Pattern-based assessment of the influence of rainfall characteristics on urban stormwater quality

Abstract

Urbanisation increases pollutant generation within catchments and their transport to receiving waters. Changes to rainfall patterns, particularly in the age of climate change, make pollution mitigation a challenging task. Understanding how rainfall characteristics could influence the changes to stormwater pollutant runoff is important for designing effective mitigation strategies. This study employed a pattern-based assessment of relationships between rainfall characteristics and stormwater quality in urban catchments to develop this understanding. The research outcomes showed that rainfall events could be distinctly clustered based on intensity and duration, and each cluster of events would produce different stormwater quality responses. The high-intensity bursts occurring in the latter part of long-duration events were found to produce uniform and low concentrations of suspended solids. One the contrary, high intensity bursts occurring in the initial part of short-duration events triggered the first-flush effect, thus producing high concentrations of suspended solids. Furthermore, the first-flush effect was likely to present when the high intensity bursts occurred in the mid portion of rainfall events and produced variable concentrations of suspended solids. It was also found that the average rainfall intensity plays a key role in mobilising and transporting pollutants accumulated on urban surfaces. HIGHLIGHTS Rainfall events were clustered based on stormwater quality responses.; Different portions of rainfall produce different stormwater quality responses.; High-intensity bursts in short-duration rainfall events trigger first flush.; High-intensity bursts in the mid portion of rainfall are likely to trigger first flush.; The average rainfall intensity plays a key role in mobilising and transporting pollutants.;

Keywords

• first flush
• rainfall characteristics
• rainfall pattern
• stormwater quality
• urban water pollution