Journal cover Journal topic
Hydrology and Earth System Sciences An interactive open-access journal of the European Geosciences Union
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
10 Feb 2017
Review status
This discussion paper is a preprint. A revision of this manuscript was accepted for the journal Hydrology and Earth System Sciences (HESS) and is expected to appear here in due course.
Should seasonal rainfall forecasts be used for flood preparedness?
Erin Coughlan de Perez1,3,4, Elisabeth Stephens2, Konstantinos Bischiniotis3, Maarten van Aalst1,4, Bart van den Hurk5, Simon Mason4, Hannah Nissan4, and Florian Pappenberger6 1Red Cross Red Crescent Climate Centre, The Hague, 2521 CV, The Netherlands
2School of Archaeology, Geography and Environmental Science, University of Reading, Reading, RG6 6AH, United Kingdom
3Institute for Environmental Studies, VU University Amsterdam, 1081 HV, The Netherlands
4International Research Institute for Climate and Society, Columbia University, New York, 10964, USA
5Royal Netherlands Meteorological Institute (KNMI), De Bilt, 3731 GA, Netherlands
6European Centre for Medium-Range Weather Forecasts, Reading, RG2 9AX, United Kingdom
Abstract. In light of strong encouragement for disaster managers to use climate services for flood preparation, we question whether seasonal rainfall forecasts should indeed be used as indicators of the likelihood of flooding. Here, we investigate the primary drivers of flooding at the seasonal timescale across sub-Saharan Africa. Given the sparsity of hydrological observations, we input bias-corrected reanalysis rainfall into the Global Flood Awareness System to identify seasonal indicators of floodiness. Results demonstrate that in wet climates, even a perfect tercile forecast of seasonal total rainfall would provide little to no indication of the seasonal likelihood of flooding. The number of extreme events within a season shows the highest correlations with floodiness consistently across regions. Otherwise, results vary across climate regimes: floodiness in arid regions in Southern and Eastern Africa shows the strongest correlations with seasonal average soil moisture and seasonal total rainfall. Floodiness in wetter climates of West and Central Africa and Madagascar shows the strongest relationship with measures of the intensity of seasonal rainfall. Measures of rainfall patterns, such as the length of dry spells, are least related to seasonal floodiness across the continent. Ultimately, identifying the drivers of seasonal flooding can be used to improve forecast information for flood preparedness, and avoid misleading decision-makers.

Citation: Coughlan de Perez, E., Stephens, E., Bischiniotis, K., van Aalst, M., van den Hurk, B., Mason, S., Nissan, H., and Pappenberger, F.: Should seasonal rainfall forecasts be used for flood preparedness?, Hydrol. Earth Syst. Sci. Discuss.,, in review, 2017.
Erin Coughlan de Perez et al.
Erin Coughlan de Perez et al.


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Short summary
Disaster managers would like to use seasonal forecasts to anticipate flooding months in advance. However, current seasonal forecasts give information on rainfall instead of flooding. Here, we use a hydrological model to explore which seasonal rainfall characteristics are related to flooding in different regions of Africa. We recommend several forecast adjustments and research opportunities that would improve flood information at the seasonal timescale.
Disaster managers would like to use seasonal forecasts to anticipate flooding months in advance....