Science Service System

Summary of Proposal HYD2903

TitleInSAR/GNSS time series detect sinking cities along downstream of the Three Gorges Reservoir in China
Investigator Zhou, Zhiwei - Wuhan University, Global Navigation Satellite System Research Center
Team Member
Prof Li, Zhenhong - Newcastle University, School of Civil Engineering and Geosciences
Prof Shi, Chuang - Wuhan University, Global Navigation Satellite System (GNSS) Research Center
Dr Li, Peng - Wuhan University, Global Navigation Satellite System (GNSS) Research Center
SummaryThe Three Gorges hydropower plant began in 1994, started impounding in 2003, and completed in 2009. Between 2003 and 2011, the Three Gorges Reservoir (TGR) impounded four times, and raised the water level up to 175 m, which cause the drawdown of downstream water level, such as lower reaches of the Yangtze River and lakes conjoined to the Yangtze River. During the past 10 years, water level records of downstream of the Yangtze River (such as Dongting/Poyang Lake, Wuhan/NanjingCity with population of 10/8.2 million) show that they broken the historic lowest records frequently. The decline of downstream water level lower the underground water level, which may cause the bank instability and the surface subsidence along the river, and results in damages to the surrounding building structures, infrastructures assets, underground pipelines and other public facilities. Therefore, a reliable mapping of the bank instability and the subsidence along the Yangtze River is of crucial importance to protect the surrounding building structures and public infrastructure assets, and ensure public safety. This proposal aims to apply InSAR time series (SBAS-InSAR/PS-InSAR) technique to the archived TerraSAR-X, ERS/Envisat-C (another proposal to ESA) band SAR images in order to further understand the relationship between the water level change of the Yangtze River and its associated instability and/or subsidence hazards.Specifically, this proposed research aims are: (1) Develop a reliable InSAR processing chain (using existing or modified processing packages). (2) Identify subsiding areas over three selected study cities and their corresponding patterns and trends, the three cities are: Yueyang, with population of 5.5million, is connected with the Yangtze River and Dongting lake; and the YangtzeRiver through the other two cities Wuhan and Nanjing with population of 10 and8.2 million respectively. (3) Compare InSAR subsidence results for assessing hazards associated with GNSS (GPS and Beidou) time series and water level records. (4) Model the identified subsidence to assess the geophysical mechanisms for bank instability. The final deliverables will be: (i) A quantitative hazard assessment for each selected city. (ii) A peer-reviewed article containing the comparison between ERS/Envisat, TerraSAR-X, GNSS, water level records for the bank instability and city subsidence monitoring. (iii) A final report will submitted to both the TerraSAR-X science team and the funding agency.

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