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Monitoring the landslide in Three Gorge Area by using corner reflector differential interferometry SAR

Qiminng Zeng(1) and Ye Xia(2)

(1) Peking University, Zhongguancun, Beijing, 100871, China
(2) GFZ, Telegrafenburg, 14473 Potsdam, Germany

Abstract

Three Gorge Dam is the greatest hydraulic project on the world. The dam height designed is 185 meters, the water level designed is 175 meters, about 1.2 million of 15 million people lived in 13 counties and cities in the area will immigrate out because their homeland will be occupied by rising water. On the history, there were many serious landslides occurs in Three Gorge Area. For example, the Xintan Slide on early morning of June 12, 1985, destroyed Xintan Town in Hubei Province, the front of landslide body thrashed into Yangtze River, the third of river width was jammed, and the height of wave tide blown up to 54 meters and propagated along the river in range of 42 kilometers, 9 people were killed on 70 boats which had been destroyed in the river. Another example is Qianjiangping Landslide on July 13, 2003 in Hubei Province, the landslide body of 240 million cubic meters (stretched in about 1.2 kilometers long and wide) destroyed an industrial area and 543 houses, 4 factories and 129 families lost their home, the landslide body slide into Qing'ganhe which is a branch to Yangtze River, the landslide lasted for about 4 hours from slightly precursors to the final avalanche, because of the local monitoring system and early warning, about 1200 people moved out safely in time, only a few people were injured, disappeared or killed when transferring or on the boats in the river.

Chinese Government paid much attention to against the landslide in Three Gorge Area, the fund of 4 billion RMB (about 500 million USD) had been input to repair and fasten all known landslides in the area, and to setup monitoring and warning system. Although these known landslides had been fastened by engineering measures, there still are possibilities these landslides reactive. Furthermore, along with the rising of water level and the construction of immigration settlements, hydrological geological condition and ground load changes, the occurrence frequency of landslide would increase much. Currently, the monitoring is mainly based on visual inspection by local trained people or instrument measuring periodically on some sites. These methods could help saving people's lives, however, the precision, frequency and coverage could not meet the requirement to research the landslides.

Many attempts failed to monitor the landslide in Three Gorge Area by using conventional differential InSAR due to low coherence in vegetated mountainous region. Dr. Xia proposed to setup corner reflectors on Xintan and Lianziya Rocks in Hubei Province of China for monitoring rock body movement. Based on the initial experiment results which showed corner reflector DInSAR is a promising means to achieve our goals, we have chosen 20 sites along the Yangtze river from over 2000 known potential sites, to setup 20 corner reflectors as key networks to monitor relative movement. We wish we could identify more natural stable scatters as complimentary to corner reflectors, which could include bare tops of mountain, steep bank of rivers, man made structures and so on. The most challenging problem is atmosphere correction which need knowledge about atmosphere, in particular, three dimensional distribution of water vapor content.

In this paper, we will show the research proposal and initial result, also discuss the interferometry phase correction caused by atmosphere.

 

Keywords: ESA European Space Agency - Agence spatiale europeenne, observation de la terre, earth observation, satellite remote sensing, teledetection, geophysique, altimetrie, radar, chimique atmospherique, geophysics, altimetry, radar, atmospheric chemistry