3.6.1 Landform Manipulation

Manipulation of landforms is an effective tool for modifying the visual scale of roadside elements. Landform manipulation also adds variety to the setting and reduces the sense of visual clutter common to urban centers and complex interchanges.
Design solutions that employ landform modification are most cost effective when undertaken in concert with the horizontal and vertical alignment of the roadway. Highway planners and engineers are encouraged to collaborate with landscape architects on projects where landform modifications can be used as part of the overall landscape and aesthetics design concept.
Consider landform modification as part of the overall solution in these areas:
  • Interchanges;
  • ROW that require noise walls;
  • Embankments; and
  • Medians
3.6.1.1 Interchanges
Large urban highway interchanges, with numerous concrete columns and supports, can create a sense of visual disorder for the driver. Since these large interchanges frequently contain sufficient space to generate significant grade changes:
  • Utilize the ground plane around these elements to create grade changes that reduce the visual scale of the vertical structures.
  • Keep slopes within maintainable grade range.
Landform modifications at interchanges can reduce the apparent scale of the structure.
Figure 3-13: Landform modifications at interchanges can reduce the apparent scale of the structure.
3.6.1.2 Embankments
Roadway embankments often form large physical landmarks so their aesthetic character can have a significant impact on the surrounding community.
  • Excessively steep and abrupt embankment slopes do not blend well visually with adjoining landscapes, are difficult to maintain, may erode easily, and may limit or prevent the use of other landscape enhancements.
  • Many visual problems associated with embankments are related to the degree of difficulty in maintaining vegetation on steep slopes, near or between barrier devices, or in inaccessible areas close to structures, signs, or luminaires.
  • To reduce these problems, consider the following practices:
    • Employ measures to prevent vegetation growth within or between barrier devices;
    • Include paved mow-strips along the edges of walls or other structures;
    • Reduce slopes where possible to increase maintainability (max 4:1) and reduce the chance of erosion and slope failures by maintaining slopes; and
    • Combine signage and structures where possible to reduce obstacles to maintenance.
3.6.1.3 Medians
  • Where space and drainage patterns allow, berms may reduce or prevent median crossings and reduce headlight glare.
  • Careful consideration should be given to the cross section to ensure driver recovery, mowing access, and drainage.
  • No berms should be placed within the sight triangles at intersections or at crossovers on multi-lane divided highways.