Contribution of extreme rainfall-induced hyper-concentrated flows to downstream channel siltation in the Yellow River

It is well known that hyper-concentrated flows (HCF) in the middle reach of the Yellow River can cause a severe channel siltation in the Lower Yellow River to develop a world-famous “Aboveground River”. However, there has long been debate about the relative importance of HCFs from the Loess regions versus from the desert regions in the middle basin in causing such a severe channel siltation. In this study, we used 188 HCFs’ events in the lower reach in response to extreme rainfall events (daily precipitation records in 107 stations) in the middle basin from 1965 to 1985, and showed that HCFs from the desert regions (Type-N) contributed to about 3.1×10⁹ t of sediment deposition in the lower river channel, or about 58.1% of the total sediment deposition, and that only about 16.8% from HCFs from the Loess regions (Type-S). Our results also indicated that the HCF with the SSC value more than 92 kg/m³ furnished about 83% of the total sediment deposition in the lower reach of the Yellow River, which primarily originated from the desert regions, rather than the loess areas, as has been traditionally anticipated before. Because the desert region can be a major source of coarse sediment contributor to the channel siltation of the lower Yellow River, its control should be a priority in protecting the Yellow River and ensuring its stability.