The Effect of Rainfall Intensity on the Flood Generation of Mountainous Watersheds (Chalkidiki Prefecture, North Greece)

Rainfall intensity constitutes one of the most significant factors that affects directly the flood generation mechanism. The aim of the present study was to determine the rainfall intensity level point (mm/24 h), critical for the cause of high severity flood events. The study area is located in the mountainous part of Chalkidiki Prefecture, consists of 14 watersheds and covers an area of 1481.42 km(2). Investigation was conducted to record all the flood events that took place in the study area. Totally, 54 flood events were recorded from the year 1966 till 2015 that were classified in 4 categories, accordingly the severity of the damages caused. For each flood event, three different rainfall intensity values were assigned from each of the three meteorological stations, where rainfall data were obtained from. Moreover, statistical analysis was conducted on the rainfall time series, to choose the appropriate statistical distribution and to determine the return period of the extreme rainfalls. According to the results, the very high severity flood events of the study area occurred between the return period of 20-50 years. Significant number of these floods could have been avoided if the infrastructures design and construction were based on a return period of 50-100 years.