甘肃葫芦河全新世特大洪水水文学研究

Holocene Mega-Flood Palaeohydrology of the Hulu River,Gansu Province

古洪水水文学是全球变化科学领域的新兴学科.通过对黄河支流葫芦河甘肃秦安段峡谷详细考察,在庙咀附近路基岩坡处发现全新世古洪水滞流沉积物,通过剖面田野观察和沉积学实验分析,表明该沉积物为洪水悬移质泥沙沉积形成,主要成分为粉沙,分选良好.其磁化率值低,表明它们是全新世晚期的沉积物,还未受到风化成壤作用的改造.通过与周边其他的全新世古洪水沉积剖面地层学、考古年代学对比,确定其表示的洪水年代介于3200~3000aBP之间,即全新世大暖期末期阶段的变化剧烈期.利用水文学比降法,计算该组沉积层所记录的特大洪水洪峰流量在14120~16700 m^(3)/s之间,经验证表明该计算结果是可信的.所获得的历史特大洪水水文学数据,使得葫芦河洪水水文数据序列延长至万年尺度,在工程设计、防灾减灾领域具有重要应用价值,对揭示全球变化背景下的水文响应同样具有十分重要的科学意义.

Paleoflood hydrology is an emerging field within global change science.In the Qin’an section of Gansu Province,through an in-depth exploration of the Hulu River,a tributary of the Yellow River,Holocene Paleoflood sediments were discovered within the rocky slope near Miaozui.Field profile observations and sedimentological analyses revealed that these sediments resulted from flood suspension sediment deposition,predominantly comprising well-sorted powdered sand.Their low magnetization values signify late Holocene sediments relatively untouched by weathering and loam formation.Comparative analysis of stratigraphy and archaeological chronology with neighboring Holocene ancient flood deposits suggests the flood age falls between 3200-3000 years BP,a period coinciding with significant changes at the end of the Holocene Great Warming Stage.Employing the hydrological ratio drop method,the peak flow of the mega-flood within these sedimentary layers was estimated at 14120 to 16700 m^(3)/s,a result validated as credible.The acquired hydrological data from this historical mega-flood extends the Hulu River’s hydrological data series to a 10000-year scale,holding immense value for engineering design,disaster prevention,and mitigation.Additionally,it contributes significantly to understanding hydrological responses within the context of global changes.