It is difficult to build a road on steep slopes, so you’ll calculate slope to take into consideration the slope of the land.

Do do so, in the Spatial Analyst Tools toolbox, expand the Surface toolset. Click and drag the Slope tool onto the ModelBuilder window. Right-click the Slope tool element and click Open. Click the Input raster drop-down arrow and click the elevation layer. Accept the default path for the Output raster parameter value and type “Slope_ex3” for the name. The default path is set to the scratch workspace (for example, C:\Spatial\Results) you set earlier on the Environment Settings dialog box. Type “0.3048” for the value of the Z factor parameter to convert the z-values to the same unit of measure as the x,y units (from feet to meters). Click OK.

Click the Auto Layout button, then click the Full Extent button to apply the current diagram properties to the elements and place them within the display window.

Right-click the derived data element for the Slope tool and click Rename. Type “Slope output” and click OK.

Right-click the Slope output derived data element and click Add To Display.

Right-click the Slope tool element and click Run to run the process.

Examine the layer added to your ArcMap display. Steep slopes are displayed in red and less steep slopes in green in the output layer.