Rock-edge pools
When constructing a rock-edge pool, it is extremely important the stones rise out of the water and are not simply perched on the rim. If onlookers can see any hint of construction materials (e.g. concrete or plastic liner) peeping out beneath the stone, then the illusion is immediately lost. Rather than appearing natural, the rocks will look obviously placed, putting the entire water feature’s authenticity into question.
To prevent this, the basics of water feature design need to be understood. For instance, the first order of business, whether building a stream, pond or pool, is ensuring the water feature will retain water. If someone is fortunate to enjoy a constant spring or stream in their garden, then this problem is solved. However, very few have this luxury; therefore, water features must be lined with an impervious coating (e.g. clay, sodium bentonite, concrete, butyl rubber or ethylene propylene diene monomer [EPDM] rubber) to ensure water retention.
There are a number of different flexible liners on the market; however, for ease of use and cost effectiveness, fish-safe EPDM liners are typically used. These liners are extremely elastic and resilient, and when sandwiched between two layers of non-woven geotextile fabric for protection, they make an excellent, durable pond liner.
To install the liner, a level shelf around the water feature’s inner perimeter should be formed during initial excavation. Its depth depends on the size of the feature; however, as a rule of thumb, 305 mm (12 in.) will allow for a protective layer of concrete or gravel onto which the rocks can be placed. The amount of rock hidden below the water can then be adjusted to suit the angle, shape and position that best conforms to the geology of the area.
When placing rocks, complete freedom of expression and movement is needed to get the best fit in all three dimensions. Therefore, by creating a reasonably wide ledge, there will be plenty of room to manoeuvre. The added benefit of using a flexible liner system not only provides an opportunity to increase its size should a large stone require more space, but the liner can also be brought up behind the finished rockwork to eliminate any unnecessary hydric (i.e. extremely wet) areas.
On the edge
Now, with the liner in place, focus should be directed to the water feature’s edge detail. No matter the water feature, the border will determine its appearance (e.g. formal or natural, rocky or marshy, beautiful or ugly). In fact, creating the edge will likely be the project’s greatest expense due to the attention to detail and excellence in construction required.
When creating the edge, do not attempt to incorporate more than three different edge types or the water feature will look cluttered and more like a garden centre exhibit. Examples of elements that work well together include rock with sand, gravel and marsh plants, or possibly even a large expanse of emergent plants (i.e. plants with underwater roots that grow above the surface) and marsh planting with timber decking and lawn to the water’s edge. More or less, any combination can be made to look as though the pond had always existed. The more artistic and imaginative the edge design is, the better the result.
