Study region

Trelleborg is a mid-sized coastal municipality in southern Sweden that has experienced repeated pluvial flooding in recent decades. The city comprises areas served by both combined and separate sewer systems and is increasingly exposed to intense short-duration rainfall events. This study uses 17 years (2006–2023) of property-level flood reports, in situ rainfall observations from multiple local gauges, and detailed information on sewer system configuration and property type.

Study focus

The study investigates how rainfall characteristics and urban infrastructure are associated with flood frequency and recurrence at the property level. Flood reports were linked to rainfall event characteristics and analysed using non-parametric statistical tests and tree-based models, including Poisson regression and classification trees. Rainfall intensities across multiple durations were evaluated to identify relevant temporal scales, while infrastructure and property characteristics were assessed as influencing factors.

New hydrological insights

Short-duration rainfall intensity, particularly at the 60-minute scale, is more strongly associated with flood frequency and recurrence than total rainfall volume. Higher 60-minute intensities are linked to increased numbers of reported cases and a greater likelihood of repeated flooding at affected properties. Flooding was observed across a wide range of rainfall conditions, including events below nominal design thresholds, indicating that moderate rainfall can still result in substantial impacts. The results further show that flood recurrence is influenced by interactions between rainfall intensity and property characteristics. These findings provide empirical evidence on rainfall–infrastructure interactions in Trelleborg and support improved urban drainage assessment and adaptation planning.