Kun-Yeun Han

Development of a Flood Runoff and Inundation Analysis System Associated With 2-D Rainfall Data Generated Using Radar III. 2-D Flood Inundation Simulation

In this study, a 2-D flood inundation model was developed to evaluate the impact of levee failure in a natural basin for flood analysis. The model was applied to analyze the inundation flow from the levee break of Gamcheon river during the typhoon Rusa on October 31 through September 1, 2002. To verify the simulated results, wide range field surveys have been performed including the collection of NGIS database, land use condition, flooded area, and flow depths. Velocity distributions and inundation depths were presented to demonstrate the robustness of the model. Model results have good agreements with the observed data in terms of flood level and flooded area. The model is able to compute maximum stage and peak discharge efficiently in channel and protected lowland. Methodology considering radar-rainfall estimation using cokriging scheme, flood-runoff and inundation analysis in this study will contribute to the establishment of the national integrated flood disaster prevention system and the river or protect lowland management system.

Development and Verification of Inundation Modeling with Urban Flooding Caused by the Surcharge of Storm Sewers

Urban flooding is usually caused by the surcharge of storm sewers. For this reason, previous studies on urban flooding are mainly concentrated on the simulation of urban drainage systems. However these approaches that find the pipes which have insufficient drainage capacity are very approximate and unreasonable ways in establishing both flood prevention and flood-loss reduction planning. In this study, a two-dimensional model linked the existing ILLUDAS model is developed to calculate the accurate and resonable solution about urban flood inundation and it is verified by using the simulation of July 2001 flood in Seoul. In the urban area with a small difference of ground elevations, the two-dimensional flood propagation phases must be considered to make a accurate analysis for inundated area and depth. The result of this study can be used to construct fundamental data for a flood control plan and establish a urban flood forecasting/warning system.

Establishment and Application of 2-Dimensional Flood Inundation Analysis System by the Collaboration of River and Lowland in Nam River Basin

Due to the recent proliferation of hurricanes and heavy rains, occurrence probability of the collapse of river banks and overflow has increased and has brought about large loss of life and severe property damage in lowland. It is imperative information related to the collapse of levee and overflow systems, flood inundation ranges and overflow spots be generated. Real damage causes include flood waves; understanding streams of flood waves as they flow into the lowland is vitally important. The purpose of this study is to generate data that will protect life and the property of residents in damage areas. Flood analysis is preformed to prepare for emergency situations in lowland due to the collapse of dams and river banks due to extraordinary foods and severe rains. Additionally, through simulation and analysis related to flood distribution patterns in lowland, forecasted inundation depth and time, range of flood, and estimated size of damage expectation can be generated. Data targets include the Nam River watershed using the FLDWAV model. Calculating the water level in lowland and introducing flooding hydrograph are vital to success. This is all related to the collapse of river banks and takes into consideration analysis of flood waves and collapse patterns of river banks. Using this data to create a two-dimensional flood model and by examining flood wave transfer characteristics at the point of real bank collapse, progress can be made. Calculating the range of flood, inundation depth and time in lowland, comparing and reviewing results with actual data and flood marks that showed the goodness of fit is over 90% is key. Calculate the range of flood data by assuming extreme situation of 200 years frequency on the same region, these results are able to contribute establishment of flood damage mitigation measures.

Development and application of dynamic water quality model in Nakdong river.

The objective of this study is to develop an accurate and stable dynamic water quality model which is capable of reflecting various flows and irregular cross sections and handling numerical oscillations under the low flow conditions. In order to solve the oscillation problem under the low flow conditions, diffusive wave method was applied to the low flow condition in developing a hydraulic model, DyHYD. DyQUAL is also developed as a water quality model to calculate up to 12 water quality variables including autochthonous BOD, water temperature, DO, TN and TP. The developed model is applied to both hypothetical river channels and actual Nakdong river watershed. Additionally, the applicability and reliability of the models are verified by comparing simulation results with observed values. Nash-Sutcliffe coefficients are estimated by comparison between simulation results and observed values. In the calibration and verification process, the coefficients varies from 0.391 to 0.591 and 0.704 to 0.902 for discharge, BOD, TN and TP, respectively.

Development of a Flood Runoff and Inundation Analysis System Associated With 2-D Rainfall Data Generated Using Radar I. Quality Control and CAPPI Composite Calculation

The need for economical and accurate presentations of equivalent radar reflectivity( ) data in an orthogonal coordinate system has existed for some time. So, in this study, a fast and efficient procedure has been developed which allows the systematic interpolation of digital reflectivity data from radar space into Cartesian space. At first, QC(Quality Control) of radar data has been executed for extracting uncontaminated Constant Altitude Plan Position Indicator(CAPPI) data. The algorithm is designed so that only one ordered pass through the original Plan Position Indicator(PPI) scan data is necessary to complete the interpolation process. The model can calculate various resolution and altitude reflectivity data for many kinds of hydrological usage.