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close this bookCrucibles of Hazard: Mega-Cities and Disasters in Transition (UNU, 1999, 544 pages)
View the document(introduction...)
View the documentAcknowledgements
View the document1. Introduction - James K. Mitchell
View the document2. Natural disasters in the context of mega-cities - James K. Mitchell
View the document3. Urbanization and disaster mitigation in Tokyo - Yoshio Kumagai and Yoshiteru Nojima
View the document4. Flood hazard in Seoul: A preliminary assessment - Kwi-Gon Kim
View the document5. Environmental hazards in Dhaka - Saleemul Huq
View the document6. Natural and anthropogenic hazards in the Sydney sprawl: Is the city sustainable? - John Handmer
View the document7. Disaster response in London: A case of learning constrained by history and experience - Dennis J. Parker
View the document8. Lima, Peru: Underdevelopment and vulnerability to hazards in the city of the kings - Anthony Oliver-Smith
View the document9. Social vulnerability to disasters in Mexico City: An assessment method - Sergio Puente
View the document10. Natural hazards of the San Francisco Bay mega-city: Trial by earthquake, wind, and fire - Rutherford H. Platt
View the document11. There are worse things than earthquakes: Hazard vulnerability and mitigation capacity in Greater Los Angeles - Ben Wisner
View the document12. Environmental hazards and interest group coalitions: Metropolitan Miami after hurricane Andrew - William D. Solecki
View the document13. Findings and conclusions - James K. Mitchell
View the documentPostscript: The role of hazards in urban policy at the millennium - James K. Mitchell
View the documentAppendices
View the documentContributors
View the documentOther titles of interest

4. Flood hazard in Seoul: A preliminary assessment - Kwi-Gon Kim

Editor's introduction

Seoul is sometimes known as the Phoenix City because of its ability to re cover from disaster (Williams, 1993, p. 450). Such disasters have usually been the result of military actions, most recently the Korean War, which completely destroyed the city. Today's rebuilt Seoul lies only 20 miles south of the demilitarized zone with the People's Republic of Korea; the city exists in an uncertain political relationship with its flood- and famine-stricken northern neighbour. There is also uncertainty about the country's ability to weather recent economic shocks that are linked with a broader crisis of East Asian economies. Although blizzards, winter freezes, and earthquakes are significant natural risks, and the city's best-known environmental hazard may be its severe air pollution, this chapter focuses on the relatively neglected - but worsening - hazard of riverine flooding.

Flooding is an increasing problem in metropolitan Seoul and the management of floods and floodplains is a neglected priority for urban planning. The causes of flooding are well known but the effects are poorly documented. Typically, floods are triggered by heavy rain, rapidly melting snow, or tropical storms, especially under conditions where soils are already saturated. Rivers overflow into surrounding built-up areas, bringing death and injury to people as well as considerable damage to buildings. During the past four decades, particularly serious floods occurred in 1966, 1972, 1977, 1984, 1987, and 1990. Between 1960 and 1991 more than 130 people died, 975 were injured, and over 185,000 buildings suffered flood damage at a total cost of around US$ 80 million (table 4.1). Among the residents of Seoul, flooding is most often attributed to failure of the pumping system that is the city's chief line of defence against inundation. However, other analysts believe that a major reduction in the amount of green open spaces is contributing to increased flood risks. Issues of urban poverty are also mixed in with the flood problem. This is made clear by a newspaper report:

The residents who live in the frequently inundated areas regard flood disasters as man-made disasters rather than natural disasters. Those people, who are low income class people, believe that flood disasters are due to their poverty. (Dong-a, 15 September 1990)

Table 4.1 Flood damage in Seoul, 1960-1991

Year

Population ('000)

Total precipitation (mm)

Monthly peak precipitation (mm)

WLHRBa (metres)

Damage (million won)

Buildings lost

1960

2,445

1,188

313

6.84

3

216

1961

2,577

1,437

361

6.25

57

687

1962

2,983

986

139

7.04

8

42

1963

3,255

1,627

514

8.30

30

2,380

1964

3,424

1,794

504

8.27

64

7,654

1965

3,471

1,216

632

10.80

442

10,770

1966

3,793

2,020

898

10.78

605

23,000

1967

3,969

1,269

284

6.60

16

1,170

1968

4,335

1,288

412

7.75

33

1,584

1969

4,777

1,737

455

9.71

67

2,196

1970

5,525

1,708

426

9.02

33

8,557

1971

5,851

1,360

530

6.75

120

1,728

1972

6,076

1,770

882

11.24

1,980

41,200

1973

6,290

928

191

4.97

15

134

1974

6,542

1,251

319

7.22

11

44

1975

6,890

1,067

385

7.45

3

198

1976

7,255

1,110

462

8.41

52

497

1977

7,526

1.148

405

4.28

713

8,158

1978

7,823

1,161

375

8.86

63

732

1979

8,114

1.269

354

7.98

57

218

1980

8,367

1.242

332

7.72

24

3

1981

8,676

1,216

464

8.12

188

122

1982

8.916

949

256

4.99

15

134

1983

9,204

1,057

399

4.23

188

121

1984

9,501

1,250

348

11.03

20,274

34,905

1985

9,639

1,545

439

4.58

173

218

1986

9.799

1,247

370

5.05

287

14

1987

9,991

1.751

651

7.00

15,595

17,603

1988

10,287

761

382

5.46

16

6

1989

10,577

1,426

344

3.98

119

17

1990

10,613

2,356

570

1127

22.528

21,599

1991

10.905

1.158

488

6.74

993

614

Total





64,771b

186,521

Mean


1.353

436

746



Source: Annual records, Seoul Municipal Government.
a. WLHRB = Water level at Han River Bridge.
b. Approximately US$ 80 million (1995)

This chapter emphasizes recent changes in the relationship between flood risks and urbanization in Seoul. It also assesses the consequences of development plans for human safety and well-being and it explores possible management solutions. An overview of urban problems, processes, and issues in Seoul is followed by what is believed to be the first systematic assessment of Seoul's flood hazard. A simple procedure for identifying flood risks is described. Opportunities for making hazards reduction a priority of urban government and community life are also reviewed.

Urbanization and urban issues in the Seoul Metropolitan Area

It is important to understand how particular factors of geography, history, economics, climate, ecology, culture, and politics have combined to create a distinctive contemporary context for flood hazard in Seoul.

Physical setting

Seoul occupies a location that commands major transportation routes through Korea. It is sited on the banks of the Han River in a mountain-rimmed basin near the edge of the western coastal plain (fig. 4.1). The Han drains much of central Korea into the Yellow Sea. Nearby mountain peaks of up to 836 metres are linked together by scenic ridges, and well-vegetated smaller hills are scattered throughout the built-up area. The ocean port of Inch'on lies approximately 30 km to the west, and intervening areas are served by a network of major highways and interconnecting railroads.

Urbanization

The earliest traces of urban settlement in this vicinity date from 2,000 years ago when the town of Viryesong was chosen as capital of the Paekche Kingdom (18 B.C. - A.D. 660) (Seoul Metropolitan Government, 1992). Following a number of name changes, Seoul became capital of all Korea at the beginning of the Choson Dynasty (1392 - 1910). The new capital was laid out in 1394 according to principles of geomancy. After 600 years of existence it now houses around 11 million people - more than a quarter of the entire population of the Republic of Korea.


Fig. 4.1. Seoul Metropolitan Area

In 1428, approximately one-third of a century after Seoul's founding, 103,328 people lived within the city walls and approximately 110,00 more lived outside them. Thereafter, the urban population remained close to 200,000 for over 400 years. Then, in the late nineteenth century - when the country was opened to foreign contacts - the population of Seoul began to grow. This process continued when Korea was annexed by Japan in 1910, and by 1936 about 700,000 people lived in the city. After the Second World War, municipal boundaries were expanded to include 268.35 km2, which encompassed about 1,400,000 people.

Seoul was devastated during the Korean War (1950 - 1953) and had to be extensively rebuilt. By means of a special legislative measure the Seoul Metropolitan Government came under the direct control of the Prime Minister in 1962 and this enabled it to develop rapidly. The municipal boundaries were further expanded in 1963 to encompass 613.04 km2 and were redrawn yet again in 1973 to include 627.06 km2 (table 4.2, fig. 4.2). If present trends continue, it is estimated that the city's population may reach 15 million by the year 2000, at a density of 400 persons per hectare. However, it is also government policy to disperse urban activities to less developed areas. A Capital City Construction Plan has been prepared, which includes incentives and other provisions for moving industries out of Seoul as well as increased taxes on urban in-migrants (Working Group for the Middle-Range Development Plan of Seoul, 1979).

Table 4.2 Population and area of Seoul, 1961-1991

Year

Population ('000)

Total area (km2)

1961

2,577

268.35

1962

2,983

268.35

1963

3,255

613.04

1964

3,424

613.04

1965

3,471

613.04

1966

3,793

613.04

1967

3,969

613.04

1968

4,335

613.04

1969

4,777

613.04

1970

5,525

613.04

1971

5,851

613.04

1972

6,076

613.04

1973

6,290

627.06

1974

6,542

627.06

1975

6,890

627.06

1976

7,255

627.06

1977

7,526

627.06

1978

7,823

627.06

1979

8,114

627.06

1980

8,367

627.06

1981

8,676

627.06

1982

8,916

627.08

1983

9,204

627.08

1984

9,501

605.38

1985

9,639

605.43

1986

9,799

605.42

1987

9,991

605.42

1988

10,287

605.40

1989

10,577

605.43

1990

10,613

605.34

1991

10,905

605.33

Source: Seoul Metropolitan Government, Seoul Statistical Yearbook, 1992, p. 4.

Fig. 4.2. Expansion of the Seoul Metropolitan Area, 1926-1990 (Source: Seoul Metropolitan Government)


Seoul 1926


Seoul 1961


Seoul 1990

Table 4.3 Land-use changes in Seoul City, 1979-1991


1979

1991

Change (km2)


km2

%

km2

%


Built-up area

253

42

390

65

+137

Agricultural land

87

14

36

6

-51

Forest land

242

40

153

25

-89

Water

23

4

26

4

-3

Source: Seoul Metropolitan Government.

Table 4.4 Land-use changes in Seoul Region, 1979-1991


1979

1991

Change (km2)


km2

%

km2

%


Built-up area

528

11

997

20

+469

Agricultural land

1,543

31

1,342

27

-201

Forest land

2,805

56

2,525

50

-280

Water

151

3

163

3

+12

Source- Seoul Metropolitan Government.

Recent demographic trends have brought about considerable land-use changes in Seoul. Based on an analysis of LANDSAT imagery carried out by the Korea Research Institute for Human Settlements, it is known that built-up areas within the municipal boundaries increased by 54.2 per cent between 1979 and 1991. During the same period, agricultural land declined by 58.6 per cent and land in forests decreased by 36.8 per cent (table 4.3). In the larger Capital Region (within 40 km of Seoul City Hall), built-up areas have increased by 8.9 per cent, while agriculture and forests have decreased by 13.1 per cent and 10.0 per cent, respectively (table 4.4).

During the years leading up to the 1960s, Seoul maintained a single central business district and grew by peripheral expansion along major access highways. Thereafter, the pattern of urban functions began to change. In the 1970s, large-scale city planning projects resulted in rapid development of selected localities such as Kangnam. Following construction of an extensive subway system in the 1980s, urban functions have become more decentralized. Now subway stations are the foci of secondary business districts. In other words, multiple economic nuclei have emerged to challenge the dominance of the downtown business core.

Table 4 5 Centralization of functions in Seoul, 1989


Country

Seoul

% in Seoul

Area

99,237 km2

605 km2

0.6

Population

42,380,000

10,577,000

25.0

Central





government organizations

45

31

69.0

Headquarters of large firms

1,711

851

50.0

Loans

62 trillion won

35 trillion won

56.0

Cars

2,660,000

990,000

37.0

Physicians

34,498

14,577

42.0

Colleges

474

161

34.0

Publishing companies

1,654

1,546

94.0

Newspapers (daily and weekly)

195

162

83.0

Source Seoul Metropolitan Government

Urban environmental problems

Seoul suffers from a variety of urban environmental problems, including overcrowding, housing shortages, transportation congestion, air pollution, building fires, and flooding. The city is the pre-eminent centre of national life in Korea and a magnet for the rural population. Political, economic, social, and cultural organizations of Korea are heavily concentrated in Seoul. For example, half of the headquarters of large businesses are here and 56 per cent of all financial loans are made for investments in Seoul (table 4.5). The city produces 40 per cent of the country's gross national product, houses 90 per cent of the nation's administrative functions, and hosts 70 per cent of Korea's college students (Koo, 1989). The country's publishing industry and most of its public institutions are also located here. Inner districts of Seoul are now centres of labour-intensive industries while suburban Seoul is occupied by capital-intensive industries. Technical and computer services are also concentrated in the city.

In-migration from rural areas is heavy, demand for housing and public services is acute, and urban population densities are among the highest in the world. Between 1980 and 1990 housing units grew from 1 million to over 1.4 million, while numbers of schools increased from around 1,100 to over 2,600. The population density is around 18,000 people per km2. Because the city's population is growing so fast (about 4 per cent per year), there is strong pressure to develop existing open spaces within the metropolitan boundaries and to permit expansion further into the countryside. High-rise construction helps to ease some of the pressure on land and the city is surrounded by an officially designated green belt, which was created in 1971. More than 27 per cent of all land within the boundaries of the Seoul administrative area is included in the green belt. It has been effective in minimizing the spread of non-conforming urban land uses (Kim, 1990).

Housing shortages are severe. In 1988 there were fewer than six dwellings for every ten families (Clifford, 1989), and squatters now make up about 20 per cent of the metropolitan population. Most squatters are poor migrants from rural areas who congregate in the peripheral districts of the city. With demand for downtown land at record levels, housing and land prices there have risen steeply. Closely packed wooden homes are also susceptible to fire, and total fire losses are accelerating. In the years between 1980 and 1990, annual losses rose by about 400 per cent and by a further 50 per cent in the two succeeding years (fig. 4.3).


Fig. 4.3. Trends of fire damage in Seoul, 1961-1992 (Source Seoul Metropolitan Government)

During the 1980s it was estimated that 400,000 additional housing units would be required in the near future. These will consume about 34 km2 of land. Some of the land will come from redevelopment of existing residential areas and abandoned factories, but at least 12.6 km2 of green open space land in the outer parts of the city will also be consumed. By 1989 work was already under way to convert 8.5 km2 of green areas to housing sites in 17 city districts. Profits from the sale of housing are routinely reinvested in the construction of roads, public utilities, and additional houses (Seoul Metropolitan Government, 1989). Conversion of green spaces inside Seoul's boundaries for new towns-in-town is believed to increase flood risks and lessen human safety.

Crowding produces other serious problems. These include traffic congestion, air pollution, water pollution, and solid waste disposal (Shin, Lee, and Song, 1989; Moon, Lee, and Yoon, 1991; Sohn, Heo, and Kang, 1989; Shin, Koo, and Kim, 1989). More than 40 per cent of Korea's vehicles are concentrated in Seoul and approximately 300 more cars are being added every day (Won, 1990). In contrast, relatively little land is devoted to streets and roads - around 14.5 per cent compared with 20 - 35 per cent in American and European cities of similar size. Since 1981, road space has risen from 15 per cent to 17 per cent of the city's total area. Traffic accidents have increased from 27,483 in 1981 to 49,413 in 1987 (Lee, 1988; Parsley, 1993).

The Han River provides a major barrier to surface transportation systems and is a main contributor to congestion. Roads are funnelled over nine major as well as eight lesser bridges; and there are three main railroad bridges. Only one of the seven cross-river subway lines uses a tunnel, the remainder being carried on combined road and rail bridges. Because Seoul occupies a mountain basin protected from high winds, the potential for air stagnation is high. Especially in winter there is a high frequency of inversions marked by calm atmospheric conditions and limited vertical mixing. Urbanization and industrialization have combined with a rise in living standards to produce a dramatic increase in energy consumption. As a result, the air over Seoul contains high levels of sulphur dioxide and suspended particulates. Most of these problems are traceable to the use of particular fuels: anthracite briquettes for home heating and cooking; bunker oil for industry and power stations; and gasoline for motor vehicles (UNEP/WHO, 1992).

Flood-risk assessment

Framework for the assessment of flood risk in Seoul

The following conceptual and methodological framework for flood-risk assessment is based on two premises: (1) urbanization and land-use decisions are important determinants of flood risk; and (2) urban planning and decision-making have not effectively incorporated flood risks or made provisions for their reduction. The analytic procedure used here produces estimates of likely future losses by combining floodplain location data from Geographic Information Systems with statistical analysis of flood probabilities and populations at risk (fig. 4.4). Public perceptions of floods and appropriate responses are also examined by means of a survey of newspaper articles.


Fig. 4.4. Framework for flood-risk assessment in Seoul

The Han River basin covers 26,200 km2, or 26 per cent of Korea's land area, and contains nearly one-third of the country's population (Republic of Korea and Asian Development Bank, 1982). In Seoul, floodplains border the Han and its tributaries (fig. 4.5). Although flood risks are increasing, no systematic analysis of these risks has ever been completed.

Methods

For the purposes of this analysis, exposure to flooding in Seoul is assumed to be a function of two variables: (1) elevation; and (2) distance from a river channel. Generally, in Seoul's reach of the Han River valley, land up to 10.5 m above sea level is at risk of flooding. LANDSAT images were analysed to identify three levels of elevation corresponding to three different probabilities of exposure to floods: less than 10 m above mean sea level; 10 - 15 m above mean sea level; and more than 15 m above mean sea level. The three elevation land classes are shown in table 4.6 (areas below 15 m appear in fig. 4.5). Areas under 10 m include 31.37 per cent of the total area of Seoul. Areas between 10 and 15 m include 7.2 per cent of Seoul. And areas above 15 m include 61.43 per cent of the city. Thus, about one-third of Seoul is below the threshold elevation for serious flood risk. There are many dwelling units and other buildings in this area. Of the 22 wards (gu) of Seoul, Yongdungp'o-gu has the greatest percentage of land under 10 m (84.21 per cent).

The study area was also divided into three zones based on distance from the boundary of the Han River channel: within 500 m; 500 - 1,000 m (1 km); beyond 1 km. Table 4.7 illustrates these three distance classes. Just under 6 per cent of the area of Seoul is within 500 m of the Han River channel. An additional 5.24 per cent lies between 500 m and 1,000 m, but most of the city is located further away from the river (88.79 per cent). Map'o-gu contains the largest amount of land closest to the river (19.83 per cent within 500 m).

The results of combining elevation and distance data are shown in table 4.8. It is clear that a significant number of city wards are at risk of flooding. These include: Map'o-gu, Kangdong-gu, Songdong-gu, Yongdungp'o-gu, Yongsan-gu, Songp'a-gu, Kangnam-gu, and Dongjak-gu. Only one ward (Chung-gu) is considered to be safe from flooding by virtue of its high elevation and distance from the river. This ward contains much of the central business district, including Seoul City Hall and many government buildings, as well as hotels, foreign embassies, and the headquarters of major firms.

Ideally, it should be possible to identify the numbers of people and buildings that occupy different elevation and distance zones. However, technical limitations of the Geographic Information System that was used in the analysis precluded this possibility. To determine the accuracy of the preceding analysis it was checked against the record of flood damage for three recent years (1984, 1987, 1990) (table 4.9). This shows that there is a high degree of agreement between wards that are assessed as having a high risk of flooding and actual losses.

It was also observed that water rose to a height of more than 11 m at the Han River Bridge on three occasions between 1960 and 1991. This indicates that the potential for flooding in Seoul is large. Flood events with a frequency of once in 400 years could rise to 13.85 m above sea level at this bridge.

Table 4.6 Elevation zones in Seoul wards

Code No.

Ward

Total area

Under 10 m

10-15 m

Over 15 m



Ha

%

Ha

%

Ha

%

Ha

%

1

Tobong-gu

4,580.75

100

4.85

0.11

60.71

1.33

4,515.18

98.56

2

Nowon-gu

3,558.98

100

523.00

14.70

445.76

12.52

2,590.22

72.78

3

Map'o-gu

2,450.94

100

1,667.74

68.32

287.47

11.78

485.74

19.90

4

Yangchon-gu

1,757.45

100

905.63

51.44

163.75

9.30

691.07

39.26

5

Kangdong-gu

2,611.61

100

899.06

34.43

273.61

10.48

1,438.93

55.09

6

Songdong-gu

3,365.56

100

2,105.73

62.57

331.96

9.86

927.88

27.57

7

Unpyong-gu

3,152.11

100

292.58

9.28

199.98

6.34

2,659.54

84.38

8

Songbuk-gu

2,458.33

100

120.12

4.89

123.04

5.01

2,215.18

90.10

9

Chongno-gu

2,317.64

100

96.36

4.16

115.84

5.00

2,105.45

90.84

10

Chungnang-gu

1,849.87

100

528.82

28.59

124.47

6.73

1,196.58

64.68

11

Sodaemun-gu

1,925.32

100

100.94

5.24

147.35

7.65

1,677.03

87.11

12

Tongdaemun-gu

1,502.33

100

1,049.27

69.84

174.38

11.61

278.68

18.55

13

Kangso-gu

4,333.93

100

3,126.81

72.14

300.15

6.93

906.98

20.93

14

Chung-gu

875.19

100

-


1.18

0.13

874.01

99.87

15

Yongdungp'o-gu

2,437.54

100

2,052.52

84.21

173.86

7.13

211.15

8.66

16

Yongsan-gu

2,160.43

100

1,180.36

54.63

211.19

9.78

768.89

35.59

17

Songp'a-gu

3,412.39

100

2,020.54

59.21

205.97

6.04

1,185.87

34.75

18

Kangnam-gu

3,962.04

100

935.72

23.62

470.15

11.87

2,556.17

64.51

19

Socho-gu

4,884.51

100

676.41

13.85

173.10

3.54

4,035.00

82.61

20

Dongjak-gu

1,605.11

100

217.08

13.52

84.34

5.25

1,303.70

81.23

21

Kuro-gu

3,478.80

100

1,636.48

47.04

321.80

9.25

1,520.52

43.71

22

Kwanak-gu

3,024.97

100

10.31

0.34

49.16

1.63

2,965.51

98.03

Total


61,705.84

100

20,150.33

32.66

4,439.22

7.19

37,109.28

60.15

Source: Calculated by the author.


Fig. 4.5. Han River valley in Seoul (Source Seoul Metropolitan Government and various others)

Statistical risk assessment

Clearly there is a significant potential for serious flooding in Seoul. Floods are likely to become worse as the amount of green space declines and undeveloped land is replaced by impermeable paved surfaces that shed runoff quickly and speed up the arrival of flood waves in populated areas downstream.

To what extent does conversion of green space contribute to increasing future floods? The procedure employed to answer this question is shown in figure 4.6. Several simple regression analyses were performed for Seoul using historical data on green spaces and flood damage. It is important to note that there are insufficient data to produce a reliable statistical analysis of the relationship between green space and flood damage for Seoul at this time. What follows is illustrative of the procedure that might be used with more confidence if better information becomes available. Those who might wish to adopt this method elsewhere must be aware that it requires long-term data, which may be difficult to acquire in places where human and material resources are limited.

Table 4.7 Distance from Han River in Seoul wards

Code no.

Ward

Total area

Within 500 m

Within 1 km

Beyond 1 km

Han River Channel itself



Ha

%

Ha

%

Ha

%

Ha

%

Ha

%

1

Tobong-gu

4,580.76

100

-

-

4,580.76

100

-

2

Nowon-gu

3,558.97

100

-

-

3,558.97

100

-

3

Map'o-gu

2,450.94

100

485.97

19.83

464.36

18.95

1,093.71

44.62

406.90

16.60

4

Yangchon-gu

1,757.45

100

0.60

0.03

71.11

4.05

1,685.75

95.92

-

5

Kangdong-gu

2,611.61

100

397.44

15.22

323.77

12.40

1,147.63

43.94

742.77

28.44

6

Songdong-gu

3,365.57

100

593.17

17.63

554.08

16.46

1,876.26

55.75

342.06

10.16

7

Unpyong-gu

3,152.10

100

-

-

3,152.10

100

-

8

Songbuk-gu

2,458.33

100

-

-

2,458.33

100

-

9

Chongno-gu

2,317.64

100

-

-

2,317.64

100

-

10

Chungnang-gu

1,849.88

100

-

-

1,849.88

100

-

11

Sodaemun-gu

1,925.32

100

-

-

1,925.32

100

-

12

Tongdaemun-gu

1,502.33

100

-

-

1,502.33

100

-

13

Kangso-gu

4,333.94

100

463.39

10.69

429.84

9.93

3,135.39

72.34

305.31

7.04

14

Chung-gu

875.19

100

-

4.74

0.54

870.45

99.46

-

15

Yongdungp'o-gu

2,437.53

100

307.19

12.60

255.88

10.50

868.09

35.61

1,006.37

41.29

16

Yongsan-gu

2,160.43

100

392.96

18.19

341.84

15.82

1,068.26

49.45

357.38

16.54

17

Songp'a-gu

3,412.39

100

298.33

8.74

305.89

8.96

2,532.22

74.25

275.94

8.09

18

Kangnam-gu

3,962.04

100

277.63

7.01

268.99

6.79

3,172.17

80.06

243.24

6.14

19

Socho-gu

4,884.51

100

203.91

4.17

192.84

3.95

4,343.50

88.93

144.26

2.95

20

Dongjak-gu

1,605.12

100

263.84

16.44

286.84

17.87

975.35

60.76

79.09

4.93

21

Kuro-gu

3,478.80

100

-

-

3,478.80

100

-

22

Kwanak-gu

3,024.97

100

-

-

3,024.97

100

-

Total


61,705.84

100

3,684.43

5.97

3,500.19

5.24

50,617.90

82.46

3,903.32

6.33

Source: Calculated by the author.

Table 4.8 Distribution of flood hazard zones by ward

Code No.

Ward

Areas within 500 m of Han River

Under 10 m above sea level

Flooding experienced (inundated area)

1

Tobong-gu


0


2

Nowon-gu


0


3

Map'o-gu

0

0

0

4

Yangchon-gu

0

0


5

Kangdong-gu

0

0

0

6

Songdong-gu

0

0

0

7

Unpyong-gu


0

0

8

Songbuk-gu


0


9

Chongno-gu


0


10

Chungnang-gu


0

0

11

Sodaemun-gu


0

0

12

Tongdaemun-gu


0

0

13

Kangso-gu

0

0

0

14

Chung-gu




15

Yongdungp'o-gu

0

0

0

16

Yongsan-gu

0

0

0

17

Songp'a-gu

0

0

0

18

Kangnam-gu

0

0

0

19

Socho-gu

0

0

0

20

Dongjak-gu

0

0

0

21

Kuro-gu


0

0

22

Kwanak-gu


0


Simple regression analysis

A series of simple regression analyses was carried out for the city of Seoul involving area of green space (open vegetated land) as the independent variable and a series of measures of flood loss as the dependent variables. The results are shown in table 4.10. These calculations reveal that several measures of loss are strongly explained by the amount of green space. Indeed, the presence of green space explains 31 per cent of the total variation in deaths and a comparable amount of the building damage. This finding is consistent with the hypothesis that green space helps reduce the risk of floods.

Regression equations:

Log (Death and...) = 4.28198 - 0.000125644 x Green Space

(R2 =.31068. SIGNIF F =.1936)

Log (Building Damage) = 5.28678 - 0.000161053 x Green Space

(R2 =.27955. SIGNIF F =.0772)

Table 4.9 Flood damage in exposed areas, 1984,1987, and 1990

Damaged area

1984

1987

1990


Inundated areas (ha)

Inundated dwellings (dwelling units)

Cause of damage

Inundated areas (ha)

Inundated dwellings (dwelling units)

Cause of damage

Inundated areas (ha)

Inundated dwellings (dwelling units)

Cause of damage

Goduck







132.0

557

No levee, etc.

Chunho







28.0

3,190

Excess water in pumping station

Sungnae-Pungnap

449.0

15,053

No levee




181.0

15,080

"

Chamsil

17.3

204

Excess water in pumping station




44.6

4,185

No levee, etc.

Banpo

10.2

300

"

76.0

600

Excess water in pumping station

2.5

239

Excess water in pumping station

Daebang







17.0

1,322

Rise in the water level of the Han River

Yung-dungp'o

25.8

1.112

"

230.0

6,781

"

62.6

2,618

Excess water in pumping station

Guro

39.3

835

Rise in the level of outside water

180.5

13,135

"

124.0

6,596

Excess water in pumping station, etc.

Gayang







2.0

174

Rise in the water level of the Han River

Magock Gonghang







5.0

157

"








1.0

61

Inadequate pumping of inside water

Nanji

15.8

933

Rise in the water level of the Han River




50.0

950

Rise in the water level of the Han River

Eunpyung







8.4

510

Rise in the level of out side water

Mangwon

229.0

11,942

Rise in the level of outside water

53.0

4,170

Long-term rainfall and excess water in pumping station

6.0

610

Excess water in pumping station

Bongwon

18.0

1,065

Excess water in pumping station




51.0

4,862

"

Yongsan

35.4

2,194

"

5.9

232

Excess water in pumping station

13.0

1,005

"

Oksu

58.7

1,269

Rise in the water level of the Han River

1.0

168

Excess water in pumping station

2.0

239

"

Sungdong

288.0

3,290

Excess water in pumping station




160.2

10,232

Excess water in pumping station

Myunmok

96.4

5,516


76.1

5,025

Excess water in pumping station

50.9

3,191

"

Jayang

25.4

523

Rise in the level of outside water




4.0


"

Source: Seoul Metropolitan Government.


Fig. 4.6. Procedures employed to determine the relation between flood damage and land use

Table 4.10 Results of simple regression analysis of green space and flood losses, 1980-1991

Dependent variable

Constant

Independent variable (green space)

R2

SIG F

Total Damage

16145.98543

-0.55955

.084

.3608


(0.3022)

(0.3608)



Log (Total Damage)

5.32885

-0.000130613

.15159

.2109


(0.0566)

(0.000097714)



Life Damage

245.0611

-7.34254

.04276

.5191


(0.4005)

(0.3608)



Log (Life Damage)

3.85621

-0.000100735

.165

.2439


(0.0934)

(0.2439)



Death & Life Loss

129.19862

-0.00401596

.04608

.5029


(0.3975)

(0.5029)



Log (Death & Life Loss)

4.28108

-0.000125644

.31068

.1936


(0.1001)

(0.1936)



Public Facilities Damage

174.91123

-0.000107922

.0000

.9986


(0.9090)

(0.9986)



Log (Public Facilities Damage)

5.28678

-0.000161053

.27955

.0772


(0.0291)

(0.0772)



Other Building Damage

5860.98634

-0,20861

.13429

.2413


(0.1967)

(0.2413)



Log (Other Building Damage)

5.03357

-0.000127812

.15094

.2672


(0.1016)

(0.2672)



Source: Calculated by the author.

The amount of green space is known for every year during the period 1980 - 1991. A regression equation was developed to allow annual estimates of the amount of green space remaining to be made up to the year 2010. It is of the form:

Green Space = 48634.342 - 309.88532 x year

(R2 =.9417. SIGNIF F =.0000)

The results of projecting this equation into the future are shown in table 4.11. This provides estimates of the increased flood losses that are likely to occur as green space disappears. A visual display of the relationship between future land-use changes and flood risks can be obtained by superimposing table 4.12 on the land-use plan contained in the General Development Plan of Seoul Towards the Year 2000. At present these maps and tables on flooding should be regarded as inexact guides to the future. They can be refined as more and better data on damage and land use become available.

Responses to flooding

City leaders in Seoul face a dilemma over what to do about flooding. Much of the potentially developable land is exposed to significant risks of flooding, but in a large, densely populated, fast-growing city it is difficult to leave that land in open space uses. Already the costs of rehabilitating flood-damaged property and land are substantial (table 4.12); over a recent eight-year period they exceeded US$ 50 million. There is no adequate insurance programme for floods, so most (70 per cent) of the costs are borne by individual victims.

At present, the city of Seoul relies on a combination of forecasting and protective engineering works to help reduce flood losses. Flood-risk zoning is not practised and public officials appear to believe that there are no standard planning methods for incorporating this kind of zoning into urban planning strategies. However, this study shows that much can be done toward that end even with the limited information that is now available.

Flood forecasting

The Action Plan for Preventing Flood Damage (1994) recognizes that meteorological information about water levels and discharge volumes should be provided to the public through the mass media (Seoul Municipal Government, 1994, p. 9). However, because it does not take long for excess water that accumulates in upland catchments to create a flood wave in the populated lowlands of the Han valley, it has proven difficult to institute a system for disseminating effective flood warnings.

Table 4.11 The estimated impact of green space on flood risks, 1980-2010

Year

Green space (ha)

No. injured

No. of deaths

No. of claims for damage

No. of claims for building damage

No. of claims for public facility damage


Actual

Estimated

Actual

Estimated

Actual

Estimated

Actual

Estimated

Actual

Estimated

Actual

Estimated

1980

31,115

23,843.52

2

28.47

0

19.59

24

163.90

2

27.97

13

96.82

1981

29,547

23,533.63

7

30.59

7

21.10

188

179.91

4

31.38

0

106.07

1982

26,921

23,223.75

1

32.87

1

23.08

15

197.48

3

35.20

9

116.20

1983

26,477

22,913.86

11

35.32

5

25.24

188

216.77

7

39.49

163

127.32

1984

26,177

22,603.98

95

37.95

43

27.61

20,274

237.94

3,084

44.29

3,612

139.48

1985

25,585

22,294.09

14

40.78

3

30.20

173

261.19

20

49.69

92

152.79

1986

24,404

21,984.20

3

43.82

0

33.03

287

286.70

7

55.74

252

167.38

1987

23,725

21,674.32

106

47.08

39

36.13

15,595

314.70

376

62.53

4,734

183.36

1988

22,888

21,364.43

2

50.59

0

39.52

16

345.44

15

70.14

0

200.86

1989

22,504

21,054.55

0

54.36

0

43.22

119

379.19

94

78.68

6

220.04

1990

21,821

20,744.66

76

58.41

44

47.28

22,528

416.22

580

88.27

8,067

241.10

1991

21,692

20,434.78

0

62.76

0

51.71

993

456.88

32

99.01

158

264.09

1992


20,124.89


67.44


56.56


501.51


111.07


289.31

1993


19,815.01


72.47


61.86


550.49


124.60


316.94

1994


19,505.12


77.87


67.67


604.27


139.77


347.20

1995


19,195.24


83.67


74.01


663.29


156.79


380.35

1996


18,885.35


89.91


80.96


728.08


175.89


416.67

1997


18,575.47


96.61


88.55


799.19


197.31


456.46

1998


18,265.58


103.81


96.85


877.26


221.34


500.05

1999


17,955.70


111.54


105.94


962.95


248.29


547.79

2000


17,645.81


119.86


115.88


1,057.01


278.53


600.10

2001


17,335.92


128.79


126.74


1,160.26


312.45


657.42

2002


17,026.04


138.39


138.63


1,273.58


350.50


720.17

2003


16,716.15


148.70


151.63


1,397.99


393.18


788.94

2004


16,406.27


159.78


165.86


1,534.54


441.06


864.28

2005


16,096.38


171.69


181.41


1,684.43


494.78


946.80

2006


15,786.57


184.48


198.43


1,848.96


555.03


1,037.21

2007


15,476.61


198.23


217.04


2,029.57


622.62


1,136.25

2008


15,166.73


213.00


237.39


2,227.81


698.45


1,244.74

2009


14,856.84


228.88


259.66


2,445.42


783.50


1,363.60

2010


14,546.96


245.94


284.02


2,684.28


878.92


1,493.81

Source: Calculated by the author.

Table 4.12 Costs of rehabilitating flood damage (million won)


Paid by victims and loansa

Payments by government

Totals

1984

15,445

273

15,718

1985

0

5

5

1986

0

5

5

1987

6,663

370

7,033

1988b

-

-

-

1989

1

19

20

1990

7,836

11,694

19,530

1991

67

30

97

Totals

30,012 (71%)

12,396 (29%)

42,408 (100%)

Source: Seoul Metropolitan Government.
a. Losses of less than 100,000 won register as 0.
b. Data not available.

Protective engineering works

Pumping stations and river improvements constitute the main countermeasures against floods that are practised in Seoul. According to the Seoul Municipal Government's Action Plan for Preventing Flood Damage (1994, p. 3), the main efforts are directed toward strengthening and maintaining flood disaster prevention facilities such as pumping stations, levees, and reclamation works. Although there are many reservoirs in the surrounding hills, nearly all are designed for water supply purposes - not to assist flood control. Many people in Seoul believe that additional flood-control reservoirs are necessary if flooding is to be curtailed.

Land-use controls

Little attention has been paid to risk zoning as a means of reducing flood damage in Seoul. For example, risk zoning and other hazard land-use controls are not included in the Second Comprehensive National Physical Development Plan (1982 - 1991) (Government of the Republic of Korea, 1982). This document is intended to ensure orderly improvement and balanced growth of the capital region by affecting the distribution of population and industry. Under the plan's provisions, Seoul is divided into five areas characterized by different physical conditions and different degrees of prospective development: an improvement promotion area; a restricted development area; a development promotion area; a re source conservation area; and an area reserved for development (Korean Planners' Association, 1980, p. 34).

Seoul also possesses a General Development Plan that was prepared by the Ministry of Construction in 1990. It is intended to guide the city's emergence as a fully fledged world city. Under the provisions of this plan, the Seoul of the future will be: (1) an international city with a mature spatial structure that is built around information and intelligence-oriented industries; (2) a city that meets citizens' needs for improved living; (3) a city that offers a diversity of opportunities for citizen participation; (4) a city that discharges metropolitan functions; and (5) a city of upgraded culture, recreation, and social welfare. Although the criteria for commercial, industrial, residential, and open space land uses are spelled out in some detail, natural hazards - including flooding - are not included among them. Likewise, flood-risk zoning or related land-management measures are not mentioned in the local-level Action Plan for Preventing Flood Damage prepared by the Seoul Municipal Government (Seoul Municipal Government, 1994, pp. 1 - 2).

Unless they are substantially amended, existing development plans will probably place substantially more people and buildings at risk of floods. For example, according to the General Development Plan of Seoul, two of the most frequently inundated wards - Map'o-gu and Kangso-gu - are targeted to receive significantly increased populations. In this document, areas near the Han River are generally designated for low-density residential development. It is clear that the criteria that are used to identify potential development districts in Seoul do not include flood risks. As a result, undeveloped areas of Nowon-gu, Map'o-gu, Kangnam-gu, Kangso-gu, and Songp'a-gu that are at risk of floods are designated as suitable for future development. Nor are other frequently experienced natural hazards, such as wind and landslides, taken into account. Clearly, controls on new buildings and gradual relocation of residents currently at risk are worthwhile measures that should be adopted by city leaders.

Citizen participation might well be employed to good effect in the design of flood-sensitive city development plans. The 1981 Urban Planning Act of Korea requested municipal governments to provide citizens with opportunities for participation by means of compulsory public hearings and public displays of proposals. However, this mechanism still does not operate effectively for a number of reasons. These include: lack of communication between officials and the public; citizen indifference; and opposition by planning professionals. Research on flood-risk perception by local populations could provide important inputs to the participation process and should be encouraged.

Conclusion

The recent rapid growth of Seoul has been accompanied by the development of a serious flood problem in areas adjacent to the River Han. If present trends continue, large numbers of people and buildings will be at risk in the twenty-first century. Thus far, the city has relied almost totally on structural engineering works to provide protection against floods. However, the limits of these measures are already evident, as indicated by increased pumping failures and subsequent floods. Non-structural flood-reduction measures have been neglected in Seoul.

This study is the first to identify relationships between flood damage and land use in Seoul. Its shortcomings are many, but - even in the present preliminary form - it has produced useful information that can be used to guide future land-use plans and development programmes.

REFERENCES

Clifford, Mark. 1989. "Through the roof: South Korea's soaring real estate prices spark protests.'' Far Eastern Economic Review, 8 January, pp. 102 - 103.

Government of the Republic of Korea. 1982. Second Comprehensive National Physical Development Plan (1982 - 1991). Seoul.

Kim, K. G. 1990. Land use changes in the urban fringes: The case of the Seoul Capital Green Belt, Republic of Korea. UNESCO Research Report, Seoul.

Koo, Chamun. 1989. "New housing construction and the poor: A study of chains of moves in Seoul (Korea).'' Ph.D. dissertation, University of Southern California.

Korean Planners' Association. 1980. The year 2000: Urban growth and perspectives for Seoul. Seoul.

Lee, Kyu B. 1988. "Urban housing, land development, and urban public enterprise.'' Municipal Affairs 23(10): 31 - 40.

Moon, H., Y. S. Lee, and T. H. Yoon. 1991. "Seasonal variation of heavy metal contamination of topsoils in the Taejun Industrial complex (II).'' Environmental Technology 12(5): 413 - 419.

Parsley, E. 1993. "Walk, don't run: US evacuation plan could be stalled by traffic.'' Far Eastern Economic Review 1 April, p. 24.

Republic of Korea and Asian Development Bank. 1982. Han River Basin Environmental Study, Final Report, vol. 1. Seoul.

Seoul Metropolitan Government. 1989 Seoul Statistical Yearbook.

- 1992. Seoul Metropolitan Administration. Seoul.

Seoul Municipal Government. 1994. Action Plan for Preventing Flood Damage. Seoul.

Shin, E. B., S. K. Lee, and D. W. Song. 1989. "Acidity of rainwater in the Seoul area.'' In L. Brasser and W. C. Mulder (eds.), Man and his ecosystem. Proceedings of the 8th World Clean Air Congress, The Hague, 11 - 15 September 1989, vol. 2. New York: Elsevier Science Publishers, pp. 263 - 267.

Shin, Hang-Sik, Ja Kong Koo, and Jong-Oh Kim. 1989. "Design of economic solid waste management system in Seoul, Korea.'' Resource Management and Technology 17(1): 9 - 14.

Sohn, D., M. Heo, and C. Kang. 1989. "Particle size distribution of heavy metals in the urban air of Seoul, Korea.'' In L. Brasser and W. C. Mulder (eds.), Man and his ecosystem. Proceedings of the 8th World Clean Air Congress, The Hague, 11 - 15 September 1989, vol. 3. New York: Elsevier Science Publishers, pp. 633 - 638.

UNEP/WHO (United Nations Environment Programme and World Health Organization). 1992. Urban air pollution in mega-cities of the world. Oxford: Basil Blackwell.

Williams, Jack F. 1993. "Cities of East Asia.'' In Stanley D. Brunn and Jack F. Williams, Cities of the world: World regional development, 2nd edn. New York: HarperCollins, pp. 431 - 477.

Won, Jaimu. 1990. "Multi-criteria evaluation approaches to urban transportation projects.'' Urban Studies 27 (February): 119 - 138.

Working Group for the Middle-Range Development Plan of Seoul. 1979. Comprehensive plan for Seoul: Toward the year 2000. Seoul.