# Estimating Flood Inundation in Urban Areas Using a Scenario Generation Method and Inundation Graphs
## 5 Conclusions  
Urban areas and infrastructure are impacted by disaster damage when the frequency and severity of natural catastrophes rise due to climate change. Among these catastrophes, inundation occurs in urban areas as a result of increasing water surface height caused by storm surge-induced concentrated rainfall or drainage failures. In order to prepare for disasters and lessen damage, a scenario generation method for calculating flood inundation was developed for this research. Scenario generation methods can be important for flood inundation analysis because they help simulate various flood scenarios, which can provide quick critical information for emergency management and flood risk assessment. A scenario generation method was developed and applied to create input values and boundary conditions for the flow model for inundation analysis. By simulating multiple scenarios using a two-dimensional flow model and storing its results in a graph-form database called an inundation graph, it is possible to assess the probability and potential impact of different flood events quickly, which could be later used for disaster prevention. Flood risk and flood vulnerability of each section of the urban area could be evaluated based on the input data from the scenarios and the results of the flood analysis. By using two widely used extreme value distributions of Gumbel and GEV, the rainfall data near the site were analyzed for the estimation of rainfall frequencies, which were later used as an input for the rational flow formula for runoff. The time-discharge values from the runoff in several return periods were used as discharge boundary conditions for multiple scenarios. Then by using the generated scenarios, multiple runs of the two-dimensional model were conducted to create the inundation graph. In the analysis of the developed scenario generation method, a flood hazard rating index was also created to show what flood scenarios would be considered dangerous to individuals in certain areas. A limitation to this study is the fact that the research was based on an ungauged site. Also, there are limitations to the model since this is a two-dimensional model, and there could be some inaccuracy when depicting areas that require 3D modeling, such as the joint area of the main and tributary channel when applied to a confluent channel, due to the three-dimensional flow structure in the joint area. Furthermore, the model showed some limitations when applied to a former dam break problem, showing some discrepancy immediately after the break which has three-dimensional characteristics. The results of this research and its scenario generation algorithm showed that they could be used as a useful tool for accurate flood inundation analysis, providing valuable insights into the potential impact of different flood events and informing flood risk management. This method in this study could be a valuable tool and guide, providing risk and safety information quickly to decision-makers related to water management administration who may not be familiar with flow models, especially in rural areas or local government. **Author Contributions:** Conceptualization, J.S. and D.S.R. ; methodology, J.S. and D.S.R. ; software, J.S. ; validation, J.S. ; writing--original draft preparation, J.S. ; writing--review and editing, J.S. and D.S.R. ; visualization, J.S. ; supervision, D.S.R. ; project administration, D.S.R. ; funding acquisition, D.S.R. All authors have read and agreed to the published version of the manuscript. **Funding:** This study was supported by the Korea Environment Industry & Technology Institute (KEITI) through Environmental R&D Project on the Disaster Prevention of Environmental Facilities, funded by Korea Ministry of Environment (MOE) (202002850001). This study was supported by the Korea Ministry of Environment on the preparation of revising river design standards considering climate change. **Data Availability Statement:** The raw data supporting the conclusions of this article will be made available by the authors on request.