Following the completion of the project scoping, development of the baseline habitat network, and a landscape level assessment of habitat fragmentation, an assessment of project alternatives can be performed. At this point in a typical project timeline the alternatives have been identified and initial efforts to avoid critical habitats and habitat fragmentation impacts can be incorporated in the initial alignment selections using the habitat network mapping. The impact analysis is also predicated on having an understanding of the habitat features of the target species and familiarity with the qualities of habitats present along each alternative. The GIS mapping and modeling process does not supplant the need for gathering field data to support mapping and model assumptions: knowledge of field conditions is implied throughout the assessment process.
The level of effort and detail required for this assessment is dependent upon the size and complexity of the project (culvert replacement versus new alignment), complexity of the project landscape (urban vs. rural), number of target species, requirements for data collection through field work, and other factors. The three main steps of this process, as outlined in Figure 4, can be read in the following links: