Projects and activities associated with linear alignments include rights-of-way, roads, trails, pipeline developments, and underground and overhead utility lines. The visual impact of a linear project depends largely on where it is located and how it is molded to the natural terrain. Proper location can often contribute significantly to the reduction of line and color impacts, making other measures either unnecessary or less costly and easier to accomplish.
Finding the best route for linear alignments involves:
- Identifying and analyzing all possible corridor alignments and selecting the one most feasible for the proposed project.
- Locating the proposed project within the selected corridor after a thorough analysis of all environmental, socioeconomic, and engineering factors.
There are several major considerations for determining an alignment:
- Topography is a crucial element in alignment selection. Visually, it can be used to subordinate or hide manmade changes in the landscape. Projects located at breaks in topography or behind existing tree groupings are usually of much less visual impact than projects located on steep side slopes. By taking advantage of natural topographic features, cut and fill slopes can be greatly minimized.
- Topographic breaks frequently exhibit a natural line element that the proposed alignments can repeat or blend with to strengthen the design. This line element is partly established by a visual shadow zone, which will further aid in reducing the contrast of the project.
- Soils are especially important when selecting an alignment. They should be analyzed for stability and fertility and a revegetation program should be planned.
- Hydrological conditions can strongly affect the visual impact of buried and surface construction. The risks of surface and subsurface erosion within the corridor should be analyzed and evaluated.
- Crossings with other linear features or structures should be designed to minimize their visual impact:
- When possible, crossings should be made at a right angle.
- Structures should be set as far back from the crossing as possible.
- In areas with tree and shrub cover, the rights-of-way and structures should be screened from the crossing area.
It is important to remember that when a system is planned and designed:
- Other services that will be needed to support the system must be analyzed and included in the design considerations. For example, a construction access road, electrical power with a backup system, and sanitation facilities are usually needed for most projects. At times, the visual impact of the support facilities is the deciding factor for the specific location of the main project.
- How the system is to be maintained must also be considered.
- A rehabilitation plan should also be developed. All areas of disturbance that are not needed for operation and maintenance should be restored as closely as possible to previous conditions.
Determining the engineering design, landscape design, and visual considerations for a linear alignment must be accomplished together to ensure that all three are addressed and included in the final design solution.
The following examples depict proper and improper linear project alignments.