全新世以来永定河洪水的发生规律

THE REGULARITY OF THE FLOOD OF THE YONGDING RIVER DURING THE HOLOCENE

本文通过对永定河流域内全新世地层、考古遗址和历史文献的综合分析,表明在距今约10000—9500年、7700—7500年、5200—4600年、3200—3000年、1900—1700年前以及公元1801—1896年间,永定河流域曾出现过六次暴雨洪水频繁发生的时期。

The researches on the Holocene statum, the archaeological sites and the historical records show that the frequency of the flood of the Yongding River changed many times in the Holocene.The periods of frequent occurrence of rainstorm flood bear some evidences. 1. The erosion surface and the silt layer formed by flood are extensively distributed in the stratum. 2 . The lower reach of the Yongding River channel changed greatly and lakes and swamps were buried by silt; 3. Some ancient cities and towns being destroyed by flood or buried by silt, have to be moved out to other places; 4 . Many records about rainstorm flood can be found in historical documents.An inference can be drawn from the study of the Holocene stratum that the rainstorm flood of the Yongding River occurred frequently in the 10,000-9,000, T, 700-7,500, 5,200-4,600, 3,200-3,000 years B.C. The archaeological materials on the ancient cities and towns have shown evidences that rainstorm flood appeared frequently in the Yongding River between the Eastern Han Dynasty and Three Kingdoms (i.e.about 1900-1700 yesrs B.C.).A conclusion can be drawn from the study of the historical records and surveys of flood that the highest frequency of the rainstorm flood of the Yongding River in recent 1,000 years appeared in the 19th century.The spectral analysis of the historical records in recent 1000 year by computer shows that under the back ground of the super-long term change of the flood frequency, the flood of the Yongding River has 100, 133, 200, 400, years long-term circles and about 3 years short-term circle.