Tips for Teaching: Drain Dips
By Barbara Budd
Cleaning drainage is a staple of trail maintenance, and yet, doing it well can be quite challenging. How many times have you helped other volunteers clean drain dips (also called rolling grade dips) only to come across several narrow trenches perpendicular across the trail. Now you’re thinking, “How do I explain this and still make the volunteer feel good about their work?” Here are a few tips on how to do just that.
Giving a good example and setting expectations up front with help with whatever feedback you give to volunteers, as well as keep them from feeling like they’re floundering.
In order to do this, I like to use a modified “see one, do one, teach one” technique. This is a teaching tool that can be used for any task that is repeated along a trail (berm removal, tread widening, even brushing). First, the example - show your crew how to properly clean a drain.
While you’re digging your example drain, here are some tips to cover:
- Drain dips are generally larger than folks think. The USFS specifications for drains are that the ramp down into the dip is usually 6-10 feet long, even though that can be hard to see. The ramp below the dip should be 10 feet long or longer. These will vary a bit with the width and steepness of the trail.
- That ramp below the trail should be a ramp, and not just a berm across the trail. Berms are easily kicked out by hikers, horses, and cyclists, which will cause your drain to fail.
- Water takes the path of least resistance and doesn’t make 90 degree turns. The bottom of the drain dip should be about 45 degrees across the trail, so that the water doesn’t simply jump right over a drain that is perpendicular to the trail.
- The funnel at the bottom of the drain on the outside of the trail should be 6-8” deeper than tread level. Yes, this looks really deep when it’s a little tiny trench, but when it’s built correctly, it turns into a little roll in the trail that hikers barely notice. The drain should drop gradually and smoothly from the tread level to the point of outflow.
- The ditch should be steep enough to keep water flowing and end at a steep drop off if possible. If there is no steep drop off, the ditch should be a minimum of 8 ft long, and if terrain is not steep, should have a sump at the end (please note that this is not ideal, having a drop off is much more effective).
- At this point, you’ve just been waving your arms and talking. Now start your demonstration dig, explaining that you should start with the ditch first so that you know how deep you can make your drain. Follow that by digging the funnel part of your drain across the trail.
- Finally, just before you finish, have the volunteers step back several feet up trail, down trail, below the ditch, looking for any bumps, divots, or other problems. Leave a couple for them to see so that you can smooth them out while they’re watching.
Now it’s time to let each of them clean their own drain or three while you’re around to answer questions. If you see them doing something not quite right, ask questions instead of directing. Some examples: What do you see here? How would you get water off the trail? Do you see any puddles or bumps? This will help them recall what they know without feeling under too much pressure.
Once they are comfortable, then have them teach another volunteer who may have been doing a different task, say cleaning ditches or working on berm removal. This will help cement what they’ve learned. Stick around for this, again asking questions more than giving suggestions.
Remember that folks learn differently and need multiple kinds of input to understand. If someone is working on a drain and they’re struggling, perhaps try to build a mini-drain (a few inches long) in the dirt to give them a refresher. Some folks have found “thinking like a raindrop” useful. Others have found it helpful to watch an orange or a tennis ball roll down the trail and out the drain, or simply imagining that same activity. Or show them the article and pictures in the USFS Trail Construction and Maintenance Handbook.
This article has described maintenance of existing drain dips. Similar structures are knicks (a semicircle cut into the tread), and most of the same maintenance tips apply.
Finally, keep in mind that different trails have different drainage needs and possibly even restrictions given by the land manager, so it’s always best to check in with your Blue Hat to see what the drainage needs are before diving in.
- USFS Trail Construction and Maintenance Notebook: 2007 edition, pages 29-42 https://www.fs.fed.us/t-d/pubs/pdfpubs/pdf07232806/pdf07232806dpi300.pdf
- Tread and Retread the Trails by Julian “Pete” Dewell, Chapter 5 Drainage
- Lightly on the Land by the Student Conservation Association, Chapter 11 Trail Drainage