The distinct utmost source of prosperous creation in history has been conversion of rural land in to urban land represents urbanization. This development occurred at a slower rate in earlier periods, and the shape of the city that resulted was dense. Nowadays, urbanization is more rapid [1]. Currently, urbanization is increasing in both developed and developing countries.

However, rapid urbanization, particularly the growth of large cities and the associated problem of unemployment, poverty and environment degradation pose difficult challenges in many developing countries. Furthermore, urbanization refers to process by which an increasing proportion of population comes to live in cities by growth and migration of population transformed from predominantly rural to urban area and closely associated with the level of economic activities, land-use/land-cover, population distribution and urban facilities [2]. In addition to this, urbanization is an endemic phenomenon that is causing significant town planning and service delivery challenges globally in most developing and emerging economies. According to Abebe [3], urbanization is the major driving force for population growth, modernization, economic growth and other development, there is an increasing concern about the effects of expanding cities and environment.

Urbanization is a process usually expanding and growing to its surrounding areas at the expense of nearby agricultural farmlands, the process of urban expansion involves both the internal reorganization and outward expansion of the physical structure of urban areas. Such process of urban expansion is a worldwide phenomenon, which could see in the history of all urban centres. Similarly, Ethiopia has a long history of urbanization that developed next to the ancient Egyptian civilization in East Africa: like; Axum, Gonder, Lalibela, Harar. Then finally, in the 1880s Addis Ababa has become the capital city of Ethiopia [4].

Currently, Ethiopia, has nine nationally recognized regional states; with each of them having its own capital city. Tigray region is one of these regional states, which is located in the northern part of Ethiopia, and its capital is Mekelle. Mekelle, the capital city (socio-economic and political centre) of Tigray regional state is also dynamic experiencing of rapid urban expansion and population growth. Urban growth is a spatial and demographic process and refers to the increased importance of towns and cities as concentrations of population within a particular economy or society. According to [5], the history of urban growth indicates that urban areas are the most dynamic places on the Earth’s surface. Despite their regional economic importance, urban growth has a considerable impact on the surrounding ecosystem. Most often, the trend of urban growth is towards the urban-rural-fringe where there are less built-up areas, irrigation and other water management systems. The uncontrolled urban growth and migration to the urban areas results in urban sprawl. Whether, the urban growth is good or bad depend on its pattern, process and consequences. Mekelle is one of the fast growing urban centres in the Tigray regional state, Ethiopia. The city has a significant spatial expansion, increasing in population growth, physical sizes and developmental activities such as building, road construction, and many other anthropogenic activities. The basic problem is that the rapid urbanizations have been one of the crucial issues of global change that affect the physical dimension of cities. Moreover, population migration from rural to urban areas is one of the most impacted for urban problems resulted from regional imbalances and causes uncontrolled urban growth. Therefore, understanding the dynamics of urban systems and evaluating the impacts of urban growth on the environment are needed [6]. According to the Municipal of Mekelle city, the future land-use was propose based on detailed investigation of relevant spatial factor, current growth trends of city and functional compatibles between various activities. However, no research has been conducted at Mekelle city with regard to Geo spatial Technology Analysis for urban growth modelling. Therefore, we fill this gap. We have main objective of this research was to detect, analyse and map urban sprawl expansion of Mekelle city by quantify the patterns of urban growth in different period using high resolution Multi-temporal aerial and satellite imageries. To find out the urban trends and magnitude of urban land use changes of years 2006 and 2018.

Description of the Study Area

Mekelle is the capital city and commercial centre of the Tigray National Regional State in the northern Ethiopia. The city Mekelle was established as a national capital during Emperor Atse Yohannes the 4^th era in 1864 E.C and got its urban structure during his region [7]. The altitude of Mekelle is between 1965 m and 2220 m above sea level. The city is located between latitude 13°24′ 30"-13°36′ 52'' N and Longitude 39°25′30"-39°38′ 33" E is situated in the central highlands of Ethiopia (Figure:1). Mekelle is a city in Ethiopia located at 784km drive north of national capital city, Addis Ababa. The area of the study covered about 32601.72 ha.

Figure 1: Study Area.

Data Collection

Primary Data

Ground truth points, as an input for image classification and accuracy assessment, were we collected using Global Positioning System (GPS) from the ground. In addition, open and close ended questionnaire and field observations.

Landsat Imageries Data

For urban growth Land use modelling studies, appropriate selection of imagery acquisition dates is an integral component of the urban growth analysis. Consequently, cloud free Landsat data (2000-2018) with 30mx30m resolution downloaded from United States Geological Survey (http://earthexplorer.usgs.gov/) free after registration. The Landsat imagery of the study area includes Landsat Enhanced Thematic Mapper plus (ETM+) for 2006, 2012 and Landsat 8 (OLI) for 2018. In addition, Landsat 8 Operational Land Imager (OLI) consists of eleven spectral bands with a spatial resolution of 30 meters for Bands 1 to 7 and 9 for the year 2018 were included in the analysis.

Data Analysis

Image Classification and Urban Land-Use Mapping

Classification is a technique of developing interpreted maps from remotely sensed imagers, which requires a classification algorithms and scheme. The necessities for understanding urban sprawl are doing well urban land-use change detection. The amount of urban land-use changes as loss and gain were investigated by mapping the area for all study years through the process of classification. The urban land-use classes applied in this study were adapted urban land-use classification scheme which is widely applied in East African Countries [8] Moreover, land-use/land-cover classification scheme and visual interpretation, the following land-use class (Table: 1) are described for the study area considering the urban land use diversity.

Table 1: Urban Land Use Name and Descriptions.

The Detecting Urban Land-Use/Land-Cover Change Detection Pattern

The classification of the Landsat satellite images for the three different times of 2006, 2012 and 2018 has resulted in a highly simplified and abstracted representation of the study area. The maps was presented a clear pattern of increased urban land use extending from the centre to all directions. However, growth is limited in the east direction because it was bounded by mountain choma. The study started out from classification, both land-use/land-cover classes (Bare lands, urban Area, Vegetation and Water bodies) have different spectral reflectance property and pattern. The bare lands area covers none of farming area, Urban Area also including all build up, road area, vegetation area is farming area, grass area, and green area includes and the water bodies cover the water areas.

Figure 3: Urban Land Use Maps for 2006 and 2012.

Figure 4: Urban Land Use for 2018.

Accordingly the urban land use classification show in (figure2 – figure3), above and Table1 blow the total area of the study was covers 32160.72ha the land use land cover have those bare lands 5977.00ha (18.52%), 5573ha (17.33%), and 5342ha(16.61%).

In receptively year (2006, 2012 and 2018), urban Land use classes was 5183.45ha (16.12%), 5952ha (18.50%) and 6789.72ha (21.11%) in year (2006, 2012 and 2018), Vegetation covers 20165.35ha (62.70%), 19873ha (61.79%) and 19389.72ha (60.29%) (2006, 2012 and 2018) and water body coverage 854.92ha (2.66%), 762.72ha (2.37%) and 639.5ha (1.99%) (2006, 2012 and 2018) respectively.

Table 2: Table: Urban Land-Use Area In Year 2006-2018.

The study was carry out to investigate the overall urban land-use changes occurred from 2006 to 2018 year. As the purpose of the study was to look at urban land-use map visualized and extracted. The Landsat image classified, a remarkable the urban land use trends was observe in Mekelle city.  Rapid trend was between 2006 to 2018 year. The results of images classifies from 2012-2018 urban Land Use classes was increasing from 2.39%, 2.60% (2012 and 2018), Bare lands was decreased from time to time -1.19%, -0.72% and -1.91% (2006, 2012 and 2018), Vegetation areas was also decreased in percentage from the total coverages -91%, - 1.50% and -.42% (2006, 2012 and 2018) and the water body was decline -0.29%, -0.38% and -0.67%. Finally, it was observed that the analysis of urban land-use development using remote sensing data is accurate, rapid, and cheap and release with repetitive coverage. Therefore, the strategy advocates the implementation of higher residential densities. The urban growth is a development strategy that serves the community, economy and the environment. The study may help for decision makers, Land Administrator and planners to consider the impacts of disorganized urban development by identifying the current trend of urban land-use growth potentiality.

I am thankful to municipality of Mekelle city, urban land development and urban planning, for their kind and collaborative effort in providing the needed document to my thesis. My heartfelt thanks go to my friends and colleagues; Last, I would like to thank all my family who helped me in various ways to make the writing my thesis possible.

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