Research on the Flood Distaste of Southern Shaanxi in Ming Dynasty

Through the collection and analysis to the historical materials,the characteristic and the reason of the interannual and the season has been researched.The results show that,Ming Dynasty flood disaster level may divide into small,middle,big and super-big in southern Shaanxi.Their occurrence probability is 33%,40%,21% and 6%.From 1369 to 1644,flood disaster of the Ming Dynasty altogether has 76 times,and averagely occurred one time per 3.6 year.From the early Ming Dynasty to the late,floods occurred on the whole showed an upward trend fluctuation.The disaster has been divided into three periods.During the first period,from the 1369 to 1435,there were few disasters.During the second period,from 1436 to 1550,this region had the most disaster.During the third period,between 1551 and 1644,there were fewer disasters.On season,the disaster occurrence frequency concentrates on summer and autumn.Main factors producing flood disaster are geography,precipitation,climatic anomaly undulation and the synthetically action of artificial flexible affection.