The Kanda River flows through densely urbanized area. Therefore, the Kanda River basin has large-scale sewerage systems and many flood-control reservoirs along the river. The inflow discharge hydrograph from sewerage into river influences flood hydrograph of the Kanda River, but its volume is unknown. So, estimating the inflow discharge hydrograph from sewerage into the Kanda River is important for river managements. We applied the two-dimensional analysis of flood flow using time series of observed surface profiles in Kanda River. As a result, the calculation method provides good results for evaluation of inflow discharge hydrograph from sewerage. It is found that the discharge ratio of main stream to sewerage discharge is 5:2 at the confluence of Jyuniso trunk line and 3:2 at the confluence of Momozonogawa trunk line.