Fencing waterway margins is an important step in protecting freshwater from nutrients, faecal matter and sediment.
A guide from DairyNZIt creates a buffer between water and the land. Fencing riparian zones will create a habitat for birds and freshwater species and will also help maintain and improve water quality.
Under the Sustainable Dairying Water Accord:
- All stock must be excluded from any permanently flowing rivers, streams, drains and springs, more than a metre wide and 30cm deep by May 2017
- All lakes must have all stock permanently excluded by May 2017
- Any significant wetlands, as identified in your regional plan or policy statement must also have stock permanently excluded by May 2017. Check with your dairy company to see if you have one on your property.
This means that the fencing of waterways should be a priority on your farm.
Consider the overall layout of your farm when planning for waterway fences. Along with protecting waterways, new fencing could improve grazing management and stock control1. The setback for your fence will depend on how you are going to manage the area between the fence and the stream. Do you want to maintain it as a grassy strip to filter nutrients and sediment from runoff or do you want to plant it with trees?
What is your waterway like?
Surrounded by rolling land/ flat land
Fence set back needs to allow for a grass margin and changes in stream shape and size. If you are planting natives you will need a margin of five metres, this will allow for a one metre strip of grass and two to three rows of native plants.
Surrounded by steep land
Steep areas generate fast runoff and the margin required to capture it will be wider than that used for rolling or flat land. Allow for a grass strip on the fence side of the riparian zone. If you are planting natives you will need a margin of five metres, this will allow for a one metre strip of grass and two to three rows of native plants. The larger the riparian zone, the more likely that runoff will be captured before it reaches the stream.
Erosion prone banks
Fences will need to be set back further on erosion prone banks. Allow for some erosion and changes in stream meander, particularly on the outside of bends. Erosion is a natural process and in some areas will be hard to stop or slow without appropriate planting or structures. Your regional council will be able to give you ideas and advice on how to fix it.
Consider how far the stream moves during large storm or erosion events and how many events occur yearly. Vegetation will not protect the stream straight away so fence back far enough to allow for three years of erosion. For more information on erosion management see Waterway Technote: Erosion.
Surrounded by poorly drained soils
Poorly drained soils require a wide setback. Water does not easily infiltrate the soil resulting in overland flow directly into waterways. Wetlands can be used to remove nutrients and sediment, so try to fence these off also. Dense riparian plantings will slow flow and also act as a filter before runoff enters the waterway. Your setback should allow for several rows of trees and a grassy margin.
Surrounded by free draining soils
Free draining soils will require a riparian area large enough to accommodate deep rooted plants. In well-drained soils water will easily move through the soil into groundwater and then potentially into surface water. Roots of riparian plants help to filter this, removing nutrients and other contaminants. Plants with strong roots will also help to stabilise banks and prevent erosion.
Weed growth can be a problem in fenced grass margins if not managed early on. For information on identifying and controlling specific types of weeds see Waterway Technote: Pests.
Type of fence
Investment in a robust, stock proof, good quality fence provides the best waterway protection and minimises maintenance issues long term. Ensure your fence is suitable for all classes of stock that will be near waterways.
Different milk suppliers have different minimum requirements around fencing so it is best to check with your milk supplier before finalising your choice of fence. Waterways that are required to be fenced due to a resource consent condition may have specific fencing requirements and fence setbacks. Ensure you comply with any regional council requirements.
Funding may be available from regional councils or QEII Trust. Usually it is for fencing above the minimum standard, for example fencing an environmentally significant waterway or wetland. In these circumstances, specific fencing standards may apply. For further information on fencing design and what materials to use see openspace.org.nz.
Fencing in flood prone areas
These areas may need a wider set back than other areas, to ensure that the fence is not subjected to high velocity flows. Where possible erect fences above any flood prone areas or leave a good setback from the waterway. This is particularly important on the outside of bends of rivers and streams where there is greatest potential for banks to break and erosion to occur. Think about what the stream does in regular high flow events before fencing.
Download the full guide from DairyNZ.