Proceedings of the 10th Intl. Conf.on Hydroscience & Engineering, Nov. 4-7, 2012, Orlando, Florida, U.S.A.
A STUDY ON SIMULATION OF FLOOD INUNDATION IN A COASTAL URBAN AREA USING A TWO-DIMENSIONAL NUMERICAL MODEL
Woochang Jeong1, Jun-Whan Lee2, Yong-Sik Cho3
ABSTRACT
In this study, the simulation and analysis for the inundation in a coastal urban area according to the storm surge height are carried out using a two-dimensional numerical model. The target coastal urban area considered in this study is a part of the new town of Changwon city, Gyungnam province, Korea and this area was extremely damaged due to the storm surge generated during the period of the typhoon "Maemi" in September 2003. For the purpose of the verification of the numerical model applied in this study, the simulated results are compared and analyzed with the temporal storm surge heights observed at the tide station in Masan bay and inundation traces in urban areas. Moreover, in order to investigate the influence of super typhoons possible in the future, the results simulated with the storm surge heights increased 1.25 and 1.5 times greater than those observed during the period of the typhoon "Maemi" are compared and analyzed.
1. INTRODUCTION
Recent global warming has led to extreme weather conditions, and the 2007 Fourth Assessment Report of United Nations Intergovernmental Panel on Climate Change predicted a temperature rise of up to 6.4oC by the end of the 21st century (IPCC, 2007) and revealed that the sea level would rise by 28~43cm. In Korea, which is surrounded by the sea on three sides, typhoons and storms have frequently caused extensive damages including coastal inundation and erosion, and destruction of coastal structures. These include the No. 14 Typhoon "Sarah" in 1959, No. 5 Typhoon "Thelma" in 1987, No. 15 Typhoon "Rusa" in 2002, and No. 14 Typhoon "Maemi" in 2003, which caused enormous loss of both life and property owing to coastal inundation in areas along the southern coast. The coastal inundation is generated by a combination of various factors, such as seawater level changes due to long period high waves mainly created by tides, storm surges, and tsunamis. The coastal inundation caused by the massive Hurricane "Katrina" in August 2005 brought about enormous damage to the southeast areas of New Orleans in the United States. The property damage (including destruction of houses, harbor bridge facilities, and refinery facilities) was estimated to be
1 Assistant Professor, Department of Civil Engineering, Kyungnam University, Changwon, Korea ([email protected]) 2 Master course's student, Department of Civil and Environmental Engineering, Hanyang University, Seoul, Korea 3 Professor, Department of Civil and Environmental Engineering, Hanyang University, Seoul, Korea, ([email protected]) Proceedings of the 10th Intl. Conf.on Hydroscience & Engineering, Nov. 4-7, 2012, Orlando, Florida, U.S.A. more than $100 billion, the death toll was more than 1,800, and 80% of the city area was submerged because of the failure of the lake floodgates. Typhoon "Winnie", which occurred during the spring tide period on July 15 (according to the lunar calendar) in 1997, caused flood damage in the areas of the west coast, including Mokpo, Sinan, and Muan in Chonnam Province, South Korea, rising the need for systematic investigation into coastal disasters. Therefore, investigations into origins of coastal floods and analyses necessary for establishing comprehensive countermeasures were carried out. Further the enormous damage suffered by Busan and Masan city in Kyungnam Province because of Typhoon "Maemi" in September 2003 also raised social concerns related to storm surges, and theoretical studies on the occurrence of tidal waves and floods and research on the construction of various coastal disaster prevention systems were carried out (Kang, 2004; Choi et al., 2004; Heo et al., 2006a, 2006b; Yi, 2004; Kim et al., 2007). Disasters such as coastal floods are caused by combined factors related to waves and surges. Ozer et al. (2000) attempted to use bi-directional combined models of waves and surges to simulate these phenomena, and Bao et al. (2000) and Cheung et al. (2003) developed a combined model for MM5, POM, WAM, and SWAN to simulate three-dimensional wind structures and ocean currents. Moon and Oh (2003) and Choi et al. (2003) simulated surges caused by typhoons using a combined model that considered interactions between surges, tidal waves, and waves. Recently, using the MIKE 21 model, Mun et al. (2006) simulated and analyzed floods by storm surges in the sea area of Mokpo, and Hur et al. (2008) simulated and analyzed storm surges heights in the coastal areas of Busan and Kyungnam Province in virtual super-storm invasions. The results of their analyses suggested that these storm surge heights may be nearly 1.5~2.0 times higher than the heights that occurred during Typhoon "Maemi", and at least four times higher than the levels that occurred during Hurricane "Katrina". By applying the two-dimensional non-linear shallow water equations to the events of Typhoon "Maemi", they carried out simulations of the flood phenomena caused by storm surges in shore areas. However, most of this research, using storm surge heights observed from tide stations, assumed shores to be impermeable wall structures, estimated only storm surge heights in sea areas, or analyzed only the floodwater occurring in shore areas. Until now, few simulations and researches have focused on the effect on flood inundation of buildings, etc., in coastal urban areas due to storm surges. In this study, the flood inundation in a coastal urban area due to storm surge heights was simulated and analyzed by using the two-dimensional numerical model. The target coastal urban area is a part of new towns of Changwon city which suffered the most extensive damage during Typhoon "Maemi". In order to verify the applied numerical model, we use the storm surge heights recorded during Typhoon "Maemi" and compare the flood traces. Further, in order to investigate the influence of super typhoons that could occur in the future, we compare and analyze the results of flood inundation simulated under the assumed conditions that the storm surge heights increased to 1.25~1.5 times higher than the heights recorded during Typhoon "Maemi".
2. TWO-DIMENSIONAL FINITE VOLUME MODEL
2.1 Governing Equations
The governing equations are two-dimensional conserved-type shallow water equations and can be expressed as follows:
2 Proceedings of the 10th Intl. Conf.on Hydroscience & Engineering, Nov. 4-7, 2012, Orlando, Florida, U.S.A.
U FUSU (1) t U h,hu,hvT (1a)
(1b)
where h is the water depth, u and v are the depth-averaged velocities in the x- and y-axis directions, respectively. G(U) and H(U) are the flux vectors in the x- and y-axis directions, respectively. S(U) is the source term, g is the gravity acceleration, and n is the Manning’s roughness coefficient.
2.2 Finite Volume Method with Well-Balanced HLLC Scheme
By integrating eq. 1 over an arbitrary cell Ai as shown in Figure 1, the equation of a finite volume method can be written in vector forms as follows: U dA F U ni d S U dA (2) AAAit i i T where F=(E, H) , ∂Ai is the boundary of cell Ai, and ni is the outward unit normal vector to the boundary of cell Ai.
Figure 1 Triangular and quadrilateral cells in a two-dimensional unstructured grid system. 3 Proceedings of the 10th Intl. Conf.on Hydroscience & Engineering, Nov. 4-7, 2012, Orlando, Florida, U.S.A.
The discretized form of eq. 2 is given for the cell Ai as follows: dU m Ai F U n ij L ij A i S U (3) dt j1 where |Ai| is the surface area of the cell Ai, m is the number of sides of the cell Ai, (m=3 for a triangular cell and m=4 for a quadrilateral cell), Lij is the length of the side j, and nij is the outward unit normal vector from side j. The finite volume method allows directly spatial discretization by introducing the property of the rotational invariance (Toro, 2001). If this property is applied to the flux term in eq. 3, the flux term can be written as follows: F U n T1 G T U (4) ij nij n ij where Tnij is the transformation matrix expressed by Eq. 5.
1 0 0 T 0 cos sin (5) nij ij ij 0 sin ij cos ij
By substituting eq. 4 into eq. 5, the following equation can be obtained for the cell Ai.
m dU 1 ATGTU,TULASUi (6) i nij ninjijiii ij ij dt j1
where G(TnijUi, TnijUj)=Ğ(UL, UR) is the flux at the boundary of cell Ai and resolved from an approximate solver of the Riemann problem having a left state variable UL and a right state variable UR for cells L and R in Figure 1.
Figure 2 Schematic illustration of HLLC flux approximation.
In this study, to compute the flux term, the HLLC scheme proposed by Billet and Toro (1997) is employed. This scheme has the first-order accuracy both in time and space and an improved version of the HLL scheme (Harten et al., 1983). Unlike the HLL scheme which considers only two wave 4 Proceedings of the 10th Intl. Conf.on Hydroscience & Engineering, Nov. 4-7, 2012, Orlando, Florida, U.S.A.
* speeds SL and SR, the HLLC scheme takes into account the intermediate wave speed S between two wave speeds, as shown in Figure 2. In the HLL scheme, the flux terms in eq. 6 can be expressed as follows:
F ULL if S 0 HLL F ULRLRRR , U F U , U F U if S 0 (7) * F ULRLR , U if S 0 and S 0 * where F (UL, UR) can be estimated by the following formula
* SFUSFUSSUURLLRRLRL FU,U LR (8) SSRL
The wave speeds SL and SR can be calculated from
SLLLLRRRR u c p , S u c p (9)
where cL(=sqrt(ghL)) and cR(=sqrt(ghR)) are the wave celerities in the cells L and R, hL and hR are the water depths in the cells L and R, and pL and pR can be determined by the following condition:
11*** h h hkk if h h pk L,R h2k (10) * 1 if h hk where h* is the water depth at the boundary between cells L and R. In order to determine h*, first of * all, it needs to investigate whether h 0, being expressed by eq. 11, is dealt with a rarefaction wave condition or a shock wave condition (Loukili and Soulaimani, 2007).
* hhLR URLLR U h h h0 (11) 2 4 cLR c
* * If h 0 is under a rarefaction wave condition (i.e. h 0 ≤ min(hL, hR)),
* 2 h cLRLR c/2U U/4/g (12)
* * If h 0 is under a rarefaction wave condition (i.e. h 0 > min(hL, hR)),
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* h hLLRRLRLR a h a u u / a a * (13) g h0k h ak * , k L,R 2h0k h In a simpler version of HLLC scheme, remaining the HLL fluxes for the first two components of the flux, the third component (huv) is only considered as follows (Toro, 2001):
HLL * HLLC vL F 1 U L , U R if S 0 FU,U3 L R HLL * (14) vR F 1 U L , U R if S 0 where S h u S S h u S S* LRRRRLLL (15) hRRRLLL u S h u S
When the HLLC scheme is applied to the river with an abrupt and irregular bed geometry, it is difficult to obtain accurate results for the flow analysis because of the numerical oscillation due to the unbalance between the flux and source term (Perthame and Simeoni, 2001). To resolve this problem, the bed slope is directly considered (Leveque and George, 2004) to calculate F(UR) in eq. 7 in this study: 0 1 s F UR F U R g h L h R z b,R z b,L (16) 2 0
where zb,R and zb,L are the bed elevations at the cells R and L, respectively. Eq. 16 is used instead of F(UR) in eqs. 7 and 8. When the well-balanced HLLC scheme with the bed slope is applied, Eq.3 can be expressed for the cell Ai as follows:
dU m ATGU,ULASUi 1 s f i nij i j ij i i i (17) dt j1
f where S i(Ui) is the friction term and can be written by
2 2 2 0 f n uLL v Si U i g4/3 u L (18) h vL
In order to compute the water depth and velocity with time, a simple explicit Euler scheme is adopted in this study and can be written as follows:
6 Proceedings of the 10th Intl. Conf.on Hydroscience & Engineering, Nov. 4-7, 2012, Orlando, Florida, U.S.A.
m n 1 nt 1 s n n f ,n Ui U i T j F U L , U R tS i U i (19) Ai j1 n n+1 n n+1 f,n where U i and U i are the approximation of U computed at times t and t , respectively, and S i f n (Ui) is the value of S i (Ui) computed at time t . It is well known that the simple explicit Euler scheme is very efficient for the repetitive computation in the system of non-linear equations, such as the shallow-water equations. However, it is necessary to satisfy the CFL (Courant-Freidrichs-Lewy) condition to achieve the numerical stability. The condition is expressed by (Loukili and Souhaimani, 2007):
max gh u22 v CFL t (20) min dL,LR
where dL,LR is the distance between the cell center and the center of the interface of cells R and L. In this study, the wet and dry bed situations are dealt with the analytical method given as (Toro, 2001): * SLRRRRRLL u 2gh,S u gh,S S,ifh 0 (21) * SLLLRLLRR u 2gh,S u gh,S S,ifh 0
Eq. 21 is very efficient for the flat bed (i.e. ∆zb=0). If ∆zb≠0, however, the solution becomes numerically unstable (Honnorat, 2007). To resolve the problem, a minimum water depth h(>0) is introduced. If the water depth is less than h, the dry bed condition is imposed and the velocity is set -6 -3 at zero. In general, the range of h is between 1.0×10 ~1.0×10 m. In this study, the value of 1.0×10-3 m is used for an irregular bed geometry.
3. INUNDATION SIMULATION IN A COASTAL URBAN AREA
3.1 Target Coastal Urban Area and Configuration of Grid System
The target coastal urban area is a part of the new town of Changwon city which is located on the southern coast of the Korea and Masan Bay (Figure 3(a)). This town was extremely damaged by high tides and storm surge during the typhoon "Maemi" from September 12 to 13 in 2003. The major points with records of inundation traces are A, B, C, and D, which are located at 660, 569, 394, and 173 m, respectively, from the coast. Figure 3(b) shows the cross-sectional diagram of the area along A-B line in Figure 3(a), and the range of inundated water depth surveyed at each point. Point D, which is the closet to the coast, was recorded to be inundated approximately 1.0~1.5 m, point C was inundated 1.5~1.7 m, and points A and B were inundated 0.2~0.5 m.
7 Proceedings of the 10th Intl. Conf.on Hydroscience & Engineering, Nov. 4-7, 2012, Orlando, Florida, U.S.A.
(a) (b) Figure 3 Target coastal urban area (a) and schematic cross-section along A-B line (b).
Figure 4(a) represents the elevation distribution of the target area. The elevation along the coastal line varies from EL. 1.90 to EL. 2.10 m and the mean elevation is EL. 2.00 m. The elevation range of the urban area is between EL. 2.00 and EL. 39.90 m. The region from the coast to point C represents an almost flat terrain, but regions 1 and 2 become steeper with a mean slope of approximately 0.09. The elevation of point A is EL. 2.01 m, point B EL. 2.08 m, point C EL. 1.40 m, and point D EL. 1.24 m. Figure 4(b) shows the grid system of the target coastal urban area and boundary conditions. The grid system consists of 57,503 non-structural triangular cells and 32,885 nodes, and buildings are considered to be impermeable. Hence, the flow occurs only along the roads between buildings. The coastal line is considered as an inflow boundary condition, and the road exits connected with the boundary of the target coastal urban area are considered as free outflow boundary conditions.
(a) (b) Figure 4 Elevation distribution (a) and grid system with boundary conditions (b).
4.2 Simulation Conditions
The numerical model applied in this study cannot directly apply storm surge heights to itself as an inflow boundary condition. To resolve this problem, the coastal line is considered as a broad-crested weir, and the storm surge height is replaced as the overflow depth. The overflow depth is estimated by considering the storm surge height and the weir height from the mean sea level, that is, storm 8 Proceedings of the 10th Intl. Conf.on Hydroscience & Engineering, Nov. 4-7, 2012, Orlando, Florida, U.S.A. surge height - weir height. If the storm surge height does not exceed the weir height, the overflow depth becomes 0. The overflow discharge is estimated by the broad-crested weir formula (Lee, 2011), as follows: 1.5 2 (22) Q Cbw b g H 3 where b denotes the weir width, to which the length of the coastal line, taken to be 736.8 m, is applied. g is the acceleration of gravity, H is the height of the free water surface on the weir crest (or the overflow depth), and Cbw is the weir coefficient and is calculated using a formula as follows:
0.65 Cbw (23) 1 H / Pw where Pw denotes the weir height from the mean sea level, and is 2.0 m. Figure 5 represents the temporal variations of the storm surge heights observed at the tide station in Masan bay from September 12 to 13, 2003, during Typhoon "Maemi". The maximum value of the observed storm surge heights was 2.10 m at 21 hr 50 min September 12. In this study, we simulate the period September 12 16:00 to 23:00 (25,200 seconds), which included the maximum storm surge height.
Figure 5 Temporal variation of storm surge heights observed during typhoon "Maemi".
In order to analyze the inundation characteristics in the coastal urban areas in accordance with the storm surge scales, three different cases of storm surge heights are considered. As shown in Table 1, Case 1 corresponds to the storm surge heights observed during Typhoon "Mamie" and overflow discharges calculated using eq. 22. The overflow discharge for the maximum storm surge height of 2.10 m is 486.01 m3/sec. Considering the storm surge scales by a super typhoon that could occur in the future, Cases 2 and 3 assume the occurrence of storm surges that are approximately 1.25 and 1.5 times larger than those considered in Case 1. In Cases 2 and 3, the maximum overflow depths are 2.62 and 3.15 m, respectively, and each of the corresponding maximum overflow discharges is 641.62 and 773.69 m3/sec.
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Table 1 Storm surge heights and overflow discharges with time for three cases.
1 2 3 Cases Overflow Overflow Overflow Overflow Overflow Overflow Time height discharge height discharge height discharge (H, m) (Q, m3/sec) (H, m) (Q, m3/sec) (H, m) (Q, m3/sec) (yr, mon, day, hr:min, sec) 2003. 09. 12 16:00 0 0.10 7.34 0.13 10.20 0.16 13.28 16:10 600 0.22 22.29 0.28 30.80 0.33 39.73
16:20 1200 0.22 21.37 0.27 29.54 0.32 38.13
16:30 1800 0.16 14.05 0.20 19.47 0.24 25.23
16:40 2400 0.09 5.89 0.11 8.20 0.14 10.69
16:50 3000 0.08 4.52 0.09 6.30 0.11 8.22
17:00 3600 0.09 6.10 0.12 8.48 0.14 11.06
17:10 4200 0.13 10.06 0.16 13.97 0.19 18.15
17:20 4800 0.17 15.13 0.21 20.95 0.26 27.14
17:30 5400 0.18 16.14 0.22 22.35 0.27 28.92
17:40 6000 0.20 19.09 0.25 26.41 0.30 34.12
17:50 6600 0.27 30.20 0.34 41.64 0.41 53.52
18:00 7200 0.36 44.00 0.45 60.46 0.54 77.28
18:10 7800 0.43 57.50 0.54 78.80 0.65 100.25
18:20 8400 0.44 58.97 0.55 80.79 0.66 102.73
18:30 9000 0.37 45.77 0.46 62.88 0.55 80.31
18:40 9600 0.39 49.96 0.49 68.56 0.58 87.44
18:50 10200 0.49 69.69 0.62 95.28 0.74 120.78
19:00 10800 0.60 92.32 0.75 125.74 0.90 158.48
19:10 11400 0.66 104.27 0.82 141.77 0.99 178.21
19:20 12000 0.66 105.82 0.83 143.84 1.00 180.75
19:30 12600 0.66 105.05 0.83 142.81 0.99 179.48
19:40 13200 0.66 104.27 0.82 141.77 0.99 178.21
19:50 13800 0.69 111.90 0.87 151.98 1.04 190.72
20:00 14400 0.84 145.20 1.05 196.38 1.26 244.91
20:10 15000 1.15 222.58 1.44 298.71 1.72 368.35
20:20 15600 1.30 261.83 1.62 350.25 1.95 429.97
20:30 16200 1.32 268.00 1.65 358.33 1.98 439.59
20:40 16800 1.37 280.85 1.71 375.16 2.05 459.62
20:50 17400 1.45 302.03 1.81 402.84 2.17 492.51
21:00 18000 1.60 343.62 2.00 457.07 2.40 556.74
21:10 18600 1.76 387.67 2.20 514.33 2.63 624.30
21:20 19200 1.94 439.00 2.42 580.85 2.90 702.49
21:30 19800 2.03 466.36 2.54 616.23 3.05 743.97
21:40 20400 2.09 485.91 2.62 641.49 3.14 773.54
21:50 21000 2.10 486.01 2.62 641.62 3.15 773.69
22:00 21600 1.94 441.42 2.43 583.99 2.92 706.17
22:10 22200 1.67 364.04 2.09 483.64 2.51 588.11
22:20 22800 1.46 304.95 1.82 406.65 2.19 497.04
22:30 23400 1.14 220.35 1.42 295.76 1.71 364.82
22:40 24000 0.69 112.44 0.87 152.70 1.04 191.61
22:50 24600 0.42 55.10 0.52 75.54 0.63 96.18
23:00 25200 0.09 6.20 0.12 8.62 0.14 11.24
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4.3 Simulation Results and Analyses
Figure 6 shows the spatial distributions of inundation depths with time for Case 1. The storm surge starts to inflow in from the coast, moves along the roads between buildings, stops moving around E square because of high slope, and then moves along other roads with relatively small slopes. With the first half of the buildings placed close and parallel to the coast, rapid increases in the water depth occurs, which means that buildings may become barriers that delay the movement of the storm surges flowing in from the coast. Since the beginning of the simulation, the inundation depth with time increases from 0.84 m after 5,000 seconds (1 hr 23 min), to 1.07 m after 10,000 seconds (2 hr 47 min), to 1.4 m after 15,000 seconds (4 hr 10 min), and up to 2.09 m after 21,000 seconds (5 hr 50 min), and then starts to decrease. After 25,000 seconds (6 hr 57 min), the inundation depth decreases down to 1.25 m.
5,000 seconds (1h 23m) 15,000 seconds (4h 10m)
21,000 seconds (5h 50m) 25,000 seconds (6h 57m)
Figure 6 Spatial distribution of inundation depths with time for case 1.
Figure 7 shows the temporal variations of inundation depth for four points. In the case of point D, the maximum inundation depth is 1.22 m and occurs after 21,204 seconds (corresponding to September 12, 21 hr 53 min) from the beginning of the simulation, which is 204 seconds (nearly 3 min) after 21,000 seconds when the maximum storm surge height occurred. In the case of point C, the maximum inundation depth is 1.71 m after 21,265 seconds (corresponding to 21 hr 54 min), 11 Proceedings of the 10th Intl. Conf.on Hydroscience & Engineering, Nov. 4-7, 2012, Orlando, Florida, U.S.A. which is estimated to have occurred approximately 60 seconds after the maximum storm surge height at point D occurred. For points A and B, the maximum inundation depths are 1.07 m and 0.79 m, respectively, and they occur after 21,308 and 21, 317 seconds, respectively, almost simultaneously since the beginning of the simulation. In the case of points C and D estimated in this study, the maximum inundation depth represents values within the range of, or considerably close to, the inundation traces shown in Figure 3(b), but in the case of point A and B, the maximum inundation depths are overestimated by approximately 0.5 m. Considering the uncertainty of the inundation traces, however, the simulated results are comparatively appropriate. In the case of point D and C, the inundation starts after approximately 1,189 seconds (corresponding to 16 hr 19 min) and 1,254 seconds (corresponding to 16 hr 21 min), respectively. For points A and B, the inundation starts after 9,027 seconds (corresponding to 18 hr 30 min) and 14,328 seconds (corresponding to 19 hr 58 min), respectively.
Figure 7 Temporal variation of inundation depths at four points for case 1. Figure 8 shows the spatial distributions of the inundation depths with time for three cases. As the scale of storm surge heights is relatively large, the inundation depth tends to be increasingly larger, but in the case of the distribution of inundation depths, there is no apparent difference between the cases because the storm surge flowing in from the coast to the urban areas move along the flat roads and stop moving on the roads with relatively steep slopes.
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Time Case 1 Case 2 Case 3 (sec)
5,000 (1h 23m)
21,000 (5h 50m) Max
25,000 (6h 57m)
Figure 8 Spatial distribution of inundated water depth with time for three cases.
Table 2 presents a comparison of the maximum inundation depths with time for three cases and reveals that as the scale of storm surges increases, the maximum inundation depth tends to increase as well. For Case 2, in comparison with Case 1, at 21,000 seconds (5 hr 50 min) after the beginning of the simulation, the maximum inundation depth is 2.45 m with an increase of 0.36 m and in Case 3, it is 2.70 m with an increase of 0.61 m.
Table 2 Maximum inundated water depth with time for three cases.
Maximum inundated water depth (m) Time(seconds) Case 1 Case 2 Case 3 5,000 (1h 23m) 0.84 0.88 (▲ 0.04) 0.91 (▲ 0.07) 10,000 (2h 47m) 1.07 1.15 (▲ 0.08) 1.22 (▲ 0.15) 15,000 (4h 10m) 1.40 1.55 (▲ 0.15) 1.68 (▲ 0.28) 21,000 (5h 50m) 2.09 2.45 (▲ 0.36) 2.70 (▲ 0.61) 25,000 (6h 57m) 1.25 1.36 (▲ 0.11) 1.44 (▲ 0.19)
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5. CONCLUSIONS
Using the 2-dimensional numerical model and the data of storm surge heights observed from the tide station of Masan bay, we simulate and analyze the inundations caused by storm surges in a part of new town in Changwon city, Kyungnam Province, Korea. The main conclusions drawn in this study are as follows: 1. The maximum inundation depths for points D, C, A, and B in the target coastal urban areas are 1.22, 1.71, 1.07, and 0.79 m, respectively, and in the case of points D and C, the calculated values are considerably close to those from the surveyed inundation traces, whereas in the case of points A and B, the maximum inundation depths are overestimated by approximately 0.5 m. Considering the uncertainty of the inundation traces, however, the maximum inundation depth estimated in this research is appropriate in principle. 2. The storm surge starts to flow in from the coast, moves along the roads between the buildings in the urban area, stops moving around E square because of roads with high slope, and then moves along other roads with relatively small slopes. With the first half of the buildings placed close and parallel to the coast, rapid increases in the water depth occur, and the buildings in the urban area probably become barriers that delay the movement of the surges flowing in from the coast. 3. As the scale of the storm surges increases, the inundation depth tends to increase, and in Case 1 for storm surges generated by Typhoon “Maemi”, the maximum inundation depth is 2.09 m, but in Case 2, it is 2.45 m with a 17% increase, 1.25 times larger than that in Case 1. For Case 3, it is 2.7 m with a 30% increase, 1.5 times larger than in Case 1
ACKNOWLEDGEMENTS
This research was supported by Basic Science Research Program through the National Research Foundation of Korea(NRF) funded by the Ministry of Education, Science and Technology(2012- 0005685).
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