Practical Drainage

After what has been the wettest autumn and winter in living memory, many Course Managers/Head Greenkeepers are trying to organise drainage contractors to carry out drainage work on their courses, but if they have not scheduled the desired work by now it may be too late to undertake it this year without it disrupting the summer playing season.

This year the golf course drainage industry is in chaos because all the courses that had work scheduled for last autumn have been caught out by the weather and as a result the contractor has had to raise his prices, a further season has been missed and much revenue has been lost. This seems a very high price to pay for insisting that the work is undertaken in September or October.

As a drainage consultant I feel very strongly about this for it is my opinion that the autumn and winter periods should be used for assessing and planning drainage schemes and NOT installing them. Undertaking course drainage work during unsuitable weather conditions creates a terrible mess, which in itself will negate the effect of any new drainage for up to a further two years.

Beware of unscrupulous contractors, who tend to design drainage schemes to suit their own machinery and not the area of land to be drained. These contractors usually suggest laying drains 450mm deep at 5m centres and refer to the golf course as the ‘sports turf situation’. Although it is sports turf that they are expecting to work on, in almost all cases they are working in virgin ground and it should be drained as such – not as a football pitch on a cut and fill site.

When assessing the drainage requirements of a golf course, I try to picture the land as it was before the golf course was built, with many hedgerows or stone walls. Hedgerows were usually planted to define distinct sub-soil changes, on one side the farmer could cultivate and sow what was lighter land than on the other, which was much heavier. These observations are very important because the lighter land, i.e. sand and gravel, will require draining at a greater depth than the clay land.

Heavy clay sub-soil is the easiest land to drain because the sub-soil water is more uniform, being held in the many fissures in the clay. It is also a common mistaken belief that there is no water table in heavy clay land. The water does not move through clay as quickly as through sand and gravel or indeed silty sub-soils but move it does and the water table needs to be kept at least 750 mm from the surface to create a well drained course. If a golf course with a clay sub-soil has been waterlogged for many years, the fissures in the clay will have become sealed and the sub-soil will have lost its structure. Under these circumstances, after the drainage pipes have been laid at the required depth, a secondary treatment, ie mole draining, becomes of paramount importance in order to restore the structure that is so important in a clay sub-soil.

If the areas of the course which are built on clay are fairly flat with up to 2% fall on the land, it is suggested that a system of lateral drains should be laid 800 – 850mm deep at 15m centres, followed by mole draining 450mm deep at 2m centres at right angles to the pipe drains. The pipes should always be laid across the steepest fall in order to get the maximum interception of sub-soil water movement. Thus, the mole drains will be laid up the steepest fall, which means that they will empty quicker and last a lot longer. If the falls are particularly steep the depth and width of the drains will have to vary accordingly.

There is another good reason for laying new drains at the depths given above which is to intercept the old tiles systems that could have been laid up to 150 years earlier. If these old drains are not intercepted they will cause trouble on the surface for years to come, as they start to break down.

The depth of the drains is more crucial on lighter soils and more preparatory work must be carried out before designing the drainage scheme. Initially it is necessary to consider why an area of mainly light soil is so wet. Is it overlying clay? Is it an area surrounded by clay or is it an area where sub-soil strata change? To answer these questions will mean either excavating many trial holes or, as is more suitable on existing course, taking many auger borings down to a minimum depth of 1m. It does not matter how many drains are laid, they will not work efficiently without both the surface being looked after properly with the grass roots being encouraged to penetrate ever deeper and all outfalls being regularly maintained.

A cautionary note to the Chairmen of Green. It is always a temptation to get the green staff laying drains during the winter, but this is a false economy for with today’s modern machinery and technology drainage work can now be carried out much quicker and more efficiently – a Head Greenkeeper has enough to do in the winter anyway.