Characterization of urban stormwater runoff

The purpose of this study is to investigate the characteristics of pollutants overflow on storm events, relationships between pollutant load and runoff, and the first flush effect in urban areas. Nine watersheds in the cities of Taejon and Chongju, Korea were selected for sampling and study with different characteristics during the period from June 1995 to November 1997. Runoff and quality parameters such as BOD5, COD, SS, TKN, NO3-N, PO4-P, TP, Pb, Fe, and n-Hexane extracts were analyzed for the development of relationships between runoff and water quality. From the hydrograph and pollutograph analysis, the peak of pollutant concentration preceded that of the flowrate in an area smaller than 100 ha in which impervious area occupied more than 80%. The peak of pollutant concentration, however, was followed by that of flowrate in the watershed in an area larger than 100 ha in which the impervious area was less than 50%. This phenomenon appeared to occur more frequently in the watershed which has the combined sewer systems. In the storm event, the relative magnitude of the pollutants unit loading rate was in the following order; high density residential>low density residential>industrial>undeveloped watershed.