• Proceedings of the KSRS Conference
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• 2006.03a
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• pp.36-40
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• 2006

The objective of the study is to develop a GIS-based flood map. Hydraulic model (HEC-RAS) is linked with hydrologic model (HEC-HMS) for flood map. Geospatial data processors, HEC-GeoHMS and HEC-GeoRAS, are used for operating HEC-HMS and HEC-RAS. HEC-HMS was calibrated and validated at the Hwa-Ong watershed. HEC-HMS was used for calculating runoff from the Hwa-Ong watershed which consisted of Nam-Yang, Ja-An, U-Eun river sub-watersheds, and HEC-RAS was applied and validated for river flow routing at the Hwa-Ong watershed. The simulated results from HEC-HMS and HEC-RAS were reasonably good compared with the observed data. HEC-RAS and HEC-HMS were applied to simulate flooding from probability rainfall at the Hwa-Ong watershed, and the simulated result was used to develop a flood map. Flood map developed in this study will be used for mitigating and predicting the flood damages.

• Journal of Environmental Science International
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• v.13 no.9
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• pp.759-765
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• 2004

HEC-RAS model is used for estimation of rating-curve of Musung in Wi stream. Discharge is computed from stage estimated by HEC-RAS model, is compared with the discharge of water surface slope method. The relative deviation of observed and computed discharge is 5.37%, and shows as a good results. A rating-curve by HEC-RAS model shows better results than by water surface slope method.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.4
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• pp.726-733
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• 2016

Recently, the flood frequency and magnitude have increased due to heavy rainfall. Considering the present condition, a flood risk map has been published in many countries to raise awareness about flood damage to people. A flood inundation analysis model, which is used to publish the flood risk map, can be classified as river and inland inundation models according to the inundation cause. Although a variety of flood inundation analysis models are utilized both domestically and overseas, their usability is limited by the expensive price, except for the HEC-RAS model developed by U.S. Army Corps of Engineers (USACE). In the situation, the USACE has developed a 2-D HEC-RAS model that can be linked to the existing 1-D model. This model has been released as a beta version under the name, HEC-RAS 5.0. In this study, the HEC-RAS 5.0 model's features, usability, applicability, and accuracy were evaluated by comparing the performances on Gokgyo-cheon with the FLUMEN model, which is used for domestic flood risk mapping. The results of this study will contribute to river inundation analysis in many different ways after the HEC-RAS 5.0 model is stabilized.

• Journal of The Korean Society of Agricultural Engineers
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• v.46 no.2
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• pp.15-25
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• 2004

For the effective operation of irrigation reservoirs, a general and systematic policy is suggested to make balance of the conflicting purposes between water conservation and flood control. In this study, the flood effective analysis system was developed through the integration of long-term water budget analysis model, GIS-based HEC-HMS model and HEC-RAS model. The system structure consists of long-term water budget model using modified TANK theory, flood runoff and flood effects analysis model using HEC-GeoHMS, HEC-HMS and HEC-RAS models. The flood effects analysis system simulated the flood runoff from the upstream, downstream flood and long-term runoff of the watershed using the observed data collected from 1998 to 2002 of Seongju dam. The simulated results were reasonably good compared with the observed data. The optimal management method of the reservoir during the whole season is suggested in this study, and the flood analysis system can be a useful tool to evaluate a reservoir operation quantitatively for the mitigation of flood damages of reservoir basin.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.4B
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• pp.347-356
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• 2009

This study simulates the dam break situation by a probable maximum precipitation of Soyang-River Dam using HEC-HMS model and HEC-RAS model and compares the simulated results. The probable maximum precipitation was calculated using the flood event of the typhoon Rusa occurred in 2002 and using the mean areal precipitation of the Gangreung region and the moisture maximization method. The estimated probable maximum precipitations were compared for the duration of 6, 12, 18, and 24 hrs and were used as input data for the HEC-HMS model. Moreover, the inflow data calculated by HEC-HMS were utilized as ones for HEC-RAS, and then unsteady flow analysis was conducted. The two models were used for the dam break analysis with the same conditions and the peak flow estimated by HEC-HMS was larger than that of the HEC-RAS model. The applicability of two models was performed from the dam break analysis then we found that we could simulate more realistic peak flow by HEC-RAS than HEC-HMS. However, when we need more fast simulation results we could use HEC-HMS. Therefore, we may need the guidelines for the different utilizations with different purposes of two models. Furthermore, since the two models still include uncertainties, it is important to establish more detailed topographical factors and data reflecting actual rivers.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2001.10a
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• pp.314-318
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• 2001

The analysis of the spatial extent of flood inundation is important for flood mitigation. Geographic Information System (GIS) has advantage of analyzing spatial distributed data. Hydrologic Engineering Center's River Analsysis System(HEC-RAS) with HEC-GeoRAS was used to analyze flood inundation. HEC-GeoRAS, which is an ArcView GIS extension designed to process geospatial data for HEC-RAS, is a useful tool for storing, managing, analyzing, and displaying spatially distributed data. Rational formula and 24-hr duration probability precipitation data of Suwon meteorological station were used to estimate the flood runoff. And water profiles were calculated using the HEC-RAS model with HEC-GeoRAS. The flooded region is 8.24ha when 50-yr probability precipitation was applied and 8.8ha when 100-yr was applied to Bahlan study watershed which is located in Whasung county, Kyunggi province, having an area of $29.79km^{2}$.

• Journal of the Korean Association of Geographic Information Studies
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• v.6 no.1
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• pp.132-142
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• 2003

A significant deficiency of most computer models used for stream floodplain analysis, is that the locations of structures impacted by flood waters, such as roads, buildings, and bridges, cannot be effectively compared to the floodplain location. The purpose of this study is the integration of the HEC River Analysis System(HEC-RAS) with ArcView geographic information system to develop a regional model for floodplain determination and representation. Also this study presents to enable two- and three-dimensional floodplain mapping and analysis in the ArcView. The methodology is applied to a Yeoju of Kyunggi-do, located in South Han River Basin. A digital terrain model is synthesized from HEC-RAS cross-sectional data and a digital elevation model of the study area. The flood plain data developed in ArcView was imported into HEC-RAS where it was combined with the field surveyed channel data in order to construct full floodplain cross sections that reflected accurate channel and overbank data for the HEC-RAS model. The flood plain limits could be expressed more accurately on ArcView by using water level data to be computed in HEC-RAS program. The computed water surface elevations and information of cross-section must be manually plotted in order to delineate floodplains. The resulting of this study provided a good representation of the general landscape and contained additional detail within the stream channel. Overall, the results of the study indicate that GIS combined with HEC-RAS is proven to be very useful and efficient for the automatic generation of flood maps, and an effective environment for floodplain mapping and analysis.

• Journal of the Korean GEO-environmental Society
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• v.15 no.1
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• pp.69-77
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• 2014

The objective of this study is to compare flood inundation models for small stream basin. HEC-RAS model was used for the analysis of one dimensional hydraulics and HEC-GeoRAS, Ras Mapper and RiverCAD models were applied for the flood inundation analysis in Gum Chung stream. Flood inundations are to simulate by flood inundation models using observed data and rainfall on each frequency and to compare with inundation area based on the flood plain maps. The results of this study are as follows; Area of flood inundations by HEC-GeoRAS model is similar to that of flood plain map and appears in order of RAS Mapper and RiverCAD model. Flood inundation area by RiverCAD model is to estimate lager than that of RAS Mapper and HEC-GeoRAS model in flood area on each frequency and the results show that they have a little difference in models of flood inundation analysis at small stream. Comparing the area of flood inundations by flood depth, the results of three models are relatively similar in flood depth as 2.0 m below, and RiverCAD model shows a significant difference in flood depth as 2.0 m or more.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2002.10a
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• pp.105-108
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• 2002

In this study, flood influence analysis in the downstream of Sung-Ju dam was simulated using HEC-RAS model. Input data for the simulation was which measured water level, water velocity, stream section etc. HEC-RAS model could be applied to steady flow or gradually varied flow in natural or artificial stream. HEC-RAS model which can simulate real-time changing water level and compute water surface curve was supplied to show the standard influent amount of Sung-Ju dam. Through this study the submerged damage of Sung-Ju dam's downstream would be minimized.

• Journal of The Korean Society of Agricultural Engineers
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• v.54 no.2
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• pp.87-94
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• 2012

This study is to evaluate flood inundation and to recommend measures of damage reduction on sediment by concentrated torrential rainfall at Gonjiamcheon Watershed (183.4 $km^2$). Firstly, the SWAT (Soil and Water Assessment Tool) was simulated streamflow and sediment at upstream. Then, we produced a map of floodplain boundary by using HEC-RAS (Hydrologic Engineering Centers River Analysis System) at downstream. The SWAT model was calibrated with 2 years (2008~2009) daily streamflow and validated for another years (2010~2011. 7. 31). The SWAT model was simulated with 3 years (2008~2010) by monthly water quality (Sediment) at Gonjiamcheon water quality station. The streamflow and sediment from SWAT model were input as boundary conditions to HEC-RAS. The results of HEC-RAS indicated that mapping of floodplain boundary was Jiwol and Jiwol 2 district. Additionally, inundation area and depth were assessed and applied BMPs scenario for managing the sediment yield.