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The estuary delta is an area where human economic activities are active and natural ecological environment is fragile. With global change and the intensification of human activities, coastal and seabed erosion around the world is becoming more and more serious. In this paper, we used the Delft 3D numerical simulation to compare the hydrodynamic effects of sediment transport paths in the Yellow River delta (river-controlled type), Yangtze River delta (tidal type) and Mekong River delta (tidal wave type) in the East Asian monsoon area, and analyzed the causes of accumulation erosion landform distribution in three different types of subaqueous deltas. This study finds the Yellow River Delta has experienced varying degrees of erosion at the estuary, but its subaqueous delta is still dominated by deposition; the Yangtze River Delta has ensured the stability of its shoreline under the influence of artificial shoreline reinforcement, but the subaqueous delta (water depth: 0–15 m) is in a state of erosion all year round; and in the Mekong River Delta the erosion occurs in both its shoreline and subaqueous delta. Additionally, only by analyzing the erosion and deposition within the transport range of resuspended sediment, the changes in the properties of the entire subaqueous delta could be recognized. The research results can not only be helpful to analyze whether the change of river sediment will lead to the change of delta type under human influence, but also provide more powerful scientific support for the protection of delta ecological environment, geological environment safety and geological disaster prevention. [ABSTRACT FROM AUTHOR]

As the population and economy boom, more and more dams are being built in the Mekong River basin. Previous studies have revealed that Manwan Dam had little influence on the runoff-SSC (suspended sediment concentration) relationship, and the sediment load was relatively stable over the past 40 years. However, little is known at present on the relationship among monsoons, El Niño Southern Oscillation (ENSO), precipitation, runoff, and the impact of dams on the delta dynamics. A comprehensive hydropower GIS database covering the entire Mekong basin is presented in this study. Mann-Kendall trend analysis showed no significant change in precipitation and runoff over the past 50 years. Spectral analysis showed that the runoffs of the middle to lower reach of Mekong River are correlated with the Indian Monsoon, where as the East Asian Monsoon's influence is mainly on the lower reach. With another 200 new dams to be added to the basin in the next couple of decades, changes are expected in both hydrological regime and delta dynamics. On one hand, the runoff showed a closer connection with the regional precipitation and ENSO in the post-dam period (1993-2005) than in the pre-dam period (1950-1993). Such a relationship is expected to be even closer when more dams are completed. On the other hand, both daily maximum and minimum water levels on the delta plain have shown an abrupt drop since the end of 1994. This reduced water-level gradient between the river and sea inevitably weakens the sediment discharge to the coast, which might intensify the ongoing coastal erosion on the eastern part of the delta plain. Copyright © 2010 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

High-resolution seismic profiles from the North Yellow Sea reveal a 20–40-m-thick subaqueous clinoform delta that wraps around the eastern end of the Shandong Peninsula, extending into the South Yellow Sea. This complex sigmoidal-oblique clinoform, containing an estimated 400 km3 of sediment, overlies prominent relict transgressive surfaces. The nearshore topset of the clinoform, <30-m water depth, has a ≪1:1000 gradient, with high sedimentation rates (210Pb) ∼6–12 mm/year. Foreset beds (30–50 m) dip seaward at a steeper gradient (2:1000) and have sedimentation rates ∼3 mm/year. Bottomset strata, in water depths >50 m, contain less than 1 m of Holocene sediment, with low sedimentation rates, <1 mm/year. In contrast to other clinoforms, the Shandong clinoform appears to be a compound subaqueous deltaic system, with what we interpret to be proximal and distal phases of clinoform development. The underlying proximal sequence formed proximally between ∼11 and 9.2 ka in response to a temporary pause in the rapid postglacial sea-level rise after the meltwater pulse 1B (MWP-1B) and increased discharge from the Yellow River to the North Yellow Sea due to intensification of the summer monsoon. A flooding surface appears to separate the proximal and distal phases, corresponding to the next rapid sea-level rise 9.5–9.2 ka BP (MWP-1C). Since 9.2 ka BP, an overlying distal sedimentary sequence has accumulated, reflecting the back-stepping and shifting river mouth westward to the Gulf of Bohai. Some inputs from coastal erosion and nearby small streams may be locally important. Along-shore transport, cross-shelf advection, and upwelling in the North Yellow Sea have reworked post-LGM sediment and have helped maintain the morphology of the clinoform in the Shandong mud wedge. [Copyright &y& Elsevier]