Comparing a 1D hydraulic model with a 2D hydraulic model

Abstract

Glacial outburst floods (j¨ okulhlaups) destroy a significant amount of infrastructure in proglacial areas. Nevertheless, few studies have simulated extreme j¨ okulhlaup inundation using hydraulic modelling. In this study, we demonstrate the capability of one-dimensional j¨ okulhlaup simulation (HEC-RAS modelling software) and compare simulation results with those from a two-dimensional finite element model (TELEMAC-2D modelling software) to determine the potential and limitations of one-dimensional modelling for j¨ okulhlaup simulations. In both models, a pre-defined hydrograph was used as an upstream boundary condition for the j¨ okulhlaup, which was simulated on the M¨ oðrudalur floodplain, northeast Iceland. An unsteady flow simulation of the rising stage of the flood (5 h 15 min) was undertaken with both models to produce maps of flood inundation and flow depth. The study shows that simulations had a 200 m horizontal difference in inundated area at the peak discharge stage. Additional differences were also detected in the rising stage of the hydrograph. The most significant differences between the models was found at the time when the front of the j¨ okulhlaup inundated a new area through a sinuous gorge, or when inundation took place through a complex flow route (maximum difference ¾1800 m). This study demonstrates that one-dimensional modelling of j¨ okulhlaup propagation provides results broadly comparable to data derived from more complex simulations. Copyright © 2007 John Wiley & Sons, Ltd