This is generalised information about work to reduce landslide risk before a slip occurs. You should obtain advice appropriate to your property.

If there is no evidence of instability and you are pro-actively improving the site, a specialist contractor may be able to recommend an established erosion-protection product and install it in accordance with the manufacturer’s specifications.

We feel that it is generally worth obtaining engineering advice, particularly where the slope is close to a house or other structure. Manufacturer’s specifications are not a substitute for site-specific engineering advice where slope instability may be present.

Surface erosion, due to water flowing over the ground, can contribute to the deterioration of a slope. Erosion protection products can reduce the loss of surface soil and help vegetation establish, even on steep or damaged slopes. This can reduce landslide risk where surface erosion contributes to instability.

Surface erosion protection will not necessarily stabilise an unstable slope. If there are signs of movement, cracking, or previous slipping, you should obtain advice from a suitably qualified geotechnical professional.

A product that protects against surface erosion does not necessarily reduce water infiltration into the slope.

Uncontrolled water infiltration, or water soaking into the ground, can be a major cause of instability. Most landslides we have seen have happened after a heavy rain event.

This risk can be reduced by controlling infiltration or using sub-soil drainage to get water out of the ground.

Collected or diverted water must be discharged to a suitable place without increasing erosion or instability elsewhere.

Simple erosion-protection and planting generally does not require a building consent.

Structural or drainage work generally requires building consent. A minor works building consent may be required if you need new drainage connections. Consent fees are a small cost compared to the potential cost of a landslide.

Resource consent requirements must be considered separately.

If there is evidence of instability, we suggest that you contact your insurer before undertaking work.

For preventive work where no damage has occurred, check your policy or ask your insurer or broker whether the proposed work needs to be disclosed.

Any engineering design and the product manufacturer’s specifications must be followed. We can provide a statement that work has been completed to these specifications.

Maintenance requirements are important, particularly around keeping drains clear.