Landslip, Tidal Inundation And Filled Ground – Have You Checked With Council?
Believe it or not, there’s a lot more to buying a property than making sure everything’s ok on your side of the fence. Sure, it’s crucial to get all your ducks in a row when it comes to finance, building and pest inspections. But you’ve also got to look at the bigger picture. Have you considered whether your parcel of land could be at risk of a landslip, tidal inundation or issues caused by filled land? Here’s how to uncover these hidden problems.
A landslip is also known as a landslide, a slope failure or a ‘slump’. It’s a phenomenon that occurs where the forces of gravity outweigh the ability of the soil to support its own weight on a sloped surface. Consequently, the soil, boulders, rocks, water and debris forming the hillside can shear away, tumbling or sliding down the slope. That can happen very suddenly or over many years.
Why landslips happen
A landslip can be caused by a multitude of factors. Whilst they’re relatively common in earthquake prone areas and areas of volcanic activity, they’re also a significant hazard in south-east Queensland. That’s because there’s a heightened risk of landslip activity where there’s sloped surfaces exposed to heavy or prolonged rainfall. Landslips can also be triggered by
• construction or excavation works
• removal of vegetation
• bushfire activity
• mining, blasting, or logging
• groundwater, cracked or broken waterpipes, stormwater or sewerage pipes
In fact, most fatal landslips in Australia have been caused by human activity as opposed to naturally-occurring triggers. A 1997 landslip at Thredbo, NSW, killed 18 people and destroyed two ski lodges. The genesis of that disaster was the combination of an access road built on poor fill and a leaking water main pipe.
Why landslips are a problem you need to know about
Landslips can contaminate water supply and destroy large tracts of vegetation and local habitat. Moreover, a landslip has the potential to cause immense damage to property, buildings and infrastructure such as roads, drains and sewers. They can also disrupt phone and internet services, block train lines and cut off electricity supply. They have enormous potential for causing mass casualties.
That’s why it’s a hazard that’s taken very seriously.
Living in an area that’s prone to landslip can mean
• limitations in terms of what you can do with your property
• higher insurance premiums.
Landslip-prone areas are also subjected to far more rigorous regulation and scrutiny when it comes to proposed development. That can be bad news for you if you’re planning to
• remove vegetation
• excavate or fill
• repurpose the land.
If you don’t do your research first, you might find you can’t do what you want to do with the property.
Finding out if you’re in an area at risk of a landslip
There’s no obligation on a vendor to disclose that a property is within a landslip hazard area. You must do the checks yourself as part of your due diligence.
Geoscience Australia keeps records of landslip activity. You can search for previous landslip activity here. However, you also need to consider potential for future landslip activity. That’s where your local council’s planning scheme comes into the picture. More of that later.
Other hazards to watch for: Tide Inundation and filled ground hazards
Landslips aren’t the only hazard you need to watch for. There are other hazards that could potentially affect the property you’re looking to purchase or your plans for its extension or development. Tidal inundation and problems created by filled land are two examples.
Tidal inundation is a form of coastal flooding that’s a risk to properties. Affecting low-lying coastal areas, it occurs when there’s an abnormally high tide.
Coastal areas may also be at risk of flooding due to storm surges; that is, a rise of sea water to a level beyond what’s considered normal during a storm or cyclone. These events can cause extensive erosion and undermine the footings or foundations of buildings. Again, there’s no obligation on a vendor to disclose flood information in relation to a property, so it’s up to you to make your own inquiries and searches.
With land at a premium, old quarries, swamps and tips are reclaimed for development. As part of that process, the ground can be levelled using ‘fill’. The quality of fill used can cause subsidence as it breaks down, decomposes or becomes compacted. A poorly filled site can result in structural damage or complete collapse of a building it was supporting. That’s not the only problem that can be caused by filled land though: if the content of the fill includes waste, there’s issues of contamination from toxins such as lead, mercury, arsenic and asbestos, gas, oil and leachate (liquids).
How do you check whether your property contains fill? You can do this by arranging for soil sampling, testing and classification as per Australian Standards. If the soil is classified ‘P’ that indicates there could be problems with your soil: fill is one of those problems.
The fact your property has filled ground isn’t of itself a problem. It’s what’s in the fill that can create structural and contamination issues. If you’re buying a property you should consider insisting on a clause in the contract of sale that makes the purchase conditional on a favourable soil test.
You can also check with the Environmental Protection Agency’s contaminated land register. However, the fill that might cause instability might not necessarily cause contamination. Whilst there’s a clear obligation on a seller to disclose contamination, it’s up to you to find out if the site is filled with material that may cause subsidence or other issues down the track.
When you’re the one wanting to use fill or excavate a property
If you’re proposing to fill or excavate land on your property, you’ll be subjected to more stringent scrutiny. That means complying with additional requirements imposed by your council’s planning scheme. Those requirements may include that you obtain a compliance permit or development permit, depending on which council planning scheme applies.
Your local council and the role it plays
Landslips, tidal inundation and filled land pose a significant hazard to infrastructure, buildings and lives. That’s why local councils play a crucial role in monitoring at-risk areas and implementing strategies geared towards mitigating that risk. Crucial to this is your local council’s planning scheme and ‘overlays’.
An ‘overlay’ is a mapping tool. It’s used to determine the boundary of an area designated by the council’s planning scheme as needing special attention, regulation or protection by the council. ‘Development constraint overlays’ are overlays applied to areas that are at greater risk of
• landslip / landslide hazard
• tidal inundation / storm surge.
There are other types of overlays, too. Some exist to give special protection to areas of significant habitat for flora or fauna, or places of historical value. A property can be subject to several overlays at once. Overlays affecting your property impact on the approval you need to obtain before commencing work on the property. It also impacts the number of hoops you need to jump through to get it.
Your council can provide you with detailed information as to the overlays affecting your property. Some of the information is available free of charge online. Other information is available for a modest fee.
Who to contact in your area for more information
Here’s your starting point for information about these hazards:
Morton Bay Regional Council
You can visit the Moreton Bay Regional Council website here https://moretonbay.qld.gov.au/subsite.aspx?id=143120 to use the My Property Lookup tool and access overlay maps. For more information contact the Morton Bay Regional Council on (07) 3205 0555.
Start your property search at http://www.ipswichplanning.com.au/planning-documents/planning-scheme or contact the council by telephone (07) 3810 6888 or email firstname.lastname@example.org
For more information about the overlays applicable in Redlands , click here https://www.redland.qld.gov.au/info/20181/redlands_planning_scheme , phone (07) 3829 8999 or email the council at email@example.com
Brisbane City Council
You can access the Brisbane City Plan 2014 and mapping at https:///www.brisbane.qld.gov.au/planning-building/planning-guidelines-tools/brisbane-city-plan-2014/city-plan-2014-mapping or contact the council directly on (07) 3403 8888.
Other safeguards you should insist on in the conveyancing process
There are a few additional searches that can also be taken as part of the conveyancing process including inspection of records, building search and a search for planning and development certificates.
It’s always a good idea to get a legal practitioner involved in the conveyancing process. The insertion of a carefully drafted ‘due diligence’ clause in the contract of sale is an important protection for you as buyer. It enables you to back out of the sale if you discover something untoward whilst making your own investigations about zoning, overlays and development potential for the property.
Where your building inspector comes into the picture
A comprehensive, professional building inspection will look for conditions or factors conducive to structural damage like a potential landslip or use of fill. A building inspector is the best person to give you the sort of technical advice about additional searches you should consider undertaking. The more energy you expend now in identifying these problems, the more heartache you’ll save later on.