A dry streambed adds depth
This small backyard was just a flat, rectangular lawn. Now it has rolling berms, a curving dry streambed, a deck for entertaining, and attractive plantings.
When building a dry streambed, you want to create the illusion of a passage of water. Gentle curves in the streambed add authenticity and create a sense of rhythm. Boulders placed strategically in and around the streambed add credibility and help to frame the composition, while rounded river stones fill the streambed, adding dimension and breaking up the terrain. Plantings add a nice finishing touch.
Dry streambeds should be located on low ground, with the surrounding earth graded higher to imply running water’s erosive tendencies. And while a dry streambed remains dry most of the time, it also serves an important role in handling runoff during rainstorms. So when grading a site, not only does your streambed have to be lower than the surrounding terrain, but it also must follow a downward grade so that water runs through it without puddling. In this case, the streambed runs to a hidden storm drain, where the runoff is carried away.
We used two kinds of rock in this garden. For the larger boulders, we opted for locally quarried basalt. Some of these boulders were used in and along the edge of the streambed to imply continuous geologic ridges over which the stream meandered. In the streambed itself, we used rounded river cobbles of various sizes. The larger cobbles were rescued from a highway construction site. These stones made the stream bed a success by adding a realistic scale to the design.
A mix of plants and boulders helped create a natural-looking beginning and end to the streambed. At the stream’s “origin,” we installed a bubbling boulder, which had been drilled so that water could be plumbed through it. The boulder sits on a metal screen over a concrete basin, and the pump is located in the basin. This feature, though not essential, adds the sight and sound of water year-round, even though the water does not flow the length of the streambed.
Ornamental grasses like Acorus gramineus ‘Ogon’, A. g. ‘Variegatus’, leather leaf sedge (Carex buchananii), sweet flag (Acorus calamus), blue oat grass (Helictotrichon sempervirens), and soft rush (Juncus effusus), along with irises (Iris spp.) and bog plants, punctuate the stream bank, much as they might in nature. They add authenticity to the setting when grouped in and around the stream and when juxtaposed with the boulders.