How did the geography of China allow for early civilization to develop there?

Like in Mesopotamia, between the Tigris and Euphrates, and the Nile Valley, civilization in China developed around rivers. Ancient China grew up in the Yellow River Valley, which lay between the Yangtze and Yellow Rivers. This was an area of rich fertile soil with excellent agricultural prospects. Unlike in Mesopotamia and Egypt, the land in the Yellow River Valley actually stayed flooded for a period during the year, allowing the Chinese to grow rice in addition to the grains more common in the fertile crescent. These rice crops were a crucial staple and led to population growth and density.
The first Chinese empire was united under the legendary Huangdi, the so-called "Yellow Emperor", around 2700 BC. His wife, Leizu, was said to be the first person to discover the process of making and weaving silk, a commodity long associated with China and a key to its development.
Life in the Yellow River Valley could be difficult, as the flooding that was crucial for rice growing could also wash away homes and villages. The typical farmer in China lived a hard life, but nonetheless the conditions in that area led to the development of one of the world's great civilizations.