main source of sediment is the sediment token by the debris flows in 1996, 1997 and 1998. It should be paid more attention on the environment issues,such as basic characteristics, underwater topography of Lake Qionghai and the effect of Goose Foot River debris flows on Lake Qionghai.