Low impact and water-sensitive approaches to urban development.
Can we design cities to cleanse urban waterways and increase NZ's biodiversity? Low Impact Urban Design and Development (LIUDD) is an approach which works with nature, using design features such as rain gardens and green roofs to reduce pollutants entering urban streams and harbors, while creating green spaces for NZ plants and animals to live in and green spaces for people to enjoy.
LIUDD is based on avoiding or minimising impervious surfaces (surfaces water can’t seep through like concrete), minimising earthworks in construction, using vegetation to trap sediment and pollutants and minimizing energy, material use and waste in urban development.
LIUDD is about learning how natural systems regulate water flows and surface temperatures so that through designing-in natural features, cities can reduce flooding, filter pollutants and keep buildings cooler in summer without expensive air conditioning. As the climate changes, with more heat waves and heavy rain events predicted in many parts of NZ, cities will need to adapt and LIUDD is a sustainable way to do this.
Landcare Research have been researching and developing LIUDD approaches across NZ.
Our research has covered a range of topics including:
You can find detailed information about our LIUDD research on the Landcare Research website or check out the OurFuture stories on greenroofs and creating a greenroof, rain gardens, using home raintanks as stormwater control, and working with a community when using LIUDD in an urban intensification project.
How do you control flooding through nature and the home rain tank? Glencourt Place is a suburban neighbourhood in the North Shore, Auckland. The area lacked any official stormwater reticulation system and was experiencing repeated flooding. Glencourt Place needed a retrofit of its stormwater system. Instead of the conventional method of installing stormwater pipes to carry all the rainwater (and pollutants swept up by rainwater ) directly to the local stream, the North Shore City Council piloted a low impact on-site storm water management approach.
Landcare Research monitored the pilot and this story describes the results.
The low impact approach used an engineered system of ditches, gravel trenches, contoured flowpaths and minimal piping, backed up with rainwater tanks retrofitted to the existing properties.
As part of the pilot, we compared the performance of the low impact approach with the conventional one based on the criterion of cost minimisation. Cost is an important criterion in what approach developers and councils use in urban development and increasing our understanding of what environmental approaches cost can remove uncertainty and risk in low impact adoption.
Raintanks primarily slow down the quantity of rain water flowing off roofs into stormwater drains and out into waterways, they can help reduce the need for extensive stormwater piping and can help prevent flooding in high rainfall events. Their water quantity benefits are dependent on the spatial distribution of the raintanks in a catchment, the detention capacity at the beginning of the storm event, and the timing and intensity of storm flows through the catchment (Hardy et al., 2004). They also have minor water quality benefits, the use of roof runoff for domestic non-potable use will reduce contaminant discharge into receiving waters because some of the runoff will enter wastewater treatment systems or be discharged on to permeable surfaces such as lawns and gardens (Auckland Regional Council, 2003). Lastly they can help water conservation, Coombes et al. (2004) identified a 53% reduction in mains water use as a result of raintank installation at an inner city small house in Newcastle, New South Wales.
So how did we go about comparing costs and what did I find;
It was important to estimate the costs comprehensively for both approaches. Life cycle costing provides a thorough coverage of the different cost elements of each system; from initial acquisition, to operation, to maintenance and finally to disposal. Conventional and low impact devices have different life expectancies (e.g., raintanks 25 years; pipes 50 to 100 years), and for comparison the adopted time horizons were identical for both systems. We also included water saving benefits of rain tanks to examine their significance.
Getting buy-in from the households disadvantaged the low impact approach, as the consultation process was costly and time consuming. As some residents perceived the low impact approach as a second-rate solution, a certain level of trust had to be built up with the involvement of a third party as an intermediatory between the two major stakeholders, the residents and the council. This reflects the problems and related costs of introducing new stormwater approaches. Conventional stormwater approaches tend to be out of sight and out of mind while low impact approaches requires greater participation of local residents to make them successful.
Overall, our research revealed higher life cycle costs for the low impact approach; however, with the inclusion of the water saving benefits, the net present value of the two approaches becomes similar. In addition the low impact approach generated increased technical understanding, new policies, organisational systems, revised standards, and increased experience. These changes are expected to reduce the life cycle costs of similar low impact systems in the future. The associated costs can therefore be considered as investments in innovation.
Learning to turn a cold old house into a sustainable healthy home.
We wanted to retrofit a 1950s state house to improve the lives of the family who lived there and to significantly improve the building's energy efficency. Our team for the job - Team Housewise was a partnership between Landcare Research, Housing New Zealand Corporation University of Auckland, School of Population Health and the New Zealand Housing Foundation.
The house we renovated had chronic symptoms associated with underperforming New Zealand Housing stock from its era; damp and mouldy, yet still draughty; too cold in winter; too hot in summer and in need of extensive maintenance and design modification to suit modern lifestyles. One of the tenant's children has asthma and her symptoms are likely aggravated by the poor conditions inside the house.
Retrofititng an existing old building is always a challenge. We worked with the family on the design to ensure that renovations met their needs and also to build their awareness and ability to manage the ongoing operational decisions involved with balancing energy and water cost savings with comfort and health improvements.
What we achieved:
You can also view a slideshow and more information on the project on the Sustainable Habitat Challenge Website . The Sustainable Habitat Challenge had teams around New Zealand designing and constructing more sustainable homes. Visit the site for more examples of new or retrofitted sustainable building examples.
Water is becoming a costly and diminishing resource – to be harvested and re-used rather than disposed of into stormwater pipes and our harbours as fast as possible. As our awareness of the impacts of urbanization grows, in particular the increase in impervious, warm and reflective surfaces and the absence of plants and water, the need to retrofit our increasingly densely populated cities becomes more urgent.
Raingardens are a key approach to using nature to slow down and filter pollutants out of rainwater runoff, pollutants which would normally flow into our urban waterways and harbours. Raingardens are described as a bio-retention device as are green roofs, swales, tree pits, and permeable paving.
Rain gardens look very much like any other garden except they receive more runoff than normal gardens, are usually lower than the surrounding surface, and often have imported or sand-amended soils so they drain well. They also have under-drains, and usually overflows that are connected to stormwater pipes. They need far less watering than normal gardens and should need no fertilising. Most raingardens also have a dense groundcover of perennial plants that filter water and protect the soil surface. There is no bare soil once plants are established and no annual plants.
What plants are best?
What plants are best?
The best raingarden plants form a dense, weed-suppressing cover and tolerate dry conditions as well as short-term flooding – these are plants typically found on the edges of wetlands that dry out in summer.
This is why native rushes (Juncus and Apodasmia/Leptocarpus species), sedges (Baumea and Carex species) and flaxes are commonly used in raingardens.
Generally the plants will have most of their foliage above the maximum height water will pond, however, where the rainwater is clear (e.g. roof runoff), shorter groundcovers may be suitable, e.g., Selliera, Acaena and Leptinella species).
These plants can also be used on the gently sloping edges of raingardens where the water ponds for very short periods – these edges are also suitable for plants less tolerant of ‘wet feet’ (e.g., Hebe and Muelenbeckia species). Deciduous plants are not generally used in raingardens as leaf fall can block outflows. Trees are generally restricted to larger raingardens, and are either naturally cast a light shade or are pruned (lifted and thinned) to ensure the groundcover plants get enough light to maintain a dense growth.
Creating raingardens at home
People create raingardens at home as they look great (check out the Ellerslie International Flower Shows pictures), reduce surface flooding and reduce the need for watering. Download a 10 step plan for creating your own home raingarden or visit Landcare Research’s webpages on creating raingardens at home. Raingardens on other sites, or where part of resource consents usually require specific flow attenuation and conformance to local standards, in Auckland this is Technical Publication10.
The Waitakare City Council approached Landcare Research to help design and monitor a green roof on their civic building in Henderson. They wanted a roof planted in native plants, which was aesthetically attractive, provided a habitat and food supply for insects and birds and which required low maintenance (no watering after establishment). All of this needed to be created as an extensive thin roof i.e. it needed to cope with a thin layer of substrate for the plants to grow in ≤150 mm deep and <300 kg/m2 saturated weight. They have thinner and less numbers of layers, so therefore they are. Extensive greenroofs are lighter, less expensive and have low maintenance and are built when the primary desire is for an ecological roof cover with limited human access.
NZ does not have much of a history of green roofs so there is little information on what native plants do well in different roof climatic conditions. So one of the first things we needed to do was identify the right plants. We started by asking ecologists, growers, what they thought would survive on an Auckland exposed roof and we also by surveyed walls, roofs, cliffs, and exposed habitats with thin soil substrates to identify which plants were coping well in these difficult greenroof like conditions. We also looked at spontaneous green roofs – ones which have established on their own on for example, old farm buildings– therefore choosing ideal conditions and identified that they; often have; afternoon shade, inputs of leaf litter; receive runoff and the plants include canopy epiphytes (which are grow up at the top of forest canopy supported by larger trees and drawing nutrients from the atmosphere).
We identified and trialed a dozen native plants on the Waitakere Civic Centre roof ; of these the most resilient were (in order): Festuca coxii, Coprosma acerosa (sand dune coprosma),and Libertia peregrinans. Native iceplant was spectacular in the first 18 months but succumbed to disease in the second year (so use as small proportion as a short-term filler). In slightly shaded sites, and with some summer irrigation, Dichondra repens, Leptostigma setulosa and Pimelea prostrata (native Daphne) surivived. On other roofs, with some afternoon shade, Selliera radicans and the fern Pyrossia serpens have formed attractive groundcovers, and on the trial roofs at Tamaki, some native rock-dwelling Hebes (e.g Hebe obtusata), daisies (Celmisias) and Crassulas have survived.
Our monitoring of the roof identified that;
We also needed to develop and test substrates for the plants to grow in, that were light and drained rapidly so that it didn’t slump or pond but still held enough water for plants to survive during summer. Substrate mixes can be tailored to individual roofs, but in general the mix has 70 to 85% pumice, 5 to 10% zeolite and 10 to 15% stable organic matter (a mixture of composted bark and coconut fibres). The mixes have a very low proportion of fines (fine sand, silt and clay) so they don’t clog up.
So what does the roof look like now and what’s living in it?
The Waitakere Civic building greenroof as helped develop knowledge and experience in New Zealand of designing native plant based extensive greenroofs.
Checkout more OurFuture stories on greenroofs
Find detailed information on Landcare Research’s Greenroof research
Green roofs are roofs covered with living plants, usually growing in light-weight substrates.
Green roofs have a long history, think of Irish/Icelandic sod roofs, burial mounds and the hanging towers of Babylon - but green roofs have only recently been seen as a sustainability solution for New Zealand cities. Greenroofs are fantastic for towns and cities because they can;
They are increasingly used to gain multiple greenstar and other sustainable building credits.
While green roofs are becoming widespread in Europe and North America, the lack of local knowledge and experience has created barriers to Greenroof development here.
To address this Robyn Simcock and her team at Landcare Research have been designing green roofs specifically for New Zealand conditions and evaluating their performance.
Modern green roofs include intensive roof gardens or extensive roofs with a thin layer of substrate and plants. The extensive green roofs need to be lightweight so the structure needs less reinforcing to support its weight. That means you can develop a green roof on many existing house, school or office, especially if it has a tile or concrete roof.
The team has a series of extensive green roof trials at Landcare Research Auckland. The roof trials are identifying a range of plants that can be used on roofs with a strong focus on NZ native plants, and different substrates to grow the plants in. The team has helped create green roofs from scratch for the Engineering Building at Auckland University, the Waitakere Civic building, and two small roofs at the Auckland Botanic Gardens.
Create your own green roof letterbox (or dog kennel)! A great project for schools or for creating in your own home - check out the video below for a step by step process of making a mini green roof.
Find detailed information on Landcare’s green roof research and more on green roofs in New Zealand. Also check out the OurFuture stories on creating a native greenroof, rain gardens, using home raintanks as stormwater control, low impact urban design approaches (LIUDD)and working with a community when using in an urban intensification project.
Green roofs are growing in New Zealand. If you own a building with a green roof which can be seen from the road email us and we’ll put it on the map as another great sustainability project people can check out.
Can intensive urban development be green? And how have local residents found living in an intensification suburb which has taken a low impact urban design approach? These were two questions that Landcare Research explored in the Talbot Park redevelopment project in Auckland.
Talbot Park is a 5 hectare, state housing neighbourhood in Glen Innes, which has recently been redeveloped into a medium density area. The urban design brought together principles of Low Impact Urban Design and Development (LIUDD) and Crime Prevention through Environmental Design (CPTED). As a demonstration site, Talbot Park was a learning model of how sustainable urban redevelopment can be undertaken and Housing New Zealand Corporation (HNZC), Landcare Research and Auckland University collaborated in this wider learning process.
As an anthropologist on the urban team at Landcare Research, my research focused on residents’ experiences and perceptions of these changes to the neigbhourhood. How did local residents find living in a redeveloped intensified suburb? What do they understand and think about the low impact design approach? I was also interested in the renewal process itself. How were residents involved in the design process? To what extent were residents’ acute need for a safer place to live met?
The low-impact design approaches included:
So what makes my study ‘anthropological’? To take one aspect of the study – rain tanks – an anthropological approach starts from the point of understanding local conditions and people’s varied experiences of using rain tanks. At the time, there was lots of research on social barriers to the uptake of rain tanks with a focus on the individual and how to influence individuals’ behavior in relation to the environment. As an anthropologist, I took a more cultural approach, focusing on values and meanings and how these influenced what people understood and did in relation to the environment. What habits, routines, and traditions related to water use were evident and how did these change over time? What were householders’ understandings about recycling water and experiences of operating a rain tank? Did having a rain tank make them more conscious about water conservation? And in what ways?
This detailed ethnographic research (‘participant observation’, interviews, focus groups) allowed ‘cultural translation’ between the different people involved in the project. I also worked with Jeremy Gabe from Landcare Reaserch, an architect with expertise in sustainable design, and collectively we were able to use social and environmental information to contribute to residents’, HNZC’, and Auckland City Council’s, and plumbing contractors’ understanding (and possibly appreciation) of the worth and operational requirements of the rain tanks.
Anthropologists typically spend a lot of time getting to know the ‘language’, tools, practices, beliefs and social relations of people in a locality. This ethnographic approach was important in understanding what Talbot Park residents thought about living in medium density housing. My study of urban renewal in Talbot Park took place between February 2006 and March 2009, but I have been involved in research in Glen Innes since 2003. This long term engagement allowed me to see the shifting views about apartment living. I observed with fascination as local residents went from being extremely concerned about ‘high rise horrors’ during the planning stages of Talbot Park, to ‘watching with interest’ during reconstruction, to being ‘very impressed’ when it was completed. Long term engagement and interviews with residents and HNZC staff also allowed me to observe that participatory planning processes and intensive tenancy management were critical to the success of the renewal project, and that Talbot Park was something of a safe haven within the broader suburb of Glen Innes. I have taken great care to emphasize these points at every opportunity I get as I had a real concern that Talbot Park would be used to demonstrate the ‘medium density housing works well for beneficiaries’. My role was to explain exactly why, in this context, it worked, and to point out the ongoing social equity issues and the need for central and local government collaboration to address these more incessant problems of poverty, safety, and environmental degradation.
So what did we learn from the Talbot Park project?