At Yinchuan plain, when they looked down from the sky, the form of the Yellow River resembled a Chinese word. The water washed sediments accumulated at the river's bottom to the shore and formed a rich plain.
The Ocean Demons frequently encroached on Chang River and Zhu River because these rivers were situated along the coast. They found it harder to invade the Yellow River. One of the reasons was that Zhang Xiaohou had destroyed the massive underground river tunnel of Bo City. Another reason was that a large amount of sediments and impurities accumulating in the Yellow River had severely hindered the Ocean Demons from marching to it.
The Yellow River water flowed rapidly. It was difficult to control its speed. It often led to disaster. The turbulent flow of water made the low-level Ocean Demons difficult to swim.