Using the example of the Tom River, this article demonstrates the result of 2D simulation modeling of river hydraulics and describes the impact of various calculation parameters on this result. Relevance. The results obtained can enable a deeper understanding of the capabilities and limitations of the modeling system under study and provide scientifically proven recommendations on the use of various calculation algorithms and the selection of the computation mesh size in order to minimize the computation time while maintaining the required quality of results. Aim. In the modeling system under study, several basic calculation algorithms are used. Using the example of the Tom River, the aim of the study is to investigate how the selection of a particular calculation algorithm and the size of the computation mesh cells can affect the result obtained when creating models as part of engineering surveys. Methods. The study is based on computer experiments and comparison and interpretation of the computer simulation modelling results of the investigated section, using each of the calculation algorithms and two sizes of the computation mesh (conditionally, large and small) for two scenarios: actual (in the situation of current development) and designed (taking into account the effect of the projected flood control dams). Results and conclusion. The author has obtained the tables of modeled water level marks, the time spent on calculations under the two scenarios and the modeled water surface profiles under each scenario. The author draws the conclusions and gives the recommendations on the use of model calculation algorithms and selection of the size of the calculation mesh cells for engineering surveys.