Through the collection

reorganization and analysis to the historical data and materials

the time and grade of the drought and flood disasters has been compiled for Ankang City.In addition

we tried to correlate the natural disasters with the location

migration

and reconstruction of Ankang City in the history.The results showed that

from 500BC to 2000AD

drought disasters altogether occurred 79 times during these 2 500 years

averagely one time per 31.65 year

while flood disasters occurred 140 times

approximately one time per 17.86 year.During 500BC to 1000AD

the natural disasters were rarely recorded

and more were found since 1000AD.The highest frequency of the recorded natural disasters was found during the period from 1400AD to 2000AD.The extreme flood disaster was the reason for the migration of Ankang City from the old city to a new site for twice.However

the return of Ankang City back to its old site was a synthetically action effected by many factors

such as water transportation

farming and cultural psychology of the residents.