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Wenchuan earthquake induced large-scale of collapses and landslides which blocked river channels and brought about
quantities of dammed lakes. The number and the scale of dammed lakes are extremely rare in the world. Besides the
backwater of the dammed lakes can flood the road traffic, villages and farmland on the upstream, it can severely threaten
the safety of the people's lives and properties on the downstream. Once the dammed lakes burst out, they can cause severe
flood disaster. Therefore, it is urgent to monitor the dammed lakes, study their distribution and analyze their development
by means of remote sensing (RS) and geography information system (GIS) after the earthquake. In this paper, 145
high-resolution images were processed and 31 severely-afflicted counties were studied through RS monitoring and field
investigation. By the time of May 28,2008, 257 dammed lakes existing more than 14 days were identified and there were
34 dammed lakes with capacity of more than 100 000m3. Based on these conditions, the distribution and development of
dammed lakes were discussed and the findings showed that: (a) The dammed lakes induced by Wenchuan earthquake
mainly scatter in Beichuan, Wenchuan, Shifang, Mianzhu and Anxian counties, and there exist 154 dammed lakes in these
regions, which is 59.92 percent of the total. (b) 95.3 percent of the dammed lakes are within 10km of three major fault
zones of Longmen Mountains and the relationship between the number of dammed lakes and their distance to fault zone
accords with the law of logarithmic decrement. (c) Most of dammed lakes are distributed in the upper reaches of Minjiang
River, Tuojiang River, Jianjiang River and Fujiang River, etc. in rosary. (d) The distribution of dammed lakes in the study
areas is dominated by seismic intensity, lithology, slope and altitude. In the next 5-10 years, collapses, landslides and
debris flows in the study area will occur frequently and severely and they are likely to block river channels and form
dammed lakes. As rainy season comes, the risk of dammed lakes forming and bursting is increasing. So it is necessary to
reinforce the real-time monitoring of dammed lakes, make risk assessment and formulate the emergency countermeasures.
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