Given the significant cost of installing a new field drainage system, cleaning ditches and clearing outfalls is a simple, cheap and effective method of improving the effective method of improving the effectiveness of existing systems.
- Most common cause of drainage system deterioration is failure to keep outfalls clear
- Mole drains are unlined channels formed in clay subsoil
- Mole drains are not suitable for controlling rising groundwater or areas prone to flooding
Clay gives the soil the ability to hold together and reduces the chances of the channel collapsing after the mole is pulled.
Longevity of the mole depends on:
- Soil texture
- Soil calcium – high levels of calcium will increase longevity
- Climate – wetter conditions reduce longevity
- Slope – too shallow or too steep will reduce longevity
- Moisture conditions in which the moles were formed
To find out more have a look at the ADDB Field Drainage Guide which looks at the principles, installation and maintenance issues.