Sediment budget of the Yellow River delta during 1959–2012, estimated from morphological changes and accumulation rates

Abstract

The Yellow River (Huanghe) is a major sediment source of sediment to the Bohai Sea and Yellow Sea, resulting in the formation of a large and dynamic delta complex. However, the river sediment discharge reaching the delta has decreased dramatically since the middle 1960s. This study examines the sediment accumulation and morphological changes of the delta complex during 1959–2012 using a repeated bathymetry dataset, high-resolution seismic profiles, and sediment cores obtained in 2012 and 2013. Sediment accumulation rates were determined using the downcore concentrations of 137Cs and 210Pb. The average accumulation rates calculated for the delta complex range from 6.9–24 cm y−1 on the delta front slope, 1–2 cm y−1 at the toe of the slope, and < 1 cm y−1 in the northeastern shelf area. Morphological changes and sediment accumulation rates show that 1) the Yellow River delta has entered a destruction phase after 1996, 2) the amount of erosion of the whole delta reaches 210 MT y−1 of sediment, which is at least required to maintain the whole delta morphology, 3) three-quarters (487 MT y−1) of the Yellow River-derived sediment was deposited in the subaerial and subaqueous delta during 1959–2012, and 4) Whereas, one-quarter (144 MT y−1) was transported to the Bohai Sea, and as much as one fifth (117 MT y−1) was transported further offshore to the Yellow Sea, passing through the Bohai Sea during this period. The source of these sediments is a combination of the Yellow River sediment discharge and the erosion of the previous Yellow River delta lobes. Despite the sharp decline in the Yellow River sediment discharge over the past five decades, the offshore dispersal of the river discharge and eroded sediment to the Yellow Sea was more than 100 MT y−1 on average. Results of this study show that the erosion of the abandoned delta lobes can sustain the supply of sediment to remote offshore depocenters even after decades of declining river sediment discharge.