Urban Sprawl Mapping and Landuse Change Detection Using Spatial Metrics Method: A Case Study of Addis Ababa City and its Surrounding Areas, Ethiopia
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Date
2017-06
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Addis Ababa Universty
Abstract
Rapid and unprecedented urban expansion is becoming the characteristics of cities in developing countries. Hence, it is customary to assess and monitor urban growth changes using remote sensing and other spatial tools to quantify urban sprawl that provide paramount information for city planners. This study was conducted on Addis Ababa metropolitan area with aim of measuring urban sprawl in four years perspective 1984, 1995, 2006 and 2016. Landsat images of each perspective year were used and pan sharpened (fused) with SPOT-5 (5m) using hyperspectral color merging algorism to get better images with 5m spatial resolution. The resulted satellite images were classified and land-use/cover maps were produced using maximum likelihood of supervised classification method. The classification process was checked by producer’s, user’s, overall accuracy and kappa statistic accuracy assessments from confusion metrics. The results show acceptable agreement between the classified maps and reference data with a producer’s accuracy value greater than 74.14%, and user’s accuracy greater than 84.09%. Post classification change detection analysis and selected spatial metric indices calculation were made to detect, assess and monitor urban growth and quantify urban sprawl in the study area. Change detection analysis results indicated that Addis Ababa is growing rapidly with an average rate of 5% per year for the past 32 years from 1984–2016. In terms of area, the expansion of the city was found to be 12,218, 15,981.58, 22,513.29 and 38,801.35 in 1984, 1995, 2006 and 2016 out of the total area in hectare, respectively. In other words, the built-up area constituted 15% for 1984, 19.6% for 1995, 27.5% for 2006 and 47.5% for the year 2016 in the study area. From spatial metrics analysis, aggregated number of built-up area patches were 621, 476, 574 and 840 for the years 1984, 1995, 2006 and 2016. The decrease in number of patches in 1995 indicates that merging of previous patches into the main built-up area forming continuous urban agglomeration. The zonal analysis of urban sprawl shows that Addis Ababa is expanding by leaps and bounds to the east, south, south west and north east directions, particularly in the past ten years consuming a large amount of agricultural and green areas. Therefore, the city planners need to plan ahead and implement plans properly to cope up with the rapid and unprecedented growth of the city in the years to come.
Key Words: Spatial metrics, Zonal metrics, change detection, urban sprawl, Addis Ababa
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Keywords
Spatial metrics, Zonal metrics, Change detection, Urban sprawl, Addis Ababa