Impact of Artificial Floods on the Quantity and Grain Size of River‐Borne Sediment: A Case Study of a Dam Regulation Scheme in the Yellow River Catchment

Abstract

AbstractThe quantity and grain size of river‐borne sediment are critical to geomorphological evolution and ecosystem health of river deltas. Compared to quantitative aspects of fluvial systems, however, studies describing the physical properties of river sediment are still quite limited. This work examines how an unprecedented engineering effort (the Water‐Sediment Regulation Scheme, WSRS) within the lower Yellow River system has caused important changes in the volume and grain size patterns of transported sediment. After the implementation of the WSRS, artificial floods dominated the delivery of water and sediment to the delta region—the natural (seasonal) rhythm of the hydrological cycle has been replaced by impulsive delivery. Compared to natural floods, the duration of the artificial flood due to WSRS is substantially shortened, and timing has changed to early summer (June to July), which is two to three months ahead of the usual flood season. Now, as a result of WSRS, there are high sediment loads over a shorter than usual time frame. The Yellow River's sediment load rebounded and coarsened, because artificial floods have strongly scoured the river channel. These changes turned the Yellow River delta from a recession phase to one of progradation, and caused impulsive delivery and rapidly buried of terrestrial organic carbon and pollutants. For other rivers worldwide, the lower Yellow River system provides an illustrative example of how transporting coarse‐grained sediment, otherwise deposited on river bed, may be used to mitigate coastal land loss on intra‐decadal time scales, however with the potential for adverse ecological impacts.