Field evidence and hydraulic modeling of a large Holocene j?kulhlaup at J?kuls¨¢ ¨¢ Fj?llum channel, Iceland

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• 作者：Douglas A. Howard^a ; ^{dhowar16@utk.edu} ; Sheryl Luzzadder-Beach^a ; ^{slbeach@gmu.edu} ; Timothy Beach^b ; ^{beacht@georgetown.edu}
• 关键词：Jö ; kulhlaup ; Paleohydrology ; Paleofloods ; Hydraulic modeling ; Iceland ; Mars
• 刊名：Geomorphology
• 出版年：2012
• 出版时间：15 April, 2012
• 年：2012
• 卷：147-148
• 期：Complete
• 页码：73-85
• 全文大小：3573 K

文摘

Field investigation and hydraulic modeling of the J?kuls¨¢ ¨¢ Fj?llum outflow channel in the northern highlands of Iceland suggest a larger than previously modeled j?kulhlaup catastrophic release of glacial floodwaters probably occurring just after early Holocene deglaciation. Although earlier investigations described a similar large paleoflood event, our hydraulic model parameter estimates and floodplain inundation maps correlate with new field evidence presented here. Due to its temporal and voluminous outflow we consider potential j?kulhlaup sources and mechanisms and also its relevance as an Earth analog to Mars fluvial geomorphology and processes. In this study, we reconstruct this large j?kulhlaup event using HEC-GeoRAS to extract three-dimensional channel geometry and the HEC-RAS hydraulic model. Depositional and erosional landforms across the 435-485 km² flood inundation area provide field evidence of high water lines (trimlines) required for hydraulic model constraints. Hydraulic modeling results related to this field evidence and the unambiguous inundation of Ferjufjall along the Mt. Hereubreie reach gives a conservative peak discharge rate of 2.2 ¡Á 10⁷ m³ s^? and a mean flow velocity of 14.9 m s^?. By comparison, this is larger than the 1.8 ¡Á 10⁷ m³ s^? peak discharge of the Kuray paleoflood in the Altai Mountains of Siberia, which is the largest previously documented paleoflood on Earth. This study suggests that this paleoflood through the J?kuls¨¢ ¨¢ Fj?llum channel is the largest known on Earth.