Articles | Volume 18, issue 1
Research article
19 Jan 2018
Research article |  | 19 Jan 2018

The influence of antecedent conditions on flood risk in sub-Saharan Africa

Konstantinos Bischiniotis, Bart van den Hurk, Brenden Jongman, Erin Coughlan de Perez, Ted Veldkamp, Hans de Moel, and Jeroen Aerts

Abstract. Most flood early warning systems have predominantly focused on forecasting floods with lead times of hours or days. However, physical processes during longer timescales can also contribute to flood generation. In this study, we follow a pragmatic approach to analyse the hydro-meteorological pre-conditions of 501 historical damaging floods from 1980 to 2010 in sub-Saharan Africa. These are separated into (a) weather timescale (0–6 days) and (b) seasonal timescale conditions (up to 6 months) before the event. The 7-day precipitation preceding a flood event (PRE7) and the standardized precipitation evapotranspiration index (SPEI) are analysed for the two timescale domains, respectively. Results indicate that high PRE7 does not always generate floods by itself. Seasonal SPEIs, which are not directly correlated with PRE7, exhibit positive (wet) values prior to most flood events across different averaging times, indicating a relationship with flooding. This paper provides evidence that bringing together weather and seasonal conditions can lead to improved flood risk preparedness.

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 will result in increasing warning lead times, providing sufficient time for early action. Findings of this study indicate that the consideration of short- and long-term antecedent conditions can be used by humanitarian organizations and decision makers for improved flood risk management.
Final-revised paper