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Low impact design

Example of a stormwater wetland. Supplied/ Boffa Miskell

Our towns and cities are growing and one of the flow on effects from that is that our day-to-day living is having greater effects on the environment we live in. Stormwater runoff is a major cause of water pollution in urban areas.

When rain falls on our roofs, streets, and car parks the water cannot soak into the ground as it should. Instead, stormwater is directed to drain through gutters, stormwater pipes, and other engineered collection systems, eventually being discharged into nearby water bodies.

The stormwater runoff carries rubbish, bacteria, heavy metals, and other pollutants from the urban landscape to those water bodies. Higher flows resulting from heavy rains can also cause erosion and flooding in urban streams, damaging habitat, property, and infrastructure (which can be expensive and disruptive).

On the flipside, when rain falls in natural, undeveloped areas, the water is absorbed and filtered by soil and plants. Stormwater runoff is cleaner and less of a problem in those environments. Experts all over the world have realised that there are better, more efficient and more natural ways of treating our stormwater. In New Zealand, this is generally referred to as ‘Low Impact Design’ or ‘Low Impact Development’.

Learn more about Low Impact Design and how you can use such methods on your own property by clicking on the links below.

What is it?

LID stands for Low Impact Design or Low Impact Development. In other areas of the world it is referred to as Water Sensitive Design (WSD), Water Sensitive Urban Design (WSUD) and Sustainable Drainage Systems (SuDS).

LID is a design approach used to manage water runoff. Instead of managing and treating stormwater in large, unnatural and costly facilities, LID addresses stormwater through small, cost-effective landscape features where the stormwater falls. This approach to land development works with nature to manage stormwater as close as possible to its source, emphasising conservation and use of on-site natural features to protect water quality. In simple terms, it is a water management method which focuses on sustainability as opposed to disposal.

Low Impact Design principles can be integrated early within a land development process, or be adopted later, such as during a redevelopment of existing dwellings/structures/land (sometimes referred to as a “retrofit”).

Why should I do it?

There are numerous benefits and advantages of LID over conventional stormwater management approaches. Adopting LID principles ensures that (as much as possible) natures’ own stormwater management functions, such as those found in vegetation, waters and wetlands, are used and protected.

LID not only contributes positively to the natural environment but it can also create greener, more attractive urban environments. By managing runoff close to its source through intelligent design, LID can enhance the local environment, protect public health, and improve community liveability - while saving money! To learn more about what you can in your own home, have a look at our “Methods” section.

What is the point of it?

Conventional stormwater infrastructure, such as pipes, culverts and concrete channels, have traditionally focussed on conveying or disposing of stormwater runoff in order to manage particular flood risks (say, the ‘1 in 100 year’ or ‘1 in 10 year’ events). Whilst these ‘hard’ structures are good at achieving this one purpose, they also have adverse effects on our environment.

History has shown that having a single-purpose system is not only bad for the environment but is also self-limiting, as it requires ongoing maintenance, upgrades and added services. In other words, traditional systems are restrained in their efficiency to the system’s ability to cope with a certain flow (dictated for example by the size of the pipe). With rapid growth and climate change, that can quickly cause problems in our urban areas.

In order to address these issues, LID systems and practises have become the norm to reduce or eliminate stormwater runoff. These practices have a number of purposes aside from flood management, such as:

  • reducing pressure on existing networks;
  • filtering out or treating pollutants and contaminants;
  • reducing carbon emissions;
  • bringing flora and fauna into urban environments; and
  • improving the general streetscape. Read more about the benefits here.


To find out more about Low Impact Design and how it affects you, click on the links below.