February 14, 2009
Making a Dry Creek Bed Garden
BELOW ARE SOME HELPFUL INSTRUCTIONS IF YOU ARE THINKING ABOUT INSTALLING A FEATURE LIKE THIS.
First plan the course that the dry creek bed will take down the slope. Mark the 2 edges of that course with landscaper's paint. A meandering course looks more natural than a straight course. How high up the slope should you start? In some cases, there's little choice. For instance, if a landscape drainage pipe that's already in place is dumping all that excess water onto your property, your decision is clear-cut: begin the dry creek bed right under that pipe....
But in cases where you have more leeway (especially for dry creek beds that are purely decorative), attempt to disguise the "headwaters" of the dry creek bed by making it bend out from behind a large boulder or some plant material. When the source of a stream is mysterious, viewers have to use their imagination. And what we construct with our hands is rarely as pleasing as what we construct with our minds!
We've talked about how high up the slope to start. But what about where to finish down below? Some homeowners redirect excess water toward the street. But it's best to contemplate a worst-case scenario when dealing with public property, because that means dealing with the government -- which can be a real stickler when it comes to issues like redirecting excess water. So check with your local public works department first. If their response is positive, get something in writing that says so....
What if you're not allowed to redirect the water to the street? Unless you already have a landscape drainage system in place (allowing you to route the runoff into that system), you have 2 main options. You could channel the water to a location on your land (but make sure it's your land, not a neighbor's!) where it's less troublesome and where, if the soil is sandy enough, it can percolate harmlessly down into the ground. A second option is to build a pond and funnel the water into it
So much for the course of a dry creek bed. What about its depth and width? These dimensions don't have to conform to any rule exactly. Look at dry creek beds in nature: they're obviously not all of the same depth and width. But there's a general rule you can follow: dry creek beds tend to be wider than they are deep, which is good news for you -- less digging! A 2:1 ratio is about right, meaning you could make the dry creek bed 3' wide x 1.5' deep, for example.
With the planning done, now it's time for the first real work in the project: the digging. It's easy to build dry creek beds for landscape drainage, provided that the soil you'll be excavating isn't strewn with roots and rocks. Those with difficult soil to excavate can take solace in the fact that excavating the dry creek bed will be the toughest part of the project!
Take the soil that you're excavating and mound it up along the sides of your dry creek bed, as you go. This will reduce the amount of digging that you have to do, since you'll be lowering the base and raising the sides in one motion. Tamp down this excavated soil with a tamping tool.
After the trench for the dry creek bed has been excavated, lay down landscape fabric along its whole length. You want the fabric to cover the mounds of earth on both sides, as well as the trench. Hold the fabric in place using fabric pins or garden staples. Now for the part of the project that will be visible to viewer's: the rock....
For projects intended to improve landscape drainage, all rocks need to be mortared into place to form a solid channel that will carry water away (for ornamental dry creek beds, this is optional -- and probably undesirable). Apply mortar only to short sections of the fabric at a time, since mortar dries quickly. Use at least 2" of mortar. Lay the rocks in the mortar, then repeat the process with the next short section. It's easier to work from the top of the slope, down.
You can use rock of various shapes and sizes, but many homeowners prefer to select more round rocks ("river rocks") than flat ones. Round rocks conjure up an image of the water that has been gushing over them, knocking them about and causing them to become round over time.
Place small river rocks in the center of the trench; the water will flow over these.
Place your larger rocks on the sides of the dry creek bed, where they'll help channel the water and where they'll have the most visual impact. Save any boulders for the biggest bends in your stream's course and to disguise the "headwaters" of the dry creek bed (as discussed above).
After you build dry creek beds, you can dress them up a bit. Plants will soften the edges, for instance. If you're more ambitious, you can install a landscape bridge over the dry creek bed and plant tall ornamental grasses to serve as "bookends" at both entrances to the landscape bridge. Adorn the landscape bridge with hanging container gardens to create a knockout focal point for your yard
What You Need:
Fabric pins or garden staples
River rocks and boulders
Wheelbarrow for mixing the mortar