A Holistic Framework for Flood Risk Assessment and Optimal Design of Mitigation Measures

This study addresses the challenges of urban flood risk assessment using a holistic flood risk assessment methodology for the catchment area of the Garyllis River (Cyprus). This advanced methodology integrates hydraulic modeling, earth observation and geospatial information analysis, as well as socioeconomic data for risk-informed emergency planning. Two-dimensional hydraulic simulations have been conducted under three different return period scenarios (50, 100 and 1000 years). For the worst-case scenario, the highest water depth reached 6.2 m, most significantly affecting the urban regions in the southern part of the basin. Flood hazard was assessed and combined with both demographic vulnerability indicators (population density and age distribution) and economic exposure data (land economic value). To quantify flood risk, a risk matrix was developed in which hazard, vulnerability and exposure values were synthesized and classified into five risk categories. The results revealed that the highest risk levels are associated with the urban areas, since these areas are characterized by flat terrains, low surface permeability, dense population, and high land economic value. The resulting flood risk maps were used to identify safe emergency shelters and design optimal evacuation routes in the existing road network with adequate traffic capacity. The selection of emergency shelters was focused on public buildings located in zero-to-low risk zones, prioritizing accessibility for vulnerable and at-risk people. In this context, this study delivers a replicable decision-support framework that links hydraulic modeling and Earth Observation with actionable civil protection-oriented strategies, thus enhancing urban flood resilience and disaster preparedness.