Drainage based on knowledge and experience
Drainage of agricultural land has been and will always remain an important factor when Dutch soil is used for the production of food. Over time many improvements have taken place in drainage machinery and materials. A solid foundation is formed by the knowledge and expertise which has been gained by experience over many years. Drainage companies always aim for improvement, plead their causes and seek to improve their own knowledge and expertise. The Vereniging voor Nederlandse Drainagebedrijven – Association of Dutch Drainage Companies – for which the basis was created 40 years ago, exists to facilitate all this.
Ever since our country was formed we have been battling against the water. Our ancestors struggled and we are still doing so. It was always about preventing the sea from flooding inland and about safe living conditions. We even created land from the sea to have more living space and agricultural land. We not only like to live safely but would also like to keep our feet dry. Water in the streets and gardens is considered undesirable.
People involved with agriculture know as no other how much trouble water can cause. Windmills and pumping stations keep the polders dry. After World War II there was a great need for sufficient food and the development of agriculture was one of the main targets of the Dutch government. The flooding of the province of Zeeland in 1953 was an extra incentive for further improvements.
Redistribution of land took place resulting in a significant improvement in the production capacity of the agricultural land. Drainage played an important part in this. Even now the export of agricultural produce is one of the most important cornerstones of the Dutch economy. Luckily there is no shortage of food in The Netherlands but in the rest of the world there are still big shortages on a regular basis.
The Vereniging voor Nederlandse Drainagebedrijven (VND)
If everyone were to develop machinery and to lay pipes in the ground according to their own opinions, this will not result in optimal quality. Certainly, when the costs for installation are taken into account. Drainage pipes with casing materials were developed, the agricultural sector drew up its’ requirements and researchers created calculations to facilitate the installation of good drainage systems. Various theories were developed about the construction and maintenance of drainage. On this subject the Netherlands caught the attention of the world.
Forty years ago, it was decided to centralize knowledge about drainage and to start an association, the Vereniging voor Nederlandse Drainagebedrijven. Over the years, the association has become a discussion partner for the government, as well as for the parties involved in dispensing subsidies for drainage work. The VND gained in importance when the IJsselmeerpolders were constructed. Nowadays the VND is the spokesperson for drainage companies in the Netherlands. The VND is also a member of committees of the KIWA, the independent certification body. The quality of pipes, casing materials, accessories and the installation itself is guaranteed by BRL’s (Beoordelings Richtlijnen) - evaluation guidelines.
The international community is aware of the current developments. The association is heavily involved in technical developments in the area of drainage techniques and in the area of soil science.
A comprehensive scope;
The association comprises members with backgrounds in all aspects of drainage:
• companies involved with the installation of drainage;
• manufacturers of drainage machinery;
• manufacturers of pipes;
• manufacturers of casing;
• manufacturers of accessories;
• manufacturers of drainage maintenance machinery;
• maintenance companies;
Thanks to this comprehensive representation, the VND has a special position within the drainage sector. Being a member of the VND has additional value because the members are up to date with the latest developments and they exchange their experiences.
When interest is shown from abroad for the knowledge and developments in the drainage field, the VND is the organization to whom people turn.
What is Drainage?
In the Netherlands drainage means a system whereby groundwater is drained away through perforated pipes. These pipes will usually have a casing.
A well-constructed drainage system will:
• drain away surplus groundwater;
• keep the soil in better condition and the soil will be less sensitive for compaction;
• ensure that the soil warms up earlier in the spring;
• increase the production capacity;
• increase the likelihood of a better harvest.
When is drainage required?
Each installation has its own requirements and therefore needs specific expertise.
The agricultural sector in the Netherlands is a major user of drainage systems. Greater demands on the soil and more intensive rainfall means that drainage systems are needed in large parts of the Netherlands.
The general public do not want water under their houses and it is required that puddles on lawns, on streets and in playgrounds should be drained away as soon as possible.
Drainage is also used along roads and on building sites. Deep drainage is advantageous during the construction of aqueducts, tunnels, parking garages and other excavation works. Drainage is also important to speed up the settling of the ground during the construction of roads and industrial areas. Laying cables and pipes will be much simpler if no groundwater is present when the work is carried out.
How to install a drainage system
Firstly, the expected usage of the land must be understood as agricultural use, sports fields and riding schools all have their own demands.
• the usage of the land and how quickly the water should be drained away;
• the position of the outlet and the ditch water level;
• the soil make up and structure;
• the permeability of the soil, in both horizontal and vertical directions;
• the lengths of the field drains in relation to the allowance for rising groundwater;
• the prevention of iron sediment.
Based on the principles outlined above, a plan is made including:
• pipe diameter;
• the sort of casing material to be used;
• the depth of the field drains and distance between the field drains;
• the direction of the field drains and their lengths;
• choice of outlet;
• costs and the timing of the installation.
Is drainage maintenance necessary?
Well-constructed field drains can operate for many years. During the first two years following installation while the soil is stabilizing. there is a chance of in-washing of soil particles. If, approximately two years after construction a random selection of field drains are flushed with a jetter, possible problems can be tracked down. Where the soil and seepage water is rich in iron, it might be necessary to flush the field drains on a regular basis. The best check is to compare and measure the drainage during periods with a lot of rain. If in doubt about the effectiveness of the drainage, it may be necessary to flush the field drains again. There are various methods to determine this. Special equipment exists to detect blockages.
A drainage system is meant to last many years, so choosing the right system is essential for its success.
- There are a multitude of possibilities regarding materials; choose the best materials depending upon diameter and filter.
- Ensure that the depth at which the drainage system can be installed is known when making the plan.
- When the field drains are laid, the soil will be disturbed. If the soil is saturated with water, this can increase the deterioration of the soil structure around the field drain. Install the field drains when the level of groundwater is as low as possible.
- Take care that the field drain outlets are visible – and will remain so - this is important for checks and for maintenance.
- Use approved materials and well-established companies to install the drainage system.