Influence of rainfall characteristics on pollutant wash-off for road catchments in urban Shanghai

• Sectional analysis approach is used to investigate pollutant wash-off.
• Rainfall intensity and ADP are key characteristics influencing pollutant wash-off.
• Rainfall intensity parameters influence the initial pollutant wash-off.
• Rainfall duration and ADP influence the intermediate and final phases of wash-off.

The influence of different rainfall characteristics on pollutant wash-off was investigated in stormwater runoff from three road surfaces in a highly urbanized area of Shanghai, China. The relationships between rainfall characteristics and pollutant wash-off were analyzed using sectional analysis, an innovative concept of using sector parameters to investigate the relationship between the pollutant wash-off process and different sectors of the runoff hydrograph and rainfall hyetograph. Results indicated that the rainfall intensity of the initial phase of a rainfall event was critical to the magnitude of the first flush. Rainfall duration and the antecedent dry period also influenced pollutant load washed-off during intermediate and final phases of a rainfall event. No influence of rainfall depth on first flush was observed. Several rainfall characteristics played important roles in pollutant wash-off processes. These findings are critical for designing and implementing low impact development practices.