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Culverts

Freshwater Plan Factsheet

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Culverts

The Freshwater Plan has rules for installing culverts.  If you can meet all the location, design and installation requirement to install a culvert, then you don't need a resource consent:

Location of culvert 

The culvert is not in a:

  • catchment area of the stream that is less than 100 hectares.
  • wetland.
  • waterway in the city or a township or in an outstanding waterbody listed Schedule 4 of the Freshwater Plan.

If the culvert is in an important native fish area you need to let us know 5 days before construction.
See Schedule 1 of the Freshwater Plan

If the culvert is in a Council drainage area you need to let us know 10 days before construction and comply with our construction guidelines.
See Schedule 8 of the Freshwater Plan
See Schedule 10 of the Freshwater Plan - culvert construction guidelines for council administered drainage areas 

Design of culvert

  • the culvert diameter is at least 450mm
  • a 1:5 year flood can pass through the culvert
  • you include provisions for overflow
  • it has a maximum fill height of 2.5 metres
  • inlets and outlets must be protected against erosion.

Installation of culvert

  • Installed at a minimum of 100mm below the level of the bed.
  • Sediment levels and fish passage is returned to normal within 48 hours of starting work.
  • Equipment is removed from the river bed when work is completed.
  • The new culvert is regularly maintained and checked for blockages.

If you don't meet these requirements, you need to apply for a resource consent

Best practice guide

There's several things to consider when you’re installing a stream culvert.

Get the size and installation right

Avoid spending more money to fix a mistake or botched job, as well as minimising erosion and damage to the stream.

Help the fish

Poor culvert design and installation can restrict fish passage reducing the amount of habitat available for fish – which equals less fish.

Good design

♦ Choose a stable site with a minimum stream bed slope. Consider building a spillway to cope with extreme floods.
♦ Make sure your culvert is at least as wide as the stream bed during normal flows to avoid ‘perched’ outlets or other erosion problems.
♦ Make a rock ramp below the culvert or secure some rocks or small concrete blocks in the culvert bed. These can reduce water speed and provide resting areas for fish, but make sure they won’t cause the culvert to become blocked by debris during floods.

Maintain it

Regular checking and maintenance to keep the water flowing and making sure there’s no loose debris that can it block up during a flood.

Fact sheet

Download - new rules for culverts [PDF, 974 KB]

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