Sedimentation is a problematic issue concerningsewer system design. In order to reducesediment deposition in sewersystems, two new equationsarepresented with asmoothing function and Group Method of Data Handling (GMDH) to estimateminimum flowvelocity. For this purpose, dimensional analysis is used to determine the factors affecting sediment transport at limit of deposition. These factors are categorized in five different groups: transport, transport mode, flow resistance, sediment and motion. Six different models are presented for predicting the densimetric Froude number (Fr) using the smoothing function and GMDH. Themodels presented withthese two methods are compared with existing equations. The results indicate that the equations proposedusing thesmoothingfunction (MAPE= 5.05, RMSE= 0.24 & AIC= -43.04) and GMDH (MAPE= 5.39, RMSE= 0.3 & AIC= 72.78) are more accurate than existing models. Furthermore, sensitivity analysis is performed to examine the efficacy of each of the dimensionless parameters presented by the best model in estimating Fr