How can stream flow direction be determined on a contour map?

• A. By contour turnbacks and elevation differences
• B. By color shading
• C. By map scale
• D. By contour density

Answer: (A)

Understanding how contour lines reveal flow direction comes from how water always moves downhill and how elevation is shown on a map. On a contour map, streams carve through the land, and the surrounding contour lines form V shapes where they cross the water. The point of each V points upstream, toward higher elevation, which means the stream itself flows the other way—downhill, from the upstream side toward the downstream side. So you read the map by noting which way the contour lines turn to form those V shapes around the stream and recognizing that the water moves opposite to the V’s point. You can also check that elevations along the stream decrease downstream if you follow labeled contour lines or index contours. Together, contour turnbacks and the pattern of decreasing elevation tell you the downstream direction.