How to Build Subtle Streams

SUBTLE STREAMS WITH LINERS

If you think that to create a stream all you need to do is cut a sloping trench in the ground and line it with butyl or PVC and disguise it with a few stones or pebbles, then read on.  What you would have reinvented is the ditch, or with pebbles in it - a ‘French Drain’.  These are engineered devices to shift as much water as quickly as possible from an area that needs draining to an area where it can be dispersed. Here function rules over aesthetics, we want the reverse.

TIPS FROM YER MAN UPSTAIRS

A stream has a timeless quality that makes you feel as though it has always been there. In fact it is ever changing with the seasons and the years and in that time it would have etched itself into the landscape, deeper and deeper.Janet's Foss up in near Wendsleydale in North Yorkshire: An oasis of natural serenity amongst the harshness of a predominantly rocky landscape. So even if the simplest concrete or plastic performed stream unit is set down in a valley or a cleft it would instantly look right.
Streams always lead to somewhere, preferably from somewhere. Where they go to and when they arrive there is usually something of a visual treat. Where your stream emerges into your pool, it should widen out and enter with a flourish that is a fitting focal point for the whole of your water garden.

PLANTS AND STREAMS

The stream the wends its way round Dunster: Note the natural beaches.In nature, we see streams that have evolved from vast, unbridgeable valley wide rivers, to quiet wending backwaters cut into a rich sediment deposited from a former majesty. The surrounding undergrowth is lush, and if not food for grazing animals, hides a treasured atmosphere of blissful calm. So plant up your stream edges, paying as much attention to them as you would the marginal zones in the pool. There is a whole host of plants adapted to stream sides designed even enjoy the occasional flood like Iris ensata, Saponaria ocymoides and Veronica beccabunga to name only three.
Plant up the stream itself too. This is an ideal opportunity to do a little bit of extra biological filtration and oxygenation. Grasses like Acorus gramineus and Carex Bowles Golden always look happier out of the flow, but oxygenators like  Ranunculus aquaticus, Crowfoot – the true water buttercup, and Potamogeton crispa with its ruddy crinkled leaves, waft and sway dramatically, adding extra movement to the action of the water.

THE COURSE OF A STREAM

If the stream had just sprung up the day before, water being the stuff that it is, it will find the course of least resistance. Every now and then an obstruction would hold it back, the water would back up behind, widening and Random stones break up the flow and hold it back to a certain extent: As the water races over the boulders, it speeds up and churns about making white water and noise.deepening in the process until the obstruction was surmounted or breached. Either way, there would remain an area where the water was deeper wider and slower. After this it would probably speed up and perhaps become more shallow, making a noise as it rattles over the stream bed and pebbles, which accumulate in swathes creating beaches on the curves.

DREAMS LIMITED BY REALITY AND OTHER THINGS TO BEAR IN MIND

As usual the main limitation to the possibilities is cost, in the cost of the liner, the stone, the pump and the installation of the power to the pump. But if you already have a pool into which the stream is proposed to flow, there is also the limitation in the volume of water the pool can provide to keep the stream flowing without detrimental water loss in the pool. So there is a feasible limit to how big the stream could be for any particular pool, but apart from that, long streams give rise to a radical increase in the evaporation of the water from the stonework. In shallow streams the water readily heats up and combined with the lime content from cement work makes the whole system very prone to blanket weed.
However, assuming our ambitions have not gone beyond the realms of practicality we will continue to develop the theory and the method.

‘CONTROL’ IS THE KEY, AND THIS IS WHERE I CALL IN THE POLICE

If you have decided to line your stream with a flexible liner, it is ‘sleeping policemen’ that you need to employ. Yes, you know the things I am on about. They use them to slow traffic down in urban areas - big humps of tarmac or rubber lying across the road. But in your case, they are risers of brick or concrete right across the width of the stream, under the rubber liner to slow the water down. You need to slow it down so that you can widen it or stretch the water out sideways; otherwise it sticks to the middle and scoots along at high speed under the gravel and stone in the base of the stream.

HOW DO YOU DO IT?

A good level, preferably a Cowley level at least is essential. For large project it is best to drive in pegs that mark the rise and the course of the stream. These should be in pairs level with each other marking the height of the concrete block skeleton at the point that they are laid.

Excavating a stream

Laying the blockwork

Stream in side view elevation

The principles for stream construction are the same as waterfalls but the effect is different.
So start from the pool end working up stream to a level header pool area at the top.     
A low brick ridge is the outlet into your stream. This is a channel (of concrete blocks if the soil is loose or soft) cut down into the contour of the ground running down to the pool, very gently winding if you want. As the ground rises, lay a fillet of concrete or row of bricks at regular intervals. These intervals are governed by the fall of the ground, which should have an absolute minimum fall of 1 in 80.  If the fall was 1 inch in 80 inches and we were using 4inch(10cm) bricks to create our humps, then we would need a hump within every 320ins(4 x 80ins) or 8mtres (10 x 80cm). The idea is to create a shallow pool that runs from the top of the obstacle back to the base of the next obstacle upstream. The stone, gravel and even a clay base can sit in this static water as visible surface water flows over it. Working up from the bottom, take a level from the top surface of the lower hump to the point that it is level with it up stream. The next hump must be laid before this point, but not too much before. In this way you are making static pools of water over which a visible moving sheet of water flows.
If the humps are laid on top of the liner they lose their effectiveness over time and the water that should be contained within the stream when the system was not running would all seep back down into the pool.
Lay in underlay and then the liner. Each section of stream can be protected with more underlay, but remember, dont make it continuous because of the wick effect.  Gravel or fine round pebbles makes a handy cushion and backfill for the bigger stone to come.

Use rockery stone or large pebbles or boulders to bring in the sides, constrict the flow and make it deeper. If pebbles are a dominant feature, try to use a variety of sizes. You can get river washed pebbles that come in the perfect An eighteenth century built stream in the landscape garden of Hestercombe.: This stream had small stones cemented into place so that they poked up from the surface making the thin sheet of water trill with glisten.mix. Medium sized pebbles can be laid in a swathe as though they have been washed up to a particular level in a violent flood.   Rocks are used to bash the flowing water from left to right against stone facing the inside of the liner. Large stones in the flow curl the water around and in groups can create 'white water rapid' effects even in the most sedate flow. Most of this can be placed in position and backfilled with smooth gravel except at the high points of the 'sleeping policemen' or where an awkward shape needs to neatly seal with the side, here a backfill of cement will be necessary.

It is probably better to constrict the flow at the high spots working upwards and outwards from a low sill area. A little trial and error is sometimes necessary. Keep a stone hammer handy to adjust the shape of almost perfect stones that may just need a little nibble here and there to get them into place or to sit right.

Alternatively you may wish to spread the flow over a rise, splitting it and breaking it up into ribbons of flow, but essentially it is still a constriction of the flow behind which water gathers, widens and deepens.

After a constriction you can make it wider and shallower and with the right size pebbles in the base you can create patterns on the surface and a proper 'babbling' brook.

FOR PUDDLED CLAY STREAMS: there must be a heavy stone or concrete foundation extending out on the ‘fall’ side of what effectively is a weir. It must be twice the height of the ‘fall’ to stand up to the effect of the turbulence caused by the obstruction.

Big stream, big digger, but levels are still important.

Creating weirs built into the stream.: Because of the fall of this stream it was expected that the waterfalls would not entirely disappear. Where there is a waterfall, a hard based need to be built on the fall side at least three times the height of the waterfall, to prevent turbulent erosion.

Protecting the bank.: Where there is any turbulence in a puddled stream like this, the bank and base needed to be protected with a layer of heavy stone, ideally cemented into place.

These stepping stones not only aid access to the other side, they work partly as a weir.

REALLY BIG WATERFALLS AND STREAMS

You may have stood and stared in stunned admiration at the big rockbank displays at the Chelsea and Tatton Park Flower Shows wondering how those guys shift those enormous boulders into place and make them a part of suchDougie Knight was the big rock man in the heyday of the Chelsea Flower Show "Rock Bank" natural looking landscapes. It looks like magic. The truth is there is an element of a slight of hand since the project is done slightly backwards. When the digger comes in for the major excavation, its other important task is to move the really big main stones into place using chains attached to the bucket arm. These are not generally part of the face of the pool itself. They are moved in later.  The chains sometimes have a simple pincer device that grips all the more fiercely the heavier the weight it is lifting.

All the levels are done by eye, and the placing of the stones and as to what looks right, is just a matter of experience. Ledges are created for smaller stones (only relatively, they are still huge) that face the scene later. Then in comes the concrete (usually fibre reinforced) that is laid thickly through the waterfall and stream. This is effectively the integral stream and waterfall liner. Stone is placed on top of this and in front on the face of the stream. Facing stone is backfilled with concrete, but there is a great deal of effort made to completely obscure the concrete. 

See how we did it in the Caribbean. Coming soon.