Catchment-scale pollution process and first flush of urban storm runoff in Hanyang, Wuhan City

Eight storm events were surveyed at Shilipu catchment in Hanyang, Wuhan City. The flux , total suspended solids (TSS), chemical demand oxygen (COD), total nitrogen (TN), and total phosphorus (TP) in the runoff were measured. From the hydrograph and pollutography analysis, the process of urban stormwater runoff pollution was synchronously effected by the amount and availability of pollutants and the characteristics of rain-runoff. The concentration of pollutants was substantially higher during the initial period of stormwater runoff than lasted period. Based on the average of the eight storm events, 48%, 67%, and 78% of the TSS load were transported in the first 5mm, 10mm and 15mm runoff depth, respectively. The pollution load of the initial runoff was positively related to the dry weather period lasting before.