Addressing land use planning: A methodology for assessing pre- and post-landslide event urban configurations

With urban areas projected to accommodate 68 % of the global population by 2050, the imperative for inclusive, safe, and sustainable cities becomes paramount. In the timeline of urban centers, landslides represent one of the most destructive phenomena, involving several resources allocation with private and public investments, sometimes claiming human lives. By synergically connecting environmental, planning, and configurational spheres, this study seeks to support the proactive management of landslide risk. The proposed three-step methodology allowed to quantify the environmental features involved in landslide occurrence, evaluate planning framework vulnerabilities, and suggest alternative configurations for urban areas that experienced landslides. The methodology has been applied to the case study involving a tragic landslide in Casamicciola Terme (Italy) in November 2022. First, the stream network and the drainage basin corresponding to confluence point of the landslide into the sea have been calculated (environmental elaborations). Subsequently, these elaborations have been overlapped with the runoff mitigation and the sediment deposition layers, extracted through the INVEST software. Secondly, the reconnaissance of the local and superordinate planning levels has been realized, to deepen planning tools cogency on the study area, contextually deepening the constraints that characterize it. From the overlapping of these two steps, free landslide risk areas have been located. Finally, based on the available territorial surface (St_a) and the territorial cover ratio (Rc_t), two territorial configuration scenarios have been proposed, envisaging the relocation of the buildings involved into the landslide. Results show that landslide originated by three out of five gullies. Some portions of the urban areas of Casamicciola Terme are still under high and very high hydrogeological risk. Contextually, it emerges poor attention from the local planners to the superordinate planning framework. Historic settlement has an Rct of 33.64 %, while areas in which relocate the built up show an Rc_t of 32,45 % for scenario 1 and 27,9 % for scenario 2. The methodology resulted useful to address planning vulnerabilities, supporting the realization of alternative configurational scenarios. We expect our research to contribute to the evolving field of disaster risk reduction, by providing a systematic approach to manage landslide risk.