The coastlines on the west and south coasts of the Bohai Sea have changed over time due to the movement of river deltas. These deltas, like the Huanghe River Delta, have caused the coastline to shift and stabilize at different points in history. The Huanghe River, in particular, has played a significant role in shaping the local coastline due to its large sediment discharge. The evolution of these deltas has led to the progradation, retreat, and stabilization of the coastlines in the region since 7000 years ago.