Flood trends in Africa

African countries are highly vulnerable to floods, with the fatalities and economic impacts associated with this hazard that have increased over the last decades. Despite the importance of the topic, little is known about the changes in the flood hazard over the second half of the 20^th and the first two decades of the 21^st century. Here we quantify the temporal changes in flooding using a newly assembled database of daily river discharge observations. The dataset contains over 700 stations having at least 20 years of daily data between 1950 and 2017. The database includes rivers from most sub-regions of Africa and sample a wide range of catchment sizes. Flood analyses are based on both annual maxima and peak-over-threshold to examine the changes in the frequency and magnitude of these events. Seasonal patterns of flood occurrence are also investigated through a regionalization based on directional statistics and monthly flood occurrence. Results indicate that, at the continental scale, there are more rivers with statistically significant downward trends. Yet, the spatial patterns exhibit regional variations, with several rivers showing increasing trends in central and South Africa. These findings are robust when considering longer times series or different sampling strategies for extremes.