New research from Te Herenga Waka—Victoria University of Wellington addresses the adaptation of stormwater and wastewater infrastructure in coastal areas as sea levels rise and heavy rainfall events increase in frequency – significant risks identified in New Zealand’s National Climate Change Risk Assessment.
The research, funded by the Resilience to Nature’s Challenges National Science Challenge and published in Infrastructures journal, sets out a framework for mapping options to manage retreat of stormwater and wastewater infrastructure. It was led by Master’s student Rick Kool, supervised by climate adaptation experts Dr Judy Lawrence of Victoria University of Wellington and Dr Rob Bell of NIWA.
“This research is timely, as the Government has just announced it will progress a Climate Change Adaptation Act this term as part of the RMA reforms to address the barriers to managed retreat – funding, and existing uses,” says Dr Lawrence.
“The research will inform the public conversation on coastal adaptation and managed retreat that is already underway, and the wider conversation on an infrastructure strategy and new housing investments that need to be located away from coastal risks and be climate resilient.”
The research team used Dynamic Adaptive Pathways Planning to understand how a retreat of ‘two waters’ infrastructure (wastewater and stormwater) could be managed by councils faced with maintaining levels of service as climate impacts worsen over the coming decades and beyond.
“In many low-lying coastal areas, wastewater and stormwater infrastructure is located underground at the coast and is at risk from sea-level rise and increased frequency of heavy rainfall events.”Rick Kool
“To our knowledge, this is the first study to develop a framework for staging the pre-emptive retreat of stormwater and wastewater infrastructure, where ongoing sea-level rise is the primary driver.”
Dynamic Adaptive Pathways Planning (DAPP) is an approach that enables options to be tested against possible future scenarios, in this case, sea-level rise. Pathways are mapped that can manage, reduce or avoid risk. A plan is developed, with short-term actions and long-term options, and includes pre-defined decision points (triggers) where the first options can be revisited, depending on how the future evolves.
“Since 2017, dynamic adaptive planning has been a key part of the Government’s guidance to councils on coastal adaptation and it also has relevance for other climate hazards.”Dr Lawrence
“Now we’ve demonstrated a proof of concept using a scenario-based approach which can be used to develop an adaptive managed retreat strategy for wastewater and stormwater, and developed a decision-making framework which is now available for use in coastal communities around Aotearoa New Zealand.”