Look at stream flow patterns to see elevation change
Stream flow patterns on a topographic map can show you at a glance the higher elevations and lower elevations.
This map section below (from the US Geological Survey 7.5 minute map series) is in the Oregon coast range. Just by looking at the stream flow patterns (and without looking at the printed elevations (which are pretty darn hard to see anyway) can you tell where is the high ground and the low ground? And, for extra credit, what’s the lowest point on the map?
Here are a few ways to tell general map elevation from stream flow patterns.
A good starting assumption: water flows downhill. =^)
Smaller streams flow together to become larger ones.
When streams come together, they usually form a “V” shape. The two arms of the “V” point upstream, to higher ground. The tip of the “V” points downstream, to lower elevation terrain.
The origin of a stream on a map is called the “headwaters”. The stream always flows downhill from that point.
Contour lines always bend to point uphill when they cross a gully or drainage.
Let's look at a few examples.
When streams come together, they usually form a “V” shape. The two arms of the “V” point upstream, to higher ground. The tip of the “V” points downstream, to lower elevation terrain.
The origin of a stream on a map is called the headwaters. The stream always flows downhill from that point.
Contour lines always bend to point uphill when they cross a gully or drainage. (Look at the index contours, printed in bold every 5th contour line, they’re easier to see. Shown in red line below.)
So, when we put all that together, we see that Jordan Creek in the center is flowing from right to left (or east to west, if you prefer), being fed by various other creeks flowing from higher elevations.
Try this yourself. Go to Caltopo.com, zoom into a familiar area that has some streams, and see how all of these factors come into play.
And finally, because we know Jordan Creek is flowing from right to left (and because water flows downhill) the lowest point on the map is the one indicated below.
And as always, stream flow patterns, gullies, ridges and other landscape features are much easier to see when you use a map that has shaded relief. This is easily done in Caltopo for free. The map below has about 30% relief shading. Here’s a whole article on shaded relief, check it out!
If you are new to using Caltopo, it’s a wonderful mapping tool. I made a tutorial video on how to get started using it, you can watch that here.
