1. Introduction
Rising sea levels, more frequent storm surges, and intensifying extreme rainfall caused by climate change are heightening the flood risk in coastal cities. In Korea, major coastal urban areas have inherited structural vulnerabilities from rapid industrialization and urbanization—notably the expansion of impervious surfaces, weaknesses in drainage systems, and the spatial concentration of coastal development. Historical events underscore these exposures: Typhoons Rusa (2002), Maemi (2003), and Hinnamno (2022) inflicted large-scale losses of life and property, demonstrating that the existing disaster prevention and response framework is insufficient to address compound external forcings.
The societal impacts of climate change are well documented in the IPCC assessment (IPCC, 2022), and the broader public increasingly recognizes these changes through direct experience. Public discourse has also emphasized the severity of the problem; for example, the 78th UN Climate Ambition Summit remarked that the world has entered an era of “global boiling.” This global warming, now often described as “global heating,” has resulted in serious environmental, social, and economic consequences worldwide. According to the Special Report on Global Warming of 1.5 °C, global mean temperature has already risen by approximately 1.0 °C above pre-industrial levels, and the risks to human and natural systems are expected to increase substantially if warming reaches 1.5 °C. Consistent with these concerns, the IPCC Sixth Assessment Report projects that global mean sea level could rise by up to 0.93 m by 2100, implying severe social and economic disruptions, including flooding in low-lying coastal cities, damage to critical infrastructure, and saltwater intrusion.
Compound flooding in coastal zones is of particular concern because it amplifies the damage through the concurrent or sequential action of sea-level rise, storm surge, and pluvial inputs. Such multi-driver events challenge legacy disaster-prevention systems that were designed primarily around single hazards. In response, a growing body of research seeks to quantify the risk and inform adaptation. In Korea, Cho et al. (2011) analyzed the socioeconomic conditions along the coast and assessed the potential impacts in areas projected to flood under future sea-level-rise scenarios (RCP). Building on this, Cho et al. (2015) quantified the changes in risk under climate-change scenarios, integrating sea-level rise, waves, and rainfall to propose a vulnerability-assessment and management framework for coastal regions. For Busan, Hwang and Yoo (2022) estimated flood damage accounting for short-and long-term sea-level-rise effects, identified high-risk zones, and projected economic losses by the event frequency. Internationally, DEFRA (2012) developed a national-scale approach for the United Kingdom that screens, prioritizes, and evaluates eleven risk domains to support adaptation policy. Kelly (2014) assessed the risks to the U.S. Naval Station Norfolk under sea-level-rise scenarios, deriving damage-probability functions and proposing a systematic flood-risk assessment approach. Fig. 1 presents the flooding processes driven by rivers (fluvial), urban rainfall–runoff (pluvial), and storm surge, and shows that in coastal cities these three processes can occur concurrently, producing a compound-flooding mechanism.
Research on the flooding risk in coastal cities has been actively pursued worldwide. Major countries, including the United States, Japan, and China, are analyzing the flood damage linked to sea-level rise and typhoons while implementing structural measures (e.g., breakwaters, revetments, drainage pumping stations) and non-structural measures through legal and institutional frameworks. In Korea, agencies such as the National Oceanographic Research Institute, the Ministry of Environment, and the Ministry of Oceans and Fisheries have produced coastal flood-forecast maps and flood-risk maps. Nevertheless, few studies have quantitatively assessed compound flooding and derived policy response strategies. In particular, previous work has often isolated individual drivers of storm surge, rainfall, or sea-level rise without extending to quantitative loss estimation and cost –benefit analysis under multi-hazard conditions.
Accordingly, this study aimed to quantify the impacts of compound flooding in Busan Metropolitan City by jointly considering sea-level rise, storm surges, and extreme rainfall under future climate scenarios. The specific objectives are threefold. First, an integrated compound flood assessment framework was developed by coupling coastal inundation simulations (ADCIRC-SWAN model) with urban flooding data, incorporating IPCC sea-level rise projections (SSP2-4.5 and SSP5-8.5 scenarios) into 50-year and 100-year return period analyses. Second, economic damage was quantified across multiple asset categories—buildings, vehicles, agricultural assets, and human lives—using an object-based methodology that enables spatially explicit damage estimation at the district and building-type levels (Na and Choi, 2019). Third, high-risk districts and vulnerable asset types were identified through a comparative analysis of single-hazard (coastal or urban flooding alone) versus compound flooding scenarios, and the extent to which climate change amplifies regional vulnerabilities was evaluated. Based on these quantitative assessments, this paper proposes spatially differentiated adaptation strategies tailored to compound flood characteristics of Busan and outlines policy directions to enhance disaster-prevention systems in coastal cities facing the escalating challenges of the climate crisis. This research framework was designed to be transferable to other coastal urban areas confronting similar multi-hazard flood risks under climate change.
2. Study Area
Busan Metropolitan City was selected as the target area for coastal flood and damage estimation. As a maritime city, Busan faces heightened risks from coastal hazards, such as typhoons, extreme rainfall, and tsunamis. The acceleration of sea-level rise has made it essential to establish measures to address climate-change-driven flooding. Based on an analysis of the comprehensive wind- and flood-damage reduction plans from 58 of the 71 coastal local governments in Korea (excluding Jeju Island and Ulleungdo), Table 1 summarizes the status of coastal, riverine, and inland-water (pluvial/urban) disaster risk areas among the nine wind-and-flood hazard types, i.e., zones that can contribute to compound coastal disasters. Across coastal jurisdictions, 406 compound-disaster risk areas were identified: 121 coastal-disaster risk areas, 166 river-disaster risk areas, and 199 inland-water (pluvial) disaster risk areas.
Based on an investigation of coastal disaster-risk districts from 1996 to the present, Busan Metropolitan City has the largest number of such districts and records the highest casualties from natural disasters among Korea’s seven special and metropolitan cities. Between 2012 and 2021, 27 people died or went missing due to natural disasters in Busan, accounting for 31% of the 84 casualties across the seven major cities. Over the past nine years, property damage from natural disasters totaled KRW 181.9 billion, suggesting that Busan suffered the greatest monetary losses among the five special/metropolitan cities. As shown in Fig. 2, the Busan region exhibits regional characteristics with the frequent damage attributed to inadequate drainage systems and storm surges.
An examination of Busan’s disaster-damage history from 2009 to 2020 shows that frequent flooding was driven primarily by heavy rainfall and drainage-system deficiencies, with most inundation attributable to poor inland drainage and insufficient storm-sewer capacity. A comparative review of natural-disaster losses in major coastal cities, including Busan, Ulsan, and Incheon, further indicates that, as of 2022, Busan incurred the most significant damages: KRW 11,823.91 million in Busan, KRW 1,696.17 million in Incheon, and KRW 6,931.86 million in Ulsan. An analysis of Busan’s average disaster losses and its climatic and topographic context for 2020–2022 suggests that the local rate of sea-level rise has accelerated over the past three decades, outpacing the global trend. Under a 100-year tsunami-height event affecting the Busan region, sea level in some areas could exceed +2.72 m, leading to >1.5 m of inundation in adjacent low-lying zones and substantial flood damage.
Accordingly, this study preemptively selected Busan as the focal area and developed response measures for coastal sea-level rise by estimating compound flooding and associated damage to inform impact analysis and loss mitigation strategies.
3. Research Methods
3.1 Numerical Modeling Framework
To accurately simulate flooding driven by multiple interacting forcings, a numerical framework capable of representing storm surge, waves, wave overtopping, rainfall, and riverine flooding is required. At the current state of science and technology, however, it remains challenging to resolve all of these processes simultaneously within a single, fully coupled model. As a practical alternative, models that capture interactions among key components are combined to enable reasonably robust predictions.
For storm surge and offshore-to-nearshore wave conditions, we employ the well-established coupled system ADCIRC–UnSWAN (often referred to as ADCSWAN). ADCIRC (Advanced circulation model) is a depth-integrated hydrodynamic model widely used for storm-surge forecasting by the U.S. National Hurricane Center and validated across numerous hurricane events, while UnSWAN is the unstructured-grid implementation of the third-generation SWAN wave model. Wave overtopping is quantified using either process-based solvers (e.g., FLOW-3D, OpenFOAM) or empirical formulations such as EurOtop, depending on data availability and computational cost. Urban pluvial and inland inundation due to rainfall–runoff and drainage constraints is simulated with a storm-sewer network model (e.g., XP-SWMM), which can represent pipe hydraulics, surface flooding, and pump/drainage operations.
A numerical framework capable of representing storm surge, waves, wave overtopping, rainfall, and riverine flooding is required for accurate simulations of flooding driven by multiple interacting forcings. At the current state of science and technology, however, it remains challenging to resolve all of these processes simultaneously within a single, fully coupled model. As a practical alternative, models that capture the interactions among key components are combined to enable reasonably robust predictions.
The well-established coupled system ADCIRC–UnSWAN (often referred to as ADCSWAN) was used for storm surge and offshore-to-nearshore wave conditions. ADCIRC (Advanced circulation model) is a depth-integrated hydrodynamic model used widely for storm-surge forecasting by the U.S. National Hurricane Center and validated across numerous hurricane events, while UnSWAN is the unstructured-grid implementation of the third-generation SWAN wave model. Wave overtopping is quantified using process-based solvers (e.g., FLOW-3D and OpenFOAM) or empirical formulations such as EurOtop, depending on data availability and computational cost. Urban pluvial and inland inundation caused by rainfall–runoff and drainage constraints was simulated with a storm-sewer network model (e.g., XP-SWMM), which can represent pipe hydraulics, surface flooding, and pump/drainage operations.
A key limitation in coupling coastal-ocean and hydrologic models arises from their disparate spatial and temporal scales. ADCSWAN, which was developed as a two-dimensional (depth-averaged) framework (Dietrich et al., 2011), addresses this by exchanging the fields between the surge and wave components. Meteorological forcing (winds and atmospheric pressure) is applied to ADCIRC along with tidal boundary conditions; wind stress and barometric effects generate storm surge, from which the water levels and currents are calculated (typically at hourly or sub-hourly intervals) and passed to UnSWAN. UnSWAN then updates the wave field, which in turn provides radiation-stress gradients and wind-related shear contributions back to ADCIRC, closing the feedback loop consistent with classical wave–current interaction theory (Longuet-Higgins and Stewart, 1964).
In this study, ADCSWAN was implemented to reproduce sea-level fluctuations and the associated surge and high-wave conditions during typhoons, accounting for synoptic pressure drops, offshore winds, and storm translation speed. The unstructured triangular mesh (as shown in Fig. 3) allowed a refined representation of the coastline and targeted local embedding within a larger regional grid. Following the coastal flood-forecasting guidelines of the Korea Hydrographic and Oceanographic Agency (KHOA), the ADCIRC–SWAN system was applied to simulate inundation, explicitly accounting for the combined effects of storm surge and sea-level rise.
3.2 Compound Flooding
Accurate analysis of compound flooding characteristics requires estimating the external forcing mechanisms that induce compound flooding and developing numerical simulation frameworks capable of evaluating scenarios in which these forces act concurrently. On the other hand, the application of sophisticated numerical analysis techniques across all coastal regions nationwide demands substantial computational resources and effort. Busan Metropolitan City (Marine City and Centum City) was identified as a viable study area for evaluating the compound flooding effects by superimposing existing assessment results. This study adopted a proactive approach by combining individual external forces, specifically overlaying the Urban Flood Hazard Map (Busan Metropolitan City, 2020) and the Coastal Flood Hazard Map (Korea Hydrographic and Oceanographic Agency, 2021) to generate a Compound Flood Hazard Map. This composite map served as a novel hazard component in flood damage cost estimation (Fig. 4). When multiple external forces are simultaneously considered, regional variations may result in increased or decreased inundation extents. Therefore, a regional impact assessment of compound flooding necessitates a screening methodology to identify the areas amenable to single-force superposition approaches.
3.3 Scenario Setting
Climate change encompasses potential future changes driven by climate-forcing factors, including greenhouse gas emissions, land-use changes, and aerosol emissions. These changes affect the climate system parameters (temperature and precipitation), human socioeconomic activities (ecosystems and agriculture), and climate response strategies (technologies and policies). Climate projections are generated using climate change prediction models (Earth system Models) that quantify future greenhouse gas concentrations and climate system dynamics, producing information on future climate variables such as temperature, precipitation, humidity, and wind (2050 Carbon Neutrality and Green Growth Commission, 2021).
This study analyzed coastal inundation in Busan Metropolitan City under storm-surge conditions for 50- and 100-year return periods, incorporating sea-level rise projections from future climate change scenarios (SSP). The storm surge heights for the respective return periods were used, while future sea level rise values were adopted from the scenario projections of the Korea Hydrographic and Oceanographic Agency: +58.4 cm (IPCC SSP2-4.5) and +81.8 cm (IPCC SSP5-8.5) for the average rise around Korean waters by 2100. The application methodology involved selecting the 100-year return period case for Busan’s coastal areas and simulating inundation by incorporating sea-level rise into initial water-level conditions. Comparative analysis was performed by contrasting the 100-year return period coastal flood hazard map results with inundation simulations that incorporated future climate-induced sea-level rise as the initial conditions. Table 2 lists the scenarios in this study that are expected to cause inundation in the Busan region due to storm surges, urban flooding, and climate change (sea-level rise).
This study estimated future water levels using a first-order approximation that adds scenario-based sea-level rise (SLR) to present-day return levels under a location-shift assumption. Although this approach is helpful for policy screening and sensitivity analysis, it does not claim statistical equivalence between “present-day T-year level + ΔSLR” and the “T-year event in 2100.” Potential non-stationarities may introduce bias, including changes in the scale and shape of extreme-value distributions and evolving interactions between meteorology and tides. Accordingly, the findings should be interpreted primarily in terms of relative increments and spatial prioritization rather than as absolute frequency-matched projections. Future work will address these limitations by remapping the return levels via non-stationary extreme-value analysis and incorporating joint-occurrence probabilities among rainfall, river discharge, and coastal water levels (e.g., copula-based multivariate methods) to quantify the uncertainty.
3.4 Damage Cost Estimation
Climate change-induced sea level rise and increased frequency of extreme weather events resulted in continuously escalating flood risks in coastal regions. These environmental transformations exacerbate socioeconomic damage in coastal cities, particularly in terms of property losses and human casualties from flooding events. Consequently, quantitative estimation of coastal flood damage and the formulation of effective adaptation strategies are paramount. An object-based methodology was used to precisely estimate flood damage costs in coastal urban areas (Na and Choi, 2019). The object-based approach enables the identification of individual objects within spatial units (e.g., buildings, roads, infrastructure facilities) and the detailed calculation of flood impacts and associated damage costs for each object. This methodology provides considerably more sophisticated damage-estimation capabilities than conventional regional-average-based approaches and proves effective for developing site-specific and facility-specific response measures.
Using the object-based method, the damage to individual objects (buildings, agriculture, human lives, and vehicles) within spatial units was estimated. Economic damage assessments were conducted under multiple environmental pressures, storm surges, rainfall, and compound flooding based on the Coastal Flood Hazard Map, Urban Flood Hazard Map, and Compound Flood Hazard Map. Specifically, the inundation damage characteristics were analyzed according to the asset type, building type, and administrative district to develop tailored countermeasures that account for regional flooding characteristics (Fig. 5).
4. Results
A comprehensive evaluation of flood damage in the Busan region was performed across multiple flood scenarios, with an emphasis on coastal urban inundation influenced by climate change, drainage efficiency, and ancillary environmental conditions. Flood damage assessments quantified the potential economic impacts under the 50-year and 100-year return period (design standard) conditions, incorporating the present and projected climate change effects (sea-level rise) across varying scenarios. The results of the inundation damage analysis, considering single and compound external forcing mechanisms and sea level rise under climate change scenarios consistent with IPCC projections, are presented below.
4.1 Storm Surge Inundation
Coastal inundation is predominantly driven by storm surges and sea level rise, and exhibits exponential damage escalation as the intensity of external forcing increases. Inundation damage at the 50-year return period was estimated at approximately KRW 397 billion, escalating to KRW 752.8 billion at the 100-year return period, representing an approximately two-fold increase (Fig. 6). Primary damage assets comprise vehicles and buildings. At the 50-year return period, vehicle damage accounted for 64.74% while building damage accounted for 34.87%. By contrast, at the 100-year return period, building damage increased substantially to 53.24% while vehicle damage declined to 46.42%. In particular, the vulnerability of commercial and critical infrastructure facilities was pronounced because of high-density coastal development, necessitating resilience enhancement measures in these regions.
4.2 Urban Flooding
Urban flooding results from intense precipitation events and exhibits spatially distributed damage patterns throughout Busan. Approximately KRW 494.1 billion in damage was estimated at the 50-year return period, increasing to approximately KRW 729.8 billion at the 100-year return period. Vehicle damage represents the predominant damage category at 52.25% and 54.12% for the 50-year and 100-year return periods, respectively, followed by building damage at 47.19% and 45.38%, respectively (see Fig. 7). In densely urbanized areas, flood damage is exacerbated by diminished drainage efficiency, with the damage concentration particularly evident in low-elevation zones and coastal peripheries. Consequently, enhancing routine urban infrastructure management and emergency response capabilities (e.g., mobile drainage pump systems) is imperative, as is expanding drainage systems suited to high-density areas and integrating them with long-term urban development planning.
4.3 Compound Flooding
Compound flooding represents an increasingly prevalent disaster modality resulting from the concurrent occurrence of storm surges and intense rainfall, generating multifaceted damage. At the 50-year return period, approximately KRW 893.6 billion in damage was estimated, escalating precipitously to approximately KRW 1,488.4 billion at the 100-year return period. In particular, at the 100-year return period, building damage comprises 49.10% of total damage, while vehicle damage accounted for 50.47%, manifesting a trend of proportional increases in damage categories with intensifying disaster severity (see Fig. 8). Compound flooding concentrates damage on building and vehicle assets clustered proximate to coastal and riverine zones, necessitating customized mitigation strategies such as maintaining road inundation depths below 0.6 m to minimize vehicular damage. Given the extensive spatial distribution of compound flooding throughout Busan, integrated countermeasures appropriate for high-density urban contexts must be established in conjunction with systematic urban infrastructure management protocols.
Fig. 9 illustrates district-level (gu/gun) characteristics across the Busan region, showing that western Nakdong River basin lowlands (e.g., Gangseo, Sasang, and Saha districts) exhibit pronounced damage escalation across all three scenarios (coastal, urban, and compound flooding), with the compound scenario manifesting the most substantial expansion. By contrast, eastern coastal and urban core areas (e.g., Haeundae, Suyeong, and Yeongdo districts) display spatially variable sensitivities to coastal and pluvial flooding factors, leading to divergent relative proportions of building and vehicle damage.
Table 3 lists the priority management matrix constructed by integrating administrative districts (Dong-gu, Gangseo-gu, Jin-gu, Nam-gu, and citywide) with building types (neighborhood living facilities, general factories, and detached houses) for each inundation type and return period. These findings suggest four critical policy directions: (1) lower-floor waterproofing and water-tight entrance barriers for neighborhood living facilities, (2) elevated placement and enhanced waterproofing of critical equipment in industrial areas, (3) strengthened integrated drainage and warning systems for compound vulnerable zones (Jin-gu and Nam-gu), and (4) expansion of drainage capacity throughout the urban area.
In this study, flood damage in Busan was evaluated by classifying events into coastal, urban, and compound flooding based on external forcing conditions. Across all categories, damage escalated markedly with increasing disaster intensity. The cause-specific hotspots were identified by classifying the areas into Caution, Warning, and Severe based on estimated flood-damage amounts (Fig. 10). These results provide a decision-ready screening layer for prioritizing management zones aligned with predefined flood-response objectives (i.e., target disaster intensity) in policy development.
4.4 Flood Damage Considering Sea Level Rise
Inundation damage costs from coastal flooding under the 100-year return period were assessed, incorporating climate change scenarios (SSP2-4.5, SSP5-8.5, Fig. 11). The projected coastal inundation area of Busan was estimated to increase from 14.78 km2 at the 50-year return period to 32.31 km2 at the 100-year return period (▲118.6%. Under climate-change scenarios, the area expands further to 43.74 km2 under SSP2-4.5 (+58.4 cm), which is ▲35.4% relative to the 100-year baseline (or ▲196% relative to the 50-year baseline), and to 48.85 km2 under SSP5-8.5 (+81.8 cm), which is ▲51.2% relative to the 100-year baseline (or ▲231% relative to the 50-year baseline). The results show that the damage costs will escalate by 92.4% to KRW 1,448.5 billion under the SSP2-4.5 scenario and by 154.9% to KRW 1,918.8 billion under the SSP5-8.5 scenario, relative to the baseline of current 100-year return period storm surge conditions without climate change consideration (KRW 752.8 billion).
At the district level, Gangseo-gu and Dong-gu showed the most precipitous increases in the total damage costs, with Gangseo-gu reaching approximately KRW 962 billion and Dong-gu approximately KRW 396.6 billion under the SSP5-8.5 scenario, suggesting that these regions possess elevated climate change sensitivity. On the other hand, Geumjeong-gu, Buk-gu, and Sasang-gu exhibited negligible damage occurrence, corroborating pronounced inter-regional disparities.
These findings underscore the need for tailored adaptation measures that account for regional differences in marine environmental sensitivity, given the projected increases in flood damage under climate change scenarios. Specifically, regional protection priorities for critical assets, including buildings and vehicles, were evaluated. For Busan Metropolitan City, strategies that prioritize preferential resource allocation to climate-change-vulnerable regions are essential to mitigate inundation damage effectively.
5. Conclusions
5.1 Key Findings
This study quantitatively assessed compound flood risks in Busan Metropolitan City under climate change scenarios. Compound flooding under the 100-year return period generated approximately KRW 1,488.4 billion in economic losses—approximately double those from single-source coastal flooding (KRW 752.8 billion) or urban flooding (KRW 729.8 billion) alone. Hence, traditional single-hazard approaches substantially underestimate the actual flood risks in coastal cities where multiple drivers interact.
Climate change dramatically escalates the coastal flood vulnerability. Incorporating IPCC sea level rise scenarios revealed 92.4% (KRW 1,448.5 billion) increases in damage under SSP2-4.5 and 154.9% (KRW 1,918.8 billion) under SSP5-8.5. Even moderate warming scenarios will more than double coastal flood damage by 2100, underscoring the urgency of climate adaptation measures.
Regional vulnerabilities exhibit pronounced spatial heterogeneity. Gangseo-gu and Dong-gu were identified as high-risk areas, with Gangseo-gu facing potential damages approaching KRW 962 billion under SSP5-8.5. The Western Nakdong River basin lowlands showed elevated vulnerability across all scenarios. In contrast, the eastern coastal districts (Haeundae, Suyeong, and Yeongdo) showed variable sensitivity, and inland districts (Geumjeong-gu, Buk-gu, and Sasang-gu) remained relatively protected, confirming the necessity for spatially differentiated management approaches.
Buildings and vehicles are the primary targets for damage. Across all scenarios, buildings and vehicles accounted for more than 95% of economic losses. Under 100-year compound flooding, the damage distribution approached parity (buildings: 49.10%; vehicles: 50.47%), indicating that both asset categories require equivalent protection priority.
5.2 Policy Recommendations
Based on these findings, strategic recommendations for Busan and comparable coastal cities are as follows:
Adopt compound flood risk frameworks. Conventional single-hazard flood maps and response systems are inadequate for compound events. Integrated modeling platforms, compound flood-hazard mapping, and multi-driver response protocols that account for concurrent storm surges, rainfall, and sea level rise are essential.
Implement spatially targeted adaptation measures. Considering regional disparities, priority investments should focus on high-vulnerability districts (Gangseo-gu and Dong-gu) and critical infrastructure. Universal approaches are inefficient. Hence, tailored countermeasures reflecting local topography, drainage capacity, and asset exposure are essential.
Enhance urban drainage infrastructure. Urban flooding causes damage similar to that from coastal flooding, yet drainage systems receive comparatively less attention. Expanding stormwater capacity, deploying mobile pump systems, and integrating green infrastructure in high-density areas can substantially reduce flood losses.
Establish vehicle-specific flood mitigation standards. Infrastructure design must explicitly address vehicular protection, considering that they account for approximately 50% of compound-scenario damage. Maintaining road inundation depths below 0.6 m through elevated roadways, improved drainage, and real-time warning systems would significantly reduce losses.
Develop climate-adaptive building codes and land-use regulations. High-risk zones require updated building standards (elevated first floors, flood-resistant materials, and development restrictions). Type 1 Neighborhood Living Facilities and general factories—identified as high-damage building types—warrant particular regulatory attention.
Integrate long-term climate projections into infrastructure planning. The current infrastructure is designed for historical conditions that no longer represent future risks. Incorporating SSP scenarios into design standards, investment decisions, and spatial planning will ensure resilience through mid-century and beyond.
5.3 Study Limitations and Future Research
This study used a superposition approach rather than fully coupled modeling, which may under- or overestimate localized interactions. Future work should implement tightly coupled frameworks resolving wave overtopping, tidal gate operations, and bidirectional drainage-river exchanges. Damage functions adapted from existing Korean guidelines could be improved by incorporating region-specific depth-damage curves, and unquantified indirect losses (business interruption, ecosystem services, psychological impacts) may substantially exceed direct property damages.
This study did not consider the mechanisms of inundation arising from interactions during compound flooding events, such as poor drainage and the expansion of inundated areas. In contrast, Kang (2024) found that while flood assessment results for single and compound hazards were similar in Busan Marine City, other areas showed amplified flood damage. Therefore, investigating damage costs through accurate flood analysis that considers the interconnectivity between single and compound hazards (joint occurrence probability) will enable more precise flood damage assessments that account for regional characteristics.
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