Accr etion/erosion of the Subaqueous Delta at the Yangtze Estuary in Recent 10 Year s
近10 年来长江口水下三角洲的冲淤变化 ———兼论三峡工程蓄水的影响

Based on the sediment supply from the Yangtze River and the analysis of the accretion/erosion of the subaqueous delta at the Yangtze Estuary in recent ten years, the accretion/erosion response of the subaqueous delta to the sharp decline of the sediment supply from the Yangtze River to the sea and the impoundment of the Three Gorges Reservoir was preliminarily discussed. The results show that (1) because of the impoundment of the Three Gorges Reservoir, the sediment supply from the Yangtze River to the sea decreased at an order of magnitude 1×108 t/a; (2) the proportion of accretion area to the total area is 75.5%, 30.5% and 14% in the three periods. The accretion/erosion rates of the three periods (1995-2000, 2000-2004, 2004-2005) are 6.4 cm/a, -3.8 cm/a and -21 cm/a respectively in the study area; and (3) the accretion/erosion response to the decrease of the sediment discharge from the Yangtze River in the study area has significant spacial different results in the influence of topography, the change of hydrodynamics and the engineering projects. The conclusions are that the impoundment of the Three Gorges Reservoir accelerated the decrease of the sediment from the Yangtze River which is the main cause for the change from accretion to erosion of the subaqueous delta. Attentions should be paid to the future evolution processes of the Yangtze River Delta in view of the further decrease of sediment supply of the Yangtze River, which is due to the more dam construction and land conservation in the future, and the consequent further erosion in the subaqueous delta.