■    Disruption of natural landform and drainage patterns. Even when a road follows the contour around a hill there is a need to cut into the hill on the high side and fill on the down slope side to create a level surface. As the slope percent increases, more cutting of the hill on the high side and more filling on the low side is needed to create a level travel way or building site.

Most high desert soils are loose and powdery, and only a few inches thick. A major side effect of the cut and fill activity needed for road and building construction is the increased possibility of soil erosion. The impacts here are twofold. First, when native grasses, shrubs, trees and other vegetation that hold the soils on steep slopes are removed, there is greater exposure of soil and rock that is subject to wind and water erosion. In addition to erosion, slopes without vegetation are more likely to suffer slumping and sliding. Second, the amount of cut and fill areas, and the modifications to drainage patterns created by streets, driveways, sidewalks, and utility routes, can all create erosion problems and/or the degradation of the exposed rock through winter freeze and thaw cycles.

■    Public safety. If a road, sidewalk, or other transportation route goes up the hill across the contours, then the steepness of the route can make it difficult for emergency vehicle access any time, and especially hazardous for any type of vehicle or pedestrian movement during winter conditions. Also, the increased impact on drainage and soil movement concerns with steeper slopes can create slumps, breaks or other problems with streets, sidewalks, trails, water and sewer lines, and other utilities.

■    Visual impact. Because the buttes and other sites with steep slopes can be seen from many parts of the urban area, there is interest in designing developments that minimize the amount disruption to the natural conditions. The Awbrey Butte Master Plan, which covers several hundred acres of steep slopes on the most prominent butte in town, includes street and site development standards to reduce the visual impact of development.

•    larger lots to reduce the number of building sites and corresponding disruption of the natural contour and vegetation;

•    using narrower right-of-way, pavement widths, and “hammer-head” street ends rather than cul-de-sac bulbs to reduce road cut and fills;

•    taking access off alleys on the uphill side of a street to reduce driveway cuts into the hillside;

•    placing sidewalks at the curb, or having only one sidewalk along the street to reduce the cross-slope cut and fills;

•    adjusting the building setback from property lines to minimize building site cuts and fills;

•    regulating the amount of vegetation cleared off a hillside lot;

•    requiring temporary use of hay bales, diversion dams, or other physical changes to control storm runoff during road and site construction; and

•    setting maximum grade or slopes on public streets and pedestrian corridors.