黄河晋陕峡谷2012年大洪水滞流沉积物性质分析  

Characteristics of the flood slackwater deposits occurred in 2012 in the Jin-Shaan Gorges of the Yellow River

作　　者：李晓刚[1,2] 黄春长[1] 

机构地区：[1]陕西师范大学旅游与环境学院,西安710062 [2]商洛学院地理系,商洛726000

出　　处：《干旱区资源与环境》2015年第10期165-171,共7页Journal of Arid Land Resources and Environment

基　　金：国家自然基金重点项目(41030637;41271108);教育部博士点基金优先发展领域项目(20110202130002)资助

摘　　要：通过对黄河中游晋陕峡谷段广泛细致地野外考察,发现了多处2012年大洪水滞流沉积物（SWD）地点,在其尖灭点处采集样品,室内进行了粒度、磁化率特征分析。结果表明：黄河晋陕峡谷段2012年大洪水SWD磁化率都很低,在31.2-42.3×10^-8m^3/kg之间,这与黄河中游马兰黄土L1的磁化率相当,这正是未受到风化成壤作用影响的新鲜洪水滞流沉积物的基本特征。2012年大洪水SWD粒度性质为粉沙质沙和沙质粉沙。粒度自然分布频率曲线呈现单峰、尖窄型,分选较好,说明是在高水位滞流环境下的悬移质泥沙沉积,与粒度参数（分选系数、标准偏差）反映的结果一致。平均粒径和中值粒径显示,2012年大洪水SWD从上游至下游粒度分异明显,呈现出随河流纵向的延长,粒径由粗变细的规律性变化。同时受洪水SWD沉积的微地貌环境影响,在回水湾和支沟口内沉积的悬移质泥沙较细,而在两岸缓坡台地较粗。与吴堡、龙门水文站悬移质泥沙粒径相比,洪水SWD是尖灭点处悬移质泥沙沉积,并不是整个断面。所以2012年大洪水SWD粒度特征对古洪水沉积学和水文学研究具有重要的借鉴意义。研究结果对于深入认识黄河晋陕峡谷段洪水泥沙形成规律,开展水土保持和防洪减灾具有重要意义。Slackwater deposits（ SWD） of flood occurred in 2012 were investigated and sampled in the Jin-Shaan Gorges of the Yellow River. Grainsize distribution and magnetic susceptibility were analyzed in the laboratory. The results show that magnetic susceptibility of the 2012 flood SWD are 31. 2- 42. 3 × 10^-8m^3/ kg,very close to that of the Malan Loess over the Weihe river basin. This means they were newly deposited and were not influenced by the weathering and pedogenesis. The grain size of the 2012 flood SWD in the Jin- Shaan Gorges of the Yellow River is dominated by sandy silt and silty sand. Grain- size indices show that the difference of grain- size of 2012 flood SWD is very obvious,and with the longitudinal extension of the river,the grain- size of SWD are regular changes from the coarse to fine. Grain size distributions of modern flood SWD are related to the microgeomorphology environment and hydrodynamic conditions during flood periods. Compared with Wubu and Longmen gauge station,flood SWD is suspended sediment deposition at the end- point,not the averages at entire cross- section. Obviously the use of the annual average of entire cross- section suspended sediment grain size as reference of paleoflood SWD is unscientific. The deposition process and priciples are consistent between modern flood SWD and palaeoflood SWD. Therefore grain size characteristics of 2012 flood SWD have an important reference for the study palaeoflood sedimentology and hydrology in the Jin- shan gorges of the Yellow River.These results are of great importance to mitigate flood disasters,and to soil and water conservation.

关 键 词：黄河晋陕峡谷 悬移质 洪水 滞流沉积物 粗泥沙 

分 类 号：P332.5[天文地球—水文科学]