Yu's group had its roots in the Luo River valley. It expanded outward from there to the Shandong peninsular in the east and the Fen River valley in the west. In this article, we argue that the reason the Xia empire was able to build its power base in the Zhengzhou area (and areas to its north) is because the Yellow River was diverted to flow along the Yu Huang Gu Dao, opening up the delta for habitation. The fact that the Xia empire moved its last capital back to the Luo River valley indicated that the Yellow River's floods again threatened the North China plain.