Morphodynamic Response of Yangtze River Estuary to Sea Level Rise and Human Interferences.
Mitteilungen / Institut für Wasserbau und Wasserwirtschaft, 148
Insititut für Waserbau und Wasserwirtschaft
PhD Dissertation -
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|Title:||Morphodynamic Response of Yangtze River Estuary to Sea Level Rise and Human Interferences|
Estuarine morphodynamics describe the development of estuarine bed over time. The changed morphodynamics have a direct or indirect influence on the wetland resources, water quality and ecological system, biodiversity, channel regulation and coastal protection. The morphology of Yangtze Estuary changed a lot in the past 2000 years, especially in recent 150 years. It is supposed to adjust accordingly with the further changes of water and sediment discharge due to human interferences and the possible sea level rises. To estimate and evaluate the impact on morphodynamics of human interference, like dredging of access channels to ports, and of long-term processes, like sea level rise or a changing discharge regime, is of great importance and much necessity. Therefore, the research goal of this study is to evaluate the morphological response to the variations of hydrodynamic conditions at Yangtze Estuary, based on various unknown scenarios and known project plans. Due to the different spatial and temporal scales involved in the morphological process, both field data analysis and numerical simulations are carried out in order to gain more insight in the historical and future morphological evolution of this area.
Regular and short-term field measurements at Yangtze River as well as the monthly data at Datong station in the past 50 years are analyzed. Results show that the water and sediment discharges of Yangtze River have been changed, and the morphological changes response to the correlation of water and sediment discharges. The major pattern is erosion, and the erosion rate increased 10 times in the past two decades for N-RER reach of Yangtze River. A linear correlation between the deposition volumes with the ratio of water to sediment discharges was found.
The morphodynamic numerical model TIMOR is set up at the Yangtze Estuary. The sensitive parameters are calibrated with measured water level, flow velocities and directions, suspended sediment concentrations. TIMOR is validated with field data from both dry and wet seasons; the model simulation results have very good agreement with the field data.
Simulations are done to check the seasonally and long-term morphological changes. Results show that, deposition happens more frequently during dry season than during wet season. The suspended sediment concentration is greatly influenced by tide propagation and it is in proportion to the current velocity. The spatial and temporal pattern of bathymetry changes predict that, the North Branch would degrade significantly; the South Branch and North Channel has deposition along the river banks; the right bank of South Passage is under deposition.
The major human activity at the Yangtze Estuary, the Deep Waterway Regulation Project, has been examined its influences by simulations. The morphology at Deep Waterway Area is under dynamic equilibrium. Since 2007, the middle waterway started deposition. The idea to heighten the South Training Wall may not be effective to tackle the deposition problem according to the dredging volume needed as well as the ebb and flood velocities in the channel. To maintain the waterway 15m, huge sediment must be dredged annually.
To predict the morphological response under joint effect of sea level rise and typical water discharges, attempt simulations are made. Under Sea Level Rise scenarios, the morphology of Yangtze Estuary is dominated by deposition. When the sea level rises less than 1 m, the morphological changes are similar. Under the extreme low water discharge and high sea level rise, the Yangtze Estuary is expected to be eroded. Whether extreme large or low water discharges or sea level rise occurs, the South Passage will be deposited.
This study works not only on the hydrodynamic but also the morphological simulation for the entire Yangtze Estuary area considering flows, sediments, currents and winds simultaneously. The human activity influence as the regulation work in the Yangtze has been explored. Exploratory predictions on the joint effect of sea level rise and typical water discharges are made. It is believed that this work can help to improve the understanding of morphological response to the human activities and sea level rise in estuary, thus wished to provide reference for policy-makers, estuary and coastal researchers.
|Series Name:||Mitteilungen / Institut für Wasserbau und Wasserwirtschaft|
|Place of Publication:||Darmstadt|
|Publisher:||Insititut für Waserbau und Wasserwirtschaft|
|Classification DDC:||500 Naturwissenschaften und Mathematik > 500 Naturwissenschaften|
|Divisions:||Civil and Environmental Engineering > Institut Wasserbau und Wasserwirtschaft > FG Wasserbau|
|Date Deposited:||16 Aug 2011 13:37|
|Last Modified:||07 Dec 2012 12:00|
[Darmstadt, TU, Diss., 2011]
[Darmstadt, TU, Diss., 2011]
|Referees:||Zanke, Univ.Prof. Ulrich C.E. and Kao, Prof.Dr.-I Chia Chuen and Zheng, Prof. Jinhai|
|Refereed:||25 January 2011|
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