Geomorphological impact and morphodynamic effects on flow conveyance of the 1999 jökulhlaup at sólheimajökull, Iceland
Abstract The 1999 jökulhlaup at Sólheimajökull was the first major flood to be routed through the proglacial system in over 600 years. This study reconstructed the flood using hydrodynamic, sediment transport and morphodynamic numerical modelling informed by field surveys, aerial photograph and digi...
| Published in: | Earth Surface Processes and Landforms |
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| Main Authors: | , |
| Format: | Article in Journal/Newspaper |
| Language: | English |
| Published: |
Wiley
2015
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| Subjects: | |
| Online Access: | http://dx.doi.org/10.1002/esp.3750 https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2Fesp.3750 https://onlinelibrary.wiley.com/doi/pdf/10.1002/esp.3750 |
| Summary: | Abstract The 1999 jökulhlaup at Sólheimajökull was the first major flood to be routed through the proglacial system in over 600 years. This study reconstructed the flood using hydrodynamic, sediment transport and morphodynamic numerical modelling informed by field surveys, aerial photograph and digital elevation model analysis. Total modelled sediment transport was 469 800 m 3 (+/‐ 20%). Maximum erosion of 8.2 m occurred along the ice margin. Modelled net landscape change was –86 400 m 3 (+/‐ 40%) resulting from –275 400 m 3 (+/‐ 20%) proglacial erosion and 194 400 m 3 (+/‐ 20%) proglacial deposition. Peak erosion rate and peak deposition rate were 650 m 3 s ‐1 (+/‐ 20%) and 595 m 3 s ‐1 (+/‐ 20%), respectively, and coincided with peak discharge of water at 1.5 h after flood initiation. The pattern of bed elevation change during the rising limb suggested widespread activation of the bed, whereas more organisation, perhaps primitive bedform development, occurred during the falling limb. Contrary to simplistic conceptual models, deposition occurred on the rising stage and erosion occurred on the falling limb. Comparison of the morphodynamic results with a hydrodynamic simulation illustrated effects of sediment transport and bed elevation change on flow conveyance. The morphodynamic model advanced flood arrival and peak discharge timings by 100% and 19%, respectively. However, peak flow depth and peak flow velocity were not significantly affected. We suggest that morphodynamic processes not only increase flow mass and momentum but that they also introduce a feedback process whereby flood conveyance becomes more efficient via erosion of minor bed protrusions and deposition that infills or subdues minor bed hollows. A major implication of this study is that reconstructions of outburst floods that ignore sediment transport, such as those used in interpretation of long‐term hydrological record and flood risk assessments, may need considerable refinement. Copyright © 2015 John Wiley & Sons, Ltd. |
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