Geospatial Analysis of Urbanization and its Impact on Land Use Changes in Sargodha , Pakistan

Abstract: The focus of this study is on the application of GIS and remote sensing on urbanization and its impact on land use changes in Sargodha from 1992-2015. Sargodha has witnessed rapid urbanization and due to urban expansion many changes have been detected in the land use of Sargodha. For this study, census data, multi-temporal city maps and multi spectral satellite images are used. Landsat TM 1992 and ETM+ 2000, 2005, 2010 and 2015 Landsat 8 are classified using supervised classified method (MLC) to produce land use maps. The classification accuracy has been assessed by calculating kappa index of agreement and ground control points were also collected to verify the results. The results indicate that, over the past 24 years there is a growing trend in urban land use while the agricultural land and all other categories are showing a declining trend since 1992. The total increase in urban land use is 25380.8 hectares and it has increased in 2000, 2005, 2010, and 2015 at the rate of 2.2%, 4.1%, 9.2% and 17.4% respectively. This rapid urbanization resulted into loss of agricultural land. While the overall change observed in agricultural land, water area and bare land is -11008.5, -38926.5 and 9492.7 hectares respectively.


INTRODUCTION
Urbanization is a global process and an important social and economic phenomenon.It is the most powerful anthropogenic force that brought changes in land use patterns all over the world.In developing countries, rapid urbanization is a crucial issue that is a major contributor to global change [1].Urbanization causes deep changes in the spatial structure of landscape and produces new landscape patterns [2].It is closely related to the introduction of modes of transportation like road links and rail routes [3].According to World Bank projections, the number of people residing in cities is increasing with the passage of time [4].When settlements grow human needs and activities also grow [5].Rural to urban migration has increased urban population of Pakistan from 17.8% in 1951 to 39.2% in 2015 [6].According to the report of United Nations Population Fund Pakistan ranks 163 on a list of over 200 countries.Urban population of Pakistan grew from 25% to 35% during 1975-1995.According to UN forecast, the share of urban population will increase from 35% in 1995 to 60% in 2025 [7].Rapid urbanization is responsible for numerous problems such as problems of drinking water, waste disposal, noise pollution, air pollution, traffic congestion and substandard living environment *Address correspondence to this author at the Department of Geography, Govt.Postgraduate College, Gojra, Pakistan; Tel: +923336564413; E-mail: Nasarbhalli@gmail.com [8].Uncontrolled urban sprawl is swallowing rural landscape which in turn is altering the land use patterns of urban periphery [9].Remote sensing is a chief source to provide data for urban land use mapping and monitoring [10].The integration of remote sensing with GIS is helpful in data processing and presentation of analysis.GIS also interprets spatial data with socio economic data and makes the analysis meaningful and effective.GIS maps provide visualization of spatial patterns and relationships [11].In present study census data and satellite images have been used to evaluate urbanization and its impacts on land use changes in study area from 1992-2015.For this purpose Landsat TM, ETM+ and OLI_TIRS imageries are used and the main objectives of this study are, to analyze the main factors governing urbanization and pattern of urban growth in Sargodha.The applications of GIS and RS techniques to monitor urbanization and associated land use changes in the study area have been utilized.The average annual rainfall of District Sargodha is 413.0 mm.

Data Collection and Sources
The census data of 1951 to 2015 was acquired by the District Census Reports of Sargodha.Economic Survey of Pakistan was also consulted for this study.The satellite images of 1992, 2000, 2005, 2010 and 2015 were collected from USGS website to evaluate Spatio-temporal characteristics of urbanization and associated land use changes in Tehsil Sargodha.The characteristics of these satellite images are presented in (Table 1).Extensive field work was conducted to collect Ground Control Points (GCPs) and preprocessed images and maps were verified.area and give the necessary information to comprehend the land use changes in the area.After image processing built-up areas were extracted.Then built-up areas were considered as one of the indicator to evaluate change [13].

Accuracy Assessment
After image classification accuracy assessment was done.The random points which were taken as ground referenced test points were utilized to assess the accuracy of each category in a classified map because it is not possible to visit each and every pixel of remote sensing derived classification map for accuracy assessment.Therefore, the total sample size and the number of samples required per class are calculated.
The geographic location (x, y) of these pixels were determined to visit and obtain ground reference test information.The relationship between pixels of classification map and ground reference test information is usually summed up in contingency table or confusion matrix [13].At the end final maps were prepared with the help of GIS.The results of five images produced by MLC classifier are presented in (Table 5).

Increases in Urban Population in Tehsil Sargodha
The results of satellite image analysis and discussion on findings showed that rapid urban population growth is a major factor of land use changes in Tehsil Sargodha.According to the 1998 census of Pakistan the population of Tehsil Sargodha was 1,081,459 and out of which 458,000 were living in urban area and 623,000 were living in rural area [14].The recent estimate shows that the urban population of Tehsil Sargodha was 1,422,000 and 584,000 persons were living in urban area, and 838,000 persons were living in rural area.

Change in Land Use
Table 4 depicts the relative changes in land use trend from 1992 to 2015 in Tehsil Sargodha.During 1992-2015 the overall change in water area is -38926.5 hectares and -16.4 percent.The urban/built-up area of Tehsil Sargodha has expanded.It was 2361.9 hectares in 1992 and was 27742.7 hectares in 2015.Over the past 24 years, the Tehsil Sargodha has experienced some low and high speed stages of urban growth.During this time period, the urban growth rate varies significantly.A growing trend is observed in urban land use.The overall urban/built-up land use change is 25380.8hectares and 17.4 percent (Figure 6).During the study period all other categories are showing declining trends.
The overall change in category of bare soil is 9492.7 hectares and 6.5 percent.The agricultural land showed constant decreasing trend during this time period.The overall change in agricultural land use is -11008.5 hectares and -7.5 percent.The agriculture land is being converted into urban land.The urban/built-up land is increasing in 2000, 2005, 2010, and 2015 at the rate of 2.2%, 4.1%, 9.2% and 17.4% respectively.These land use changes are showing a noticeable change in the study area in the form of residential colonies around the city.The detailed information, relevant statistics, classification results, their graphical representation and visual interpretation revealed the relative land use changes in each category of land use of Tehsil Sargodha.After that all maps were reclassified into two classes of urban/builtup and non-built-up land use. Figure 6 depicts the change in urban land use of study area during different time periods.

Kappa Index and Overall Accuracy
The classification accuracies are assessed by evaluating the overall classification accuracy and Kappa statistics.Kappa index is calculated for all classified maps to find out the accuracy result of each    Source: As in Table 3.

CONCLUSION
This study acknowledged that urbanization can change the land use patterns and alter the landscape.GIS and remote sensing techniques are found very effective to evaluate the urban growth patterns and the impacts of urbanization on land use changes.With increasing population and development pressure land use change will continue.The changes in land use of Tehsil Sargodha during the last 24 years indicate that there is 17.4% increase in urban area and 6.5% in bare land.Overall change in category of water is -16.4% and -7.5% in agricultural land.Urban land development was uneven in all parts of the study area.The major growth was observed along the major link roads such as Lahore road, Faisalabad road and Jhang road that connect the city with rest of the province.Several problems arise due to urban sprawl such as traffic conjunction, urban slums, environmental degradations, climate change, poor water and air quality and land use/and cover changes.Therefore, it is suggested that separate detailed studies should be taken up regarding these problems.
Layer stacking, radiometric and geometric correction methods are considered as the preprocessing operations for remotely sensed data.They are performed before information extraction from image.Landsat TM of 1992 and Landsat ETM+ images of 2000, 2005, 2010 and Landsat 8 for 2015 were in different format.The different bands of tiff image were converted into image format through layer stacking method in ERDAS IMAGINE to produce False Color Composite (FCC) Image.After that all images were geometrically projected in Arc GIS to Universal Transverse Mercator (UTM) system.The boundary of Tehsil was extracted by masking function in Arc GIS.In supervised classification method images of different years were classified independently.A Maximum Likelihood Classification (MLC) algorithm was applied.A spectral signature for each land use class is created through analysis of the pixels of image.After the creation of signature files for all land use classes the image was classified.Images were classified into 4 classes of land use such as urban/built-up area, agriculture land, bare soil, and water bodies.The classified images demonstrate the characteristics of

Figure 1 :
Figure 1: Map of the study area Tehsil Sargodha.

Figure 5 :
Figure 5: Built-up and Non Built-up Area in between 1992-2015.

area [12]. It has continental type of climate. The mean maximum and minimum temperatures of summers
remains 39 25 respectively and this means temperature drops to 21 to 6 in winter.

Table 1 : Description of Landsat Image Data
Source: USGS.

Table 3 : Land use of Tehsil Sargodha
Source: Calculated from satellite images.Riaz et al.

Table 5 : Built-up and Non Built-up Area in between 1992-2015
Source: As in Table3.