GNS Science have put together this guide for how to monitor for landslides and earth movement on your property
1. Know your drains.
- Drains are critical as they quickly remove water from the slope if they are maintained and working properly.
- Your downpipes from your roof should connect into the local storm-water system.
- Your retaining walls should have drains at their base that collect and take seepage away.
- Your drains can be on the surface or underground. Inspect them regularly to ensure they have not become blocked – for instance by tree roots, or by leaves and other litter if they are on the surface.
- Be aware of seepages around your property, note how the flow changes during rain and if they change over time (increase or decrease). If the seepage decreases this can be a sign that a drain has become blocked above the seepage point – a new seepage may appear. If the seepage increases this can be a sign a drain is blocked below the seepage point.
- NEVER clear your drains during heavy rain, wait for a break in the weather and listen to the land.
2. Are your retaining walls straight?
- Retaining walls are seldom built crooked and should always have a drain at their base.
- Take photos looking along your retaining walls and compare photos over time to see if the wall is moving – bulges need attention.
- Make sure the drains are cleaned out regularly and working properly.
3. Get new cracks checked out.
- Take photos of all the cracks around your property now - in the soil, in concrete paths and in driveways.
- Take photos regularly (every three to six months) and after strong earthquake shaking or heavy rainfall. This makes it easy to demonstrate if changes are occurring.
- Note if windows or doors in your home become more difficult to open/close over time. This can be a sign of ground deformation over a long period (in older wooden houses this can also be seasonal as wood can swell in damp cold conditions and shrink in warm dry conditions).
- If the cracks are new check whether they have damaged your drains.
4. Take photos.
- Photos are a great way to prove changes are occurring and that your slopes and drains need checking.
- A sequence of photos taken from the same spot showing changes over time is excellent evidence that something is moving and needs to be checked.
5. If in doubt call a professional.
If you are seeing changes in your drains or retaining walls, ground cracks or buildings get it professionally checked out. Drainlayers, plumbers, geotechnical engineers, building inspectors – find the professional you need and take the action they recommend. If in doubt get a second opinion.