Spatial analysis in environmental impact assessment (EIA) of road project using ArcGIS

Road construction brings huge economical and social benefit, however, causes complex environmental impacts. In this paper, we introduce the usual spatial analysis techniques in software ArcGIS that have been widely used in environmental impact assessment (EIA) of road construction project, including `Buffer´, `Near´, `Select by Location´, `Intersect´, `Spatial Join´. Bidirectional relationship (environment element (EE) and road) and function of these spatial analysis techniques are detailed, and illustrated using three simple schemes whose EE are point, polyline, and polygon type respectively. `Near´ is used to measure the shortest distance to road, whose bidirectional relationship is many-to-one; `Buffer´ is used to define the equi-distance region of EIA for further spatial analysis, whose bidirectional relationship is one-to-one. Based on the result of `Buffer´, `Select by Location´ and `Spatial Join´ are both used to count the number of EE in the equi-distance region; otherwise, `Select by Location´ has no bidirectional relationship. Based on the result of `Buffer´, `Intersect´ is used to measure length (polyline type) or area (polygon type) of EE in the equi-distance region, whose bidirectional relationship is many-to-many. In many related literatures, they are generally used without more specific description. The purpose of the paper is aimed to prevent misuse in EIA of road construction project.