In general, accumulation of sediment within pipelines, manholes, and other components of urban sewer have a serious effect on sewerage arrangements, such as the resistance of the passage of flows, the cause of urban flooding, the premature operation of combined sewer overflows, and the inevitable pollution of watercourses. Therefore, it is necessary to analyze that the movements and sedimentation shape of sediment loads in straight path manholes need to be explained by experiments. In this study, hydraulic experiment model and conditions were decided by the results of documentary and field survey. The experimental apparatus which can be replaced the manhole shapes(square, circle) and invert types(general type, half circular invert, inclined benching) in straight path manholes were installed to measure deposited sedimentation quantity. The quantity of deposited sediment loads was measured by different conditions, for instance, the inflow conditions of sediment(continuous and certain period) and the amount of inflow sediment. The straight path manhole that was set up a inclined benching demonstrated the considerable effect of reduction of sedimentation in manholes without apropos of the change of manhole shapes. Moreover, the improved manhole showed that the substantial influence of the prevention of sedimentation in manholes because those would be completely removed the deposited sediment in manhole by the ideal designed velocity(1.0s) that was proposed in the design criteria of sewerage facilities. As a results, the improved manholes were able to increase the drainage capacity of sewerage arrangements in urban sewer.

Urban drainage systems are generally designed as open channel flow. The system, however, shows a partially surcharged flow in its body, especially at junctions or manholes. Thus, a special case of this condition needs to be explained as pressurized flow condition for designing the sewer system. This study considered the surcharged manhole flows during an unexpected rainfall event or an excess of design frequency. Overflows from surcharged manholes and urban flooding can occur from the effect of surcharged flows. Thus, sewer systems should be designed with the concept of open channel flow and pressurized flow. Also, energy losses in a manhole need to be considered. The aim of this study is to develop the numerical model which can evaluate the effect of the energy losses at the manhole. The numerical model was verified and compared with hydraulic model and SWMM. The results showed that the water depth of numerical model was in good agreement with hydraulic model at the each manhole. However, the SWMM underestimated the water depth because that model ignored the energy losses at manholes. Thus, the developed numerical model in this study could be a useful tool for the assessment of a conveyance of urban drainage system.