马莲河全新世古洪水沉积学和水文学研究

Study on Holocene Paleoflood in Malian River Basin

通过对马莲河中下游的深入考察，在甘肃省合水县河段发现全新世古洪水滞流沉积剖面，对采集的沉积物样品进行粒度成分、石英砂表面结构等分析，证明为典型的古洪水滞流沉积物。通过地层学年代对比分析，确定马莲河在全新世中晚期发生特大洪水，年代大致为4200-4000a B．R之间。根据该组古洪水滞流沉积物所指示的洪峰水位，采用比降法恢复洪峰流量在16400～16900m^3／s之间。同时对该断面2003年和2005年洪水的洪痕进行了流量恢复计算，计算结果与实测洪水误差小于5％，证明古洪水水文学计算结果合理可靠，从而为马莲河水利工程建设及沿岸城镇的防洪减灾提供了科学依据。

Through investigations in the middle and lower reaches of Malian River, Holocene palaeoflood slack- water deposition profile were identified in Heshui County. Samples of the palaeoflood slackwater deposits were collected, and the grain-size distribution and the quartz grain surface texture were examined. All of these indexes showed that the slackwater deposits were typical in the study area. Stratigraphic correlations showed that the slackwater deposits recorded the largest floods occurred between 4200-4000 a B.P. on the river. The flood peak discharges were estimated to be 16780-17200 m^3/s by using the slope-area method. Reconstruction of the peak discharge of the 2003 and 2005 floods with the same method and indicators showed that the palaeoflood reconstruction was reliable. These results are important for hydraulic engineering and flood control along the Malian River.