The Intensity – duration (I-D) curves towards to a spatially distributed flood early warning tool (F-EWT)

Attica region suffers from rainfall events of high intensity, inducing flash-floods and significant damages in the urbanized areas. This analysis concerns the determination of the maximum intensity-duration thresholds regarding flooding (F) or non-flooding (NF) regime, using the available precipitation records and the dataset of Fire Service operations in flooded properties for the period 2005-2016. Each event is classified as ‘F’ or ‘NF’ in case of flooded properties or not, respectively. As expected, ‘F’ events prevail for the higher rainfall intensities. Based on this characteristic, it was found that when excluding outlies in these two groups of events, then two clear limits of I-D are determined using a power-law equation. The first one (‘lower limit’) defines the area below which floods are absent and above which flood occur or not, while the second (‘upper limit’) defines the minimum limit of maximum intensities above which only events linked to flooding are observed. Based on these limits, a Flood Early Warning Tool (F-EWT) that provides the corresponding limits of cumulative precipitation as a function of the event’s duration is defined and evaluated indicatively for the severe flood event of October 24, 2014.