GIS Based Road Alignment Selection Using Multi Criteria Decision Analysis: (Case Study Of Hmusite To Estie Road Upgrading)

Abstract

The main objective of this study is to describe the application of geographical information system (GIS) and multicriteria decision making for optimal road alignment selection analysis. The important factors for the optimal alignment selection analysis were identified and selected based on literature and expertise discussion and categorized as engineering (Geology, Fault Lines, Soil type, Drainage density, Topography (Slope and Elevation), social and environmental factors(Land use, Forest Area, Sparse vegetation, Agriculture Area, Settlement, Open land and Rivers). Raster map layers were prepared and reclassified to meet the factor and constraint requirements. In this study two stages of criteria weights were computed as sphase1 criteria weights for criteria classes and phase2 relative weights of criteria for two designed alternative decision making scenarios (Engineering, social and environmental decision making scenarios) using analytical hierarchical process (AHP) based on literature and expertise discussion. Then the factors have been combined to give cost layer. By combination of the origin and criteria of cost layer the weighted cost distance and cost direction layers were generated. Using weighted cost distance and cost direction (Back link) criteria layers in the least cost path analysis function from origin (Hamusit to Estia) destination two alternative route alignments were generated. The alternative alignments have been compared with the existing route and also each other by route alignment requirement criteria and the new alignment reduced the road length by about 10 kilometer and about 92. % area of route alignment passed through flat to rolling terrain which is less cost of earth work. On the other hand less environmental and social impact has been for instance from 67.5 up to 75.24 % area of route location was lied in agricultural and open areas .From which the most optimal one was engineering scenario alignment. Generally GIS is very important and efficient tool for road alignment selection and other engineering location in order to reduce the quantity of Engineering, environmental and social impacts and optimizing different linear and others infrastructures.