Water supply or drainage can be provided by open ditches or pipes. They can be classified as shown, according to their function:
Where ditches or pipes function to carry or store water, rather than to collect or disperse water, sluices or valves may need to be installed to regulate flow and water levels (Chapter 13 – Dams, weirs and sluices).
Supply and drainage lines should be straight wherever possible, with changes of direction made by smooth curves rather than abrupt angles. This is especially important at junctions, to help maintain a smooth flow of water, which reduces damage and erosion within the system.
Drain types
French drains
French drains are trenches filled with rubble which allow water to percolate through. They can collect or intercept water from the surrounding soil, and then drain it away. French drains are used on steep slopes or other situations where an open trench would quickly erode, or where an open trench may present a hazard or an obstruction. French drains do not function well in peaty soils, as the rubble becomes blocked with fine sediments. French drains can also be used to disperse water, allowing it to soak away into the surrounding soil.
Clean quarry scalpings or locally-gathered scree material is ideal. In very soft conditions or in peaty soils, the trench can be lined with a geotextile which filters out any fine sediments, and prevents the scalpings sinking into the soil. Terram, Lotrak and other types are suitable. Full details are available from the manufacturers.
Stone and box drains
Stone drains are built by laying four flat stones in a box shape. Stone drains may be found when old drains are being repaired, and it can still be convenient to build them in areas such as North Wales where slate and other flat stones are abundant. The box drain is similar, but made out of wood. Internal dimensions of about 150 x 100mm (6 x 4″) are suitable.
Piped drains
These include tile, plastic, steel and concrete pipes.
Ditches
These are the simplest method of water supply or drainage.
