Nuisance flood risk: Defining a new horizon in urban flood risk management through hydrodynamic flood hazard modelling and indicator-based vulnerability assessment

In recent years, rapid and unregulated urbanization has significantly intensified the challenges of urban flooding, particularly through the increasing prevalence of Nuisance Flooding (NF), a form of low-depth, low-velocity inundation that disproportionately affects densely populated megacities. While NF typically lacks the large-scale destructiveness, its frequent recurrence leads to persistent disruptions in mobility, public services, and the operation of critical infrastructure. Despite its growing significance, NF remains largely underrepresented in existing literature, which tends to overlook its widespread but subtle impacts, even though the associated social and economic losses are substantial. For the first time in flood management literature, this study proposes a flood risk assessment framework explicitly tailored to NF conditions over Mumbai, the financial capital of India. A sophisticated 1D–2D coupled hydrodynamic model was employed to simulate high-resolution flood hazards, while vulnerability to critical and infrastructure facilities was assessed using a Shannon Entropy-cum-TOPSIS framework. We employ a novel concept of Bivariate Flood Risk Classifier to integrate hazard and vulnerability information, producing spatially explicit NF risk maps. Our observations indicate that vulnerability drives flood risks over nearly half of the region, while more than 40 % of grids exhibit an equal contribution from both hazard and vulnerabilities. Sensitivity analysis revealed that slums are among the most critical contributors to vulnerability; excluding slum indicators resulted in a reduction in vulnerability across two-thirds of the wards. The framework offers a first-of-its-kind, robust methodology for NF risk assessment and provides crucial inputs for integrated, socially responsive flood resilience planning in rapidly urbanizing regions. • A hydrodynamic-cum-MCDM framework is put forward for quantifying Nuisance Flood Risks. • MIKE+ 1D–2D model utilized to capture shallow flooding dynamics. • Shannon Entropy-cum-TOPSIS utilized for capturing intrinsic vulnerability. • Slum areas strongly shape local vulnerability and risk concentration. • Bivariate Nuisance Flood risk maps support targeted urban flood resilience strategies.