09 Mar National Environment Standard
The main aim of the NES is to combine all the individual regional council rules into one document so there is consistency.
I have pulled out the relevant information for our customers
The main risks when installing and using river crossings are:
Sedimentation (that is, suspended sediment and bed sedimentation) of the river during construction and use of some types of crossings (such as drift decks and fords);
- Restricting or preventing fish passage and degradation of habitat;
- Activating or accelerating bed erosion by concentrating water flows or velocities;
- Accumulating debris around culvert openings and bridge abutments, which can result in
- Scour and local flooding;
- Displacing or destroying structures during floods.
The following sections set specific design requirements for each type of crossing to ensure the design of the crossing does not result in:
- damage to the environment as a result of sedimentation or bank erosion;
- damage to downstream infrastructure;
- damning of the crossing resulting in flooding or structural failure;
- disruption of fish passage;
- disruption to the navigability of rivers.
Temporary crossings – specific conditions relating to temporary crossings
1. Except as specified in bridges – condition 3:
a. Any structure is in place two weeks or less.
b. No excavation of the river banks or bed, unless a culvert is being used.
c. Where logs are placed in the bed of a flowing water body, a 300 mm or larger culvert is first placed in the bed.
d. All crossing materials are removed from the river bed within 24 hours of the completion of the operation for which the crossing was constructed or installed.
Single culverts – specific conditions relating to single culverts
- There is only one culvert per crossing and it is of the appropriate length.
- The culvert must pass a 5% annual exceedance probability (AEP) flood event of no greater than 5.5 m3 per second, with no heading up.
- The minimum culvert diameter is 450 mm.
- The total height of the crossing crest is no more than 3.5 metres above the bed (measured from the inlet) and the fill depth and construction complies with the manufacturer’s minimum height specifications.
- The culvert invert is at least 100 mm below the level of the bed of a river or lake.
- For rivers where the bank full bed width is more than 3 m, the river bed invert gradient is no greater than 6%, measured 50m either side of the crossing.
- The culvert inlet (entry point) and outlet (exit point) are protected against erosion.
- Culvert approaches and fill are built from soils free of organic matter. The fill is constructed using successively compacted layers each up to 200 mm loose depth and compacted.
Battery culverts – specific conditions relating to battery culverts
- The contributing catchment is less than 500 ha.
- The diameter of each culvert diameter is 450–800 mm.
- The invert of at least one culvert pipe is at least 100mm below the level of the bed of a river or lake to carry base flow.
- The culvert pipe inlets (entry point) and outlets (exit point) are protected against erosion.
- For rivers where the bank full bed width is more than 3 m, the river bed invert gradient, measured 50 m either side of the crossing, is no greater than 6%.
- The culvert is sized to pass annual average flow. It must be constructed to allow greater flows to pass over it without structural failure.
The document the info was taken from – http://www.mpi.govt.nz/news-and-resources/consultations/proposed-national-environmental-standard-for-plantation-forestry/