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Sustainable Spatial Development for Kwangju, South Korea

 

Summary

Seungil Lee

Problem

Environmental problems have become a serious issue in the fast growing metropolitan areas of Far East Asia. The most critical problems are the rapid expansion of built-up areas and the explosive growth in mobility. The ecosystems of these cities have become seriously damaged from the vast losses of open space and biotopes. The incessant growth in traffic demands a heavy toll in terms of noise, air pollution, energy consumption, traffic accidents and time lost in road congestion. Against them many sectoral policies such as expansion of the transport network, improvement of public transport, construction of bicycle roads, improvement of traffic and parking systems, and manufacture of less energy consuming vehicles have been proposed and adopted. However these policies alone have not been enough to reduce the problems, because the expansion of built-up areas and the growth in mobility reinforce each other and aggravate the environmental problems. It can be rather expected that the environmental problems of these cities may become worse in the near future in spite of these policies. The environmental problems in the cities, therefore, should be considered in a comprehensive way with respect to spatial urban development resulting from the relationship of land-use and transport (Wegener, 1997).

In this study the feasibility of environmentally less harmful, more compact patterns of spatial development for a city in South Korea with a population of 1.5 million, Kwangju, will be explored. The central area of Kwangju contains the most important urban and regional functions. There are still many residences in the central city. However recently many residents have moved to outer suburbs because of high land prices and the scarcity of land in this area. The rate of car ownership has increased dramatically in the recent past. Traffic volumes have grown rapidly and are increasingly causing serious problems of traffic congestion, hazardous transport conditions and degradation of the environment. Against this detrimental urban development of Kwangju a sustainable spatial structure should be suggested; urban form and planning can play a role in achieving sustainability (Breheny, 1992).

In the study different combinations of land-use and transport policies to reduce environmental problems of Kwangju are investigated. For this task a transport simulation model is combined with a environmental assessment model. The model is used primarily to analyse the prevailing environmental problems of Kwangju resulting from its present spatial urban structure. It is used further to construct three scenarios with different combinations of land-use and transport policies in order to identify a sustainable spatial development for Kwangju: a trend scenario (toward further decentralisation) and two alternative scenarios (toward a more compact city and toward decentralised concentration).

Method

The model used for the study is designed to experiment with different combinations of land-use and transport policies (scenarios), to calculate environmental impacts of the scenarios resulting from built-up areas and vehicle mobility, and to compare the results in oder to identify a more sustainable scenario. In the study different combinations of land-use and transport policies to reduce environmental problems of Kwangju are investigated. For this purpose the model consists of four components: a scenario technique, a simulation model, an environmental assessment model and a geographic information system (GIS). Figure 1 shows the components of the model and the exchange of data between them.

 

 

Each component of the model has a different type of database with a different spatial resolution. As an example the environmental assessment model requires micro spatial database for small-area simulation of environmental indicators. On the other hand the zone-based transport simulation model used for the study calculates link loads based on zonal aggregate data. The model of the project takes a hybrid approach using a GIS to combine these different scales. The GIS (Raster GIS) disaggregates zonal data as well as link loads to about 200,000 raster cells (size of a raster cell is 150 x 150 m) of the study area - one of the four functions of GIS (see below). With this spatially disaggregate database the environmental submodel calculates the impacts on environmental indicators. For this purpose many intermediate programs should be developed. Each submodel subdivided into land-use and transport modul respectively has the following functions (see Figure 2):

Geographic Information System (GIS)

The GIS supports other submodels in four fields: storage of spatial data, generation of new data, disaggregation of data and visualisation. The spatial data of the study area such as zoning system, land uses and transport networks are stored in GIS. This data can be used immediately by other submodels or processed to generate new data using analytical tools of GIS such as overlay or buffering. The raster GIS generates a probabilistic disaggregate spatial data base (Wegener and Spiekermann, 1996b) for the environmental submodels. All other submodels display their input data and intermediate and final results using the visualising function of GIS.

Scenario Technique

This submodel prepares different combination scenarios consisting of land-use and transport policies with two seperate modules (land-use and transport modules). Three combination scenarios are created taking account of existing planning documents for the future of the study area, opinions of urban planning experts in Kwangju, and theoretical arguments on sustainable urban development: a trend scenario and two alternative scenarios. Each module of the submodel converts the assumptions of the scenarios into zonal and spatial database using a GIS (generation of new data).

Simulation Model

The transport simulation model used in this study is a zone-based model adopted from an existing urban simulation model, the IRPUD model (Wegener and Spiekermann, 1996a). This transport simulation model calculates link loads in the road network based on the spatial distribution of residences, work places, schools and shops in 142 traffic zones for each scenario. The transport model also predicts the actual driving speeds of automobiles on each link as a function of its capacity. There is no submodel simulating the distribution and intensity of land uses. The land-use module uses external data which an authorized planning institution has already prepared for the future of the study area. These data are then modified for two alternative scenarios. Simulation outputs are zonal aggregate data. Therefore these data need to be disaggregated to raster cells for the environmental assessment model using a GIS (see above).

Environmental Assessment Model

This submodel was developed for the study. It calculates environmental impacts of the scenarios based on disaggregated simulation results. In contrast to some recent research on urban form and sustainability with a few environmental indicators such as Rickaby's (1991) modelling of energy consumption and urban form, this multi-criteria environmental assessment model deals with a large number of important indicators for both local resource consumption and pollutants. Its land-use module determines loss of open space, the amount of sealed-off land as well as effects on biotopes and the urban climate such as heat islands and urban ventilation resulting from the spatial distribution and intensity of land uses with respect to the existing ecological potentials of the area such as open space and biotopes. On the other hand the transport module predicts noise, air pollution (NO2) and energy consumption resulting from link loads and actual driving speeds. When calculating noise and air pollution, the spatial distribution and intensity of land uses are considered to estimate the percentage of affected population by the immissions after propagation of the indicators (Altenhoff and Lee, 1993). For the calculation of noise and air pollution German guidelines were used (RLS-90 for noise and TA-Luft for air pollution). The calculated environmental indicators are displayed in tabular and graphic form using a GIS (visualisation).

 

Figure 2. Function of submodels

The model with the above functions is used to create different scenarios, to simulate their spatial distribution and intensity of land uses and link loads of road networks, and finally to evaluate them with respect to environmental indicators. The operation of the model is illustrated in Figure 3. In this study the model is used to analyse the prevailing environmental problems of the study area resulting from its present urban structure and to experiment with three scenarios (a trend scenario and two alternative scenarios) to compare their environmental impacts in oder to identify a more sustainable urban structure for the study area.

 

Figure 3. Operation of the model

Study Area: Kwangju

The study area is the urban region of Kwangju, South Korea, located in the south-western province of Chollanam-Do. The urban region consists of the city of Kwangju and its five neighbouring rural districts (see Figure 4). The suburban area which is economically and culturally influenced by the city of Kwangju lies within a distance of 30 km from the centre of the city. This is equivalent to the 30-minute commuting-time isochrone by car from the center of the city. The urban region is very compact in the core; the city of Kwangju had in 1990 a population of 1.1 million and the suburban area a population of 0.4 million. The whole study area is subdivided into 142 traffic zones for the transport simulation according to administrative districts.

Kwangju is the fifth biggest city in South Korea. In comparison with other big cities in the country Kwangju has a relatively concentrated spatial urban form. The central area of Kwangju contains the most important urban and regional functions such as work places, schools, hospitals, services as well as shopping centres. Many residences are located also in the central area. However, after the role of a growth pole in the province of Chollanam-Do has been assigned to Kwangju in the 'Second National Physical Plan for 1982-1991', Kwangju has grown fast not only in population but also in urban and regional functions. For this reason many residents have had to move to outer suburbs because of scarcity of land and high land prices in the central area. This suburbanisation process has been strongly reinforced by the introduction of a very compact residential form, 'appartment houses'. In addition, the service sector in the central area has been much more concentrated, while factories are more and more moving to sites in the outer urban districts of the city or in the suburban semirural districts. The rate of car ownership has increased dramatically in the recent past parallel to the increase in income of the population of Kwangju. This decentralising spatial development together with the increasing car ownership generates much more traffic in the central area and inner and outer suburbs of Kwangju. Besides, Kwangju has currently a 'star network', i.e. all roads and railways run to the centre of the city Kwangju. This type of network aggravates the traffic congestion and transport conditions of the central area of Kwangju because of through traffic between suburbs.

 

Figure 4. Study area: Kwangju

Results

The transport simulation model is applied to examine all the traffic problems generated by the present urban spatial form and traffic network of Kwangju. According to the simulation results the main roads which connect the city centre of Kwangju with the centres of suburbs are heavily loaded (see Figure 5).



Figure 5. Link loads 1990 and 2011

The environmental assessment model calculates the present environmental problems of Kwangju resulting from the spatial distribution and intensity of land uses and link loads. According to the results the number of population severely affected by a noise level of more than 59 dB(A) at daytime is about 27 percent (415,453 residents) of the population in the study area (see Figure 6). The number of population affected by NO2 concentrations of more than 0.16 mg/m3 for half a peak hour is about 17 percent (256,254 residents) of the population in the area (see Figure 7). It can be seen from the graphic output of the results that the residents mostly in the city centre are severely affected by the noise and NO2. The gasoline consumption by cars for a day in the area amounts to about 157,000 litres (corresponding to 4 tons of CO2). The amount of built-up area is about 8 percent (23,128 ha) of the area. The amount of strongly sealed-off land is about 1.4 percent (3,990 ha). The ecologically valuable biotopes which are not disturbed by human activities amount to about 54 percent (156,393 ha) of the area. About 21 percent (324,127 residents) of the population of the area live in scarcely ventilated urban areas (see Figure 8). About 41 percent (619,097 residents) of the population live in heat islands. 

 

 

Figure 6. Traffic noise 1990 and 2011

 

 

Figure 7. Air pollution by traffic 1990 and 201

 

Figure 8. Ventilation 1990 and 2011


According to 'The Master Plan of Kwangju for 2011' and also the opinions of the urban planning experts of Kwangju the urban region Kwangju will be changed in 2011, so that the population in this area will be increased up to 2.5 million and large amount of new transport infrastructures will be constructed. It can be expected that the spatial structure of the future Kwangju will be much more expanded toward its suburbs. With respect to this a Trend Scenario of the most likely land-use and transport policies of Kwangju for 2011 was developed. According to the the new transport network for this scenario the accessibility within the city of Kwangju and between the city centre and inner and outer suburb centres will significantly improve. However, the accessibility of the outer suburban areas will change only little. Corresponding to this, the residential areas will expand towards the boundary, where the accessibility is improved. In comparison with the present situation of Kwangju the residences will expand very much into the outer suburbs near the city, while new work places will remain within the city Kwangju except factories.

According to the results of the Trend Scenario the road links within the city of Kwangju and between the city of Kwangju and the suburbs are most heavily loaded as in 1990 (figure 5). However, in comparison with 1990 the traffic on the roads is more than doubled.

The Trend Scenario was also investigated by the environmental assessment model with respect to its environmental impacts on residents and local resources. As expected, the environmental problems of Kwangju in the future will be severely aggravated by the enormous expansion of built-up areas and the corresponding explosive growth in mobility.

According to the calculations the number of population severely affected by a noise level of more than 59 dB(A) at daytime will be about 27 percent (705,478 residents) of the population in the area in the year (see Figure 6). It remains at the same percentage as in 2011, however because of the growth in population this represents of a growth in absolute terms of about 70 percent. This applies also to other indicators impacting on human beings. The number of population affected by NO2 concentrations of more than 0.16 mg/m3 for half a peak hour will be about 19 percent (474,915 residents) of the population (see Figure 7). The gasoline consumption by cars for a day in the area will amount to about 601,000 litres (corresponding to 14 tons of CO2). The amount of built-up area will be about 17 percent (48,036 ha) of the area. The amount of strongly sealed-off land will be about 2.4 percent (6,855 ha) of the area. The ecologically valuable biotopes will amount to about 50 percent (145,554 ha) of the area. About 13 percent (335,699 residents) of the population of the area will live in scarcely ventilated urban areas (see Figure 8). About 27 percent (692,528 residents) of the population will live in heat islands.

The changes of the impacts on environmental indicators in the Trend Scenario are summarized in Figure 9 by comparing them with the environmental assessments of the present situation. All comparisons are made on the basis of absolute numbers here. All environmental indicators will have increased by the year 2011. However, the extent of change is very different for each indicator. In comparison with the increase in population (70 percent), the loss of open space amouts to about 110 percent and the gasoline consumption by cars to about 270 percent. This means that because of the combined effect of the increase in population and the expansion of residential areas, mobility grows much faster than the other indicators. In spite of the large increase in built-up area and mobility, the number of population affected by noise, air pollution, heat islands and bad ventilation grows less than expected. The reason is that the new residential areas are less compact and therefore suffer less from these impacts.


Figure 9. Comparison of environmental indicators, 1990 and 2011

As an alternative to this detrimental urban development of Kwangju, a sustainable spatial urban structure will be suggested. For this, two scenarios discussed in the current literature were selected for investigation in this study: a compact urban settlement structure (Scenario A) based on 'the reduction of energy consumption by a dense city form' (Newman and Kenworthy, 1989) and an urban structure of ïdecentralised concentrationï (Scenario B) representing an attempt to direct suburbanisation to medium-size suburban centres (Breheny, 1992). The results of these two scenarios will be presented in the near future.

Conclusions

The model described in this summary is used to analyse the prevailing environmental problems of Kwangju and to evaluate its environmental problems that will be caused by the increase in population and the changes in urban spatial structure in the future. It was possible to analyse the environmental problems resulting from different combinations of land use and transport policies. The environmental assessment model calculates the impacts on eight environmental indicators which could be affected by policies. Therefore it was possible to compare the results of the scenarios in oder to identify the one leading to a more sustainable spatial development for Kwangju. The summary presents only first results of the project. In the near future the alternative scenarios will be simulated by the model to suggest a sustainable spatial development for Kwangju. The model can be also applied for other cities.

Acknowledgment

The research was supported by the doctoral dissertation scholarship programme in transport research of the Alfried Krupp von Bohlen und Halbach-Stiftung.

References

Altenhoff, D. and Lee, S. (1993): A decision support system for the simulation of noise immission and noise abatement measures using ARC/INFO. Proceedings 3th CUPUM, Atlanta, Georgia, 23-25 July, 1993.

Breheny, M.J. (1992): The contradictions of the compact city: A review. In: M.J. Breheny (ed.): Sustainable Development and Urban Form. European Research in Regional Science 2, London: Pion, 1-23.

City of Kwangju (1995): The Master Plan of Kwangju for 2011. Kwangju: City of Kwangju.

Newman, P. and Kenworthy, J. (1989): Cities and Automobil Depence: A Sourcebook. Aldershot: Gower Technical.

Rickaby, P.A. (1991): Energy and urban development in an archetypal English town, Environment and Planning B: Planning and Design 18, 153-175.

Wegener, M. (1997): The End of the Industrial City. Berichte aus dem Institut für Raumplanung, Institute of Spatial Planning. Dortmund: University of Dortmund, forthcoming.

Wegener, M. and Spiekermann, K. (1996a): The potential of microsimulation for urban models. In: G.P. Clarke (ed.): Microsimulation for Urban and Regional Policy Analysis. European Research in Regional Science 6, London: Pion, 149-163.

Wegener, M. and Spiekermann, K. (1996b) Efficient, equitable and ecological urban structures. In: Hensher, D.A. and King, J. (ed.): World Transport Research, Selected Proceedings of the 7th World Conference on Transport Research. North-Holland: Elsevier, forthcoming.

© 1998 Seungil Lee, IRPUD