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Jang, Daewon

Kim, Hungsoo

Kim, Soojun

Kim, Yonsoo

English

Hydraulic Engineering Repository

Conference Paper, Published VersionKim, Yonsoo; Kim, Soojun; Jang, Daewon; Kim, HungsooEstimation of Flood Discharge According to Variability ofRai Nfall Distribution Using Gis-Based Method in a BasinZur Verfügung gestellt in Kooperation mit/Provided in Cooperation with:Kuratorium für Forschung im Küsteningenieurwesen (KFKI)Verfügbar unter/Available at: https://hdl.handle.net/20.500.11970/109947Vorgeschlagene Zitierweise/Suggested citation:Kim, Yonsoo; Kim, Soojun; Jang, Daewon; Kim, Hungsoo (2010): Estimation of FloodDischarge According to Variability of Rai Nfall Distribution Using Gis-Based Method in aBasin. In: Sundar, V.; Srinivasan, K.; Murali, K.; Sudheer, K.P. (Hg.): ICHE 2010.Proceedings of the 9th International Conference on Hydro-Science & Engineering, August2-5, 2010, Chennai, India. Chennai: Indian Institute of Technology Madras.Standardnutzungsbedingungen/Terms of Use:Die Dokumente in HENRY stehen unter der Creative Commons Lizenz CC BY 4.0, sofern keine abweichendenNutzungsbedingungen getroffen wurden. Damit ist sowohl die kommerzielle Nutzung als auch das Teilen, dieWeiterbearbeitung und Speicherung erlaubt. Das Verwenden und das Bearbeiten stehen unter der Bedingung derNamensnennung. Im Einzelfall kann eine restriktivere Lizenz gelten; dann gelten abweichend von den obigenNutzungsbedingungen die in der dort genannten Lizenz gewährten Nutzungsrechte.Documents in HENRY are made available under the Creative Commons License CC BY 4.0, if no other license isapplicable. Under CC BY 4.0 commercial use and sharing, remixing, transforming, and building upon the materialof the work is permitted. In some cases a different, more restrictive license may apply; if applicable the terms ofthe restrictive license will be binding.Proceedings of ICHE2010, IIT Madras, Aug 2-5,2010 Estimation Of Flood Discharge According To Variability Of Rainfall Distribution Using Gis-Based Method In A Basin                      457    ESTIMATION OF FLOOD DISCHARGE ACCORDING TO VARIABILITY OF RAINFALL DISTRIBUTION USING GIS-BASED METHOD IN A BASIN   Yonsoo Kim1, Soojun Kim2, Daewon Jang3, Hungsoo Kim4                                              Abstract: These days, the distributed model is becoming popular because it can utilize the spatial information of watershed from remote sensing, radar, and satellite technologies. Unlike the popularity of distributed model, we are using mean areal precipitation as the input data of the model. However, in reality, precipitation has uncertain spatial distribution by variability of its movement and direction and so it is difficult to assure the mean areal precipitation of the basin is really a representative mean value of the basin. Therefore, in this paper, we selected radar rainfall data from 12 Jul 2009 to 15 Jul 2009 for consideration of spatial distribution of rainfall and a semi distributed model for consideration of spatial distribution of the basin characteristics in  SumJin river basin, Korea. We simulated the flood discharge by considering radar rainfall movement and direction using a grid- based ModClark model in HEC-GeoHMS which is a semi-distributed model. As the results, we investigated the variability of peak flow according to variability of radar rainfall movement and distribution and knew that the direction of rainfall movement affected peak flow and time of peak flow.  In conclusion, we have known that it may be important to consider the rainfall movement and direction for the investigation of flood discharge characteristics such as peak flow and peak time.  Keywords: radar rainfall, distributed model, ModClark, flood discharge.  INTRODUCTION  In recent decades, the extreme weather events due to the climate change are frequently occurred over the world. Korean peninsular has also suffered from natural disaster by localized extreme events and the damage tends to be rapidly increasing. Therefore, the estimation and forecasting of flood discharge in real time could be a very important issue for the flood damage prevention and reduction. To do the flood discharge estimation, we need rainfall data as the input of a rainfall-runoff model.  The mean areal rainfall obtained from the point rainfall data are usually used as the input data.However, the point rainfall may have its limitations for representing spatial variability of rainfall and so we used radar rainfall for its spatial variability. Also this study used a semi-                                                 1 Ph. M. Student, Department of Civil Engineering, INHA University, 253 Yonghyun-dong  Nam-gu, Incheon, South Korea, Email: civil.engineer@hanmail.net. 2 Ph. D. Student, Department of Civil Engineering, INHA University, 253 Yonghyun-dong  Nam-gu, Incheon, South Korea, Email: soojuny@empal.com. 3 Ph. D., Techincal Institute Manager, Noaa solution Co., Ltd, 304 Kolon DigitalTower Aston B/D., 505-14 gasan-dong Geumcheon-gu, Seoul, South Korea, Email: hydrojdw@noaa.co.kr. 4 Associate Professor, Department of Civil Engineering, INHA University, 253 Yonghyun-dong  Nam-gu, Incheon, South Korea, Email: sookim@inha.ac.kr.  Proceedings of ninth International Conference on Hydro-Science and Engineering (ICHE 2010), IIT Madras, Chennai, India. 2 - 5  August 2010 Proceedings of ICHE2010, IIT Madras, Aug 2-5,2010 Estimation Of Flood Discharge According To Variability Of Rainfall Distribution Using Gis-Based Method In A Basin                      458distributed model called ModClark which can consider the spatial distribution of the basin characteristics such as the runoff curve number, time of concentration, and so on. Then we simulated flood discharge by considering rainfall movement and direction to investigate the effect of rainfall movement. We estimated flood discharges by considering four directions of radar rainfall and the movement directions of radar rainfall are determined by wind directions. Then we investigated how peak flow and peak time are changing according to the rainfall movement.  Modified Clark Method  Modified Clark or ModClark model in HEC GeoHMS is incorporated with radar rainfall data which can consider spatial variability of rainfall. The grid based ModClark model uses DEM cells for the distribution of radar rainfall and the CN value and time of concentration in a basin will be determined by GIS tool. Then the flood discharge is simulated with the parameters of time of concentration Tc and storage constant K.(HEC, 1996)  Study area and radar rainfall  The study area is Sumjin river which is located in the southern part of Korean peninsular. The basin area is 4,911.89 , basin length is 223.86 km, and mean width of basin is 21.94km. The 65.8% of the basin is mountain area This study uses the radar rainfall recorded in the period of 22:00 July 12, 2009 to 08:00 July 15, 2009. The basin is divided into the cell size of 1Km× 1Kim which is the same size with radar rainfall grid and the CN is extracted from the soil map and land cover map. The time of concentration, Tc and the storage constant K are estimated based on the grid sized basin of 30m × 30m in HEC-GeoHMS.     Proceedings of ICHE2010, IIT Madras, Aug 2-5,2010 Estimation Of Flood Discharge According To Variability Of Rainfall Distribution Using Gis-Based Method In A Basin                      459 Fig. 1. Sub-basin of Sumjin river Basin  Fig. 2. Model configuration of HEC GeoHMS  Analysis of Rainfall Variability  We collected wind related data from six meteorological stations near to the Sumjin river basin.Wind in the south western direction observed as the highest velocity in the period of 12 July 2009 to 15 July 2009. We also considered three more wind directions which are perpendicular to the south western direction. The flood discharges were simulated at the basin outlet by considering radar rainfall movement in four wind directions. These directions are : SouthWestern(SW), North Western(NW), North Eastern(NE), and South Northern(SN) directions for the radar rainfall movement. The rainfall is spatially distributed into four directions based on the centroid of the basin. Rainfall movement had following characteristics : NW and NE rainfall are moved and distributed from upstream to downstream of the river. SE rainfall from downstream to upstream of the river. SW rainfall from upstream to downstream(Figs 3 ~ 6). Proceedings of ICHE2010, IIT Madras, Aug 2-5,2010 Estimation Of Flood Discharge According To Variability Of Rainfall Distribution Using Gis-Based Method In A Basin                      460  Fig. 3. NW radar rainfall distribution  Fig. 4. NE radar rainfall distribution  Fig. 5. SW radar rainfall distribution  Fig. 6. SE radar rainfall distribution  Estimation of Flood Discharge  This study estimated optimal parameters from runoff simulation using SW radar rainfall and from the calibration of simulated runoff with the observed discharge in Songjung station located in the outlet. Then the runoff or flood discharge simulations were performed and compared for four directional radar rainfall movements (Fig. 7). There is nothing little to choose between the total volume. But, there’s Peak flow difference between the four directions. NW and NE rainfalls moved to the same directions with the river flow and inflow to the channel was becoming greater than outflow in the basin. Therefore, the peak flow was large and runoff was delayed in the stream. SE and SW rainfalls influenced on the runoff at the outlet and peak flows were relatively less than NW and NE rainfalls. SE rainfall showed more larger peak flow than SW rainfall. Proceedings of ICHE2010, IIT Madras, Aug 2-5,2010 Estimation Of Flood Discharge According To Variability Of Rainfall Distribution Using Gis-Based Method In A Basin                      461 Table 1. Peak flow and Peak Time at Songjung water level station Radar Rainfall  movement Peak flow (hr) Interval between  Peak flow  on the basis of SW(hr) Total Volume ( ) Interval between  Total Volume on the basis of SW (hr) NW 308.31 48.20 22,467.26 -33.04 NE 338.88 78.77 22,486.54 -13.76 SE 242.89 -17.22 22,503.13 2.83 SW 260.11 - 22,500.30 -  Fig. 7. Outflow hydrograph at Songjung water level station  CONCLUSIONS   We considered rainfall movement and direction for the investigation of runoff or flood discharge variability and for this, we used radar rainfall which can consider its spatial variability. This study have also used a semi distributed model which can consider spatial distribution of the basin characteristics for the runoff simulation.   Especially we investigated the variability of peak flow and peak time according to variability of radar rainfall movement and distribution and knew that the direction of rainfall movement affected peak flow and time of peak flow.  In conclusion, we have known that it may be important to consider the rainfall movement and direction for the investigation of flood discharge characteristics such as peak flow and peak time    Proceedings of ICHE2010, IIT Madras, Aug 2-5,2010 Estimation Of Flood Discharge According To Variability Of Rainfall Distribution Using Gis-Based Method In A Basin                      462This research was supported by a grant “The Design of Automatic Generation Module on Reach File and Input Data of Water Quality in Han River Basin” from the National Institute of Environmental Research, Ministry of Environment of Korea  REFERENCES HEC (1996), ModClark Model Development for the Muskingum River Basin, OH, US Army Corps of Engineers, Hydrologic Engineering Center Ahn, S. J., Yoon, S. H. 2005. Runoff Analysis using ModClark Model. Journal of Korea Water Resources Association, 38(3), 245-257. Park, J. H., Kang, B. S., Lee, G. S. 2008. Application Analysis of GIS Based Distributed Model Using Radar Rainfall. Journal of The Korean Society for Geo Spatial Information System, 16(1), 22-33 Park, J. H., Ham, G. U., Jang, D. J., Yoon, S. M., Choe, C. G., Lee, J. H. 2009. Runoff Characteristics Considering Rainfall Moving Direction, Proceeding of 2009 KSCE Annual Conference, 16 Lee, J. K., Kim, Y. S., Kim, H. S. 2009. Estimation of Representation parameter in the Chun  ju Dam Area using Modified Clark Model. Proceeding of 2009 KSCE Annual Conference, 6 ACKNOWLEDGEMENTS 

Estimation of Flood Discharge According to Variability of Rai Nfall Distribution Using Gis-Based Method in a Basin

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Estimation of Flood Discharge According to Variability of Rai Nfall Distribution Using Gis-Based Method in a Basin

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