Flood inundation assessment of ‎UNESCO World Heritage Sites using remote sensing and spatial metrics in Hoi An City, Vietnam

Flooding is the most frequent and damaging threat to The United Nations Educational, Scientific, and Cultural Organization (UNESCO) World Heritage Sites, and has been exacerbated by climate change. Hoi An Ancient Town, one of the world's cultural heritage sites in Vietnam, is facing inundation risks from increasing extreme flood events due to anthropogenic and natural processes. This study combines Geospatial Information System (GIS), remote sensing data, and landscape ecology metrics to assess the flood risk of Hoi An City. The analysis includes (1) classification of land-use/land-cover (LULC) using Sentinel-2 data; (2) computation of a flood risk index using hazard characteristics, physical and demographic exposures, and physical and socioeconomic vulnerabilities, together with adaptive capacity and spatial metrics, and the Fuzzy-Analytic Hierarchy Process (AHP) method to determine the weight of each index and ranking; and (3) determination of flood risks for the UNESCO World Heritage Sites of Hoi An City and the surrounding areas. By comparing model outputs with historical flood locations (N=330), the study finds that more than 75% of past floods occurred at high or very high-risk areas forecasted by the model. Results from the model verified by true flood incidents show that the inundation hotspots are concentrated in the city's heritage sites, where human and climate changes have impacted landscape structure. The flood inundation risk mapping obtained from the synthesis analysis, encompasses hazard, exposure, and vulnerability, offering holistic knowledge to help reduce and manage flood risks at Hoi An World Heritage Sites. This method can be applicable to other sites with similar characteristics.