ISSN Vol.08,Issue.21, November-2016, Pages:

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1 ISSN Vol.08,Issue.1, November-016, Pages: D Terrain Analysis and Land Suitability Mapping for the Expansion of Adigrat Town, Ethiopia Dept of Geography and Environmental Studies, Adigrat University, Ethiopia, Abstract: Geographic Information System is an important tool for geospatial studies. In order to simulate urban development plans, it is necessary to develop land use mapping but land use maps do not always reveal the appearance of the physical environment, So Land use mapping with 3D terrain analysis will be very helpful especially in hilly regions to meet the need of planning for the sustainable development of the city. GIS-based land suitability analysis using the multi-criteria evaluation approach is the best method for solving complex land use planning related problems. The objective of this study is to analyze the three-dimensional terrain analysis and spatially evaluate land suitability for urban expansion in Adigrat town, Ethiopia. Softwares like Arc GIS and Google Earth were used. Data used were aster image for slope, contour and elevation; land use data; hydrologic data; and road data. Slope calculations shows 5 % of land is Level (0 to 40), 30% Very Gently sloppy (4 to 80), 0% Gently Sloppy (8 to 10), 11% Sloppy (1 to 180) and rest more than 180. Geographical Information System was used to create land suitability map. The Euclidian distance was calculated from roads and underground water sources. Aster data was used to classify elevation and slope. Land use map was prepared using Landsat 8 data. The influence of different factors was given as Land use 30%; Elevation 5%; Slope 5%; Underground Water Sources 10%, and Roads 10%. Scale values for criteria were given 1 to 9. Closed distances from underground water sources and Roads were given higher values. Elevation above 646 meter, Slope more than 8 degree and Buildup areas were restricted. In the 3D analysis it is found that contour lines are very close to each other in western, south western and southern side of the town. As a result sq. km of area was found in the northeastern, eastern and southeastern part of the town as most suitable area for urban expansion. Keywords: 3D, Contour, DEM, GIS, Land Suitability, Slope. I. INTRODUCTION In countries like Ethiopia where the number of urban centers are increasing rapidly, urbanization is one of the most significant phenomenon (Anwar and Bhalli, 01). The urban areas in Ethiopia have witnessed tremendous changes in terms of population growth and urban expansion. However, with lack of proper urban management practices, 016 IJATIR. All rights reserved. uncontrolled and rapid increase in population pose enormous challenges to governments in providing adequate shelter to people in urban areas. This has also posed great concern among urban planners. Uncontrolled urban population growth resulting in serious problems with regards to informal settlements, environmental pollutions, and destruction of ecological structure (Sao, 000). With respect to rapid global urbanization, monitoring and mapping of urban land is of great importance. Land use suitability analysis for urban development is a prerequisite to overcome the problem with limited land availability against drastic growth of urbanization through planning for achieving optimum utilization of the available land resources (Gizachew and Yihenew, 015). The Geographic Information System is an effective tool in selecting suitable lands for a built environment as it is very effective monitoring and decision-support for urban planning (Baban et al, 007; Babu and Sivasankar,015). Geographic Information System based land suitability analysis using the multi-criteria evaluation approach is therefore the most suitable method for solving complex problems related to land-use planning and development (Malczewski, 004). For finding suitable areas for urban expansion, the three dimensional terrain analyses should be studied. Now a day the need for 3D information is rapidly increasing. Currently, many human activities, like urban planning, cadastre, environmental monitoring, telecommunications, public rescue operations, transportation monitoring, landscape planning, real-estate market, hydrographical activities, utility management and military applications make steps toward three dimensions (Reindel and Koschmieder, 1999). The three-dimensional visualization within 3D GIS requires appropriate means to visualize 3D spatial analysis tools to effortlessly explore and navigate through large models in real time. Observations on the demand for 3D City models show user preferences for photo-true texturing (Abdul Razzak and Amjed Naser, 009). Three-dimensional visualization is an important part of 3D GIS; it is also the difference of feature between 3D GIS and D GIS. The digital research of three-dimensional geographic information system of city, and the applying of 3D visualization and information query and management technology in the construction of digital city will lead the design of urban landscape situation and planning be based on

2 3D physical model expression and in 3D space form (Breunig and Schmidt, 1999). It can makes the policy-makers, designers, and users have a vivid and intuitive understanding and more profound understanding and about the present situation of urban landscape planning and the design blueprint, thus it can broaden the urban planning, design, and the perspective of management, and make the design of city planning, infrastructure more scientific, it has important significance for urban sustainable development research (Pullar and Tidey, 001). Urban residential environment is relatively concentrated areas on the earth's surface; they are also the necessary production and living space for urban people. Urban space is based on the surface, and extends into the air and underground slightly, thus it is the three dimensional space. As a result, the urban space can be divided into three parts, the surface, the ground and underground, accordingly urban terrain can be divided into surface terrain, ground objects on the ground (Minan et al, 013). The 3D visualization GIS of the city can be summarized as six categories: landscape, vegetation, drainage, roads, residents and state. And the important position is the landscape and residents. Therefore, the three-dimensional space of the city planning information can be summarized as 3D terrain, 3D buildings and surface texture image data. In the 3D visualization of GIS, the landscape is represented in the form of the digital elevation model (DEM) performance, residents is represented by the 3D buildings (Kanhua, 014). The objective of this study is to analyze the three-dimensional terrain analysis and spatially evaluate land suitability for urban expansion in Adigrat town, Ethiopia II. SITE DESCRIPTION Adigrat town is located in the Tigray State of Ethiopia at latitude of N and longitude of 39 7 E with an average elevation of 457 meters above sea level, below a high ridge to the west. The study area for landuse mapping is the municipal bounadary of Adigrat town. III. MATERIALS AND METHODS A. Data Used Data like land use data; Digital Elevation Model (DEM) for elevation and slope; hydrologic data; and road data has been used. The key thematic layers created for the selection of suitable sites for urban expansion were: Land Use data; Elevation (at one km buffer); Slope generated from DEM (at one km buffer); Road Network data; and Underground Water Source Data. These thematic layers are then added with a weightage and a corresponding rating value in order to assess their importance to be considered for potential suitable sites for urban expansion. The main data source for the terrain analysis is ASTER GDEM (ASTER Global DEM) with 30 m resolution. The missing data and error of the DEM was filled through spatial analyst tools of ArcGIS. Among the terrain features this work is concentrated on some morphometric parameters and derivatives. The chosen morphometric parameters for characterization of the structural elements of the relief are contour and slope characteristic of the study area. The slope map of the study area was generated using the 3D Analyst Tool. And then the slope is reclassified manually to the standard (i.e. 7 classes which is according to the modified FAO, 1999 classification) in degrees. The area has been calculated as follows: Area = [count]*[cell Size(X, Y)] / Area= [Count]*[ ] / Area= [Count]* / This is because the size of one pixel in the raster source data is m by m and if we multiply, its result is m. Therefore, the number of pixel counted in each class category multiplied by m and then divide it by 1,000,000 to convert in to square Kilometer. The coverage of each slope class is calculated as follows: Coverage = Class area/ Total area * 100 B. Model Used The Weighted Overlay Suitability Model was used with GIS techniques for locations suitable for urban expansion Each individual raster cell was reclassified into units of suitability and multiplied by a weight to assign relative importance to each and finally add them together for the final weight to obtain a suitability value for every location on the map; this can be interpreted by the following equation (Breunig et al, 1999) S= Σ w i x i (1) Where wi is the weight of i th factor map; x i is the criteria score of class of factor I; and S is the suitability index for each pixel in the map All the thematic layers were integrated in ArcGIS platform in order to prepare a map Fig.1. Location Map of Study Area depicting suitable areas. The total weights of each pixel of Volume. 08, IssueNo.1, November-016, Pages:

3 3D Terrain Analysis and Land Suitability Mapping for the Expansion of Adigrat Town, Ethiopia the final integrated layer were derived from the following TABLE II. Land use Classes and Assigned Values equation; S= (SL f SL c + LE f LE c + LU f LU c + DR f DR c + DG f DG c () Where, SL is Land slope; LE is land elevation; LU is land uses; DR is the distance to Road; DG is the distance to ground water potential areas. The subscript letter f represents the weight of each factor, while c represents the weight of each class of the individual factor. Areas found within a buildup land are restricted for expansion, because further construction is not possible there. On the other hand, open areas are rated with a high value (9), because these areas are readily available for expansion of the town. B. Slope Slope of the town is ranging from 0 to 54 degrees; zero degree was given high class value (9) as the best land slope in that it is most suitable for urban settlement. Since steep slope areas are not advisable for urban expansion, slope values greater than 8 degree are restricted in the evaluation. The class of slope parameter is given in the following table. TABLE III. Slope Classes and Scale Values Fig.. The Land Evaluation Model from the Basic Layers Up To the Final Suitability Layer Suitable sites for expansion of Adigrat town was estimated using the above equation for each pixel in the final integration layer and was regrouped into different classes with equal class interval to divide the entire study area into different suitable zones. IV. RESULTS AND DISCUSSION A. Land Use Classes The land uses of the area were divided into five classes: buildup land, agriculture land, open land, mangrove and woodland. The area of each class is shown in the table below (Table 1). The scale value to each class was given as shown in Table. TABLE I. Land Use Classes Fig.3. Slope Map of Adigrat Town C. Contour The figure below depicts contour lines are very close to each other in western, south western and south eastern side of the town, because of high topographic hills which are very Volume. 08, IssueNo.1, November-016, Pages:

4 difficult for every infrastructure development including construction of roads, expansion of the town to western and south western direction. Also highest altitude (depicted in red color) from 600 m.a.s.l. particularly found in western and south western side of the town. F. Nearness to Groundwater Sources The proximity of wells to expansion areas is considered as an advantage because wells will be used as sources of water. Areas lying close to the wells are considered the best and are assigned a class value (9). TABLE VI Proximity from the Wells& Scale Values Fig.4. Contour Map of Adigrat Town D. Elevation The elevation of the study areas ranges from 38 to 819 m.a.s.l. Highly elevated areas (greater than 646 m.a.s.l.) were restricted because such areas are not considered for urban expansion for many reasons like water availability and other infrastructure development problems. On the other hand, low to moderate areas were given high values. G. Suitable Locations for Urban Expansion One integrated layer from excellent to not suitable land was generated based on the weights assigned to each criterion. Finally suitability was rated and suitable sites were extracted from integrated layer as depicted in the figure below. Figure 5 shows all the sites from not suitable to most suitable for expansion. Most suitable sites comprise an area of square kilometer. TABLE IV. Elevation Classes and Scale Values E. Distances to Roads The proximity of roads to expansion areas is considered as an advantage because such roads will access transportation. Areas closer to roads are considered the best and are assigned a class value (9). TABLE V. Distance to Road and Scale Values Fig.5. Land Suitability Map of Adigrat Town Fig.6. Most Suitable Sites for Expansion of Adigrat Town Volume. 08, IssueNo.1, November-016, Pages:

5 3D Terrain Analysis and Land Suitability Mapping for the Expansion of Adigrat Town, Ethiopia V. CONCLUSION Adigrat town is partially surrounded by hilly areas. Particularly the western, south western and southern side of the town is highly elevated having very steep topography with very close contour lines. Hence, expansion is impossible particularly to the west and south west side of the town due to topographic influence. In the eastern, southeaster and northeastern side of the town, there is about square kilo meter of area which is most suitable area for urban expansion. VI. REFERENCES [1]Abdul Razzak T.Ziboon and Amjed NaserMohsin (009) 3D Virtual Maps Production for mosul city by using GIS techniques. Eng. and Technology journal Vol. 7, No 9, 009. []Anwar M. and Bhalli M. (01) Urban Population Growth Monitoring and Land Use Classification by using GIS and Remote Sensing Techniques: A case Study of Faisalabad City. Asian Journal of Social Sciences and Humanities Vol. 1. No. 1, ISSN: [3]Gizachew Ayalew and Yihenew G/Selassie (015) Evaluation of land suitability for cash and perennial cops using geographical information system in east Amhara region, Ethiopia. International Journal of Remote Sensing and GIS, Volume 4, Issue 1, 015, 1-7. [4]J. Malczewski (004) GIS-based land-use suitability analysis: a critical overview, Progress in Plg., 6, [5]M Breunig, AB Cremers, HJ Gotze, S Schmidt (1999) First Steps Towards an Interoperable GIS- an Example from Southern Lower Saxony. Phys, Chem, Earth (A). 1999; 4(3): [6]Pullar DV, Tidey ME. (001) Coupling 3D visualization to qualitative assessment of built environment designs. Landscape and Urban Planning. 001; 55(1): 9-40,15. [7]Reindel, M., Isla, J., Koschmieder, K. (1999) Vorspanische Siedlungen und Bodenzeichnungen in Palpa, Südperu Asentamientos prehispánicos y geoglifos en Palpa, costa sur del Perú. Beiträge zur Allgemeinen und Vergleichenden Archäologie, 19, pp [8]S Suresh Babu and S Sivasankar (015) GIS and remote sensing in urban waste disposal and management: A case study of Usilampatti municipality, India. International Journal of Applied Research 015; 1(9): [9]S. M.J. Baban, D. T., F. Canisius, and K. J. Sant, (007) Managing development in the hillsides of Trinidad and Tobago using geoinformatics, Sustainable development, Vol. 16, issue, 5, , 007. [10]Sao, S., 000. Identification of levels of availability of facilities of dehradun city. net/application/urban/overview/urban0039.htm. [11]Tang Minan, Wang Xiaoming, Yuan Shuang (013) Site Selection of Mechanical Parking System Based on GIS with AFRARBMI. TELKOMNIKA Indonesian Journal of Electrical Engineering. 013; 11(7). [1]Yu Kanhua (014) Urban Planning Support System Based on Three Dimensional GIS. TELKOMNIKA Indonesian Journal of Electrical Engineering, 014; 1(5). Volume. 08, IssueNo.1, November-016, Pages: