Flash Flood Susceptibility Evaluation in Human-Affected Areas Using Geomorphological Methods—The Case of 9 August 2020, Euboea, Greece. A GIS-Based Approach

Anna Karkani,Nicoletta Santangelo,Evangelos Spyrou,Hampik Maroukian,Alexandros Petropoulos,Niki Evelpidou,Lida Lakidi,Maria Tzouxanioti

doi:10.3390/geohazards2040020

Anna Karkani, Nicoletta Santangelo + Show 6 more

Open Access

https://doi.org/10.3390/geohazards2040020

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Abstract

Flash floods occur almost exclusively in small basins, and they are common in small Mediterranean catchments. They pose one of the most common natural disasters, as well as one of the most devastating. Such was the case of the recent flood in Euboea island, in Greece, in August 2020. A field survey was accomplished after the 2020 flash floods in order to record the main impacts of the event and identify the geomorphological and man-made causes. The flash flood susceptibility in the urbanized alluvial fans was further assessed using a Geographic Information System (GIS)-based approach. Our findings suggest that a large portion of the alluvial fans of Politika, Poros and Mantania streams are mainly characterized by high and very high hazard. In fact, ~27% of the alluvial fans of Politika and Poros streams are characterized with very high susceptibility, and ~54% of Psachna area. GIS results have been confirmed by field observations after the 2020 flash flood, with significant damages noted, such as debris flows and infrastructure damages, in buildings, bridges and the road networks. In addition, even though the adopted approach may be more time-consuming in comparison to purely computational methods, it has the potential of being more accurate as it combines field observations and the effect of past flooding events.

Highlights

The term “flood” refers to the overflow of the natural bed of a river, stream or artificial canal and the consequential covering of areas with water, which would normally be dry [1]
Human structurHesu(mbraidngset,rurocatudr,eestc(.b)raidlogneg, rthoaedr,iveetrc.c)haanlonneglstohfetrhievesrtucdhyananreealsreo-f the study area duced the criticarlecdruocsesd-stehcetiocrnisticoafltchreosrsiv-seercst,iocanussoinf tghleorciavleorsv,ecrafluoswinsgalnodcailnotvenersflifoicwatsioannd intensification of the phenomenoofnth, ewphheerenaosmtheenolinm, iwtehderceoanssthruecltiimonitseodfcpornosttercutciotinondsaomfspuroptsetcrteiaomn ddaidms upstream did not suffice to rednuoctesuthffiecdeytnoarmedicusceofththeedfylonwamdiocswonfstrheeaflmo.wOndotwhenostrheearmh.aOndn, tahlleuovtihael r hand, alluvial fans are very profannestaorfelovoedryinpgrownheetno flheoaovdyinrgaiwnhfaelnl ohcecauvrys,raginvfeanlltohcactutrhse, ygicvoennstihstatotfhdeey- consist of debris bris deriving fromdeprirveivnigoufrsofmloopdreevvioenutssfl
The two-fold adopted approach in this work has shown that amongst the most critical factors in flash flood susceptibility is the urbanization of the alluvial fans and the presence of artificial surfaces, covering or replacing the stream beds, which is common in the settlements of the study area

Summary

Introduction

The term “flood” refers to the overflow of the natural bed of a river, stream or artificial canal and the consequential covering of areas with water, which would normally be dry [1]. A flash flood is an intense flood that is caused by heavy rainfall in a short period of time. These phenomena occur almost exclusively in small basins (up to a few hundred square kilometers) and they are common in small Mediterranean catchments. A significant part of the European population resides in areas that are susceptible to floods [14]

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