Multi-hazard assessment in the coastal tourism city of Denpasar, Bali, Indonesia

Denpasar, the capital city of Bali Province, is a coastal city pivotal for tourism, economy, and investment. However, these activities, compounded by climate change, alter coastal characteristics, potentially increasing coastal hazards. This study aims to determine the coastal region's characteristics and analyze the distribution of coastal multi-hazards in Denpasar using the Coastal Hazard Wheel (CHW). The multi-hazards studied consist of ecosystem disruption, gradual inundation, seawater intrusion, erosion, and flooding. The results showed that Denpasar City has heterogeneous coastal characteristics. Denpasar’s coastal region is composed of a geological layout: a barrier, delta/low estuary island, sedimentary plain, sloping soft rock, and tidal inlet/sand spit/river mouth. Wave exposure in the Denpasar’s coastal region consists of protected and moderately exposed categories with significant wave heights ranging from 0.93 to 1.27 m. Tidal analysis shows that the average tidal range in the Denpasar’s coastal region is 366 cm (meso tidal). Denpasar’s coastal area also has heterogeneous flora/fauna conditions with categories such as mangrove/tidal flat, vegetated slope, not vegetated, and any (there is vegetation, but it does not have a significant effect). Denpasar’s coastal region experienced an increase in shoreline by 4.2 km (8.7%) from 2012 to 2022, dominated by anthropogenic activities. There is no tropical cyclone activity around Denpasar’s coastal area. Based on the conditions of the biogeophysical parameters, the coastal type and the level of existing hazards can identified. Ecosystem disruption has low, medium, and very high hazard levels. Seawater intrusion has a low to high hazard level. Meanwhile, gradual inundation, erosion, and coastal flooding have a low to very high level of hazard.