Disproportionate impact of compound flood events on road infrastructure damage

The resilience of road infrastructure is vital for maintaining community mobility and ensuring the continuity of critical services, particularly in the face of escalating challenges posed by climate change. Among these challenges, the increasing frequency and intensity of extreme weather events often manifest as floods, posing a substantial threat to urban road networks in low-lying coastal areas. These regions are especially vulnerable to multiple flood drivers, including tidal surges, streamflow, and precipitation. The co-occurrence of extreme rainfall with high tides and elevated streamflow levels amplifies flood inundation depths, yet the compound effects of these flood drivers on road infrastructure damage remain underexplored. This study proposes a quantitative framework to assess the dynamic interaction of compound flood events and their impacts on road infrastructure systems, with a focus on damage assessment. Using the extreme weather events of 2018 in Kozhikode, Kerala, India, as a case study, we integrate disparate flood hazards—pluvial (rainfall-induced), fluvial (streamflow), and coastal (storm tide)—to evaluate flood risk and road damage. A 1D-2D hydrodynamic modeling approach, coupled with depth-damage curves, quantifies the repair and maintenance costs for roads affected by compound flooding. Our findings reveal that pluvial flooding accounts for 93% of road damage, while fluvial and coastal flooding contribute 5.6% and 1.4%, respectively. This framework highlights the disproportionate impacts of different flood drivers and enables the identification of the primary contributors to road damage. Such insights can inform targeted adaptation strategies tailored to the unique needs of specific regions, enhancing infrastructure resilience against future flood events.