The maximum historic rainfall-runoff floods measured in the United States, the People's Republic of China and the world all plot close to a smooth curve of drainage area versus discharge. In the United States, the possibility that flood peaks were overestimated and the closeness of these peaks to the probable maximum floods suggest that this limiting curve of maximum floods will not significantly change position with more data. Data for future floods that plot above this curve need to be examined carefully. The most likely interpretations for new data points above the curve would be the confusion of a mud or debris flow with a water-dominated flood, or the damming of channels by debris or a landslide and subsequent bursting. In the United States, excluding Hawaii, the largest measured historic floods in basins less than about 1000 km2, all occurred in arid and semi-arid areas. In China, the majority of the largest measured historic floods occurred in the east and southeast in basins on the windward side of mountainous areas, and in locations affected by typhoons. One extraordinary flood that exceeds any other recorded flood in the world for the size of the drainage basin in which it occurred is the New Caledonia flood of December 24, 1981 on the Ouaieme River. Worldwide, the largest measured historic floods occurred primarily between 40??N and 40??S latitude on streams and rivers near coastal areas. ?? 1987.
