RESILIENT SYSTEMS: WHAT TO DO WHEN ENGINEERING IS NOT ENOUGH?
Stormwater Conference 2024
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Laura Robichaux (Beca Ltd), Richard Clark (Beca Ltd), Cushla Loomb (Beca Ltd), Jane Groves (Tauranga City Council), Neil Blazey (Tauranga City Council)
ABSTRACT
The 2023 Auckland Anniversary weekend floods were a visible reminder of what can happen when our stormwater systems cannot cope with extreme rainfall and runoff. In the past, the solution has been to increase the capacity of our stormwater systems to accommodate increasing flows expected, but what do we do when additional capacity might not be the best long-term option? With increasing groundwater levels and development intensification, the ability of the environment to absorb rainfall is decreasing while rainfall intensity is increasing due to climate change. Therefore, the way we manage stormwater must change.
The Mount Maunganui (Mount North) catchment in the Bay of Plenty consists of 47 hectares of high value, high density residential and commercial area. It is presently drained to Pilot Bay via a gravity-driven piped network with no overland flow outlet, and therefore is prone to flooding. Existing risk will worsen due to increased rainfall intensities, sea level rise and associated rising groundwater (likely emergent by 2070) as the climate changes.
In 2023, Tauranga City Council (TCC) began a pilot adaptation planning process in Mount North – with stormwater engineering, planning, climate adaptation, and communications and engagement specialists – to develop a 100 year strategy to respond to multi-driver flooding (sea level rise, storm surge, groundwater and rainfall). The pilot applies latest adaptation planning methods aligned with soon to be released Ministry of the Environment guidance and places engagement at the centre through use of a focus group.
This paper will outline the pilot process adopted by TCC and will identify lessons learned that could be applied in similar catchments and by similar organisations across Aotearoa by directly working with communities to develop long-term (100 years) visions for stormwater management to reduce vulnerability, increase adaptive capacity, and reduce
exposure to flooding.