Journal cover Journal topic
Natural Hazards and Earth System Sciences An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/nhess-2017-58
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
17 Feb 2017
Review status
This discussion paper is under review for the journal Natural Hazards and Earth System Sciences (NHESS).
The influence of antecedent conditions on flood risk in sub-Saharan Africa
Konstantinos Bischiniotis1, Bart van den Hurk1,2, Brenden Jongman1,3, Erin Coughlan de Perez1,4,5, Ted Veldkamp1, and Jeroen Aerts1 1Institute for Environmental Studies, Vrije Universiteit Amsterdam, 1081 HV Amsterdam, The Netherlands
2Royal Netherlands Meteorological Institute (KNMI), De Bilt, 3731 GA, the Netherlands
3Global Facility for Disaster Reduction and Recovery (GFDRR), World Bank, Washington DC, USA
4International Research Institute for Climate and Society, Columbia University, Palisades, NY 10964, USA
5Red Cross Red Crescent Climate Centre, The Hague, 2521 CV, the Netherlands
Abstract. Most flood early warning systems have predominantly focused on forecasting floods with lead times of hours or days. However, physical processes during longer – seasonal – time scales can also contribute to flood generation. In this study, the hydro-meteorological pre-conditions of 501 historical damaging flood events over the period 1980 to 2010 in sub-Saharan Africa are analyzed. These are separated into a) a short-term weather scale period (0–7 days) and b) a long-term seasonal-scale period (up to 6 months) before the flood event. Total 7-day precipitation is used to evaluate weather-scale conditions, while seasonal-scale conditions are reflected in the Standardized Precipitation Evapotranspiration Index (SPEI). Although the latter has been used for drought detection, because of its characteristics can also become a wetness monitoring tool. Results indicate that, although heavy 7-day lead precipitation is connected with the majority of the reported floods (72 %), more than 50 % of all floods exhibited higher than average antecedent conditions during the 6 preceding months. In case of extremely wet weather and seasonal scale conditions (SPEI > 2) the probability of flood is close to 50 %. The combined analysis of the two periods revealed that seasonal-scale information should not be neglected, and seasonal SPEI information could be a useful – additional – input to the weather-scale flood forecasts to improve flood preparedness.

Citation: Bischiniotis, K., van den Hurk, B., Jongman, B., Coughlan de Perez, E., Veldkamp, T., and Aerts, J.: The influence of antecedent conditions on flood risk in sub-Saharan Africa, Nat. Hazards Earth Syst. Sci. Discuss., https://doi.org/10.5194/nhess-2017-58, in review, 2017.
Konstantinos Bischiniotis et al.
Konstantinos Bischiniotis et al.
Konstantinos Bischiniotis et al.

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Short summary
Preparedness activities and flood forecasting have received increasing attention, and have led towards new science-based early warning systems. Understanding the flood triggering mechanisms can provide sufficient time for taking action, mitigating the consequences. Findings of this study can be used by humanitarian organizations and decision-makers for preventive flood risk management planning.
Preparedness activities and flood forecasting have received increasing attention, and have led...
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