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The testing of a model performance is important and is also a challenging part of scientific work. In this paper, the results of the physically-based EROSION-3D (Jürgen Schmidt, Berlin, Germany) model were compared with trapped sediments in a small reservoir. The model was applied to simulate runoff-erosion processes in the Svacenický Creek catchment in the western part of the Slovak Republic. The model is sufficient to identify the areas vulnerable to erosion and deposition within the catchment. The volume of sediments was measured by a bathymetric field survey during three terrain journeys (in 2015, 2016, and 2017). The results of the model point to an underestimation of the actual processes by 30% to 80%. The initial soil moisture played an important role, and the results also revealed that rainfall events are able to erode and contribute to a significant part of sediments.

The modeling of soil erosion processes is affected by several factors that reflect the physical-geographic conditions of the study site together with the land use linkage. The soil parameters are significant in the modeling of erosion and also runoff processes. The correct determination of a soil's parameters becomes a crucial part of the model's calibration. This paper deals with a sensitivity analysis of seven soil input parameters to the physically-based Erosion 3D model. The results show the variable influence of each soil parameter. The Erosion 3D model is very sensitive to initial soil moisture, bulk density, and erodibility.

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The scope of this study is the application of new approach for estimation of potential soil erosion in the Slovakia using a physically-based erosion model Erosion 3D for modelling potential erosion in the Myjava River basin. Erosion 3D is a physically-based computer model for predicting soil erosion by water on agricultural land (Schmidt, 1996). The model is predominantly based on physical principles and it simulates surface runoff, erosion, deposition and the detachment of soil particles for single events, and provides good tool for simulate and quantify soil erosion, but has not been established in Slovakian basins yet. The soil system of Erosion 3D is based on the fourth edition of the Bodenkundliche Kartieranleitung ("KA 4", AG Boden, 1994). Because of different soil types it was required in the first step to create an overplot of KA 4 textural system with the USDA textural system used in Slovakia. The model requires three input parameter-relief, precipitation and soil parameters. The first two parameters are easy to obtain but soil input parameters are more complicated mainly for different areas where the model was calibrated and validated. In this study we focused to creation of the soil input data sets for Slovak condition including establishment of Parameter catalog for every soil input parameters. The catalog has been configured based on overplotted textural triangle. The Erosion 3D model was applied to a small catchment Tura Luka situated in the Myjava Hill Land which is known for its quick runoff response and related muddy floods. Four scenarios of initial moisture parameter, which is considered as the most sensitive soil input parameter, were applied. Simulations were done for 100year design rainfall of 60 minutes duration. The results of potential erosion are wellcapable to point to the spatial and temporal variability of the rainfall event with the wide range of the values.

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The study presents a validation of the physically-based EROSION-3D model and the USPED empirical model and compares them with actual measured data. During the last decade there has been an intention to develop a new generation of erosion models in order to replace the Universal Soil Loss Equation used worldwide with more effective methods. One of those methods is represented by physically-based models, which provide a tool that relies upon descriptions of the processes that occur in actual natural conditions. The essential element of physically-based models is that they are process-based and reflect the most recent advances in erosion and hydrological research. In the modelling of soil erosion, the validation and verification of the methodologies used are considered as general problems. The importance of a model´s validation can be seen in the building of confidence in the ability of the model to generate satisfactory simulation results in order to discover the strengths and weaknesses of the model used. The physically-based EROSION-3D model is suitable not only for research purposes, but also for engineering practices, e.g., for assessing the effect of changing agricultural management practices and their impact on soil losses. The validation of the models has been performed on a continuous rainfall series for the selected period 2015 - 2016. The modelled results were compared with the actual measured sediment deposition data acquired by a bathymetry survey of the Svacenicky Creek polder using the EcoMapper Autonomous Underwater Vehicle device in the same period. The Svacenicky Creek polder is a part of the flood protection measures in the investigated territory of the Myjava region in Slovakia. The final results present a comparison between the outputs from the models used together with a confrontation of the modelled and observed results obtained by the bathymetry measurements.

The article is focused on mathematical modelling of the soil erosion processes on the selected areas within the Slovak Republic and Poland. The study includes the validation of the models used based on the actual measurements. The intensity of the soil erosion processes was calculated using the physically-based EROSION-3D model and the empirical USLE-SDR model. The simulations were done based on continuous rainfall events and a long-term simulation. The results modelled were confronted with the actual measurements in both areas investigated. Since a model's validation and calibration as well as a relevant interpretation of the results obtained are the hardest and most challenging parts of any research, it is necessary to constantly enhance the techniques and methods of the calibration and validation of models, thereby deepening the knowledge of individual models. The results show the process has to be performed before the application of the models used together with the advantages and disadvantages of the physically-based and empirical models used, including a comparison and validation of the models applied.