Maintenance of grass margins

If you have decided to leave a grass margin, rather than plant the margins of the stream, there will still be some maintenance requirements. Check for weeds such as gorse, broom, hemlock and blackberry. Be prepared to clear weeds at least once per year.

Managing weeds in stock-free areas

Water weeds (eg watercress, monkey musk and floating sweet grass) can increase dramatically in slow flowing streams where stock are excluded. This can raise water levels by 50 cm, which may be a problem in some areas.

A weed cleaning rake bucket minimises damage.

Short term:

More frequent drain/ stream clearing may be necessary in the first few years after fencing. Refer to fencing page for advice on leaving digger access.

Medium term:

Fewer nutrients and less sediment entering stream should lead to slower water weed growth. Streamside grasses and sedges along narrow streams may reduce light sufficiently to control instream weed growth.

Longer term:

Establishing trees and shrubs will reduce light levels and thus stream weed growth.

Mechanical drain maintenance

If you clear weeds using an excavator, don't clear too close to the edges of the stream, otherwise you will undercut the bank and lose plants. Use a weed clearing rake bucket. Give clear instructions to the digger operator.

In non-tidal areas, October to April is the best time to carry out drain maintenance as it will have the least impact on fish and birds. In tidal areas, October to February is best. If you suspect you have the endangered Canterbury mudfish in your drains, contact Environment Canterbury or the Department of Conservation for advice on maintenance. Mudfish need aquatic plants to live in and feed off.

Take care when clearing drains

Key:

Excavation close to the bank edge has led to banks becoming undercut and unstable.

Best practice excavation not too close to banks.