Tidal level response to sea-level rise in the yangtze estuary |
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| Authors: | Zheng Gong Chang-kuan Zhang Li-ming Wan Jun-cheng Zuo |
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| Institution: | a a State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering,Hohai University,Nanjing 210098,China b Yangtze River Estuary Survey Bureau of Hydrology and Water Resource,Ministry of Water Resources,Shanghai 200136,China |
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| Abstract: | The rise of tidal level in tidal reaches induced by sea-level rise has a large impact on flood control and water supply for
the regions around the estuary. This paper focuses on the variations of tidal level response along the tidal reaches in the
Yangtze Estuary, as well as the impacts of upstream discharge on tidal level response, due to the sea-level rise of the East
China Sea. Based on the Topex/Poseidon altimeter data obtained during the period 1993∼2005, a stochastic dynamic analysis
was performed and a forecast model was run to predict the sea-level rise of the East China Sea. Two-dimensional hydrodynamic
numerical models downscaling from the East China Sea to estuarine areas were implemented to analyze the rise of tidal level
along the tidal reaches. In response to the sea-level rise, the tidal wave characteristics change slightly in nearshore areas
outside the estuaries, involving the tidal range and the duration of flood and ebb tide. The results show that the rise of
tidal level in the tidal reaches due to the sea-level rise has upstream decreasing trends. The step between the stations of
Zhangjiagang and Shiyiwei divides the tidal reaches into two parts, in which the tidal level response declines slightly. The
rise of tidal level is 1∼2.5 mm/a in the upper part, and 4∼6 mm/a in the lower part. The stations of Jiangyin and Yanglin,
as an example of the upper part and the lower part respectively, are extracted to analyze the impacts of upstream discharge
on tidal level response to the sea-level rise. The relation between the rise of tidal level and the upstream discharge can
be fitted well with a quadratic function in the upper part. However, the relation is too complicated to be fitted in the lower
part because of the tide dominance. For comparison purposes, hourly tidal level observations at the stations of Xuliujing
and Yanglin during the period 1993∼2009 are adopted. In order to uniform the influence of upstream discharge on tidal level
for a certain day each year, the hourly tidal level observations are corrected by the correlation between the increment of
tidal level and the increment of daily mean upstream discharge. The rise of annual mean tidal level is evaluated. The resulting
rise of tidal level at the stations of Xuliujing and Yanglin is 3.0 mm/a and 6.6 mm/a respectively, close to the rise of 5
mm/a according to the proposed relation between the rise of tidal level and the upstream discharge. |
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| Keywords: | Yangtze Estuary sea-level rise stochastic dynamic analysis and forecast model tidal reaches discharge increment |
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