Basic Civil Engineering (3110004)

BE | Semester-1   Winter-2019 | 08-01-2020

Q5) (a)

Describe with sketches the characteristics of contours.

The following characteristics help in plotting or reading a contour map.
  • All the points on a contour line have the same elevation.
  • he elevations of the contour are indicated by inserting in a break in respective contour or printed closed to contour.
  • The contour lines are closer near the top of hill or high ground and wide apart near the foot. This indicates a very steep slope towards the peak and a flatter slope towards the foot.
  • The contour lines are closer near the bank of a pond or depression and wide apart towards the centre. This indicates a steep slope near the bank and flatter slope at the centre.
  • Two contour lines do not intersect with each other.
  • Contour lines form closed circuit. But these lines may be within or outside the limits of the map.
  • Contours do not have sharp turning.
  • Uniformly spaced, contour lines indicate a uniform slope.
  • A series of closed contour always indicates a depression or summit. The lower values being inside the loop indicates a depression and the higher values being inside the loop indicates a summit.
  • Contours deflect uphill at valley lines and downhill at ridge lines. Contours lines in U shape cross a ridge and in V shape cross a valley at right angles. The concavity in contour lines is towards higher ground in case of ridge and towards lower ground in case of valley.
  • Contour lines meeting at a point indicate a vertical cliff.
  • Contour lines cannot cross one another, except in case of an overhanging cliff. But the over hanged portion must be shown by a dotted line.