Contour lines cross a watershed or ridge line at _____ .
90°
Understanding Contour Lines and Ridge Lines
Contour lines are lines drawn on a map that connect points of equal elevation. They are used to represent the shape and slope of the land surface, also known as topography.
A watershed or a ridge line represents a line of highest elevation on a topographic map. This line separates drainage areas, meaning water flowing downhill on one side goes into a different stream or river system than water flowing downhill on the other side.
How Contour Lines Interact with Ridge Lines
When contour lines encounter a ridge line or watershed, they exhibit specific behavior:
- Contour lines bend uphill towards the ridge line. As you move along the ridge line, you are moving along the highest points in that area.
- Since a ridge represents a crest or a line of highest elevation separating slopes, the slope is steepest directly perpendicular to the ridge line as you move down either side.
- Contour lines are always perpendicular to the direction of the steepest slope.
Angle of Intersection
Because the ridge line represents a line where the steepest slope is perpendicular to it (down both sides), and contour lines are perpendicular to the steepest slope, the contour lines must cross the ridge line at an angle of $90\degree$.
Imagine walking along a ridge line. Any path directly downhill from that ridge will be perpendicular to the ridge at the point you leave it. Contour lines, representing lines of constant elevation, are always perpendicular to these downhill paths (lines of steepest descent). Therefore, when a contour line reaches a ridge line, it makes a sharp turn and crosses it at a right angle.
This characteristic right-angle intersection is a key principle for interpreting topographic maps and identifying ridge lines and watersheds.
Thus, contour lines cross a watershed or ridge line at $90\degree$.
Important Questions from Contouring
Which of the following statements are CORRECT for contour map?
1) Parallel contour shows uniform slope.
2) Very closed contour shows steep slope.
3) Very closed contour shows flat area.
4) Two contours at different elevation cut at right angle.While drawing a cross-section of a contour map, the following values were noted from point A to point B on a strip of paper to draw the graph - 500 m, 400 m, 300 m, 200 m, 200 m, 300 m, 400 m, 500 m.
Which cross-section would be drawn by using the above values?
Identify the correct statements.
i. Contour lines form sharp V-shaped curves across valley line, with the convex side of the curve towards the higher ground.
ii. Contour lines form U-shaped curves across valley line, with the convex side of the curve towards the higher ground.
iii. Contour lines form U-shaped curves across ridge line, with the concave side of the curve towards the higher ground.
iv. Contour lines form sharp U-shaped curves across ridge line, with the convex side of the curve towards the higher ground.
In case of uniform slope, the contour lines:
The horizontal distance between two consecutive contours is termed as
