Should seasonal rainfall forecasts be used for flood preparedness?

E.R. Coughlan, E. Stephens, K. Bischiniotis, M. van Aalst, B.J.J.M. van den Hurk, S. Mason, H. Nissan, F. Pappenberger

Research output: Contribution to JournalArticleAcademicpeer-review


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 indicators 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 some regions of western, central, and eastern Africa
with typically 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 western 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 to
avoid misleading decision-makers.
Original languageEnglish
Pages (from-to)4517-4524
Number of pages8
JournalHydrology and Earth System Sciences
Issue number9
Publication statusPublished - 2017


Acknowledgements. We thank our colleagues for their insights and suggestions on indices to consider. We are grateful to the German Federal Foreign Office for their support of the development of forecast-based financing pilots around the world, which have inspired these research questions. This work was supported by the UK Natural Environment Research Council (NE/P000525/1). This work was also funded in part by grants/cooperative agreements from the National Oceanic and Atmospheric Administration (NA15OAR4310076 and NA13OAR4310184). The views expressed are those of the authors and do not necessarily reflect the views of NOAA or its subagencies. Elisabeth Stephens’ time was funded by Leverhulme Early Career Fellowship ECF-2013-492.

FundersFunder number
National Oceanic and Atmospheric AdministrationNA13OAR4310184, NA15OAR4310076
Natural Environment Research CouncilNE/P000525/1
Leverhulme TrustECF-2013-492


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