The progradation and retrogradation of two newborn Huanghe (Yellow River) Delta lobes and its influencing factors

In this paper, 342 Landsat satellite images were used to study the evolution of the Qingshuigou and Qing8 Lobes during 1976-2016. Sea-level correction and statistical analysis were used to eliminate the effect of sea-level fluctuations on the shoreline positions. The results revealed that the evolution of the two newborn Huanghe Delta lobes was mainly influenced by the river sediment discharges, river channel changes, course shifts, floods, droughts, and marine hydrodynamic forces. During 1976-2016, the total land gain of the two lobes was 377 km(2) according to mean-tide line, and the average epeirogenetic efficiency of river sediment discharge was 0.020 m(2)/ton, which was greatly less than that when the channels were natural. The artificial stabilization of the deltaic channels had negative impact on the land gain. Assuming no artificial adjustment to the deltaic channels, the total land gain would increase 435 km(2). The land gain of the two lobes was a function of the cumulative sediment discharges, shoreline lengths and Course Shift Bonuses under the circumstance of historical river channel changes. The critical sediment discharge maintaining the area balance of the two lobes was a function of historical shoreline lengths, which increased linearly from 61 M ton in 1976 to an average of 163 M ton during 1996-2016. In the future, there are two ways to increase the land gain under the less Huanghe sediment discharge: reducing artificial disturbance of deltaic channels and letting the river enter the sea through the southwest coast of Qingshuigou Lobe.