The region of the middle and lower Yellow River valley is characterized by various geographic features, and has witnessed constant climatic and geomorphic change through time. These environmental conditions have in many ways affected economic adaptations and social organizations. Increasing temperature and humidity would have encouraged agricultural activities, mainly millet cultivation, spreading toward the north, and allowed a larger scale of rice cultivation in the Yellow River region. Decreasing rainfall and temperature, on the other hand, would have forced a return to millet, a southward retreat of the agricultural zone, and the development of pastoralism in the north. These environmental changes have had a major impact on the hydrology of river systems (Quine et al. 1999; Ren and Zhu 1994). In warm–moist climatic episodes the heavier vegetation cover would have stabilized the landscape, resulting in rivers with steady flow, a light sediment load, less alluvial build-up and soil formation. In colder–drier climatic episodes the reduction in vegetation cover would have led to more soil erosion, heavier sediment loads, and a flash flood regime in river systems. Human land use also had a major impact on the environment.