据史料记载,自汉初到清末两千多年来,长江流域共发生洪灾214次,大约平均十年一次。后来随着人口增加、围湖垦荒加剧,蓄洪面积逐渐缩小,致使洪水灾害更加频繁,从清初到建国前,发展到平均每五年左右即发生一次较大的洪灾。长江洪水根据其水位的高低,流量的大小和灾情的轻重,可以分为一般洪水、大洪水和特大洪水,通常所说的特大洪水是 According to historical records, a total of 214 floods occurred in the Yangtze River Basin during the early Han dynasty to the late Qing Dynasty for more than two thousand years, or about 10 years on average. Later, as the population increased, the reclamation and reclamation of the lake surrounded the area gradually reduced, resulting in more frequent flood disasters. From the early Qing Dynasty to the founding of the PRC, a major flood occurred on average every five years or so. According to the level of the Yangtze River floods, the size of the flow and the severity of the disaster, can be divided into general floods, floods and catastrophic floods, commonly referred to as catastrophic floods