When crossing a stream valley from one side to the other, how are contour values encountered?

When crossing a stream valley from one side to the other, how are contour values encountered?

• A. The last contour value on the descending side is the first contour value on the ascending side.
• B. Contour values completely reset to zero at the stream.
• C. Contours on opposite sides are unrelated.
• D. Contour lines are not drawn near streams.

Answer: (A)

Contour lines show equal elevation and form a continuous surface across the map. When you cross a stream valley from one side to the other, you’re still moving through the same elevation values, just on the opposite slope. The elevation right at the stream is the same whether you’re on the near bank or the far bank, so the contour line you’ve just crossed as you approach the stream continues across the stream and becomes the first contour line you encounter on the opposite side. In other words, the last contour value on the descending side matches the first contour value on the ascending side because elevation is continuous across the valley; it doesn’t reset to zero. This also means contour lines can and do appear near streams, and the values on opposite sides are related through the same elevations.

Contour lines show equal elevation and form a continuous surface across the map. When you cross a stream valley from one side to the other, you’re still moving through the same elevation values, just on the opposite slope. The elevation right at the stream is the same whether you’re on the near bank or the far bank, so the contour line you’ve just crossed as you approach the stream continues across the stream and becomes the first contour line you encounter on the opposite side. In other words, the last contour value on the descending side matches the first contour value on the ascending side because elevation is continuous across the valley; it doesn’t reset to zero.

This also means contour lines can and do appear near streams, and the values on opposite sides are related through the same elevations.