Components of a drainage scheme function and installation
2.1 Field drainage
2.1.1Peripheral, cut-off or interception drainage
It is important to ensure that the field to be drained is protected against the influx of water from surrounding land. Within-field drainage then needs to be designed to cope only with the excess rain falling onto the field itself. In some cases it may be found that a good system of perimeter drainage will obviate the need for anything more.
If there is the slightest risk of extraneous water reaching the area to be drained, either on the surface or below ground, its interception must be assured by the installation ...