Abstract
Abstract. Recent flash flood impact studies highlight that road networks are often disrupted due to adverse weather and flash flood events. Road users are thus particularly exposed to road flooding during their daily mobility. Previous exposure studies, however, do not take into consideration population mobility. Recent advances in transportation research provide an appropriate framework for simulating individual travel-activity patterns using an activity-based approach. These activity-based mobility models enable the prediction of the sequence of activities performed by individuals and locating them with a high spatial–temporal resolution. This paper describes the development of the MobRISK microsimulation system: a model for assessing the exposure of road users to extreme hydrometeorological events. MobRISK aims at providing an accurate spatiotemporal exposure assessment by integrating travel-activity behaviors and mobility adaptation with respect to weather disruptions. The model is applied in a flash-flood-prone area in southern France to assess motorists' exposure to the September 2002 flash flood event. The results show that risk of flooding mainly occurs in principal road links with considerable traffic load. However, a lag time between the timing of the road submersion and persons crossing these roads contributes to reducing the potential vehicle-related fatal accidents. It is also found that sociodemographic variables have a significant effect on individual exposure. Thus, the proposed model demonstrates the benefits of considering spatiotemporal dynamics of population exposure to flash floods and presents an important improvement in exposure assessment methods. Such improved characterization of road user exposures can present valuable information for flood risk management services.
Highlights
Flash flooding is considered one of the most dangerous natural hazard in terms of human losses
Even though MobRISK model development is at the scale of the Gard department, we present a first application of the model in the subregion of Alès located in the north of the Gard administrative area (Fig. 2)
The MobRISK microsimulator is to our knowledge the first of its kind in combining social and hydrometeorological state-of-the-art knowledge to understand the dynamics of human exposure and behavioral response to short-fuse weather events
Summary
Flash flooding is considered one of the most dangerous natural hazard in terms of human losses. Daily mobility is pointed out as one of the primary causes of population exposure and vulnerability to flash floods (Ruin, 2010). Mobility aspects are not systematically included in studies assessing human exposure and vulnerability to natural hazards. In order to integrate social vulnerability in risk measurement, population density data is often used assuming a static distribution, which contrasts with the fast dynamics of the flash flood phenomenon. It has progressively been acknowledged that variation of population distribution may provide a more accurate assessment of human exposure to natural hazards. Freire and Aubrecht (2012) considered nighttime- and daytime-specific population densities for assessing population exposure to earthquake hazard in the Lisbon Metropolitan Area. In the context of flash floods, Terti et al (2015, 2017) and Spitalar et al (2014) showed that daily and sub-daily variation of population dis-
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