With the aid of contour plan, it is easy to trace a contour gradient of desired inclination on a paper, and even transfer it later to the ground (Figure 18.1).
To locate a rising gradient of 1 in 100 from a point say P situated on 200 m contour on the map having contour interval 5 m at a scale of 1: 5000, draw an arc of radius
with radius at P. The arc cuts the 205 m contour at Q. Locate R and S on 210m and 215 m contours taking arcs of radius of 10 mm with centres at R and S, respectively. Join P,Q,R and S. The line P to S represents the contour gradient on the ground having constant slope of 1 in 100.