We live on one of those unlivable roads here in Costa Rica. You know the kind I am talking about: mainly rocks and ruts with a few holes thrown in for good measure. The kind of road that’s great for horses, cattle, and ox carts, but not so great for cars. Well, they decided to fix ours. That should have me jumping for joy, right? Not so much. I had a lot of plants along the road, about a half kilometers worth, and some of them have been ripped up. I can live with that, we have lots of plants. The problem is drainage ditches.
Drainage ditches, for those of you who are thinking about having some dug, should not have straight
up and down sides. If they do, it means that there will be a lot of dirt washing off the sides and into the ditch, filling it rapidly or at least impeding the flow of water. The sides might even fall directly into the ditch blocking it completely. The sides of a ditch, like the sides of the road, should be sloped at the angle of repose.
The angle of repose, the angle at which the dirt, properly seeded will not fall into the ditch or road, is different for each type of dirt, but lets take a nice angle of 30 degrees as an example, the angle of a steeply sloped lawn. Chances are that it will stick around instead of sliding downhill.
Now look at the roadside as you drive. See any nice 30-degree slopes? I haven’t. I have seen a lot of 60 degree and 80 degree and even some close to 90 degree but not roadsides that match the angle of repose.
It’s a small problem for me. My gardener and I are pulling rocks out of the piled up dirt and planting vetiver grass and maní to hold what is left (see prior columns for information on both these plants). It’s time consuming, but we think it will be effective. No, the problem comes when the sides of a main road are set at insupportable angles. That’s when we have events like landslides that block roads or the landslide that killed a father and son last year. That’s when there is a problem.
Most of us can’t, of course, re-contour the land we live on, but we can plant things with deep roots and we can do something about the edges of our property that border roads. We can change the slope near the road and plant it with shrubs and grasses that will hold the soil. If we do that, the future will hold a lot more gardening and a lot less digging out ditches.