Modelling flood hazard at Paratrechos/Peritsi stream, Naxos Island (Cyclades, Greece)

Abstract

Flash floods are one of the most significant natural hazards in the Mediterranean, affecting most basins in the region. Flash floods usually occur in ephemeral streams after particularly heavy rainfall. Although the average annual rainfall in the Cycladic islands (Greece) does not exceed 400 mm, flash floods are frequent, since most of that rainfall is often concentrated in few but very intense events. The case study is the drainage basin of Paratrechos or Peritsi stream in Naxos Island. This particular basin was selected due to the recorded flood events, the stream's proximity to the city that intensifies the flood impact, the slopes' gradient abrupt changes and the diverse infiltration rate of the geological formations. Furthermore, some parts of the basin are intact by human activities, while others are severely affected. This study investigates the relationship between rain and runoff through Unitary Hydrographs, in order to estimate and evaluate the flood potential of the aforementioned hydrologic basin and to determine the causes of the hazard and vulnerability. The Clark method was implemented and its results were further evaluated by field measurements.