By Bala Tikkisetty
Current and potential erosion are significant factors for soil sustainability and economic sustainability of our
Erosion is the process whereby the land surface is worn away by the action of water, wind or other geological processes.
The resultant displaced material is known as sediment. Sedimentation is the deposition of this eroded material.
The main factors influencing soil erosion are climate, soil characteristics, topography, ground cover and
Climate affects erosion potential both directly and indirectly. The direct relationship arises from the action of rain –
a driving force of erosion – where raindrops dislodge soil particles and carry them away.
Soil characteristics are important in determining soil erodibility. Good soil structure increases water permeability and
water holding capacity. Soil permeability refers to the ability of the soil to allow air and water to move through the
soil. Soils with a higher permeability produce less run off at a lower rate than soils with low permeability.
When soil surface is compacted or crusted, water tends to run off rather than infiltrate. Erosion potential increases
with increased run off.
Topography is another important characteristic for erosion. Slope length and slope angle are critical factors in erosion
potential because they play a large part in determining the velocity of run off.
Soil erosion can be managed by mechanical and biological methods. Mechanical measures such as terracing, debris dams and
other engineering structures have an immediate effect and operate at maximum efficiency, but their construction and
maintenance costs will be high. Biological methods, such as use of live vegetation established from cuttings, rooted
plants and poles, are relatively cheaper but their immediate effect is smaller. However, once established the vegetation
provides a self-perpetuating and increasingly effective permanent control.
Waikato Regional Council’s catchment management officers are available to provide advice on soil conservation, riparian
management and other good land management practices.
We can also provide you with advice and assistance on planting willow and poplar poles/bare rooted plants, including on
various aspects of planting to ensure the best possible strike and survival rates.
Poplar and willow poles are ideal to plant on erosion-prone hillsides as their extensive root systems bind and hold the
soil in place. Some varieties are also used to provide shelter and windbreaks.
Successful establishment of poles requires careful handling, storage, siting, planting and follow-up management.
When transporting poles, make sure the bark is not bruised or damaged in any way which would allow access to diseases.
When securing loads, use straps or ropes and protective pads, rather than chains.
If planting is to be delayed more than a day after delivery, cut the poles diagonally on the butt end with a sharp axe
or slasher, to give two slicing cuts approximately 15cm long. This will facilitate water uptake. Then place the poles in
clean, well aerated water, or keep moist under a sprinkler, to assist future root and shoot growth, and also increase
survivability. Some varieties are susceptible to over soaking. We can provide advice to ensure correct handling.
The council is organising a field day focusing on “sediment loss mitigation and pole planting” on Thursday 24 October
starting at 9.30am at Sir Don Rowlands Centre, Karāpiro. If you are planning to attend, please let us know.
The farming economy depends on good quality water for stock. Better water quality means healthier animals, and healthier
animals mean higher productivity.