Solve garden drainage problems

Article Gallery: 

On clay and water retentive soils, the flow of water slows down causing drainage problems.
On new housing estates, subsoil and topsoil is often mixed due to foundation excavation and other construction works. Add this to soil compaction by the builder’s trucks and you end with a heavy compacted, wet soil with almost no drainage at all.
 
For shallow water table lands, solutions are scarce, because after a heavy rain the water table may rise to the surface of the land.
On lands with drainage problems patches of water will appear on the surface after the rain, as the most common cause of the problem.
 
How to check your garden drainage:
Make a square hole about 24 inch deep and 12 inch wide, then fill it half full with water.
Leave it for 24 hours. On a well-drained soil it should empty, but on a wet soil, it may actually fill.
 
Possible solutions:
If the topsoil is very water retentive but fertile, you can double-dig it incorporating large amounts of bulky organic materials. If the soil is heavy and waterlogged, drainage will be necessary.
There are several different types of drainage (ditches filled with gravel, clay or plastic pipes).
 
Whatever method you’ll choose, an underground network (soak away) must be made, heading to a large hole (collector ditch) located in the lowest point of your garden.
The excess water will be guided through this network to the collector ditch. In this way you will also keep the water on your property.
 
The main ditch must be at least 6 feet deep and the same across in order to be effective. Fill it with large rocks at the bottom, then smaller rocks and then gravel. Finally, you should lay about 15 inches of fertile soil on top of it.
 
Drainage ditches must be 3 to 5 feet deep. If you don’t use drainage pipe, just fill the ditch with gravel, then 10 inches of topsoil above.
When using plastic pipes they must be placed with the holes down to prevent clogging, sloping toward the main ditch. Fill the ditch around the pipes with gravel and then topsoil.