历史时期关中平原水旱灾害与城市发展

通过对历史时期以来关中平原旱灾、水涝灾害发生频率的统计与分析,发现从370 BC-2000 AD的2 300多年里,关中平原有2个时期水旱灾害的发生最为频繁,即610-850 AD(隋后期至唐后期)和1580-2000 AD(明后期以来).而且,水旱灾害的发生相互联系,旱灾频繁的时期,也是水涝频繁发生的时期.深入分析发现,水旱灾害的发生一方面与关中平原气候变化、中心城市的建设发展与衰落有密切联系;另一方面也与人口数量的增长密切相关.其根本原因在于城市建设和人口增加,对自然资源的开发利用和消耗大幅度增长,对城市周边山地和丘陵地区环境的压力剧增,造成环境的迅速退化,导致平原地区水旱灾害频繁发生.

Study on the Historical Drought and Flood Disasters in the Guanzhong Plain and the Urban Development

In this paper,the historical data of drought,flood and waterlog disasters in the Guanzhong Plain in more than 2 300 years from 370 BC to 2000 AD are analyzed.The results show that the drought,flood and waterlog disasters occurred most frequently during two periods from 610 to 850 AD(from the late Sui Dynasty to the late Tang Dynasty) and from 1580 to 2000 AD(after the late Ming Dynasty).In the Guanzhong plain,different natural disasters occurred synchronously,that is the high occurring frequencies of drought,flood and waterlog disasters occurred in the same periods.The occurring frequencies of these natural disasters,on the one hand,are closely related to climate change and development of ancient cities,on the other,to the population growth.Excessive exploitation of natural resources and the degeneration of ecological environment due to the increase of human activities are the major reasons resulting in the frequent occurrence of drought,flood and waterlog disasters.The analyzed results of historical data also reveal that,before the Ming Dynasty and Qing Dynasty,the drought, flood and waterlog disasters occurred frequently when the capital city was constructed in the Guanzhong Plain,otherwise the occurring frequencies of these natural disasters were significantly reduced.The occurring frequencies of these natural disasters were not so high at the early stage of constructing the capital city,they were obviously increased with the urban expansion,decreased to some extent when the capital city was stabilized,and sharply reduced when the capital city came down.The flood and waterlog disasters have been significantly decreased but the drought disasters increased because of the climatic warming-drying trend since the 1950s.