Spatial Analysis
This section outlines the methods used to analyze computed fuzzy images in a weighted analysis in order determine appropriate plant locations. Weighted criteria were then combined in order to produce a final raster image demarcating regions of low, moderate and high suitability. Although module operations were performed individually, their methodological procedure using the IDRISI modules “WEIGHT” and then “MCE” are outlined in Figure 5.1. The first weighted linear combination (WLC) multi-criteria evaluation applies emphasis to factors based on the perspective of the developer of the plant, a private corporation or BC Hydro. Therefore, the most important factors from this perspective include proximity to municipalities in order to supply and support a viable work force for the plant and proximity to water bodies in order to reduce cost of water pipelines into the facility (Duffy, 1997). Additionally, limited slopes help to decrease cost of construction and are important for nature of the plant operations, in addition to the understanding that increased distance from earthquake threat zones helps to reduce the risk of a reactor containment failure (Duffy, 1997). These factors subsequently have higher weights than the other factors. A pairwise comparison matrix using a nine point continuous weighted scale was utilized to determine the eigenvector of factor weights for each criterion (Table 5.1).
Figure 5.1: Although these operations were not carried out using the Macro Modeler, this is a cartographic model outlining the methodological process used to calculate the three weighted images as well as the final multi-criteria evaluation image.
The second WLC analysis places emphasis on environmental sustainability in order to reduce the generating station’s impact on local ecosystems and aims at decreasing the threat of environmental degradation of the most vulnerable regions. Thus, this weighted combination places increase valuation on the wood bison habitat, wetlands, distance from rivers and streams in addition to distances from outdoor recreational and protected areas such as provincial parks (Table 5.2).
The final WLC evaluation is focused from a First Nations perspective and heavily weights increased distances from First Nation reserves above all other criteria. Factors based on environment preservation are also valued. This is based mainly on the historical position of Ontario First Nations disagreement with nuclear energy sources, but a further in-depth study would review First Nation opinion on a case-by-case basis (McDermott, 2008) (Table 5.3).
Once each of these weighted raster images were calculated, they were reclassified from a numerical continuous range into order qualitative groups based on a natural breaks reclassification method using the module “RECLASS” to enhance cartographic output. The final step in the WLC multi-criteria analysis is to combine each of these weighted images together to produce one image from which final site suitability locations can be determined. This was completed through IDRISI’s “OVERLAY” module utilizing the INTERSECTION (AND) map algebra boolean logic which combines only those spatial extents which are present in all images. These final output images, possible site locations and conclusions are discussed in the Results section of this project.
In order to provide supplemental information and separate criteria to help draw conclusions about the location of the nuclear plant facility, an additional least-cost pathway analysis was performed to determine the relative distance and easiest routes between proposed site locations and existing main BC Hydro electricity lines. Although the development of a nuclear power plant for the primary purpose of producing energy would warrant the construction of power lines across almost any distance or terrain in order to justify the building of such power infrastructure, this type of analysis works to boost or discourage suitability locations. This least-cost pathway determines a linear pathway across terrain based on construction transmission lines on certain types of land uses in comparison to others. A cost friction surface was calculated in order to determine which surfaces were easier to traverse. A rating scale is used starting with a base cost of 1 being the easiest and most cost-effective land use type to build on and a value of 1000 identifying areas of virtual barriers to construction (Table 5.4). The raster land use data was reclassified based on friction values using the “ASSIGN” module and then a complex cost surface was created using “COST” with a target source image being proposed nuclear plant sites (Figure 5.2). Four possible site locations were then digitized based on conclusions drawn from the multi-criteria analysis stage of this project. Digitized locations were determined based on using the centroid of suitable regions and sites within realistic water sources and suitable municipalities. The module “PATHWAY” was then used to connect existing primary BC Hydro power lines to the site location.
Figure 5.2: Cartographic model showing the methods and operations used to derive friction cost surface images and pathway images.