The study used satellite images and mapping technology to track changes in siltation and erosion in the Yellow River Delta from 1976 to 1998. They found that the area of the delta increased the most between 1976 and 1981, but decreased significantly from 1989 to 1992. The mouth of the Yellow River filled with silt, while the north and east coasts eroded. Overall, the rate of siltation is slowing down over time.