Viewing China Flood Control Standard Based on Quantity of Dam-Failure

In 1981,the total existed reservoirs in China is 86 881,of which,small and medium sized ones 81 215.In 2006,the total number is 85 849,of which,small and medium sized ones 82 367.During 52-year period from 1954 to 2006,there are all together 3496 dam failures,of which,1 800 dam breaks because of flood overtopping,making up 51.49% of the total.While only 316 dams,including 2 large ones,17 medium sized and 297 small sized ones burst because of over standard floods.The paper calculates and analyzes the issue by using two methods of transcendental probability and the effective service life of project.The outcomes show that there are 297 small sized dams failure because of over standard floods among 80 000 ones during 40-50 years and the relevant flood frequency has reached to ones happened in 10 000-13 000 years.The reasons are as follows: a) during the calculation of design flood,it is getting greater and greater for safety purposes and finally the results of calculation become much greater and;b) on hydraulic design,the dam all has a certain limit of freeboard.