: This paper presents a hydraulic analysis of unsteady flow due to a possible dam break of the Tribistovo reservoir located in the Municipality of Posušje, Bosnia and Herzegovina. Flood wave propagation is calculated and flood maps are derived for different dam break scenarios. The methodology adopted for the development of the flood wave propagation model is based on the use of available tools for collection, processing and graphical display of geospatial data and tools for hydrodynamic modeling of transient flow. The selected approach is conservative and results are, as a rule, the worst case scenarios. Flood areas are obtained on the basis of hydraulic calculations with the most unfavorable assumptions: maximum water level in the reservoir, maximum inflow in the reservoir (with the return period of T = 10 000 years), instantaneous/gradual and total dam break, all of which result in extreme flooding.

Some usual hydrological methods and the hydrological model EBA4SUB are used in the paper to determine the design peak discharge for various return periods for catchments in Bosnia and Herzegovina. The aim of the paper is to test for the first time the EBA4SUB model in the selected catchments. The results obtained by the EBA4SUB model compare well with other related methods. The advantages of the model lie in the fact that it takes into account physical processes taking place in the catchment, influencing formation of surface runoff.