 Two hazards are uniquely identified with the dam . One is that sedimentation projections are not agreed upon , and the other is that the dam sits on a seismic fault . At current levels , 80 % of the land in the area is experiencing erosion , depositing about 40 million tons of sediment into the Yangtze annually . Because the flow is slower above the dam , much of this sediment will now settle there instead of flowing downstream , and there will be less sediment downstream . 
