A rainfall distribution and their influence on flood generation in the eastern slovakia

Abstract

This paper aims to geographically assess the fl ood occurrence in eastern Slovakia by using one of the methods of multi-criteria analysis - rank sum method. Flood risk assessment is conducted in three specifi c cases: the long term period 1989-2009, the extremely wet 2010 year, and the extremely dry 2011 year. In the analyses, some of the causative factors for fl ooding in a basin area are taken into account. We use set of causative factors concerning mostly hydrological and physio-geographical characteristic of the target area that can be measured and evaluated such as soil type, daily precipitation (for the years 1989-2009, 2010, 2011), land use, catchment area and basin slope. For recommendation which causative factors should be preferred we use method of multicriteria analysis - ranking method. In the ranking method (RM), every factor/criterion under consideration is ranked in the order of the decision-maker's preference. Geographic approach to fl ood risk assessment provides a descriptive presentation of the results obtained. Geographic information systems as a visualization tool is presented in a manner that aids understanding in a user friendly way. Regarding our task of fl ood risk assessment, the partial results are three composite maps, which present comparison of fl ood risk zones in percentage of the area in years 1989-2009, 2010, and 2011. The composite maps are background for risk assessment of the impact of rainfall on fl ood generation. This study of hydrological data and physio-geographical characteristic was carried out with the purpose of the identifi cation of fl ood risk occurrence in eastern Slovakia. Results from our study shows, that rainfall distribution has high infl uence on fl ood risk of the area. Area percentage with very high fl ood risk index was calculated for "wet" year 2010 as 11.73 %, for "dry" year 2011 as 0.01 % and for period 1989-2009 as 0.28 %.