Ponds and Waterfalls

Few gardens are blessed with natural waterfalls, although some with natural streams have what amount to small rapids. These are best left undisturbed, especially if well worn by the water and coated with algae.

In most cases, a waterfall must be constructed, but this must be done with care and sympathy for its surroundings. It is not aesthetically desirable simply to create a mound of rocks or soil to provide sufficient height for a cascade; a waterfall must flow naturally from adjacent garden and landscape features if it is to be completely effective.

A Suitable Backdrop

The normal method of integrating a waterfall is by building a rock garden as a backdrop to the pool. When done tastefully, this can be very successful, but it must be a true rock garden, not a heap of rocks with stones protruding from it. If you intend constructing this type of feature, do not use the spoil from the pool’s excavation for the mound, as this subsoil will not be suitable for growing alpine plants. The structure of a rock garden should be formed by placing the rocks carefully in layers so that they look like natural rocky outcrops. You will then need to backfill them with a suitable free-draining growing medium.

Of course, the soil removed from the main excavation can be used to support a waterfall if the backdrop is not to be a rock garden. A planted mound can be quite effective if the soil is contoured in such a way that the mound appears to grow out of the ground, rather than being placed upon it. This is not always easy to achieve by soil profiling alone; often, thoughtful planting to obscure or enhance views is the most effective way of coping with the problem.

Provided a waterfall is considered during the planning and construction stages of a pool, there should be no undue difficulty in fitting it into the garden landscape. Only when the water garden already exists, and the feature is considered as an addition, will any significant difficulties arise.

A Lined Cascade

While pre-formed waterfall units are doubtless the easiest and most secure method of construction, they can be inflexible and difficult to integrate naturally into the garden landscape. Heavy planting and liberal use of rocks is the only way to disguise them. If you want to have an unobstructed view of water movement, or to create a completely natural effect, you will need to consider alternative forms of construction.

Using a pool liner to create a waterfall or cascade provides great opportunities for the skilled designer, for it is possible to produce all manner of tumbling and splashing effects by careful manipulation of the structure. In some cases, the liner may simply be concealed with a layer of pebbles, but using it as a waterproof barrier behind an arrangement of rocks and gravel is preferable. With careful construction, there need be no visual evidence of the liner at all.

Digging Out

The excavation for a lined waterfall should begin adjacent to the garden pond or pool. If the finished feature is to comprise the liner alone, perhaps covered with a layer of washed pebbles and a rock edging, it is important to dig out the soil to the final shape, but with an allowance for a bedding layer of sand. As far as possible, the excavation must be cut from compacted soil; a little slippage is not as critical with a lined waterfall as with a pre-formed unit, but it can destroy the entire effect and make reconstruction necessary. If the falls will be of rock with the liner forming a waterproof barrier behind, provision must be made when digging to accommodate the rocks, though of course adjustments can be made in the excavation as the rocks are installed.

One of the most critical points to remember is that each area at the base of a drop must tilt backwards. Water should be able to cascade into it, then by sheer volume overflow into the next section. If the base of a fall is flat, or slopes forward, it will dry out when the pump is switched off.

The edge of a fall can also be designed to provide interesting water movements, A continual curtain of water will result from a uniform edge, but violent tumbles can be arranged by pinching the water and forcing it through narrow gaps. This can be achieved with a plain liner, but it rarely looks natural. Placing suitable rocks along the edge of the drop, in a manner that gives the desired water effect, will look much better and be easier to arrange.

Adding the Liner

As with lining a pool, remove any sharp objects from the excavation and spread a layer of sand over the base and sides to cushion the liner. (Fleece and similar materials are difficult to install without creating lumps and creases.)

Ideally, a single sheet of liner should be used, but in many cases this will be impractical. Where two or more pieces are necessary, work from the pool upwards and ensure that each has a generous overlap in the direction of water flow. If there are any awkward corners in the shape of the waterfall, make bold folds and pleats, rather than trying to spread the irregularities, which will only introduce unsightly wrinkles The edge of the liner must be buried or covered with stone, but make sure it is above the highest intended water level of the waterfall, otherwise extensive seepage will occur into the surrounding soil.

Making a Lined Garden Waterfall

1. Excavate the shape of the garden waterfall feature, ensuring that the back part of each bowl is deeper than the front so that when the pump is switched of some still water remains for pleasing effect.
2. Line carefully with pool liner, ensuring a generous overlap where necessary. Smooth out the liner so that any folds are large and deliberate. These will be much easier to disguise.
3. Trim back the surplus liner and place rocks in position to hide the edge. For the best effect, the rocks should be from the same source so that they are of similar colour and strata.