长江流域历史洪水的周期地理学研究

从周期地理学的角度,探讨长江历史洪水的频发特点和周期规律,认为影响长江历史洪水的基本周期因子,与近日点日月交食年周期、太阳黑子活动周期和历史气候周期等因素有较大的关联性。而近几个世纪以来长江洪水频率的不断加快,表明人类活动扰乱和改变了历史洪水原有的周期值,使长江历史洪水周期打上了人类活动的深刻烙印。

THE CYCLIC GEOGRAPHY STUDY ON THE HISTORICAL FLOODS IN THE YANGTZE RIVER

As a newly-developed science, Cyclic geography mainly studies geographic phenomena and their regularities of change and their cyclicity.The present paper, from the point of view of cyclic geography, discusses the frequency and cyclic regularities of the historical floods in the Yangtze river, and reaches the following conclusion: (1) There exists a connection between the essential cyclic factors that influence the historical floods in the Yangtze river and the cycle of having both the solar and lunar eclipse in the same year at the perihelion, the cycle of the movement of the sunspot, and the historical cycle of climate;(2) The cyclic features of the historical floods in the Yangtze river are shown on two different scales, either big or small. The smaller cycle as obtained from the historical statistics is 9.73 years, identical with that of the year having both the solar and lunar eclipse at the perihelion (about 9 years) and the cycle of the movement of sunspot (the average is 11 years, with the shortest being 9 years). Analysis through the multi-regression equation shows that the tendency of the historical floods advance wave upon wave, with each trough and each wave crest leaping over one or two centuries. It reflects one great cycle which coincides with the tendency of the global climatic wave motion;(3) The cycle of the historical floods in the Yangtze river is greatly influenced by human activities. The soil erosion in the Yangtze river valley, the silt up of rivers and lakes, the raise of water level all resulted from the unplanned development of the land and over-reclaimation and cultivation of wasteland. The cycle of frequent floods coincides with the cycle of the historical population growth in the river valley. The accelerated pace of the frequency of the floods in the Yangtze river in the past few centuries reflects that human activities have obvious intervening function upon the cycle of floods, which have changed the essential cycle of floods in the Yangtze river.