Urban stormwater pollutant dynamics, SuDS performance, and public health risks under intensifying extremes

Urban areas are increasingly exposed to short, intense rainfall that mobilises pollutants and concentrates public health risks within the first minutes of storms. This review synthesises evidence on pollutant build-up and wash-off, first flush behaviour, event mean concentration and peak metrics, and the performance of Sustainable Urban Drainage Systems and treatment trains, with emphasis on device ageing, hydraulic overloading, operations and maintenance, and nonstationary design. Case studies across continents show that surface type, impervious connectivity, antecedent dry period, and rainfall microstructure govern pollutant export; roadway-dominated catchments drive particle and metal pulses; and storage elements can function as sinks or sources depending on loading. Event mean concentration alone underestimates short-lived peaks that drive exceedances and exposure. This supports the need for combined reporting with time-resolved indicators. Public health studies connect urban stormwater to higher levels of pathogens, risk hotspots, and mixture toxicity in receiving waters. Meanwhile, microbial source tracking and network diagnostics uncover cross connections that undermine protection goals. Evidence on Sustainable Urban Drainage Systems demonstrates robust event scale removal for particulates and particulate-bound species, with performance tapering under high inflow and with ageing; targeted maintenance restores function; and catchment planning and siting determine realised benefits. The review concludes that climate-resilient protection requires nonstationary rainfall in design, mixture-aware monitoring, and performance-based standards coupled to lifecycle operations. Future research should standardise high-frequency sampling, integrate quantitative risk with design practice, resolve microplastics and trace organic fate under extreme hydraulics, and evaluate ageing and maintenance triggers across diverse urban forms.