Integrating Flood-Induced Mobility Disruption Modelling into CityNexus as a New Advanced Application Service on Destination Earth

Urban mobility and air quality are tightly coupled in cities: travel demand, network performance, and the spatial distribution of activities shape transport-related emissions and accessibility, and therefore underpin policy instruments such as low-emission zones, speed regulation, network reconfiguration, and land-use adjustments. Urban transport systems, however, operate within a broader set of constraints that extend beyond traffic and emissions management. Flooding and other water-related disruptions are a recurrent and increasingly relevant challenge for cities, with the potential to severely affect the transport network functionality. These challenges are often addressed through separate analytical tools, reflecting isolated approaches to mobility, environmental quality, and climate resilience topics. This fragmentation limits the ability of decision-support systems to effectively evaluate interventions across interrelated domains, motivating the need for modular and extensible services capable of integrating multiple processes within a single analytical framework.

CityNexus Pro, an Advanced Application Service (AAS) onboarded on Destination Earth, addresses this need through an operational and modular architecture designed to support integrated and cross-cutting scenarios analysis. The service builds on CityNexus, initially developed to support scenario-based assessment of mobility patterns, transport-related emissions, and air quality, and extends this baseline by incorporating an interoperable module for modelling mobility disruptions caused by flooding.

Within CityNexus Pro, urban mobility dynamics are represented by coupling data-driven origin–destination estimation with a traffic simulation engine, generating high-resolution spatio-temporal traffic flows. These flows are translated into emission estimates and linked to air quality models to quantitatively assess pollutant concentrations under alternative urban scenarios. Model assumptions, data sources, and parameterisations are explicitly documented to ensure transparency and reproducibility. Flood modelling outputs derived from hydrodynamic simulations based on the SFINCS model are mapped onto road network elements and incorporated into the mobility simulation chain, enabling dynamic modification of traffic conditions through configurable speed-reduction and road-closure thresholds.

The service, which already supports a range of policy-relevant scenarios—including low-emission zones implementation, speed limit changes, partial or full road inaccessibility, land-use reallocations, and shifts in mobility demand—is further complemented by compound scenario analysis in which flood hazards and mobility-related policy interventions are evaluated jointly. Users can configure flood scenarios by adjusting parameters such as precipitation timing and duration, river and sea discharge, and the presence of flood defences. In addition, CityNexus Pro is designed to integrate forecast products from the DestinE Digital Twin for Weather-Induced Extremes, enabling the impact assessment of extreme rainfall and flooding on mobility patterns and accessibility. 

CityNexus Pro is operational in Copenhagen, Seville, Bologna, and Aarhus, and is currently being deployed in Bucharest and Vitoria-Gasteiz. The service demonstrates how modular urban analytics on Destination Earth can be incrementally enhanced to address compound climate risks and support non-siloed, policy-relevant scenario analysis for urban resilience.