The deposition of solids in combined sewer systems results in a loss of flow capacity that may restrict flow and cause a local flooding and enhanced solids deposition. In order to solve these problems and proper pipe management, estimations of solid loads on land surface in a drainage basin and solid deposition in sewer system due to rainfall are needed but these tasks are very difficult and very expensive. In this study, procedures for estimating solid loads on surface in a drainage basin were applied and analyzed in Gunja drainage basin in Korea. Also, this paper presents the development and application of estimation equation for solid deposition in sewer system due to rainfall based on the solid deposition estimated using MOUSE model. As results, the comparison between estimated and measured solid deposition is difficult due to the absent of measured data, but the estimated values using developed equations show applicability compared with the results of MOUSE model and the application of the other basin. The developed estimation equations can be used usefully for the management of combined sewer system.