Reconstruction of the largest Holocene jökulhlaup within Jökulsá á Fjöllum, NE Iceland

• Published in: Quaternary science reviews 2005-11, Vol.24 (22), p.2319-2334
• Main Authors: Alho, Petteri, Russell, Andrew J., Carrivick, Jonathan L., Käyhkö, Jukka
• Format: Article
• Language: English
• ISSN: 0277-3791; 1873-457X
• DOI: 10.1016/j.quascirev.2004.11.021

Glacial outburst floods (jökulhlaups) have a significant role for landscape evolution in NE Iceland. A number of jökulhlaups have routed from the northern margin of Vatnajökull during the Holocene. In this study, reconstruction of the largest Holocene jökulhlaup along Jökulsá á Fjöllum, NE Iceland was undertaken using the HEC-RAS hydraulic modelling and HEC-GeoRAS flood mapping techniques with a Digital Elevation Model (DEM) derived from ERS-InSAR data and field-based wash limit evidence. The largest jökulhlaup produced extensive erosional and depositional landforms across an inundated area of ∼1390 km 2 and is calculated to have had a peak discharge of 0.9×10 6 m 3 s −1. Power per unit area within this jökulhlaup varied from 6 to 46,000 W m −2. Jökulhlaup hydraulics are related to geomorphogical evidence at three key sites: in Vaðalda, Upptyppingar and Möðrudalur sub-areas in order to explain the abrupt spatial variation of the flood characteristics on a regional scale and to relate erosional and depositional features to spatial variations in jökulhlaup hydraulics. These process-form relationships of the largest jökulhlaup along the Jökulsá á Fjöllum are compared with large outburst floods elsewhere. The largest Jökulsá á Fjöllum jökulhlaup had a factor of ∼20 times smaller discharge and ∼a factor of 20 times lower power per unit area than Altai palaeoflood—the largest known flood on the Earth.