On a topographical map extract drawn at a scale of , a river valley features V-shaped contour lines that point consistently toward the south-west. Point X lies directly on the contour line, while Point Y lies further down the channel path on the contour line. Based on these topographic observations, toward which direction does the river flow, and what is its average channel gradient between Point X and Point Y?
- AToward the south-west at a gradient of
- Toward the north-east at a gradient of Answer
- CToward the north-east at a gradient of
- DToward the south-west at a gradient of
Answer
The river flows toward the north-east at an average channel gradient of .
In topographic map interpretation, contour lines form 'V' shapes when crossing river valleys, with the apex of the 'V' pointing upstream toward higher elevation. Because the V-shapes point south-west toward the contour, the river must flow downstream toward the lower contour in the north-east direction. Furthermore, the gradient calculation requires dividing the Vertical Interval () by the Horizontal Equivalent (), giving (or ).
Step-by-Step Solution
Key Concept
Valley Contour Interpretation and Topographic Stream Gradient Analysis