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14 - Modelling of subaerial jökulhlaups in Iceland
- Edited by Devon M. Burr, University of Tennessee, Paul A. Carling, University of Southampton, Victor R. Baker, University of Arizona
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- Book:
- Megaflooding on Earth and Mars
- Published online:
- 04 May 2010
- Print publication:
- 24 September 2009, pp 265-272
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- Chapter
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Summary
Summary
The flow of subaerial jökulhlaups is in principle similar to other subaerial water floods, such as dam-break floods, although some jökulhlaups may carry so much suspended sediment and ice fragments that they would be more appropriately described as rapidly flowing debris flows or lahars. Many subaerial jökulhlaups start out as subglacial floods and propagate as subaerial floods below an outlet at the glacier terminus. Other jökulhlaups, in particular many outburst floods caused by volcanic eruptions, lead to a partial or almost complete breakup of the glacier along the flow path and become subaerial after flowing only a short distance subglacially. The dynamics of the subaerial part of jökulhlaups differs fundamentally from the dynamics of the part of the flood that flows along the bed of the glacier or ice cap. The estimated discharge of jökulhlaups observed at many locations in Iceland during the twentieth century ranges from 0.1 to 300 × 103 m3 s−1 and prehistoric jökulhlaups have been estimated to have reached on the order of 106 m3 s−1. The subaerial propagation of jökulhlaups can cause widespread damage to buildings, roads, communication lines and farmland. Two-dimensional numerical modelling, based on a depth-integrated formulation of the dynamics of shallow water flow, has been used to study the flow of subaerial jökulhlaups at four locations in Iceland, two of which are described in this chapter. Model results include estimates of travel times, the most probable flood routes and the extent of lowland areas that might be flooded.