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3.1. Research Domain

Figure 1 shows the geographical location of the study domain, the Baeksan–Nakdong river
catchment. Nakdong river has three water level observation stations—Jeock-po, Jing-dong and
Jeong-am stations—where the upstream and downstream boundary conditions used for this simulation
were computed. The flow domain digital elevation model used for this research was provided by
the National Geographic Information Institute of Korea. The flow rate and water level upstream and
downstream boundary conditions (Figure 2) used as input data were calculated using the HEC-RAS
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one-dimensional river routing model. The upstream boundary condition is a flow hydrograph of
discharge over time, while the downstream boundary condition is a water surface elevation stage
one-dimensional river routing model. The upstream boundary condition is a flow hydrograph of
one-dimensional river routing model. The upstream boundary condition is a flow hydrograph of
hydrograph versus time.ile the downstream boundary condition is a water surface elevation stage
discharge over time, wh
discharge over time, while the downstream boundary condition is a water surface elevation stage
hydrograph versus time.
hydrograph versus time.

Figure 1. Geographic location of the Baeksan catchment in Nakdong river basin, Korea.
Figure 1. Geographic location of the Baeksan catchment in Nakdong river basin, Korea.
Figure 1. Geographic location of the Baeksan catchment in Nakdong river basin, Korea.
River: RIVER-2 Reach: Reach-1 RS: 753.23 River: RIVER-1 Reach: Reach-2 RS: 191.08
1800 River: RIVER-2 Reach: Reach-1 RS: 753.23 14 River: RIVER-1 Reach: Reach-2 RS: 191.08
Legend
Legend
1800 Legend 14 Legend
1600 Flow 12 Stage
1600 Flow Stage
1400 12
1400 10
1200
Flow (m3/s) 1000 Flow (m3/s) 1200 Stage (m) 6 Stage (m) 8 10 8
1000
800
600 800 6
600 4
400 4
400
200 2
08 09 10 11 12 13 14 08 09 10 11 12 13 14
200 2002-08-01 2 2002-08-01
08 09 10 11 12 13 14 08 09 10 Date 11 12 13 14
Date
2002-08-01 2002-08-01
(a) Date (b) Date
(a) (b)
Figure 2. (a) Upstream discharge and (b) downstream water level boundary conditions calculated
Figure 2. (a) Upstream discharge and (b) downstream water level boundary conditions calculated
Figure 2. (a) Upstream discharge and (b) downstream water level boundary conditions calculated
using the U.S. Army Corps of Engineers Hydrologic Engineering Center River Analysis System (HEC- using
using the U.S. Army Corps of Engineers Hydrologic Engineering Center River Analysis System (HEC-
the U.S. Army
RAS) 1D model. Corps of Engineers Hydrologic Engineering Center River Analysis System (HEC-RAS)
RAS) 1D model.
1D model.
3.2. Methodology
3.2. Methodology
In order to run the simulation for the HEC-RAS coupled 1D–2D model, the results from the
In order to run the simulation for the HEC-RAS coupled 1D–2D model, the results from the
HEC-RAS one-dimensional model were used for the input data. These 1D data were also used in
HEC-RAS one-dimensional model were used for the input data. These 1D data were also used in
previous research in simulating Baeksan flood inundation. The mesh domain for the 2D flow was set
previous research in simulating Baeksan flood inundation. The mesh domain for the 2D flow was set
up, as well as the lateral structure and boundary conditions. After running the simulation, the
up, as well as the lateral structure and boundary conditions. After running the simulation, the
resulting flood data—flood extent, water surface elevation, water depth, change in flooded area and
resulting flood data—flood extent, water surface elevation, water depth, change in flooded area and