New evidence of Yangtze delta recession after closing of the Three Gorges Dam

X X Luo,P Li,R S Wang,C Y Zhang,S L Yang

doi:10.1038/srep41735

Abstract

Many deltas are likely undergoing net erosion because of rapid decreases in riverine sediment supply and rising global sea levels. However, detecting erosion in subaqueous deltas is usually difficult because of the lack of bathymetric data. In this study, by comparing bathymetric data between 1981 and 2012 and surficial sediment grain sizes from the Yangtze subaqueous delta front over the last three decades, we found severe erosion and significant sediment coarsening in recent years since the construction of Three Gorges Dam (TGD), the largest dam in the world. We attributed these morphological and sedimentary variations mainly to the human-induced drastic decline of river sediment discharge. Combined with previous studies based on bathymetric data from different areas of the same delta, we theorize that the Yangtze subaqueous delta is experiencing overall (net) erosion, although local accumulation was also noted. We expect that the Yangtze sediment discharge will further decrease in the near future because of construction of new dams and delta recession will continue to occur.

Highlights

Since the mid-Holocene, delta progradation has played an important role in the history of human society
Bathymetric data are usually lacking for the outer margin of the Yangtze subaqueous delta[9,20,21,22]
Our objectives were to determine: 1) whether net erosion has occurred in the new study area and 2) whether the border between the subaqueous delta mud and the Pleistocene relic sand has retreated landward in recent years

Summary

Introduction

Since the mid-Holocene, delta progradation has played an important role in the history of human society. Yang et al.[9] found that the progradation rate in the Yangtze subaqueous delta decreased with riverine sediment discharge during the edu.cn) www.nature.com/scientificreports/. To ascertain the trends of progradation or recession in the Yangtze subaqueous delta front (Fig. 1), in this study, we determined recent accretion/erosion trends using bathymetric data collected in 1981, 1997 and 2012 from a previously unstudied area in the Yangtze subaqueous delta front and examined the temporal change in the grain size of surficial sediments in the transitional zone between the subaqueous delta and the Pleistocene sand seabed over the last 30 years. Our objectives were to determine: 1) whether net erosion has occurred in the new study area and 2) whether the border between the subaqueous delta mud and the Pleistocene relic sand has retreated landward in recent years

Objectives

Methods

Results

Conclusion