Drainage can be described as either the artificial or natural removal of surface water and sub-surface water from any given area. Some examples of areas that require drainage to function are agricultural soils, where crops have to be kept at the correct moisture level to improve production or to manage water supplies.
The earliest history of an advanced drainage system comes from around 3000 BC where the Indus Valley Civilisation (from what is now known as Pakistan). They created both a sewerage and drainage system that were developed and used throughout the civilisation and proved to be far more effective than any other system found in Middle-East or even some modern areas of surburbian Indian or Pakistan today. All houses in the major cities had access to both water, and drainage facilities and waste water was redirected to covoered drains that lined major streets.
Why use artificial drainage?Depending on the land used for farming, certain areas are unable to maintian crop yields in their current state. Particularly in wetlands, drainage is used to remove as much of the surface, and sub0surface water as possible so that crops do not drown. In the northern USA and Europe, glaciation created numerous small lakes which gradually filled with humus to make marshes. Some of these were drained using open ditches and trenches to make mucklands, which are primarily used for high value crops such as vegetables.
Coastal plains and river deltas may have seasonally or permanently high water tables, yet contain very rich and fertile soils. In order to be able to use these areas affectively for crop cultivation they must have drainage improvements.
In the garden and patio areas of your house, drainage can be the vital key to not getting problems with damp. Because of the fact that solid surfaces, such as driveways and patios are made of non-porous materials and are mostly impermeable, water is unable to pass through them, which can lead to two possible outcomes. Surface runoff is where the water finds a natural channel on the surface of the drive or patio and finds it's way to the lowest area. The other outcome is that puddles will be created on the surface that can lead to moss and other moisture-liking fungus to grow.
The best way to avoid this scenario whilst building your drive or patio is to create a slight slope where the water can runoff, essentially creating your very own surface runoff channels, which don't need to be at a great slope and should be guided away from any buildings, or property as it would be likely to cause damp.