Selecting A Trail: Reading Trail Maps

Did you know that you can actually determine how steep a trail is BEFORE you head out from the trail head, and find out the hard way that it's way too steep for your little hiker?

Allow me to introduce the idea of the topographic map.  You've probably noticed the slender, squiggly lines on your trail maps.  "Topos," as they are called, use detail lines to show the elevation change of any given area.

Last weekend, Lil' H and I enjoyed a nice hike in Sanborn County Park.  We wanted to check out Lake Ranch Reservoir, and a quick check of the Park Map showed two trails to access the Reservoir.

Two trails to Lake Ranch Reservoir

The trail in the northwest corner, leaving from Sanborn Rd, is the short and direct Lake Ranch Trail, listed at .6 miles.  Starting in the southeast corner of the map, with the trailhead off of Black Road, is the John Nicholas Trail, listed at 1.4 miles.  The shorter trail seems like the better option, right?  But let's look at what the topo lines show us.

Each bold line represents a major elevation delineation.  All maps are different, so you want to read the legend on a new map, but on this map, each bold line represents 200 feet in elevation change.  In between each bold line are four slender lines.  These represent 40 feet in elevation change.   The closer together the lines are, the steeper the terrain.  Let's use this information and apply it to our map.

The Lake Ranch Trail to the Reservoir

We'll start with our shorter trail - the Lake Ranch trail to the Reservoir. I have marked the bold topo lines in green.  The trail (in yellow) starts three slender lines below the 1600' bold line.  This means the trail starts at approximately 1480'.  Remember, each slender line represents 40' feet. The end of the trail, at the reservoir, ends right at the 1800' bold line.  This means an elevation gain of 320 feet over .6 miles, an incline of 10%.  Another way to think about it is for every 100 feet you walk forward, you gain 10 feet in elevation, or one flight of stairs.  If this is starting to sound a lot like algebra, you are correct.  You calculate incline by dividing "rise over run," sound familiar?

The John Nicholas Trail to Lake Ranch Reservoir

Now, let's see how that compares to our longer trail, the John Nicholas Trail.  The trail starts two slender lines above the 1800' bold line, at approximately 1880 feet.  The trail stays mostly between the lines.  In map lingo, this is known as hugging the contour.  Right where the map says "1.4", the trail actually dips below the bold line, meaning that you lose some elevation, so we've actually gone downhill by about 120' .  The trail ends right at the 1800' bold line, so we do have to regain that altitude.  The trail will have gentle ups and downs, but overall, your elevation gain, and the incline, will be negligible.

So, in this case, a 1.4 mile gently rolling trail may be longer, but is going to be easier on young hikers or parents carrying kids in Keltys than a steep .6 mile climb. Hopefully you can use this information to help you evaluate trails for your future hiking plans. Knowing how to read the topos can help you determine whether a trail is appropriate for your family.  Which trail did we choose, you might wonder?  We actually opted for the short and steep Lake Ranch Trail because I'm training for Mt. Whitney and need as much uphill climbing as I can get!

Mrs. H and Lil' H setting off for Lake Ranch Reservoir as part of the Parks For Life Challenge

If you are interested in viewing more topo maps, the USGS website allows you to search for and download maps for the entire country.  You can also purchase paper versions on durable, water-resistant paper.  Download and print the Half Dome map (just click on the preview image for a free high-res download) and practice tracing the trail and calculating the elevation for a fun activity with your kids.