Spatial and Temporal Variation in Erosion and Accumulation of the Subaqueous Yellow River Delta (1976-2004)

Abstract

Yellow River Delta (YRD), one of the most heavily human-influenced delta systems, had undergone dramatic changes since 1976. To determine the erosion and accretion pattern of the subaqueous YRD, bathometry data as well as the sediment discharge from the Lijin station over the period of 1976 to 2004 were analyzed. The erosion and accretion pattern of the subaqueous YRD was delineated by 1) the northern abandoned delta lobe, consisted of the heavily eroded Diaokou (DK) and Shenxiangou (SXG) lobes; 2) the active delta lobe, comprised of Qingshuigou (QSG) and Q8 lobes and featuring fast progradation; 3) the Laizhou Bay (LZB) with slight accumulation. Three stages were summarized based on the evolution of the northern abandoned delta lobe. During 1976-1980, the northern abandoned delta was severely eroded due to the cutoff of sediment supply. As the subaqueous slope became gentler during 1980-1996, the deeper part of the subaqueous delta turned into slight accretion state while the shallow part continued to be eroded. However, the erosion rate of the northern delta slowed down to a relatively balanced state during 1996-2004. Meanwhile, the development of the active delta lobe was a product of riverine sediment supply, channel geometry and estuarine hydrodynamics. Multi-depocenter was formed along the coastal area of the active subaqueous delta during 1976-1980, when multiple channels were active for sediment transportation. As the main river channel developed, the depocenter progradated eastward with an exceptional high accumulation rate during 1980-1985. The progradation direction turned southeastward with a lower accumulation rate during 1985-1996. Then, the depocenter shifted to the newly formed Q8 river mouth after a channel diversion in 1996, leaving the QSG river mouth in severe erosion. The channel diversion also caused erosion at the offshore area in LZB, where slight accumulation dominated before 1996. The erosion and accumulation pattern of the subaqueous YRD showed significant spatial and temporal variability during 1976-2004. A comprehensive understanding of their driven mechanisms would be critical for the prediction of the evolution of the YRD in the context of global change.