HARMONY IN BROWNFIELD REVITALISATION: A HOLISTIC NATURE-BASED APPROACH

B. Pathirage, P. Wadan, S. Singh (Woods/ LEAD Alliance)

ABSTRACT

Continued urban expansion leads to redevelopment in brownfield areas that are often susceptible to flooding, posing significant challenges for sustainable development and intensification. This paper explores the strategic approach of using nature-based solutions to enable development in existing flood hazard areas while intensifying land use. The paper specifically focusses on a brownfield development area within the Waikōwhai suburb of Auckland, where residential intensification is proposed as part of the Auckland Housing Programme. Woods, as part of the Land Enablement and Delivery (LEAD) Alliance, has been involved in this project with our alliance owner participant Kāinga Ora. A Stormwater Management Plan (SMP) was prepared to support the development, with the solution discussed in this paper proposed as the flood mitigation measure. The SMP has been adopted under the regionwide Network Discharge Consent by Auckland Council.

The Waikōwhai neighbourhood, approximately 90ha, is located within the upstream portion of the Te Auaunga Awa (Oakley Creek) catchment. Te Auaunga Awa is one of the major waterways situated in central Auckland with its headwaters located within Molley Green Reserve in Waikōwhai. The creek is partially piped within Molley Green Reserve and conveyed to discharge to Keith Hay Park, which is located immediately downstream of the neighbourhood.

A comprehensive assessment was undertaken to initially understand the existing flood risk in the area and how adverse flood effects that may emanate from intensification can be mitigated. Several nature-based solutions were explored in conjunction with traditional infrastructure upgrades such as pipe network upgrades, re-alignment of existing roads and landform changes. These were then simulated via flood models to understand the resulting impacts on the development and other third-party lots and public roads. The proposed solution consists of providing flood storage by utilising existing green infrastructure, which includes increasing the storage capacity at Molley Green Reserve and the creation of a new attenuation basin, referred to as Albrecht Basin. The proposed solution also includes daylighting of streams to promote integration of ecosystem into the existing built form. This innovative strategy embraces the principles of green infrastructure, encourages community wellbeing by providing green areas for recreational purposes, and incorporates natural elements to manage stormwater and reduce flood impacts.

The basins were proposed to ensure the volumes stored would mitigate flood flows and be sufficient to reduce the downstream flood risk and enable development. The proposed solution enabled connection of waterways and effectively increases the upstream reach of Te Auaunga Awa by approximately 300m. The daylighted stream is further proposed to continue to Keith Hay Park, which will allow for additional conveyance and connection of waterways. This is proposed to be constructed in the later stages of development.

The proposed solution is considered holistic as it also creates cultural connections to waterways, while reducing flood risk and improving overall water quality, ecology, and community wellbeing. By prioritizing the integration of nature-based solutions, this paper discusses a sustainable and forward-thinking model for brownfield development in existing flood-prone areas, demonstrating the potential for coexistence between urban expansion and ecological restoration.