黄河中游马莲河历史与现代洪痕沉积与水文学研究

通过对马莲河流域深入调查研究，在马莲河下游峡谷峭壁发现了一组4个显著的洪痕。洪痕沉积物分析看出，马莲河洪水悬移质泥沙以粉沙为主，粘粒和沙粒含量都较低，磁化率值也很低。将这些数据与流域内马家原剖面黄土土壤的的分析结果对比，可知马莲河现代洪痕沉积物是暴雨洪水对于流域内黄土和土壤侵蚀、搬运沉积形成。采用面积－比降法对该组洪痕所记录的4次洪水事件进行了洪峰流量恢复计算。表明高于常水位3.3 m、5.5 m、6.7 m洪痕洪峰流量分别为1 170m³/s、4 060 m³/s、5 690 m³/s。它们与雨落坪水文站观测2005、2003、1977年的洪水洪峰流量值相当，误差小于5 %。最高洪痕高出常水位10～12 m，计算恢复其洪峰流量为13 980 m³/s，洪水发生年代为1841年（清代道光21年）。这些研究结果对于马莲河流域的防洪减灾、水利水电工程设计和水土流失防治具有重要科学意义。

Sedimentological and hydrological studies of flood Deposit along Malianhe River in middle Yellow River Basin

Storm rains and floods are major natural disasters occurring in the middle reaches of the Yellow River and the tributary rivers. They have caused serious soil erosion and economic losses in the drainage basins. Historical and modern flood stage indicators were investigated in the bedrock gorges of the Malianhe River, which is a major tributary of the Jinghe River in the middle reaches of the Yellow River. During our widespread fieldwork, A group of four flood stages was identified by the clay and silt deposit of 1－3 cm in thickness on the cliff bedrock walls of the river channel in the lower reach gorges of the river. Sediment samples of this flood deposit at the SZZ site were taken during fieldwork. And another group of samples was taken from the MJY loess soil profile in the drainage basin for comparative study. Laboratory analysis of the grain size distribution indicates that silt content is very high, clay and sand contents are low in these flood sediment. These features are very similar to that of the loess and soil in the MJY profile in the drainage basin. Magnetic susceptibility of the flood deposit is very low and much similar to that in the Malan Loess and modern soil in the MJY profile, but much lower than that in the Holocene soil S0 in the MJY profile in the drainage basin. The grain size distribution indicates that this flood deposit was sourced mainly from the erosion and transport by storm rain and floods over the loess regions in the drainage basin of the Malianhe River. The low magnetic susceptibility indicates they are fresh deposit without weathering and pedogenic alteration. The peak discharges of the first three flood events were 1 170 m3/s, 4 060 m3/s and 5 690 m3/s, respectively, as reconstructed by using the hydrologic method. These results correspond with the peak discharges of the gauged flood in 1977,2003 and 2005 on the Malianhe River. The peak discharge of the forth flood event was reconstructed 13 980 m3/s. It occurred in 1841 during the Daoguang 21 year in the Qing Dynasty as known by the local villagers. These flood events also well correlated to the flood events recorded on the Jinghe and Weihe Rivers. This research is of great importance for hydraulic engineering constructions, for flood control and for soil and water conservation in the Malian River basin and the middle reaches of the Yellow River.