Viscous debris flow, oneof the debris flow types, is scattercd extensively in China and Japan. It is frequently strong enough to causc catastrophic hazards and environmental detrrioration due to its high density (2.2-2.3 t/m3)， complete components (from clay to boulder) and powerful effects of motion, dynamic, erosion and deposit. The primary statistical data show that in the almost 100 years, the heavy losses caused by debris
flow in China are dispersed at about 125 sites, 82 of which, that is， 65 percent of the total are resulted from viscous debris flow. In fact, viscous debris flow in China has a main distribution in the southwest mountain regions， particularly the typical area is the Xiaojiang River Basin, Dongchuan Municipality of Yunnan Province.

Having achieved the first stagc (1991-1994) of thc Sino-Japan joint rescarch on thc debris flow hazards, the debris flow scientists of both sidcs applied again for a joint research on themechanism of viscous dehris flow and countermeasurcs against them. This joint research project consists of thespecial proect NO.951105 sponsored by the Chinesc Academy of Sciences and Ministry of Water Conservancy and the special project c-3
sponsored by the Japanese Ministry of Education, Science and Culture. And the research would have been compleled in 5 years (1994-1998).

During the past 5 years, through lots of field investigation‘ observation, experiment and analysis, the debris 1l0w scicntists 01" both sides surmounted numerous difficulties and dangers of high mountains, precipitous roads. humidness and high tempcraturc. As a result, they have acquircd a vast amount of the first-hand scicntific data on debris flow. furthcrmore, they have comc up with the study on mechanism of occurrence.
motlon‘ dynamic and crosion and dcposit of viscous debris t10w and the methods for its predication, waming, and controlling. Some neW viewpoints and latest creativity have been worked out on these achievements ， especially on the model for two-phasc double fluid, thc resistance to motion, the law of crosion and deposition and the prcdication for the scale of viscous debris flow, etc. Thcse will improveour understanding of the basic law of dcbris tlow and lay a solid foundation for the theory, method and data of science， reasonability, reliability and safety to control viscous debris. This reasearch therefore has the lates level of this area in China. Finally, besides the formal members of Chinese side who have taken part in the Sino-Japan jiont research project, there are Zhao Qin, Liu Zuchan, Yang Renwen, Diao Huifang, Chen Shuili and Hong Yong who have particpated early or late in the instrmentaion, survey, observation and experiment of this project. And all these members of Dongchuan Debris Observation and Research Station have actively cooperated and supported it so that the project has been smoothly accomplished.