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Riparian Planting & Stream Restoration

Riparian Planting and Stream Restoration.

Riparian planting doesn't just mean planting a few new trees along the banks of the stream and then hoping that nature will do the rest.

Hydrology

The natural flow needs to be restored, and any obstructions to water flow need to be removed.

Water pollution

Industrial pollution, farming effluent runoff, water treatment plant overspill and stormwater drainage are the biggest obstacles to cleaning up the Mangatarere water. Stormwater is rainfall which runs off roofs, roads and other surfaces. When paints, detergents, oil and litter such as cigarette butts flow into the stormwater network they end up in waterways, damaging aquatic life.

Mangatarere Plant and Tree Images
Old Man's Beard Willow roots Poplars
Old Man's Beard is an invasive weed Red willow roots hold the banks together Riparian planting poplars
Hay bale plastic
Hay bale plastic

Removal of undesirable plants

Invasive weeds need to be removed, because otherwise the stream provides a natural pathway for the seeds of these species to be transported downstream and cause more problems.Below are a few of the problem species.

Broom

Broom












German ivy

German ivy












Onionweed

Onionweed












Blackberry

Blackberry












Riparian Planting

There has been some fragmented riparian planting done along the Mangatarere stream banks in the past, using willows and their cousins the poplars. Willows and poplars are introduced species that are commonly used for riparian purposes in England and Europe, and they are common along the Mangatarere banks, where they provide windbreaks, shelter for trout and regenerating native plant species, a home for birds, and a source of food for bees. Willows are effective for holding banks together, provided they are moderately spaced out. However branches that break off can take root downstream and block watercourses, so they are a mixed blessing. We prefer to re-introduce native species like the ones below in preference to imported exotics.

Pukio
Pukio

Pukio forms a thick trunk (made up of old roots and stems) that can grow up to 1 m tall.The leaves and flower heads are very droopy giving it a tussock-like appearance and allowing it to hang over the water and provide valuable shelter for stream life. It is tough, likes open sunlight and is frost hardy when mature.Pukio can be planted right up to the stream edge but the plants need to be knee high as anything else will get washed out by high flows, pulled out by pukeko or swamped by grass and other weeds.



Flax
Flax

Flax has tough sword shaped leaves and its flowers produce a lot of nectar, making it a favourite of tuis in particular. The soils most suitable for flax are sand, silt, clay, gravel, or organic matter deposited by flowing water, or deep loams containing mostly organic matter like rotting leaves. It has a sprawling and tenacious root system and is often found just above the waterline in swampy ground, and this makes it an ideal riparian planting species.




Toetoe


Toetoe

Toetoe, better known to kids as "Cutty grass", is a New Zealand native species with leaves that look like a skinny kind of flax and which has white droopy flower heads. South American Pampas Grass is an introduced species now classified as an invasive weed that can easily be mistaken for toetoe, but the leaves are smooth and break off easily when pulled. Toetoe's are ridged and much stronger, making it a good riparian species.




Bank reconstruction


The banks need to be shored up in some places to prevent erosion. The stream also needs to be completely fenced to keep stock out of it.

Walking paths

The stream is a community asset and at present there is public access to very little of it. The construction of a walking track to improve the stream's accessibility would give a tangible result to the community, and frequent pedestrian traffic would also mean that the condition of the stream could be more easily monitored.

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