Large areas of the Carpathian Basin are susceptible to inland excess water due to superfluous precipitation in combination with insufficient infiltration, evaporation and runoff. The modelling of areas threatened by these floods is nowadays often GIS based, using conceptual modelling techniques, where the risk/hazard of inland excess water is determined based on a set of weighted GIS and/or remotely sensed data layers each representing a specific factor. This type of modelling is difficult to verify and apply in other areas. To avoid these problems, in this research, a numerical approach is presented where a hydrological model is applied to determine inland excess water development. The input data have been determined by measurements of physical phenomena. The advantages of our approach are that (1) simulated inland excess water inundations can be verified with actual flood data, (2) physical computations can be repeated in other areas susceptible to inland excess water as well, and (3) the model can be used to calculate different scenarios simulating the impact of human intervention in inland excess water. This study shows the applicability of the approach for inland excess water modelling and aims to determine its data requirements and limitations. The results are compared to inundations digitized from a high resolution satellite image and show that the method gives accurate results using the available data.