Mitigation and best practice options

Some simple steps to minimise the effects of urbanisation on water quality and mahinga kai.

The mitigation options or recommended best management practices suggested below can be linked to the effects described in the impacts pages.

Maintain stream flow

Urban streams often need to cope with increased size and frequency of flooding. However, if engineered stream channels are too wide and water depths extremely shallow (as a result of being designed to cope with high peak flows) then this can impede fish passage and affect water quality. Reduce the damaging effects of peak flows by retaining water on land within the catchment and by reusing water. Employing pervious surfaces in urban design to encourage infiltration and capturing roof water with on-site tanks for watering gardens can greatly reduce urban stormwater runoff.

Maintain fish habitat in streams

Retain or re-engineer natural meanders that create habitat diversity. Low flow channels and rest areas for fish species are important for the natural movement of mahinga kai. Native riparian planting enhances shoaling and decreases water temperatures by shading. Planting can also add cover habitat instream from wood, leaves, and overhanging plants and provide a food source from terrestrial invertebrates that drop into the stream.

Nutrients and contaminants

Reduce nutrients and contaminants from entering the system by planting riparian margins, and maintaining and incorporating vegetated swales and constructed wetlands within gardens and streets; these all filter runoff before it reaches the stream.

In-stream barriers

Use fish friendly culverts that maintain the natural slope of rivers and streams while keeping the culvert floor below stream level. Ensure flow is low but depth adequate to maintain fish passage to upstream habitats.

Impervious areas

Minimise impervious areas by using paving blocks that allow rainwater to move through to the ground below. Plant 'rain gardens' in parking areas and along roadsides to capture stormwater discharge.

Best management practices for stormwater runoff and fish passage were sourced from Tasman District Council and Environment Waikato.