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How to Determine Direction of Creek Flow by Looking at Maps

Creeks and streams must always follow one simple rule: gravity makes water run downhill. Unless it ends up in a lake, the water in a small creek flows into a larger stream, and that stream flows into a river, and the river eventually finds its way to the ocean. There are clues on a map to tell you which way running water is flowing.

Instructions

- 1
  Evaluate the type of map you have. Some types of maps make flow direction very easy to determine. It is easiest if you have a topographic map, with printed elevation contours--the water flows from higher elevation to lower. There are other methods for other types of maps.
- 2
  Follow topographic contours that cross the stream. All contours that cross a stream valley bend uphill as they approach the stream. The result is a V shape that points upstream. The contour and the line of the stream make a sort of arrow that points opposite the direction of flow. If the map does not have contours, observe the pattern made by all the streams on the map.
- 3
  Trace the pattern formed by the creek and all creeks that join it or that it joins. Most patterns look like a tree, with branches that form Y and V shapes where they join. The Y and V shapes point in the direction that the streams flow. If the streams don't form a tree shape, there are still other methods.
- 4
  Look for other clues. Almost all streams become larger in the direction the water flows, so if the line marking a stream ends without joining another stream, it is most likely the upstream end of the creek. This is especially likely if the line ends at a spring or a small natural pond.

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