Milly et al (2002) investigate the prospect that global warming due to enhanced greenhouse gas concentration in the earth's atmosphere will lead to an enhanced hydrological cycle and hence more occurrences of extreme rainfall events that might lead to extreme (events occurring less than once every 100 years) floods. Global climate models suggest this is a plausible result of global warming. Milly et al (2002) examined records of the past flood events and they find the rate of occurrences of such events has increased since 1953. They consider their linkage of this increase in extreme flood events with increase in anthropogenic greenhouse gases to be a tentative conclusion subject to additional study.
Reference
Milly, P. C. D., R. T. Wetherald, K. A. Dunne, and T.L. Delworth, 2002: Increasing risk of great floods in a changing climate. Nature, 415, 514-517.