SENSITIVITY OF TRANSPORT MODEL TO HYDRAULIC MODEL FOR FLOOD RISK ASSESSMENT OF ROAD INFRASTRUCTURES

Urban inundations cause large impacts to road infrastructures which are especially important during emergencies because the resilience of a community relies upon fast connection to shelters and critical facilities (e.g. hospitals, fire stations). Moreover, during riverine floods the inundation propagates in the urban environment mostly following the road network where most injuries and fatalities take place. This works aims at understanding the sensitivity of transport model and human vulnerability estimates to the resolution of the flood maps, which can be used to increase preparedness. Three different hydraulic approaches are compared: a quasi-2D model adopted for official flood hazard maps, a full 2D model (TELEMAC-2D) with a 30 m resolution (e.g. like common global DTMs) and a full 2D model with a mesh resolution able to capture single buildings and roads (LiDAR-derived 1 m resolution). Changes in time and distance between origin and destinations as a result of flooding are analyzed by coupling a network model with flood hazard, using a transport network disruption model. The vulnerability of pedestrians is based on a dimensionless stability threshold, based on subject characteristics and inundation parameters. The methodology is applied to a district of Florence (Italy) placed at the crossing of two streams and in a crucial road junction for the area. The results in terms of road accessibility, service areas and citizens vulnerability are compared and discussed for the three different hydraulic approaches to provide support for decision makers and civil protection rescuers.