A Probabilistic Model for Predicting the Performance of a Stormwater Overflow Structure as Part of a Stormwater Treatment Plant

The purpose of this study was to attempt to develop a stochastic model that describes the operation of the stormwater overflow located in the stormwater sewerage system. The model built for this study makes it possible to simulate the annual volume of the stormwater discharge, the maximum volume of the overflow discharge in a precipitation event, and the share of the latter in the total amount of stormwater conveyed directly, without pre-treatment, to the receiver. The dependence obtained with the linear regression method was employed to identify the occurrence of stormwater discharge. The prediction of the synthetic annual rainfall series was made using the Monte Carlo method. This was performed based on the determined log-normal distribution, the parameters of which were specified using 13-year rainfall series. Additionally, simulation of the stormwater overflow operation was performed with the use of a calibrated hydrodynamic model of the catchment. The model was developed using the Storm Water Management Model (SWMM). The results of the hydrodynamic simulations of the volume and number of discharges were within the scope of the probabilistic solution, which confirms the applicative character of the method presented in this study, intended to assess the operation of stormwater overflow.