Recent changes in the erosion–accretion patterns of the active Huanghe (Yellow River) delta lobe caused by human activities

To evaluate changes in the erosion–accretion patterns of the active Huanghe (Yellow River) delta lobe since 1996, shorelines extracted from remote sensing images, bathymetric data off the river mouth together with river sediment discharge to the sea were analyzed. The results indicate that the erosion–accretion patterns in the subaerial and subaqueous areas of the active delta lobe have changed significantly since 2002. The extent of subaerial portions of the active Huanghe delta lobe and the Q8 subdelta lobe shifted from a decreasing trend to an increasing trend in 2002. The slope of the subaqueous delta off the river mouth also increased markedly after 2002, corresponding to the changes in the erosion–accretion patterns of the subaerial area. An increase in the sediment particle size due to the Water-Sediment Regulation Scheme (WSRS) resulted in more sediment being deposited in the nearshore area, which caused most of the changes in the erosion–accretion patterns of the active delta lobe. Moreover, two groins constructed after 2005 trapped a portion of the Huanghe sediment in the nearshore area, which may partially contribute to the accretion of the active Huanghe delta lobe. Based on the subaerial extent of the active Huanghe delta lobe, sediment discharge and time, a binary regression model was developed to calculate the critical sediment discharge for maintaining the equilibrium of the active delta lobe under the impact of intense human activity. This value is approximately 50 Mt/yr, approximately one third of the previous estimate that was based on the data before the WSRS and construction of the groins near the river mouth.