北洛河中游白水段峡谷全新世特大洪水水文学研究

Palaeo-flood hydrological studies in the middle reaches of Beiluo River

通过对北洛河中游峡谷河段的深入调查研究,在白水县张家船村段河谷台地的全新世黄土古土壤剖面中发现了古洪水滞流沉积夹层。采集了古洪水滞流沉积物典型样品,利用第四纪地质学和沉积学方法,通过磁化率、粒度、烧失量、碳酸钙含量等分析,发现其为中全新世后期(4 500～4 000a BP)特大洪水的典型悬移质沉积物。利用比降法模型计算得出,该组古洪水滞流沉积所指示的洪峰流量在13800～15600 m3/s之间;同时对该断面上游方向150m处的铁路桥1994年9月洪水洪痕进行了测量计算,其结果与水文站实测流量一致,证明古洪水水文学计算方法及相关参数的选取是合理的。该研究成果对北洛河的防洪减灾、交通和水利工程建设具有重要的参考价值。

Holocene palaeo-flood slackwater deposits were identified in the Holocene loess-paleosoil profile in the middle reach bedrock gorges of the Beiluo River. This slackwater deposits recorded the largest flood occurring be- tween 4 500 - 4 000 a BP on the river. Analysis of grain size distribution, magnetic susceptibility, the loss on igni- tion and the content of calcium carbonate indicates this SWD is the suspended sediment load of the flood water. Using the slope -area method and the related index, the peak discharges of the palaeoflood were determined to be between 13,800 - 15,600m3 · s^ -1 We also reconstructed the peak discharge of the 1994 flood of the river with the stage indicator at the site with the same method. The error between the reconstructed and the measured discharge is 2.1%. This proves that the reconstruction of the palaeofloods is credible. These results give a meaningful reference to flood mitigation and hydraulic engineering on the Beiluo River.