From Equality to Equity: The Dual Socioeconomic Inequalities of Mobility-Based Exposure and Exposure Avoidance Options during Urban Floods

Urban pluvial flooding creates unequal risks that are not fully captured by residence-based exposure measures. We developed a framework that jointly evaluates mobility-based flood exposure (MFE) and exposure avoidance constraint (EAC), defined as the additional travel distance required to reduce flood susceptibility. Within Beijing’s Fifth Ring Road, we combined AlphaEarth Foundation Embeddings with mobile phone signaling data to quantify flood exposure and flood-avoidance routing constraints for 614,510 residents. EAC is measured by constructing Pareto frontiers through Monte Carlo path simulation, while multinomial logit models with interaction terms are used to examine the relationships between socioeconomic status (SES) and the dual inequalities. The results show: (1) residence-based assessment suffers from the Neighborhood Effect Averaging Problem, leading to systematic bias relative to mobility-based measures; (2) low-SES groups experience dual disadvantages, characterized by higher MFE and higher EAC; and (3) the interaction between exposure and avoidance constraint is state-dependent, reinforcing the relative disadvantage of low-SES residents beyond an additive pattern under finite EAC, while limiting further socioeconomic differentiation under infinite EAC. We argue for a shift from an equality-oriented to an equity-oriented perspective, providing actionable insights for disaster risk reduction and the achievement of SDGs 3, 10, and 11.