THE FIRST FLUSH ANALYSIS OF STORMWATER RUNOFF IN A HUMID CLIMATE

This study focuses on the pollutants from urban runoff to Zarjoob River, which is one of rivers leading Anzali International Wetland, was listed in Montreux Record 1993 as a site need priority conservation. Storm water residential area Rasht (the largest city Iran’s Caspian Sea coast) monitored this during thirteen rainfall events, with total 58 storm samples collected 2018 2019. In most mean concentration suspended solids (TSS) and chemical oxygen demand (COD) were higher than other pollutants. The event concentrations (EMC) TSS loads ranged 57.3 mg/L 682.5 46.7 590.4 for COD. (SMC) TSS, COD, phosphorus (Total P), nitrate-nitrogen (NO3-N), lead (Pb) 219, 205, 1.91, 20.63, 0.25 mg/L, respectively. first flush coefficient (b) used evaluate flushing various events. results confirmed that occurred all average ranking strength among COD > NO3-N TP Pb TSS. Controlling one-third initial volume appeared be critical managing quality humid regions. findings can applied management strategies cities similar climatic conditions.