• Journal of Wetlands Research
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• v.6 no.4
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• pp.45-57
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• 2004

This study analyzed the effect of land-use enhancement benefits with the flood safety which it is not quantified in the flood damage analysis, Korea. The land-use enhancement benefits mean the enhancement of land-use value according to the rise of flood safety of the protected area by the flood control projects and we performed the analysis of land-use enhancement benefits with the publicly announced land price which can objectively represent the land-use value of a specific area. We verified the statistical significance of the floating rate of land price according to the effects of flood control projects and the characteristics of a river through the analysis of variance. As a result of the verification, the increase of land-use value was represented by the net annual average floating rate of land price. The flood safety was classified as flood damage potential and flood prevention capacity. The flood damage potential was classified according to the rate of urbanization and flood prevention capacity was represented by the conditional annual non-exceedance probability obtained from the frequency analysis with uncertainty for the flood discharge. The study areas were small urban cities and we calculated the conditional annual non-exceedance probabilities of 200-year flood event for the levees constructed with the conditions of 10- and 50-year design frequency. The result was shown that the net annual average floating rate of land price would be raised nearly 5 times for 10%-increase of the conditional annual non-exceedance probability in small city areas.

• Journal of Korea Water Resources Association
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• v.45 no.9
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• pp.959-968
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• 2012

HEC-RAS has been applied to simulate water level variation in the Ara waterway during the flood season. To support decision making necessary for operation of the hydraulic structures especially during the flood season, it is important to consider various factors such as water level of the Han River, Gulpo River, and tidal level of the west sea in conjunction with operation of the hydraulic structures such as the Gyulhyun Weir, the West sea gate, and pumping stations. Especially for operation of the west sea gate, the Rule-script option was employed to determine the opening height considering the variation of the water level in the waterway and the west sea simultaneously. For model verification, comparison of water level computed at the upstream and downstream of the regulation weir shows a good agreement with observed data measured during the flood event in September 2010. The HEC-RAS model developed in this study will contribute to support operation of the waterway during the flood season.

• Spatial Information Research
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• v.19 no.1
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• pp.1-11
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• 2011

Recently urban area has suffered from frequent flood event by local heavy rain. This study performed flood tests for the Jungnang river using HEC-RAS model. Based on 1m LiDAR data, river geometry data were produced using HEC-GeoRAS. For 100-year frequency flood, 200-year frequency flood, and PMF, flooding areas were estimated. Ten sub-zones of the entire flooding area were identified based on the nearest refugees and used to analyze evacuation paths to the refugees. The results showed that approximately 70% of flooded area were residential, commercial, and transportation areas so that much loss of life and property could be possible. Path analysis showed that the shortest path distances to refugees were about 1000m average. Evacuation warning given at a proper period could minimize loss of life and property. This study provides the guideline for flood evacuation plan in urban area.

• Journal of Convergence for Information Technology
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• v.9 no.11
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• pp.125-133
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• 2019

In this paper, probabilistic flood risk maps were produced for levee break caused by possible flood scenarios. The results of the previous studies were employed for flood stages corresponding to hydrological extreme event quantified uncertainties and then predicted the location of a levee breach. The breach width was estimated by combining empirical equation considered constant width and numerical modeling considered uncertainties on compound geotechnical component. Accordingly, probabilistic breach outflow was computed and probabilistic inundation map was produced by 100 runs of 2D inundation simulation based on reliability analysis. The final probabilistic flood risk map was produced by combining probabilistic inundation map based on flood hazard mapping methodology. The outcomes of the study would be effective in establishing specified emergency actin plan (EAP) and expect to suggest more economical and stable design index.

• Journal of Ocean Engineering and Technology
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• v.23 no.2
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• pp.37-46
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• 2009

Typhoon Rusa in 2002 was recorded as causing the biggest damage due to flood in our country. With the enormous damage to the land, the flood was totally discharged to the open sea. As a result, in the coastal area, the discharging of a river had a big influence in comparison to the scale of the coastal area, which suffered damaged due to the discharging of the river. As it cleared the land, the load was totally discharging into the sea, where it caused various problems due to its influence on the ecosystem. These included changes to the environment, like a difference in salinity and the inflow of a land load. Therefore, in this study, a Lagrangian particle tracking model was constructed using a flow model capable of solving the behavior of a river plume, supposing Sachon Bay. It is performed the research able to tendency-like valuation and reappearance about real event. The result was that the model was well approximated the sea area tendency and the river plume of the specific event.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.3
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• pp.841-847
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• 2014

Urban runoff models have been continuously developing with concerns for urban flood. Recently, models that be able to quantitatively analyze surface inundation caused by overflowed water from storm sewer were also developed by coupling 1-dimensional sewer model and 2-dimensional surface flow model. However, only overflowed water from storm sewer can be analyzed by the models have been developed until now. They are limited to be not able to analyze surface inundation caused by surface runoff that could not flow into the storm sewer. In order to overcome the limitation, basin-overlap method was devised adding a dummy 1-dimensional sewer layer to the model, so it can consider the efficiency of inflow to the storm sewer system. XP-SWMM 2011 is applied for urban runoff model and the flood event occurred on July 27, 2011 in basin-shaped Sadangcheon watershed is chosen for study inundation event. According to simulation results basin-overlap method reappear the observed inundation event more precisely than traditional method. This results suggest that drainage system has to be improved for reducing inundation caused by surface runoff and would be used as considerations for planning an urban basin design magnitude.

• Water for future
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• v.29 no.6
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• pp.237-247
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• 1996

In this study two rainfall-runoff models, the NWS-PC model and the Storage Function Model (SFM), were compared to see their applicability in the flood forecasting at the river system. The SFM has been adopted in the flood-forecasting and warning system for the major rivers in Korea since 1974, and the NWS-PC model, a physically based model, has been developed to simulate soil moisture changing as well as the surface and subsurface flow at the watershed and in the river streams. Case studies were carried out using flood event data observed at the Mihochun watershed in Geum-river basin during 1985 to 1995. Simulated results from both models were compared with the observed data with respect to the RMS errors and relative errors for peak flow discharges and total runoff volumes to show the advantages and disadvantages of both models and to suggest the way to improve their performances.

• Journal of Environmental Science International
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• v.24 no.4
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• pp.425-435
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• 2015

A number of projects for development have been done continuously due to the increase of tourist in Jeju Island. However flood disaster countermeasure due to urbanization is not considered during this development projects. This study is to make basic process for the flood estimation in Han stream of Jeju Island. The variation of stream discharge due the every 5 years' land use change from 1980 to 2005. Data for flood events (rainfall and discharge) were collected for HEC-HMS model. Clark method was used for unit hydrograph analysis. For the estimation of Clark unit hydrograph parameters, Kraven II and Sabol's empirical equations were applied. The peak discharge increased 9.9~33.67% and total discharge amount increased 12.53~30.21%. Also, time of concentration for peak discharge was reduced by 10 minutes for each event.

• Proceedings of the Korea Water Resources Association Conference
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• 2015.05a
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• pp.397-397
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• 2015

The frequency of urban floods is recently increased as a consequence of climate change and haphazard development in urban area. To mitigate and prevent the flood damage, we generally utilized a numerical model to investigate the causes and risk of urban flood. Contrary to general flood inundation model simulating only the surface flow, the model needs to consider flow of the sewer network system like SWMM and ILLUDAS. However, this kind of model can not consider the interaction between the surface flow and drainage network. Therefore, we tried to evaluate the impact of bidirectional interaction between sewer and surface flow in urban flooding analysis based on simulations using the quasi-interacted model and the interacted model. As a general quasi-interacted model, SWMM5 and FLUMEN are utilized to analyze the flow of drainage network and simulate the inundation area, respectively. Then, FLO-2D is introduced to consider the interaction between the surface flow and sewer system. The two method applied to the biggest flood event occurred in July 2011 in Sadang area, South Korea. Based on the comparison with observation data, we confirmed that the model considering the interaction the sewer network and surface flow, showed a good agreement than the quasi-interacted model.

• Journal of Climate Change Research
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• v.8 no.4
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• pp.287-295
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• 2017

This paper provides a mathematical approach for estimating flood risks due to the effects of climate change by developing a one dimensional (1D) hydraulic model for the mountainous river reaches located close to the Yeongwol thermal power plant. Input data for the model, including topographical data and river discharges measured every 10 minutes from July $1^{st}$ to September $30^{th}$, 2013, were imported to a 1D hydraulic model. Climate change scenarios were estimated by referencing the climate change adaptation strategies of the government and historical information about the extreme flood event in 2006. The down stream boundary was determined as the friction slope, which is 0.001. The roughness coefficient of the main channels was determined to be 0.036. The results show the effectiveness of the riverbed widening strategy through the six flooding scenarios to reduce flood depth and flow velocity that impact on the power plant. In addition, the impact of upper Namhan River flow is more significant than Dong River.