Gisborne District Council's Tairawhiti Resource Management Plan (TRMP) includes 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:
- The culvert is not in a catchment area of the stream that is less than 100 hectares.
- The culvert is not in a wetland.
- The culvert is not in a waterway in the city or a township or in an outstanding waterbody listed in Chapter 6.3.2.1 Section G18 of the Tairawhiti Resource Management Plan (TRMP)
If the culvert is in an important native fish area you need to let us know 5 days before construction. See Section G15 of the TRMP
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 Section G22 of the TRMP
- See culvert construction guidelines for council administered drainage areas.
- 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.
- 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.