Original paper

Rapid screening of flash flood-affected watersheds in Hungary

Czigány, Szabolcs; Pirkhoffer, Ervin; Nagyváradi, László; Hegedűs, Péter; Geresdi, István

Abstract

Flood events in small mountain watersheds, called flash floods, have been documented rather frequently over the past decades in many parts of the world. Despite the country's relative flatness, floods of this type have also been reported from the hilly and low mountain catchments of Hungary. To avoid flash-flood-triggered losses, development of a flash flood guidance (FFG) system was proposed by the concerned authorities. To generate a rapid screening-based nationwide vulnerability map as part of the FFG system, so-called passive environmental factors are considered and discussed in the present study, i.e. those that change insignificantly with time. These factors include topographical (slope angle and slope range), land use and land cover (vegetation, soil physical properties, topsoil thickness and limestone areas) and hydrological factors (number of tributary rivers and stream density). Vulnerability level is presented in two ways: (i) interpolation among the outflow points of the individual watersheds (OFPI based) and (ii) on the basis of individual watersheds (WSB type). The obtained vulnerability maps largely differ from each other depending on their way of representation, and the number of vulnerability classes. The majority of the resulting maps appropriately reflect the most flash flood-impacted areas of Hungary and indicate the areas for which flash flood events have already been documented.

Keywords

vulnerability mapflash floodrapid screeninghazard assessment