Pluvial flooding Dynamic Mapping under Historical Climatic Conditions in Rome, Italy

Urban pluvial flooding is increasingly recognized as a critical issue due to its rising frequency and severity in many cities worldwide. This study aims to develop dynamic maps at suburban scales for flood risk assessment in the city of Rome, Italy, focusing on the impacts on critical transport linear infrastructures, such as roads. Dynamic mapping incorporates temporal changes in environmental conditions (such as rainfall intensity, water levels, and storm surges), human activities (like population movements and daily routines), infrastructure status (e.g., drainage capacity and road networks), and other socio-economic variables (such as adaptive capacity and community resilience) to capture how flood risk evolves over time. For this case study, dynamic pluvial flood hazard maps are developed by using the rain-on-grid model from HEC-RAS, i.e. a 2D hydrodynamic model designed to simulate surface water flow over a grid-based terrain. In this setup, rainfall is applied directly onto each cell of a high-resolution digital DSM, creating a rain-on-grid scenario where precipitation generates surface runoff that flows across the landscape. This approach captures detailed interactions between rainfall intensity, topography, and surface flow dynamics, making it suitable for urban areas. The analyzed data includes series of synthetic precipitation hyetographs that are estimated using Intensity-Duration-Frequency (IDF) curves derived from rain gage data located in the study area. These synthetic hyetographs represent return periods of 2, 5, 25, 50, and 100 years, with durations of 5, 10, 20, 30, 40, 50, and 60 minutes, which represent different precipitation intensities to produce a sensitivity analysis under different return periods and rainfall durations. Also, observed storm events are assessed to calibrate and validate the model. It is worth to mention that this model does not consider the drainage system, thus results are in favour of safety.