RES 17-981 - Laserfiche WebLink

Figure 3: Illustration of Ridgelines and Spurs Not ridgelines per currently Ridgelne per currently proposed proposed method(green lines) method(red line) tg 3. Define Where a Ridgeline Ends. Previous mapping identified the ends of a ridgeline as the "last hill," or the two points at which a ridgeline no longer rises in elevation. Although the last hill method would protect the most prominent upper part of a cone-shaped hill, it could leave unprotected a long ridgeline that rises to a high point, and then gently and uniformly slopes down to the valley floor, similar to Pleasanton Ridge or Sunol Ridge. Therefore, staff considered all landforms with obvious high ground more than 200 feet above the valley floor to be ridgelines. The 200-foot criterion is related to Measure PP's protection of a 100- foot vertical setback below the ridgeline, described below. Because of the 100- foot-setback provision of Measure PP, ridgelines must end at least 100 feet above the valley floor (otherwise, a ridge could end 100 feet above the valley floor, and the 100-foot setback would encompass the entire valley floor). Cognizant that there are many options for determining where a ridgeline should terminate, staff selected a 200-foot rule for the mapping as a reasonable means of allowing development in the flat areas near hillsides while ensuring that structures are limited to lower elevations. In this mapping, ridgelines also terminate at the boundaries of the Southeast Hills, regardless of whether the 200-feet-above-valley-floor rule has been met. Figure 5 illustrates the difference between the "last hill" approach and the 200-foot rule, as applied to Sunol Ridge.