§ 9-32.060. Slope Calculation Procedure

A.

Slope calculations. For the purposes of the performance standards set forth in this Article, the following methods will be used to determine the slope of any land and the square footage or acreage within any slope category on land subject to the performance standards:

1.

Definition of slope. Slope is defined as the relationship between the change in elevation (rise) of the land and the horizontal distance (run) over which that change in elevation occurs. The percent of any given slope is determined by dividing the rise by the run on the natural slope of land, multiplied by 100. See figure following Subsection (A)(2) of this Section.

2.

Slope map required. For the purpose of determining the amount and location of land falling into each slope category, the applicant shall submit to the Department of Environmental Services at the time of an application a base topographical map of the subject site prepared and signed by a registered civil engineer or licensed land surveyor. Such map shall have a scale of not less than one inch to 200 feet and a contour interval of not more than two feet, provided the contour interval may be 10 feet when the slope is more than 20 percent. Such base topographical map shall include all adjoining properties within 150 feet of the site boundaries. Slope bands in the range of zero to 10 percent, 10 percent to 15 percent, 15 percent to 20 percent, and 20 percent or greater shall include, or be accompanied by, a tabulation of the land area in each slope category specified in acres. The exact method for computing the percent slope and area by percent slope category should be sufficiently described and presented so that a review can readily be made.

3.

Slope mapping method.

a.

The percent slope of any particular piece of land shall be plotted on the map described in Subsection (A)(2) of this Section by dividing the vertical rise between the contours employed by the horizontal distance between the same contours, multiplied by 100. The minimum contour interval employed shall be two feet, and the maximum contour interval employed 10 feet, with the 10-foot interval being preferred.

b.

In preparing a slope map, isolated slope areas (that is, surrounded by a flatter or steeper slope category) with a horizontal run of less than 100 feet and a vertical rise of less than 30 feet shall be disregarded and the area thereof classified as being within the adjacent category. If the isolated slope area is adjacent to two or more slope categories, the isolated slope area shall be classified with the steepest adjacent slope category.

c.

In preparing a slope map, those portions of ravines, ridges, and terraces of less than 150 feet in width at their widest measurement which are in an area generally sloping at 20 percent slope or greater shall be regarded as being of 20 percent slope or greater and shall be included as part of the bordering 20 percent slope or greater band.

(§ 5, Ord. 1085, eff. January 6, 2006)