BEGINNER'S GUIDE TO BUILDING STREAMS AND WATERFALLS, PART 5: USING PREFORMED WATERFALL AND STREAM UNITS

INSTALLING PREFORMED WATERFALL AND STREAM UNITS

Preformed waterfall units come in all shapes and sizes. Shop around.These allow you to create a gentle waterfall almost instantly for any distance that you may dare to go or can afford. Although they seem unsympathetic with the environment to begin with, a bit of a roughing up with some emery or sand paper will soon help to 'weather' them in. Milk, honey, cow muck or a concoction of all three sloshed on will speed that up as well.

But talking of the environment, this is where these products really win out against natural stone. When you consider that the stone for even a modest waterfall might come to the best part of a ton in weight, it has to be remembered that some hillside has to be ravaged to obtain that stone. As far as you are concerned there is all that heavy lifting and carting of the materials and then the time consuming cement work. For the owner of a small inaccessible garden, these are things that definitely weigh heavily in the balance for the easier option, especially now these preformed streams and waterfalls look so good.

These displays would look more convincing if they were nestled down into the bank.  The height you can go to above the pond water level is limited only by the power of the pump. Some of the average to smaller plastic and fibreglass units can generally handle only about a 300gallons to 1500litres per hour, so gauge the pump to suit the height of the top unit. The concrete versions can handle a bit more volume.
Some of the modern concrete units like the Rockway designs fit together in an impressive but pre-ordained design. These overcome the main visual letdown of the plastic preformed units and that is the view of the lip from which the water flows. With the plastic units, the temptation is to have the units resting one on top of the other to camouflage it, but this often allows the seepage of water along surfaces by surface tension out of designated stream area. Oasis have been doing something simila, but have also produced this year a stream bed that can be dressed with stone or pebbles of the customers choosing.More about this in the the stream portion of this beginner's guide and also the news section featuring Oasis's new products for 2009.

It is also better to avoid having too great a fall from one unit to another. I would say a fall of 10ins/25cm is a risky maximum. 6ins/15cm is safer.
Choose units of a colour that fit in with the local stone.

Start from the bottom and work up. You must finish at the top with some sort of reservoir or header pool that will even out the flow of water from the pump.

Many of these units are desined to finish almost at waterlevel to ensure that all the water gets delivered there and in retrospect this is perhaps what should have happened here since seepage backwards into the rockery seemed virtually unavoidable otherwise. We live and learn no matter how long we have been playing this game.

A bank predestined for a waterfall: The rockery is already partly in place to hold back the mound at the base to stop it from washing into the pool.

After the shape is roughly excavated, the unit is tried in position.: Then it is bedded don on an inch layer of sand.

This unit in fact needed quite a bit of stone masonry 'adjustment' to get it settle down perfectly level: But a little bit of extra effort at this stage has its dividends and it means there is a good firm level support for the front of the waterfall unit.

Building the sides up with stone and blending the unit into the bank: this is done by backfilling with plenty of top soil behind the stone used to flank the waterfall.

Excavate roughly the shape of the waterfall units into the bank next to the pool. Also dig in the hose from the pump travelling the shortest possible route.
Cutting them down into the bank to give the impression the water has cut its way through over time instantly gives a mountain of extra credibility.
Next, bed the units into an inch of sand within the excavations. To make a slightly more permanent job of it and to prevent the erosion of the sand by rainwater, a shovel of cement powder to every 6 of sand will eventually ‘go off’ to form a hard immovable base.
Rockery stone lends a certain amount of extra support and holds back the soil and bedding from washing into the pool. This is placed in front of and around the top of the unit, blending it into a rockery. Where there is a waterfall face at a certain level, this should be the level from which you create a strata or terrace of stone left and right from the waterfall, coming out initially towards you the viewer, emphasising the cut in effect. Putting pea gravel into the bottom of the units and around the top edge between the units and rocks also helps.

Sand deposited at the top use a bed for the header pool.

Header pool bedded into place.

Disguising the header edge and blending the unit into the bank: By adding stone at the side, back-filling with soil effectively nestles the waterfall into the bank. This watergarden is having a biological filter feeding into the top of the waterfall so that has to be disguised.

From a 'worm's eye view' towards the end of the project you should be looking at a solid wall of stone and waterfall: This will be effective in holding back the runoff from the soil and there should be roomto plant behind the stone to soften it visually.

The pump is hidden under a slab: The hose exits at a place where it can be conveniently hidden by a plant.Eventually it may become as well disguised as theseThe pump hose as it exits the pool to go to the top of the waterfall can be disguised with a well-placed basket of marginal plants. At the outlet into the top waterfall the hose can be disguised with some flat stones placed upright in the unit.
Check whether the outlets from the units are level with a small builder's level. Try to gauge whether there is plenty of leeway around the back edge for holding the water within the unit.
The units should be shedding the flow of water well into the unit or pool below. Run the system as soon as possible to make sure you have got it right, waiting a good 10 minutes or so until the flow has got up its full steam.
If the units are sitting in made up ground from the spoil of the excavation, over time there is a great propensity for this to sink further and the units to tip backwards. So watch out for this in the future.                                

For an impressive rock face without rock, a bespoke crafted display like this by Scenic Blue at the Malvern Flower Show

The Biodynamic Garden by Andy Jones and Amy Konig: These units do magic things to the water that help to keep it clear.