Project Twin Streams

Voluntary property acquisition in a vulnerable coastal community

Waitakere City (population approximately 204,000) is located within the Auckland Regional Council area of New Zealand. The Project Twin Streams area focused on in this case study covers 10,000 hectares of mostly urban residential development intersected by streams draining from the Waitakere Ranges to the west of Auckland and flowing into a number of other streams and the Waitemata Harbour.

Development within the catchment has enlarged the extent of impermeable surfaces leading to increased storm water runoff, erosion and sedimentation of streams and flooding of houses. Storm water studies and flood modelling carried out in the late 1990s resulted in the development of Project Twin Streams in 2002. Recognition of the likelihood of more frequent and severe storms projected from climate change have also focussed attention on addressing problems related to flooding (Atlas Communications & Media Ltd 2010).

The objectives for the Project are consistent with sustainability principles for long-term social and environmental well-being. After consideration of storm water studies, flood plain modelling and engineering options, the Council decided that acquiring the private properties lying within the 100-year flood plain level to allow natural flow paths and flood reserves would best meet these objectives.

Creative Commons / Sandy Austin

It also decided that the social impact and potentially drawn out legal costs of compulsory purchase could be ameliorated through a more conciliatory approach. Specifically, the Council’s goal was to purchase properties “in a way which respects property owners’ rights, avoids coercion and is fair,” (Atlas Communications & Media Ltd 2010, p.6). Auckland Regional Holdings, a statutory infrastructure development fund, funded the Project.

Organisational approach

A project team, with social and technical skills, spent nine months developing an action plan with clear lines of communication and responsibilities to facilitate property owners’ understanding of the local catchment, the risks, and options for sale and resettlement. Extensive information resources were produced for use in home visits, a drop-in information day, and a call centre. Communication with property owners, political representatives, legal aid and the media, was coordinated to avoid misinformation and perceptions of coercion.

Key lessons for adaptive learning

The following have been summarised from Atlas Communications & Media Ltd (2010):

  • Ensure an appropriate mix of skills relevant to the context (e.g. social and technical skills)
  • Ensure transparency, consistency and clarity in purpose and process
  • Engage affected community members from the beginning
  • Provide flexibility by ensuring a range of options
  • Provide accessible communication and support systems for community members

Adaptive behaviours and socio-ecological outcomes

  • Reduced risk of flooding of property and harm to residents
  • Improved ecosystem functionality
  • Increased recreational amenity

Some 98 properties and 83 partial properties were identified as being at risk  of  flooding.  Two  years before its planned completion date, Project Twin Streams has acquired the majority of properties at risk of flooding without using compulsory purchase statutes, created gardens and walk and cycle ways on the land now in public reserves, and re-established riparian zones (Atlas Communications  &  Media  Ltd 2010).

The decision to acquire at-risk properties through a well-resourced, collaborative approach was underpinned by a commitment to sustainability and represents a proactive approach to reducing the risk to the community from flooding. Adequate resourcing to ensure clear communication of scientific, technical, legal and logistical information, and support for property owners while they negotiated challenging and sometimes emotional decisions was important. This case illustrates how the challenges of ensuring human health and safety while restoring ecosystem function can be achieved through a partnership approach with those affected.


Atlas Communications & Media Ltd, 2010, Large-Scale Property Purchase Without Recourse To Compulsory Purchase: A Project Twin Streams Case Study, report prepared for Waitakere City Council, Waitakere, New Zealand.

References for Project Twin Streams