The Pearl River Delta was originally a shallow bay, which was formed by the subsidence of the site. Xijiang River, Beijiang River and Dongjiang River provide extremely rich materials for the estuary delta every year, and the long-term deposition has shaped the Pearl River Delta. Because it is not a typical plain flat delta, there are a lot of isolated hills scattered on the plain, and the sediment brought by rivers in the west and north is deposited along the edges of these islands. As the plains around the island hills gradually expand, they are slowly connected with each other. In other words, the development of the delta is not an overall promotion, but a mosaic development.
Pingsha area is located in the "Zhongshan thrust delta" and belongs to the downstream delta. It refers to the southern foot of Maji Mountain in Zhongshan County (Figure 1), which is located between Jiti Gate, Hutiaomen and Yamen. During the Ming and Qing Dynasties, it belonged to Xiangshan County (renamed Zhongshan County after 1925), and it lived in Huangliangdu, Chaoju Township. In the Ming Dynasty, the downstream delta developed to Koumen, and the area around Zhongshan County was developed. The scope of reclamation is concentrated in "the north of Zhongshan County and the south of Xinhui County". According to records, during this period, there were only three or five "vicious lakes" in Zhongshan County to build water conservancy projects.