Abstract: As compared with that in 1954,the flood in 1998 was characterized by medium water volume, high water level and heavy disaster. Serious disturbances of the eco system, like over felling of primitive forests in the Changjiang River Valley, diminishing of numerous lakes, and universally silting up of the river courses, lead to deterioration of the hydrological conditions in run off producing, confluence, pondage and flood discharge. These are the major causes of frequent occurrence of floods and aggravation of the disaster.