Installing a Pre-Formed Stream

Another option for creating an artificial stream is to use preformed stream units. These are similar to waterfall and cascade units and can be linked together in various configurations to suit your particular needs. As with pre-formed waterfalls and cascades, careful thought must be given to their positioning, as they are not easy to disguise or make appear natural. However, if correctly installed, they will be completely watertight.

CREATING A LAYOUT

Before marking out the position of the stream, lay out the units to achieve the desired effect. A stream should start somewhere logical, and not race and cascade down the garden. It will be most effective if it appears to start as a bubbling spring, an effect that is quite easily contrived.

Use a container such as an old plastic dustbin, sinking it into the ground and disguising it with rocks and plants; this will form the head of the stream. The hose from the pump can be led into the container, which should be filled with large stones. The water should be allowed to bubble through these as if from an underground spring. Alternatively, construct a header pool at the top of the stream, into which the pump outlet can be discreetly placed. The hose can be concealed among surrounding plants and rocks.

The only problem that arises with such an arrangement occurs when the head of the stream is a long distance from the pump. In that case, a powerful surface pump and permanent piping must be installed, for a stream will logically be recirculated from a pool in most domestic gardens. If you wish to employ a standard submersible pump, try to arrange for the head of the stream to be within easy reach of the pool. This may not look convincing if both can be seen from the same point, so shrubby planting may be necessary to separate the features. When a rock garden abuts the pool, the header may be simply arranged at the rear and form an integral part of that aspect of the rock garden. Of course, there is no reason why a stream cannot begin with a cascade, the water tumbling down another face of the rocky outcrop.

DIGGING OUT

Having decided upon the precise position of the stream, mark out its run by driving pegs into the ground. Then excavate the entire stream bed, allowing for a fall towards the pump. Make provision for any pools and similar features at the same time. Ensure that the excavation is level from side to side by placing pegs at appropriate intervals and levelling them with the aid of a short board on edge and a spirit level. The excavation should be about 15cm (6in) longer and wider than the finished units, and 7.5cm (3in) deeper. This allows for the bedding layer of sand and for any necessary adjustments during installation.

ACHIEVING THE CORRECT GRADIENT

For the best effect, a stream should be laid to a gradient of between 10 and 30 degrees. You can allow the water to run directly from the stream head to the pool, or slow its progress by running it through a series of shallow waterfalls and small pools. In such cases, the sections of stream between the pools must be almost flat so that the water flows smoothly. If you want to make the flow of water appear to speed up in places, position rocks in the stream to narrow it once construction has been completed.

When marking out the run of the stream with pegs, in the first instance, knock them in so that all their tops are level, checking this with the aid of a wooden board placed on edge and a spirit level. This will give you a clear indication of the existing soil levels. Each successive peg should then be knocked down to provide the desired angle of fall. A simple wooden set square can be tacked together to give the angle and will ensure accuracy.

Once the pegs are at the correct depth, the areas where soil needs removing or adding will become obvious, the aim being to have each peg protrude by an equal amount above the soil. Making these adjustments to the lie of the land will simplify the process of excavation for the stream itself.

INSTALLING STREAM UNITS

A stream should he constructed from the pool backwards. Do not start with the header in the hope that the last unit will meet the pool neatly and at the correct angle. However accurate you may be with a tape measure and spirit level, it is unlikely that everything will fit together satisfactorily.

Remove stones and roots from the excavated stream bed and spread a generous layer of builders’. sand evenly over the floor and sides. If damp, this will mould easily to the shape of the excavation. When using more than one unit, take care to ensure watertight overlaps. Check units are level from side to side and firmly bedded, then fill in around them with soil.

The edges of most pre-formed stream units are rather ugly, so great care will be necessary in disguising them with rocks and plants. The bed of the stream can also look stark, hut can be effectively transformed if liberally covered with a layer of washed stones. There is no need for any of the plastic or fibreglass to he exposed.

USING SECTIONAL UNITS

Some pre-formed stream units are sectional in nature, rather than being prefabricated in specific shapes. Like sectional pools, these connect together and are made watertight with a sealant. Sectional stream units come with special height adjustment panels that are invaluable when dealing with a sloping site. These ensure that the water level is maintained in each stream component, even when the pump is switched off. The other main advantage of using sectional stream units is that they make it easy to create more natural-looking sweeping arcs and curves.

INSTALLING PRE-FORMED STREAM UNITS

1. Measure out the dimensions of the stream using a series of pegs and excavate carefully. The excavation should be 15cm (6in) longer and 7.5cm (3in) deeper than the finished unit.

2. Ensure that the stream is level from side to side and the bottom has a gentle slope. If care is taken at this time to ensure the correct configuration of excavation, installation will be simplified.

3. Line the excavation with builder’.s sand as bedding so that the stream sections will rest in neatly. Some stream units come with special height adjustment panels.

4. Position the sections carefully, ensuring that each side is level and firmly embedded in the sand base. It may take several attempts to position them correctly.

5. Disguise the edges with stones and cover the stream bed with decorative pebbles. Cement edging stones in place for extra security, especially if they are intended to retain a bed or border.

6. Finish by planting the streamside with decorative moisture-loving plants. Remember that the stream is waterproof and will not supply dampness to the surrounding soil.