# Estimating Flood Inundation in Urban Areas Using a Scenario Generation Method and Inundation Graphs
###### Abstract  
As the frequency and intensity of natural and social disasters increase due to climate change, damage caused by disasters affects urban areas and facilities. Of those disasters, inundation occurs in urban areas due to rising water surface elevation because of concentrated rainfall from storm surges or urban drainage system failures. For this research, a scenario generation method for estimating flood inundation was developed to analyze the flood effects on urban areas to prepare for disasters and minimize damage. A scenario generation method using various distribution functions and return periods was developed and applied to create input values for the flow model for inundation analysis. By simulating multiple scenarios using a two-dimensional flow model and storing its results into 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 response and prevention. The 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. flood inundation; scenario generation; urban flood; inundation graph; water surface elevation Article Estimating Flood Inundation in Urban Areas Using a Scenario Generation Method and Inundation Graphs  
Flood inundation models have recently been used in combination with an approach and strategy for the mitigation and prevention of flood disasters based on risk assessment studies. As a result, research on the risk and effects of flood damage has grown in recent years [6; 7]. Also, flood scenarios were utilized for flood vulnerability analysis in order to control flood risk and mitigate disasters [8; 9]. Risk assessment studies usually include an estimation of how vulnerable flood-prone areas are, or the potential loss and damage from flood events of varying magnitudes [10; 11]. Combined with hydrological models and hydrodynamic river models, the application of flood modeling has been extended to modeling that aims to formulate risk mitigation strategies from these flood events [12]. For flood risk mitigation planning, flooding scenarios with respect to future conditions were continuously applied for flood damage evaluation [13; 14; 15]. In reference to flood modeling, this study dealt with scenario creation and its application using similar methods used by the hydraulic performance graph for data accumulation. The hydraulic performance graph is a method that calculates the drainage level curve for all possible flow conditions in a section of an arbitrary number of channels and displays them in a graph [16]. In this method, the relationship between the downstream water level and upstream water level for all possible flow conditions in each channel section is shown on a single graph, and all possible downstream water level ranges are included. The governing equation of the flow calculation in this method was originally derived from the one-dimensional energy equation. After using the topographical data, the slope, roughness coefficient, and length of the channel as the input, the area and radius of the section are calculated first, and then the water depth, uniform flow depth, and drainage level of the channel are estimated. This method has been shown to be useful in creating structural or non-structural flood defense measures [17]. To depict the stage-discharge relations for open channel flows, the hydraulic performance graph was later modified to build a theoretical water level-flow connection [18]. Additionally, a volumetric performance graph (VPG) was developed based on the earlier results and was compared with actual experimental data [19], and in later research it was also used for application in complex river networks [20].