Abstract
The world’s largest hydropower dam, the Three Gorges Dam (TGD), spans the upper Yangtze River in China, creating a 660-km long and 1.1-km wide reservoir upstream. Several recent studies reported a considerable decline in sediment load of the Lowermost Yangtze River (LmYR) and a rapid erosion in the subaqueous delta of the river mouth after the closure of the TGD in 2003. However, it is unknown if the TGD construction has also affected river channel and bed formation of the LmYR. In this study, we compared bathymetric data of the last 565 kilometers of the Yangtze River’s channel between 1998 and 2013. We found severe channel erosion following the TGD closure, with local riverbed erosion up to 10 m deep. The total volume of net erosion from the 565-km channel amounted to 1.85 billion m3, an equivalent of 2.59 billion metric tons of sediment, assuming a bulk density of 1.4 t/m3 for the riverbed material. The largest erosion occurred in a 100-km reach close to the Yangtze River mouth, contributing up to 73% of the total net eroded channel volume.
Highlights
Riverine sediment reduction due to human activities is a phenomenon observed in many river systems around the world in the past several decades[1,2,3,4]
2013, we found that on average, the 565-km Lowermost Yangtze River has narrowed by 370 m in the past 15 years
Before the construction of the Three Gorges Dam (TGD), channel bed erosion downstream of it was predicted extending to the river mouth (i.e., 1600km long channel)
Summary
Riverine sediment reduction due to human activities is a phenomenon observed in many river systems around the world in the past several decades[1,2,3,4]. A recent study showed that the new long-term hydro-morphological equilibrium may have been established in the middle and lower Yangtze[21], it is largely unknown how the sediment reduction may have affected channel morphology and sediment transport throughout the Lowermost Yangtze River, which flows through China’s most densely populated and most industrialized region before entering the East China Sea. The Lowermost Yangtze River (LmYR), starting at Datong (river kilometer, or RK 565) and ending at the river mouth Wusongkou (RK 0), is a tide-affected river reach. It is important to understand how sediment decline may have influenced the entire channel morphology of the tide-affected river reach from the river’s mouth to Datong Such knowledge is crucial for predicting long-term stability of the large alluvial river and its deltaic and nearshore continental shelf development. This region is one of the most densely populated and industrialized areas in China, contributing 24% of China’s national GDP
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
