Journal of Korea Water Resources Association (한국수자원학회논문집)

Korea Water Resources Association (한국수자원학회)
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A Study on the determination of the optimal resolution for the application of the distributed rainfall-runoff model to the flood forecasting system - focused on Geumho river basin using GRM

분포형 유역유출모형의 홍수예보시스템 적용을 위한 최적해상도 결정에 관한 연구 - GRM 모형을 활용하여 금호강 유역을 중심으로

  • Kim, Sooyoung (Department of Land, Water and Environment Research, Korea Institute of Civil Engineering and Building Technology) ;
  • Yoon, Kwang Seok (Department of Land, Water and Environment Research, Korea Institute of Civil Engineering and Building Technology)
  • 김수영 (한국건설기술연구원 국토보전연구본부) ;
  • 윤광석 (한국건설기술연구원 국토보전연구본부)
  • Received : 2018.11.07
  • Accepted : 2018.12.14
  • Published : 2019.02.28
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Abstract

The flood forecasting model currently used in Korea calculates the runoff of basin using the lumped rainfall-runoff model and estimates the river level using the river and reservoir routing models. The lumped model assumes homogeneous drainage zones in the basin. Therefore, it can not consider various spatial characteristics in the basin. In addition, the rainfall data used in lumped model also has the same limitation because of using the point scale rainfall data. To overcome the limitations as mentioned above, many researchers have studied to apply the distributed rainfall-runoff model to flood forecasting system. In this study, to apply the Grid-based Rainfall-Runoff Model (GRM) to the Korean flood forecasting system, the optimal resolution is determined by analyzing the difference of the results of the runoff according to the various resolutions. If the grid size is to small, the computation time becomes excessive and it is not suitable for applying to the flood forecasting model. Even if the grid size is too large, it does not fit the purpose of analyzing the spatial distribution by applying the distributed model. As a result of this study, the optimal resolution which satisfies the accuracy of the bsin runoff prediction and the calculation speed suitable for the flood forecasting was proposed. The accuracy of the runoff prediction was analyzed by comparing the Nash-Sutcliffe model efficiency coefficient (NSE). The optimal resolution estimated from this study will be used as basic data for applying the distributed rainfall-runoff model to the flood forecasting system.

한국에서 현재 사용되고 있는 홍수예보모형은 집중형 강우-유출모형을 적용하여 유역의 유출을 계산하고 하도 및 저수지 추적모형 등을 활용하여 하천의 수위를 예측한다. 집중형 모형은 유역을 동질의 배수구역으로 가정한다. 따라서 유역내의 다양한 공간적 특성을 고려하지 못한다는 단점이 있다. 또한, 사용되는 강우자료도 지점강우를 활용하기 때문에 공간적인 분포를 자세히 고려하지 못한다는 한계가 있다. 따라서 홍수예보모형에 분포형 모형을 적용하기 위한 연구가 다양하게 진행되고 있다. 본 연구에서는 GRM모형을 한국 홍수예보시스템에 적용하기 위해 모형의 다양한 해상도에 따른 유역유출의 결과의 차이를 분석하여 최적의 해상도를 결정하고자 한다. 모형의 격자가 너무 조밀한 경우 계산시간이 과다하게 되어 홍수예보모형에 적용하기에는 적합하지 않다. 너무 성길 경우에도 분포형 모형을 적용하여 공간적인 분포를 파악하고자 하는 목적에 맞지 않게 된다. 본 연구의 결과로 유역유출 예측의 정확성을 만족시키고 홍수예보에 적합한 계산속도가 나올 수 있는 최적 해상도를 제시하였다. 유출량 예측의 정확도는 Nash-Sutcliffe model efficiency coefficient (NSE) 값의 비교를 통해 분석하였다. 본 연구에서 도출된 최적해상도 산정 결과는 분포형 유역유출모형을 홍수예보모형에 적용하기 위한 기초자료로 활용될 것이다.

Keywords

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Fig. 1. Schematic of hydrologic input and output in control volume (KICT , 2018)

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Fig. 2. Geumho river basin and sub-basin

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Fig. 3. Radar rainfall data at maximum rainfall

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Fig. 4. The results of GRM simulation

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Fig. 5. Simulation time according to CPU Core

Table 1. Period of flood and simulation conditions

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Table 2. Roughness coefficients according to land cover

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Table 3. Green-Ampt model parameters according to the soil texture

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Table 4. Soil depth classification for soil series

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Table 5. Results of parameter calibration and simulation time

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Table 6. Results of simulation time according to number of CPU core

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