The slope and topography of a site will influence your access to sun and views, your privacy, your exposure to shading and wind. Ground stability and waterways will influence the design and structure of your home or extension.
By taking landforms and waterways into account, you’ll get a home that’s:

• safer
• drier
• more durable
• more comfortable
• easier to heat.

It’s worth considering landforms and waterways before you buy a property, or early on in the design process for any new home or renovation.

Slope and topography

Sites with hills or slopes facing north will receive greater exposure to the sun.

Slope and topography can also affect:

• privacy - whether your neighbours will be able to see into your home or section
• shadowing - whether hillsides or trees will block the sun, particularly in winter when the sun is lower on the horizon
• wind exposure
• wind strength - for example, wind speeds up as it passes over or between hills, or through valleys (this is the 'wind tunnel' effect)
• access to views.

You can find local topographical maps at regional and local councils. These might give you more information about the topography of the surrounding area than you can see from the site.

It's worth considering whether you will be able to work with the site's existing landforms to get the house and landscaping you want without expensive earthworks.

See exterior design for more information about designing a building or renovation to fit your site, and see orientation for more information about positioning a home to make the most of the sun.

Ground stability

Before you build or extend, you'll need to know that the ground is stable i.e. it doesn't suffer from slips or erosion, and it isn't in the process of settling.

Site stability may affect the type of foundations and materials you need to use. You may not be able to use heavy materials such as brick or concrete.

For new subdivisions, the developer should have an engineer's report you can look at. This should certify that the land is suitable for residential development and that any earthworks have been completed to the required standard.

A Land Information Memorandum from your local council should also have information about any past earthworks, presence of old landfills and any other site stability issues the council is aware of.

If you have doubts about the stability or compactness of the ground, it's worth consulting an engineer or ask your architect to commission a report.

Stormwater

Stormwater can result in erosion and flooding.

The slope and steepness of your site can affect the amount and direction of stormwater runoff. So can the amount of paving.

It's worth checking that the site is not affected by stormwater entering from other properties.

Note that plants and trees can help absorb stormwater runoff and prevent erosion. A site that's been cleared of vegetation may be more susceptible to erosion and flooding.

See managing stormwater for more information about dealing with stormwater on your property.

Water levels

Sea, lake or river levels can vary markedly between seasons. Find out about how much variation there is from season to season, and how much of the property is covered when the water is at its highest.

Tidal variations can contribute to erosion and affect ground stability. You won't want to build on a part of the property that might be under water for part of the year!

Legal

Any activity that affects landforms or waterways may require resource consent. Levelling a site, cutting and filling part of a site or removing trees will probably require a consent. So will any activity that results in sediment being discharged into streams or other waterways.

Check with your local council before you start work.

More information

From Smarter Homes

• Neighbourhood
• Orientation
• Climate
• Hazards
• Rural sites
• Planting and landscaping
• Native plants and wildlife
• Exterior design

From Consumerbuild

Your local or regional council will have information about issues relating to land and waterways on your property. The ConsumerBuild website’s council finder page has local authority contact details.

From other sites

The Ministry for the Environment’s website has information about land care issues such as soil and coastal erosion.

Maps, aerial photographs and topographical information can be found at the Land Information NZ website.