Abstract: There are no debates on whether floods and epidemics as disasters pose a threat to human life and health.In this study we constructed a time sequence from the Pre Qin Dynasty to the Qing Dynasty (887 BC to 1911 AD) to explore the spatial-temporal distribution characteristics of floods and epidemics in the Yangtze River basin via spatial autocorrelation,hot spot analysis,and spatial statistical approaches.The results indicated that: (1) There are at least 789 flood years and 201 epidemic years in the total 2798 years from Pre Qin Dynasty to late Qing Dynasty in the Yangtze River basin.The number of disaster years shows an fluctuating upward trend,and in particular,the number of disaster years between the Yuan Dynasty and late Qing Dynasty is twice as many as that in the period from the Pre Qin Dynasty to the Yuan Dynasty.Both periods witnessed the same fluctuation trend in decadal and centurial scales,and in the same period,the frequency of flood is higher than epidemic.(2) High-incidence seasons of flood were mainly concentrated in summer and autumn,while low-incidence seasons are linked to winter and spring.Nevertheless,the high-incidence seasons of epidemics mainly coincided with spring and summer,whereas low-incidence seasons of epidemics with autumn and winter.(3) Floods in historical periods were large-scale disasters and epidemics were mainly microscale.The incomplete mechanism of disaster-relief work mainly triggered the continuation of disaster losses.(4) The disaster-affected cities interacted with each other deeply,and presented similar spatial variation trends in a time sequence.Moreover,the significant area of hot spot of floods overlaps to a large extent with that of epidemics in the same period.

Key words: flood disaster, epidemics, temporal and spatial distribution, historical periods, the Yangtze River basin, hot spot analysis