Extreme Rainfall Analysis Including Seasonality in Athens, Greece

Extreme rainfall analysis is essential for accurate flood hazard assessment. Traditional approaches, such as the use of annual maxima, may overlook seasonal variations and lead to underestimated precipitation extremes, compromising effective flood risk management strategies. This study applies a point process model to uninterrupted daily rainfall records (1901–2023) from the National Observatory of Athens meteorological station in Thiseion. This method analyzes both the frequency of exceedances above a given threshold and the values of those exceedances, incorporating seasonality into the modeling process. Preliminary analysis using annual maxima revealed no statistically significant trend but indicated clear monthly seasonality in precipitation extremes. By incorporating seasonality, the point process method yielded estimates up to 22% higher than those obtained using traditional annual maxima approaches, such as those employed in Greece’s National Flood Risk Management Plans. These findings highlight the need for a revision of current methodologies, which could significantly impact flood risk assessments and management strategies.