摘要
对无定河流域野外考察,在其下游苏家圪坨(SJGT)地点发现夹有古洪水滞流沉积物(SWD)的全新世剖面。古洪水SWD厚度30 cm,具有平行微薄层理特征,且直接覆盖在东汉文化层之上。室内分析结果表明古洪水SWD有着与2012年洪水SWD相似的沉积学特征,以粗粉沙为主,分选良好,磁化率和烧失量较小,说明它记录了一次无定河下游的大洪水事件。文化层光释光(OSL)测年结果显示该次古洪水事件发生在1 900~1 700 a BP。古洪水洪峰水位和洪峰流量分别为765.9 m和10 530 m3·s-1。同时利用2012年洪水洪痕水位验证,在同一断面用相同参数恢复洪峰流量为1 030 m3·s-1,实测洪峰流量为1 000 m3·s-1,误差为3.09%,说明古洪水洪峰流量恢复结果合理可靠。研究结果延长了无定河下游洪水数据序列,对水资源、水能源的开发利用提供了科学依据。
In recent years,palaeoflood has been widely studied in the middle reaches of the Yellow River and its tributaries.However,Wudinghe River,Shaanxi Province,China,which is the largest tributary between Hekou and Longmen section of the Yellow River,has not been reported in these studies.A Holocene profile with palaeoflood slack water sediments was found at the Sujiagetuo(SJGT) site in the lower reaches of the Wudinghe River basin through detailed field investigation.The lower reaches of the Wuding River are bedrock canyon sections,which are suitable for palaeoflood hydrology research.The upper and lower boundaries of the palaeoflood SWD are clear with other layers and the thickness of SWD is 30 cm.The palaeoflood SWD,characterized by thin bedding,directly covers the Eastern Han cultural layer.Experimental results show that coarse silt is the main grain size composition of the palaeoflood SWD and 2012 flood SWD and accounted for 59.58% of the palaeoflood SWD and 46.52% of 2012 flood SWD.The standard deviation(σ) and separation coefficient(S0) of palaeoflood SWD are smaller,i.e.,1.51 and 0.79,respectively,which are close to the standard deviation of 2012 flood SWD(0.33 and 0.65 respectively).The smaller values of deviation(σ) and separation coefficient show an effective sampling and sampling pretreatment procedure,indicating that they are well sorted during the sedimentation process.The magnetic susceptibility of the palaeoflood SWD and 2012 flood SWD are extremely low(37.8×10-8 m3·kg-1 and 28.3×10-8 m3·kg-1),indicating that they are both fresh sediments and are hardly affected by weathering and soil formation.Palaeoflood SWD and 2012 flood SWD are also characterized by low ignition loss and high calcium carbonate content.These experimental data indicate that the sedimentological characteristics of the palaeoflood SWD and that of the flood SWD in 2012 are similar,which indicates that it recorded a large flood event in the lower reaches of Wudinghe River.OSL dating of the cultural layer shows that the palaeoflood event occurred in 1 900-1 700 a BP.According to the 22% bulk sediment of the Baijiachuan Hydrological Station in the Wudinghe River,the slack water flow depth method of palaeoflood SWD is used to restore the palaeoflood stage to 765.9 m.Based on the hydraulic parameters such as the gradient of 0.002 5 and roughness coefficient of 0.035,the peak discharge of palaeoflood was reconstructed to be 10 530 m3·s-1 by the slope-area method.Using flood mark water level in 2012,the calculated value of peak discharge is 1 030 m3·s-1 at the same section and parameters,and the error between the calculated peak discharge and the measured value is 3.09%,which shows that it is reasonable and reliable to restore the peak discharge of palaeoflood using the slope-area method in the lower reaches of the Wudinghe River.Results extend the flood data series of the lower reaches of the Wudinghe River and provide a scientific basis for the development and utilization of water resources and energy resources.
作者
李晓刚
黄春长
庞奖励
LI Xiao-gang;HUANG Chun-chang;PANG Jiang-li(College of Urban-Rural Planning and Architectural Engineering Development and Management Engineering Science,Shangluo University,Shangluo 726000,Shaanxi,China;College of Geography Science and Tourism,Shaanxi Normal University,Xi’an 710119,Shaanxi,China)
出处
《干旱区地理》
CSCD
北大核心
2020年第2期380-387,共8页
Arid Land Geography
基金
国家自然科学基金目(41701090)
陕西省创新能力支撑计划项目(2019KJXX-026)
商洛学院科研项目(18SKY002)资助。
关键词
古洪水水文学
滞流沉积物
全新世
无定河
palaeoflood hydrology
slackwater deposits
Holocene
Wudinghe River
