2009 Urban Remote Sensing Joint Event
Urban Sprawl Pattern Recognition Using Remote Sensing and GIS – Case Study Shiraz City, Iran Ab. Latif bin Ibrahim/ Mahdi Sabet Sarvestani Department of Remote Sensing Faculty of Geoinformation Science and Engineering, UTM Johor, Malaysia
[email protected]/
[email protected] Abstract— In this research with respect to increasing role of Geoinformation sciences in environmental studies and the importance of sustainable development in urban planning, Shiraz city as the most important city in the southern part of Iran was selected for urban growth studies and the estimation of natural resources destruction during past three decades. For this purpose different satellite images of the study area since 1976 to 2005, and population censuses of Shiraz city in this time period were used. Four main land use types such as water, constructed areas, vegetation and bareland areas were classified from satellite images of Shirajz city. Then land use coverage for different dates of the classified maps have been measured and with respect to population, the built-up and vegetation per capita also calculated. The results of this study showed that in despite of general belief, in recent years the vegetation coverage has not decreased extremely but it was not grown correspondingly to urban growth. It is recommended that the future planning will be more focused on protection of available vegetation and compensation of destroyed coverage. I.
INTRODUCTION
Unplanned physical growth of cities, increasing population growth, migration from rural areas to cities and economic development are the main causes of the initiation and continuation of great environmental and social problems. All these have led to the decrease of life quality in urban and nonurban societies. Destruction of vegetation, gardens and agricultural lands, air pollution, surface and underground water contamination, occupation of rivers and drainage protected area by construction, are the most common problems in urban areas. For environmental resources protection, it is impossible to stop the city growth, but it is necessary to protect and manage the urban resources in the best way. It seems that the only way in modification of destructive results of unplanned growth of the cities is robust planning based on true spatial data with guiding city growth to minimizing natural resources destruction point of view and trying to replace of lost resources. Ssatellite images can provide the most feasible and low cost solution for producing up-to-date and true spatial data and useable information for managers and planners is. Using
978-1-4244-3461-9/09/$25.00 ©2009 IEEE
the past and historical spatial data and preparation of needed thematic maps of different times can help the researchers to find the size, direction and rate of urban construction or size, direction and rate of natural resources destruction during recent years. To achieve to this goal, it is necessary to consider all natural and human resources like: vegetation cover, surface and underground water resources, soil cover, wild life protected area, historical and cultural landscapes. Meanwhile, with these kinds of studies it is possible to make a robust evaluation on efficiency and results of major and minor decisions of urban managers on the quality of urban development and natural resources destruction. II. PREVIOUS STUDIES Poorly planned urban development or sprawl, threatens our environment, our health, and our quality of life in numerous ways. Johnson [1] presents several alternative definitions for Sprawl development and come to a conclusion that there is no common consensus and it depends on the perspective of the researcher. The Sierra Club [2] describes suburban sprawl as irresponsible, often poorly-planned development that destroys green spaces, increases traffic and air pollution, crowds schools and drives up taxes. Theobald [3] stated that development along highways or surrounding the city and in rural countryside is often referred as sprawl. DiLorenzo [4] compare sprawl to a disease process, calling it a cancerous growth or a virus. Other descriptions include the scattering of urban settlement over the rural landscape by Harvey and Clark [5]. While, Pendall [6] stated that as low-density urbanization and Weitz and Moore [7] describe urban sprawl as a discontinuous development. Actually, sprawl is not simply refer to the increase of urban lands in an area. The most acceptable definition of sprawl can be a pattern of land-use/land cover conversion in which the growth rate of urbanized land (land rendered impervious by development) significantly exceeds the rate of population growth over a specified time period, with a dominance of low-density of impervious surfaces as defined by Barnes et al. [8].
2009 Urban Remote Sensing Joint Event There are so many works that have been carried out on the applications of satellite images and GIS in city growth and sprawl development studies. Sudhira and et al. [9], said that population and economic growth adjacent to natural and human resources are the main reasons of urban sprawl. Their studies from 1972 to 1999 by using aerial photographs, available maps and IRS images on Mangalore in India showed that the urban construction was increased by 145% meanwhile the population growth was increased by only 55%. This means that there was an unplanned construction and the developments have exceeded unusual resources consumption. Weber and Puissant [10] in their study using SPOT images since 1986 to 1996 found the amount and pattern of enlargement of Tunis City. They argue that one of the benefits of remote sensing is on the capability in the detection of city borders and illegal settlement around the cities that can be the main causes of damages of environmental resources. Liu and Zhou [11] designed a statistical model for helping to planning and decision making of a part of Beijing by using Landsat images of five different dates since 1986 to 1997 and concluded that it is a reliable solution for quantitative city studies. In the Middle East and Iran only a few such studies have been done. Among them are Yagoub [12] that worked on Al-Ain in UAE and Al-Awadhi [13] by using of available maps, aerial photographs and satellite images of different times since 1950 until 2003 studied Muscat in Oman. Results of the study showed that between 1970 to 2003 Muscat has grown around 650% with an annual average of 20% . Soffianian and et al. [14] carried out their study in Isfahan in Iran from 1956 to 2006 using aerial photographs and different type of satellite images. Results of their study reveal that constructed area has grown 9 times and population has grown 7 times during these years. Huge amount of agricultural lands and gardens were damaged. According to Barnes and etc. (2001) the sprawl growth is if the urban construction growth is greater than the population growth, so Sudhira et al. [9] and Soffianian et al. [14] studies can be considered as a complete examples of sprawl growth. III. OBJECTIVES OF THE STUDY
Figure 1. Shiraz location in Iran
mountains with an average elevation of 1500m above sea level. Shiraz has a moderate climate with four regular seasons. Shiraz contains a considerable number of gardens and parks. The first official census of Shiraz was carried out in 1956 and repeated every 10 years. According to UN statistics and forecast the population growth rate will be stable in future as shown in Fig. 2. All data used for this study are presented in Table 1. The spatial patterns of urban sprawl over different time periods, must be systematically mapped, monitored and accurately assessed from satellite images along with conventional ground data. Mapping urban sprawl provides a “picture” of where this type of growth is occurring, helps to identify the environmental and natural resources threatened by such sprawls, and to suggest the likely future directions and patterns of sprawling growth. The following procedure have been employed for land use classification over the 3 decades. Data acquisition, in this step satellite images and 1:25000 scale digital topographic maps of study area have been collected from internal archives. In next step or pre-processing, with selecting 8 to 21 points GCPs for different images by using topographic maps or GPS
The objectives of this study are to: • investigate the pattern of urban sprawl. • analyze the urban sprawl pattern using RS and GIS. • evaluate natural resources protection and development policies. IV. METHODOLOGY AND STUDY AREA For this purposes, more investigation on sprawl development in a developing country, the Shiraz city was selected as the most important historical, cultural, social and economical city in southern part of Iran (Fig. 1). Shiraz as the capital city of Fars province is located in (29°53’N, 52°58’E) and placed in a NW-SE elongated valley inside of Zagros
978-1-4244-3461-9/09/$25.00 ©2009 IEEE
Figure 2. UN census Shiraz population growth and prediction, [15]
2009 Urban Remote Sensing Joint Event TABLE 1-USED DATA IN THE STUDY
TABLE3-CONSTRUCTED AND VEGETATION COVERAGE, POPULATION, VEGETATION AND BUILT- UP AREA PER CAPITA IN STUDIED YEARS
Data
Year
Landsat MSS
June 1976
Landsat TM
Sep 1990
Landsat ETM+
May 2000
SPOT 4
Nov 2005
Iranian censuses
1976-1986-1991-1996-2006
UN Iran censuses
1995-2025
1:25000 topographic map
1996
Year
1976
1990
2000
2005
Built-up Area (km)
50.48
112.68
126.82
141.86
Vegetation Area (km)
25.78
39.91
40.58
37.73
Population
418000
946000
1115000
1203000
Vegetation per Capita (m/person)
60.54
42.19
36.39
31.36
Built-up per Capita (m/person)
120.76
119.11
113.74
117.92
acquisition and a generated DEM with 10m vertical spacing, all of images were geometrically corrected up to orthorectified level. Next in classification step, a uniform supervised classification have been applied on all images after choosing accurate training polygons by using maximum likelihood classification method. In this study all of image processings have been done by using ENVI 4.5 software. The accuracy assessment, overall accuracy and Kappa coefficient for different classifications presented in Table 2. To create more correspondence between produced maps, the classification has been done only with considering of four main classes: urban built-up area, vegetation land, bare land and water. The main reason for quite high accuracies might be the coarse classification in only four main classes. The produced maps are presented in Fig. 3. It must be noticed that because of ground resolution difference and different multispectral bands in different images, the generated maps did not have equal classification accuracy and also complete spatial matching; this problem can be a reason of accuracy reduction in the final conclusions. After producing complete land use maps, the total coverage of different classes have been measured, this information and population censuses of Shiraz for time of image acquisition is presented in Table 3. Also the vegetation and built-up area per capita calculated for studied years. Because of the coincidence of image acquisition and date of demography statistics, the UN data has been used in this research. Figure 3. classified maps for 1976-1990-2000 and 2005 TABLE 2-EVALUATION OF SATELLITE IMAGES CLASSIFICATION Year
Overall Accuracy
Kappa coefficient
1976
99.4
0.98
1990
98.3
0.88
2000
97.4
0.95
2005
99.1
0.95
978-1-4244-3461-9/09/$25.00 ©2009 IEEE
V. RESULTS With comparison of Shiraz total built-up area and population growth it is found that both have the same growth during the 3 decades, that is equal to 185% but the vegetation coverage has been increased only around 40%. Also with detail study of censuses it was found that a main phase in Shiraz built-up and population growth has been occurred between 1976 to 1990, the causes of this expansion were high rate of birth in early years of Islamic revolution, the war with
2009 Urban Remote Sensing Joint Event Iraq and migration of refugees, rural to city migration and merging of near villages to city during it’s development. With respect to generated maps it found that the new urban growth was mostly concentrated in north western direction. It is because of geographical position and morphological emplacement of Shiraz plain. The city is limited to the north by Babakoohi and Sa’di heights, into the south by Sabz-Pooshan heights and in eastward is terminate to coasts of the Maharloo lake that the underground water table is quite high, so the only and the best places for new constructions are north western parts of Shiraz plain. This study showed that during the past 3 decades the size of vegetation coverage growth was not proportional to built-up and population growth. As shown in Fig. 4, since the middle of 70’s to early years of 90’s, despite of greater rate of built-up growth, the gentle rate of vegetation growth was also available, but after that until 2000 the rate of construction became slower, this was by two causes, first start of a period of stagnancy in urban construction and economical problems and second change in construction pattern from horizontal to vertical construction, which means most of the new buildings were multi storey. From the start of 2000 as a result of socioeconomic reasons and high public interest and injection of great values of financial resources into real estate market, the rate of construction increased dramatically and unfortunately in some parts displaced vegetation cover. This research also showed that despite of correspondence growth of population and built-up area, but Fig4 showed that during 30 years the true story is a little different. Before 1990 these two rates was increasingly, but between 1990 to 2000 the rate of construction was less than population growth which means high density development not sprawl. But after 2000 this matter changed completely and rate of construction exceeded population growth which means sprawl as stated by Barnes and et al. [8]. In Fig. 5 it is clear that during this period the vegetation per capita was decreased continuously, after 2000 this problem was more serious. It must be said that in this study all of private and public green areas such as parks and gardens were considered. The results are shown in Table 3 and Fig. 5. VI. CONCLUSIONS All of the governors or even residents of Shiraz believe that, since long time ago, a large amount of gardens and vegetation cover destroyed and converted to built-up area, but this study showed that land use conversion mostly was from open and bare lands to built-up area, not from vegetation and gardens. Only in recent years this problem truly observed. As discussed, the total rate of city and population growth since 1976 to 2005 were equal, so according to Barnes and et al. [8] the growth of Shiraz was not possible to assigned as a exact example of sprawl growth, but if the studied time
Figure 4. Built-up (upper) and vegetation (lower) growth during 1976-2005
Figure 5. Change in built-up (upper) and vegetation (lower) per capita during 1976-2005
divided to smaller periods, the environmental disaster of Shiraz has come out that is destruction of huge amount of vegetation. Actually the main problem of Shiraz was lack of a comprehensive and applicable program for planning and management for protection and development of vegetation parallel to population growth. VII. RECOMMENDATIONS This study showed that before 2000’s, the rate of vegetation growth was smooth and only in recent years the vegetation cover is decreased dramatically. It is necessary to create an outlook in Shiraz future master plan for protection and development of all kind of resources. There is a lot of studies has been done on urban areas by using satellite images and RS methods worldwide, but there are only a few works for Iranian cities. As the role of environmental studies increased daily, it is suggest that to do similar studies for other cities in Iran as a arid country. Also the next step in Shiraz development studies will be the prediction of city growth. After finding the historical growth pattern of the city by using satellite images and old maps, it is possible to simulate the future spread by using urban growth models like cellular automata, spatio statistical or artificial neural networks. In this kind of researchs the future growth pattern is flexible by designing different scenarios for compeletly protection of natural or environmental resources and introducing some forbidden lands for urbanization. VII. REFERENCES
978-1-4244-3461-9/09/$25.00 ©2009 IEEE
2009 Urban Remote Sensing Joint Event [1]
[2]
[3]
[4] [5]
[6] [7]
[8]
Johnson, M. P. 2001. “Environmental impacts of urban sprawl: A survey of the literature and proposed research agenda”. Environment and Planning A 33:717–735. Sierra Club. 2001. “Stop sprawl: New research on population, suburban sprawl, and smart growth”. Available online. www.sierraclub.org/sprawl/. Theobald, D. M., 2001, “Quantifying urban and rural sprawl using the sprawl index”, Paper presented at the annual conference of the Association of American Geographers in New York, on March 2nd, 2001. DiLorenzo, W. 2000. “The myth of suburban sprawl”. USA Today (May) 128:54–6. Harvey, R. O. and W. A. V. Clark. 1971. “The nature and economics of urban sprawl. In Internal Structure of the City”, ed. L. S. Bourne. New York: Oxford University Press. 475–482. Pendall, R. 1999. “Do land-use controls cause sprawl?” Environment and Planning B 26:555–571. Weitz, J. and T. Moore. 1998. “Development inside urban growth boundaries: Oregon’s empirical evidence of contiguous urban form”. Journal of the American Planning Association 64 (4):424-440. Barnes K. B., Morgan III J. M., Roberge M C., and Lowe S, 2001. “Sprawl development: Its patterns, consequences, and measurement”. Towson University.
978-1-4244-3461-9/09/$25.00 ©2009 IEEE
[9]
[10]
[11]
[12]
[13]
[14]
[15]
(http://chesapeake.towson.edu/landscape/urbansprawl/download/Sprawl _white_paper.pdf) Sudhira H.S., Ramachandra T.V., Jagadish K.S. 2004. “Urban Sprawl: Metrics, Dynamics and Modelling Using GIS”, International Journal of Applied Earth Observation and Geoinformation, 5, 29–39. Weber C., Puissant A. 2003. ”Urbanization Pressure and Modeling of Urban Growth: Example of the Tunis Metropolitan Area”, Remote Sensing of Environment 86, 341–352 . Liu H., Zhou Q. 2005. “Developing Urban Growth Predictions from Spatial Indicators Based on Multi-Temporal Images”, Computers, Environment and Urban Systems 29, 580–594. Yagoub M. 2004. “Monitoring of Urban Growth of a Desert City Through Remote Sensing: Al-Ain, UAE, between 1976 and 2000”, Int. J. Remote Sensing, 20 March, 2004, Vol. 25, NO. 6, 1063–1076. Al-Awadhi T. 2007. “Monitoring and Modeling Urban Expansion Using GIS & RS: Case Study from Muscat, Oman”, 2007 Urban Remote Sensing Joint Event. Soffianian A., Yaghmaei L., Falahatkar S., 2008. “Recognition of Isfahan city growth during past 5 decades”, Geomatic 2008 proceedings, NCC, Tehran, Iran (in Persian) United Nation 2003. “World Urbanization Prospects: the 2003 revision” (http://esa.un.org/unup)
