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Numerical Simulation of the Flood Event Induced Temporally and Spatially Concentrated Rainfall - On August 17, 2017, the Flood Event of Cheonggyecheon

시공간적으로 편중된 강우에 의한 홍수사상 수치모의 - 2017년 8월 17일 청계천 홍수사상을 대상으로

  • Ahn, Jeonghwan (Dept. of Civil and Environmental Engineering, Induk Univ.) ;
  • Jeong, Changsam (Dept. of Civil and Environmental Engineering, Induk Univ.)
  • 안정환 (인덕대학교 토목환경설계과) ;
  • 정창삼 (인덕대학교 토목환경설계과)
  • Received : 2018.11.26
  • Accepted : 2018.12.20
  • Published : 2018.12.31

Abstract

This study identifies the cause of the accident and presents a new concept for safe urban stream management by numerical simulating the flood event of Cheonggyecheon on August 17, 2017, using rain data measured through a dense weather observation network. In order to simulate water retention in the CSO channel listed as one of the causes of the accident, a reliable urban runoff model(XP-SWMM) was used which can simulate various channel conditions. Rainfall data measured through SK Techx using SK Telecom's cell phone station was used as rain data to simulate the event. The results of numerical simulations show that rainfall measured through AWSs of Korea Meteorological Administration did not cause an accident, but a similar accident occurred under conditions of rainfall measured in SK Techx, which could be estimated more similar to actual phenomena due to high spatial density. This means that the low spatial density rainfall data of AWSs cannot predict the actual phenomenon occurring in Cheonggyecheon and safe river management needs high spatial density weather stations. Also, the results of numerical simulation show that the residual water in the CSO channel directly contributed to the accident.

본 연구는 2017년 8월 17일 청계천에서 발생한 시민고립사고의 원인을 규명하고, 고밀도 기상관측망의 관측자료를 이용하여 안전한 도시하천 관리 방안을 제시한 연구이다. SK 텔레콤 기지국에 설치된 고밀도 기상관측망인 SK techx와 상대적으로 공간적 밀도가 낮은 기상청 AWS의 사고 당일 강우자료를 도시유출모형에 적용하여 당시 상황을 모의하였다. 사고원인 중 하나로 가정한 CSO 관로 내 체수현상을 구현하여 수치모의한 결과, 기상청 AWS에서 계측된 강우량은 사고를 발생시키지 않았다. 하지만 실제 현상과 더 유사한 고밀도 기상관측망인 SK techx의 강우자료를 적용했을 때는 당일 발생한 사고와 유사한 결과가 나타났다. 이는 낮은 공간 밀도인 기상청 AWS는 청계천에서 일어나는 실제현상을 예측할 수 없고, 안전한 하천관리르 위해 고밀도 기상관측소가 필요하다는 것을 의미한다. 또한 CSO 관로 내 체수 유무를 독립변수로 수치 모의한 결과 비우당교의 CSO 관로 내 체수가 사고의 직접적인 원인으로 분석되었다.

Keywords

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Fig. 1. Conceptual diagram of the drainage process of the Cheonggyecheon catchment

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Fig. 2. Weather stations of KMA in Seoul

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Fig. 3. Rainfall distribution from weather radar at the event

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Fig. 4. Numerical model of Cheoggyecheon catchment constructed by XP-SWMM

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Fig. 5. Locations and cross sections of the accident in a numerical model

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Fig. 6. Rainfall records and locations of the weather stations used for numerical simulation

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Fig. 7. Water level in the main drainage channel at the event on August 17

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Fig. 8. Simulated water levels in the main drainage channel at the point of the accident

Table 1. Runoff characteristics of Cheonggyecheon catchment

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Table 2. Daily rainfall measured at weather stations near Cheonggyecheon on the day of the accident

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Table 3. Hourly Rainfall measured by SK techx weather stations on the day of the accident

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Table 4. Scenarios for numerical simulations

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