Application of Gis-based Analytical Hierarchy Process (Ahp) in Identifying Suitable Areas for Urban Development. Case Study: Trans-nzoia County.

Abstract

The world is undergoing rapid urbanization. In the developing world, Africa has the highest urbanization rate. Kenya is among the leading African countries with high urbanization rates as evidenced by the increasing urban population that currently stands at 28%. This rapid urbanization is mostly unplanned and is manifested by the sporadic emergence of small urban settlements in the country. The Kenyan counties, Trans Nzoia included have not been spared from these adverse impacts of rapid unplanned urbanization. The county is characterized by small patches of built areas scattered all over the county’s landscape haphazardly and with the new devolved governance system in place, urbanization in the county is expected to increase. The increase in urbanization means more land will be required for urban land use. For planned sustainable urban development to occur in the county, the identification of suitable areas for expansion and development of urban areas is critical for the County government of Trans Nzoia. This study focused on the identification of areas suitable for urban development and expansion in Trans Nzoia County using the GIS-based Analytical Hierarchy Process. Based on comprehensive literature review and consultations with experts in the urban development field, eight criteria namely road proximity, distance to water bodies, distance to protected areas, population, slope, soils, land use land cover, and elevation were considered. In the generation of weights for each criterion, Analytical hierarchy process method was employed. The weights were assigned based on expert opinions using pairwise comparison matrix. A constraint map was generated using Binary Overlay Method. Weighted Sum Overlay was used to generate the maps based on AHP weights. Integration of the two maps using masking tool produced the final suitability map indicating suitable areas for urban development in Trans Nzoia County. The analysis results indicated a large portion of Trans Nzoia County is not suitable for urban development with 5% of the total areas considered highly suitable for urban development. The results also indicate that approximately 64% of the existing main urban centers in the county are located in areas not suitable areas for urban development. Although the results of the study are subject to field verification, the study recommends the consideration of the results in formulation of urban development strategy for the county and the adoption of the conceptual procedure used in this study for other planning projects.