Articles | Volume 21, issue 7
Hydrol. Earth Syst. Sci., 21, 3597–3618, 2017
Hydrol. Earth Syst. Sci., 21, 3597–3618, 2017

Research article 17 Jul 2017

Research article | 17 Jul 2017

Reproducing an extreme flood with uncertain post-event information

Diana Fuentes-Andino1,2, Keith Beven1,3, Sven Halldin1,2, Chong-Yu Xu1,4, José Eduardo Reynolds1,2, and Giuliano Di Baldassarre1,2 Diana Fuentes-Andino et al.
  • 1Department of Earth Sciences, Uppsala University, Villavägen 16, 752 36 Uppsala, Sweden
  • 2Centre for Natural Disaster Science (CNDS), Uppsala University, Uppsala, Sweden
  • 3Lancaster Environment Centre, Lancaster University, Lancaster LA1 4YQ, UK
  • 4Department of Geosciences, University of Oslo, P.O. Box 1047, Blindern, 0316, Oslo, Norway

Abstract. Studies for the prevention and mitigation of floods require information on discharge and extent of inundation, commonly unavailable or uncertain, especially during extreme events. This study was initiated by the devastating flood in Tegucigalpa, the capital of Honduras, when Hurricane Mitch struck the city. In this study we hypothesized that it is possible to estimate, in a trustworthy way considering large data uncertainties, this extreme 1998 flood discharge and the extent of the inundations that followed from a combination of models and post-event measured data. Post-event data collected in 2000 and 2001 were used to estimate discharge peaks, times of peak, and high-water marks. These data were used in combination with rain data from two gauges to drive and constrain a combination of well-known modelling tools: TOPMODEL, Muskingum–Cunge–Todini routing, and the LISFLOOD-FP hydraulic model. Simulations were performed within the generalized likelihood uncertainty estimation (GLUE) uncertainty-analysis framework. The model combination predicted peak discharge, times of peaks, and more than 90 % of the observed high-water marks within the uncertainty bounds of the evaluation data. This allowed an inundation likelihood map to be produced. Observed high-water marks could not be reproduced at a few locations on the floodplain. Identifications of these locations are useful to improve model set-up, model structure, or post-event data-estimation methods. Rainfall data were of central importance in simulating the times of peak and results would be improved by a better spatial assessment of rainfall, e.g. from radar data or a denser rain-gauge network. Our study demonstrated that it was possible, considering the uncertainty in the post-event data, to reasonably reproduce the extreme Mitch flood in Tegucigalpa in spite of no hydrometric gauging during the event. The method proposed here can be part of a Bayesian framework in which more events can be added into the analysis as they become available.

Short summary
Reproduction of past floods requires information on discharge and flood extent, commonly unavailable or uncertain during extreme events. We explored the possibility of reproducing an extreme flood disaster using rainfall and post-event hydrometric information by combining a rainfall-runoff and hydraulic modelling tool within an uncertainty analysis framework. Considering the uncertainty in post–event data, it was possible to reasonably reproduce the extreme event.