Riparian Management
Riparian management is the term that describes how land users look after the margins of rivers, streams, creeks or drains.
It is a land management tool promoted by Environment Southland, which can help you improve things such as water quality, reduce erosion, silting, weed infestation, and contaminant build up. (please click on the image on the right for a larger view).
So... what are the benefits?
The benefits of Riparian management are as follows:
Water quality
A well-managed riparian margin can filter out contaminants such as soil, cow dung and urine, phosphates and nitrates from organic and inorganic fertilisers, and agricultural chemicals from farm run-off. This will help improve water quality and in turn, stock are likely to benefit from improved animal health.
Erosion control
Stream bank erosion is not only a waste of valuable assets but it also releases sediment and nutrients to waterways. Shrubs and trees which tolerate moist soil conditions and frequent silt deposition are ideal for preventing stream bank erosion. Trees and shrubs physically hold the stream banks together protecting the streambed and limiting the scouring effect of running water.
Reduce flood impact
Riparian vegetation is effective in reducing the severity of flooding by intercepting rainfall and regulating the entry of surface and subsurface flows to waterways.
Reduce water temperature
Tall growing riparian vegetation minimises temperature fluctuations by reducing solar energy input to the waterway. A lack of shading along stream sides increases water temperature, inhibits in-stream biological diversity and contributes to algal blooms, which grow rapidly up to at least 25°c. Temperature can also kill aquatic invertebrates as some are more sensitive than others and change the biodiversity of the stream.
All these effects degrade the recreational and aesthetic appeal of the waterways.
Habitat enhancement
Streamside trees provide cover for spawning fish, and food and habitat for nesting and juvenile birds. Small water plants and invertebrates become numerous, providing a better food supply for fish and waterfowl.
Aesthetic enhancement
Riparian management enhances the aesthetic and amenity values of the waterways, which helps to maintain their recreational potential.
Increased farm production
Diversification of income-generated activities on a farm may be possible by planting timber species within Riparian margin. The provision of shelter and shade is recognised as an important aspect of animal health and production.
Improved product quality
Improved milk grades are documented where dairy sheds no longer draw water from contaminated streams. On sheep and beef properties, stock are in better health and have faster weight gain when water sources are no longer contaminated.
Phytoremediation
Many years of fertilisation with cadmium-rich superphosphate has increased levels of cadmium in New Zealand soils. Recent studies by Hort Research revealed that poplars and willows can be potentially used for the decontamination of soils polluted with cadmium.
Farm management
Fenced waterways aid farm management by facilitating stock movement and decreasing stock losses.
Establishment
There are three basic principles involved in riparian management:
- Fencing the riparian margin
- Establishing appropriate vegetation
- Maintaining the vegetation
Fencing
Retirement and protection of a riparian margin by the establishment of fences is a very important step in the management of riparian areas. Removing stock pressure and access to the waterway immediately removes direct input of nutrients from animal wastes and creates an opportunity for re-growth of riparian vegetation.
The most effective retirement fence is a conventional eight-wire fence, however, in some situations it is not possible or desirable. More flexible and cost effective options such as a five-wire electric fence or even two hot wires may be satisfactory in some situations.
Establishing appropriate vegetation
Plant varieties of trees, shrub or grass that are appropriate for the intended purposes whether it is water quality improvement, erosion control, ecological restoration, or landscape enhancement.
The composition of the vegetation within the riparian margin can be divided into three broad categories (please click on the image on the right for a larger view):
Zone A – Buffer Zone
The Buffer Zone A is the area adjacent to the retirement fence. Use close ground‑covering vegetation such as pasture, which filters nutrients and sediments from surface run-off. For this buffer zone to be effective, a width of one metre or greater will give moderate to good protection on gentle slopes where less surface run-off is generated. In steeper areas, where surface flow can be greater, a strip of at least 2‑5 metres of grassed area can give good protection from sediments and nutrients.
Zone B – Mid Margin Area
Use tall growing tree species in association with pasture to provide shade over the waterway, create bank stability and shelter. There is the possibility that in the future those trees can be used as a timber resource as well as providing suitable ecological conditions for biodiversity.
Zone C – Adjacent to Stream
Use low growing shrubby water tolerant species with thick strong root systems. These species will help prevent bank erosion and not impede water flow.
Maintaining the vegetation
Weed and pest control of the riparian area is essential particularly during the initial stages of vegetation establishment.
Drainage responsibilities
Southland has an extensive land drainage system in place. The drainage system consists of artificial drainage canals and community drains. These drains periodically require maintenance works to be carried out in order to ensure that they perform the function that they were designed for efficiently and effectively.
In the case of community drains, Environment Southland rates specifically for the maintenance of that drain for the benefit of community that contribute to the rate. The efficient cleaning of community drains require access for machine cleaning and occasional erosion control works. In the case of other artificial drainage canals, it is important to ensure that access is maintained to clear any blockages that may adversely affect properties upstream.
Planting within flood alleviation structures, for example, stop banks, has the potential to interfere with designed flood flows or cause damage to the flood alleviation structures. In addition, there is potential for flooding to occur if planting interferes with normal high flows where the river banks are not over toppled. Therefore, trees, fencing or structures are to be placed so that they do not hinder access for machinery to carry out works. If the need to plant within 20 metres of a water body whose catchment extends over 200 hectares, the activity requires approval or Resource consent from Environment Southland.
Catchment approach
Agricultural export industry is coming under increasing pressure from environmentally conscious markets to line up to the "clean and green" image and produce goods in an environmentally sustainable manner.
In future years there is likely to be increased export demand for ‘environmentally friendly’ farm produce. Processing plants are increasingly likely to pay a premium for produce from farms demonstrably managed in a way that doesn’t damage the environment.
You will personally benefit from your own improvements in streamside management, but you may be able to greatly enhance those benefits by getting more people in a catchment to work toward a cleaner river or stream.
If planting, choose tree species carefully. The wrong ones can spread as weeds or collapse and block the channel. Trim trees regularly to prevent them from becoming unstable or growing into the stream channel. Manage grassy margins to ensure they continue to filter silt and nutrients from paddock runoff. Margins may need occasional grazing to stop grass from becoming rank and dying.
Unwanted species such as gorse, broom or invasive weeds on ungrazed banks can seed and spread to nearby paddocks. If you have weed or pest control problems, seek advice from Environment Southland.
There are some more points to remember for keeping our water bodies safe. Where possible discharge drains into silt traps or ponding areas before they empty into streams. Avoid burning vegetation in the riparian margin and construct stream crossings so as to avoid ponding or scouring of the streambed or banks. Land management can be improved by preventing overgrazing and pugging, targeting fertiliser application to avoid spreading any close to the water and timing of fertiliser application to avoid runoff into streams.
Useful factsheets:
For more about poplars and willows in New Zealand and information on species research, breeding programmes and factsheets, visit the New Zealand Poplar and Willow Research Trust at
www.poplarandwillow.org.nz.
Southland Environmental Enhancement Fund
Have you thought about applying to the Southland Environmental Enhancement Fund which is used to assist individual landowners and community groups to protect and enhance indigenous biodiversity on private and community-owned land in Southland.
For more information and application forms click here.
Environment Southland is the brand name of Southland Regional Council.