ABSTRACT
This chapter examines the pollutant load in a small river running through an urban area, considering the urbanization of the river basin in terms of the progress of sewering and sewer types. The pollutant load reduction due to sewering depends on both the decrease in discharge and the improvement in water quality. The chapter aims to clear the following three subjects related to receiving water: quantification of the effect of sewering in an urban river basin; the pattern of pollutant runoff including the first-flash; evaluation of the pollutant runoff from nonpoint sources. The effect of sewering is conspicuous only on solid pollutants during a small storm, but not so conspicuous on soluble pollutants or on every pollutant during a large storm event. The basin has a relatively clear pattern of land use; the upper basin is mountainous or residential, the middle is residential, and the lower is industrial or residential.
