Solutions: Putting the sting into climate change preparation at the coast
Almost seven in ten Kiwis live along New Zealand's coastline. And that's where the impacts of climate variability and change are likely to be hardest felt.
It's the job of local authorities to prepare coastal communities for more frequent and extreme incursions from the sea, in the form of damaging waves and storm surges. That task relies on good data about local risk.
The coastal sting of climate change is being evaluated using NIWA's web-based Waves And Storm-surge Prediction (WASP) tool.
It uses a sophisticated model, validated by historical data, to hindcast the scale and frequency of waves and storm surges off the New Zealand coast over a 40-year period (1960–2000), and then to predict them for two climate change scenarios. It's proving to be a hit with regional councils using its outputs to guide resource management and infrastructure planning.
"WASP quantifies the offshore drivers of coastal inundation, which, when modelled locally, allow regional councils to set robust planning guidelines for coastal development," says Dr Rob Bell, Project Manager and NIWA Hazards Programme Leader.
"The ability to extract regional information from nationally consistent data helps standardise the approach taken by local government, infrastructure operators and coastal communities in their efforts to adapt to climate change impacts."
Users log on to the WASP website and then zoom in on a map of the New Zealand coastline to locate their area of interest. Data are available at a mouse click for the 50-metre depth contour at regular intervals around the coast, providing offshore conditions that are used to drive more detailed coastal models.
Dr Bell says the WASP data were the starting point for a review NIWA has just completed of coastal inundation levels in Bay of Plenty.
Mark James, Principal Engineering Hydrologist at Bay of Plenty Regional Council, says that several coastal inundation studies recently completed by NIWA gave him confidence to invite NIWA to review and calculate the potential reach of high tides and storm surges along the coast and rivers of his region.
"WASP was a component of the review. It provides the offshore sea state information which was then translated to the shore and along the coastline. The analysis has given us reliable tidal, wave and storm-surge data to guide building of flood control schemes and help with real-time flood management of our large rivers. It is also crucial for accurate setting of things like minimum levels for coastal structures."
He says that Stage 2 of the Council's process will be to extend the open coast analysis results into Tauranga Harbour using information generated from NIWA's review of tidal expectations for Tauranga Harbour.
A feature of the WASP tool is that it can show present day likelihood of wave and storm-surge events, and indicate how that likelihood changes under two of the standard global climate change scenarios used in the Intergovernmental Panel on Climate Change assessment reports.
Under each output option, users are provided with:
- hourly time-series data of tide, storm-surge, significant wave height, wave period and wave direction
- summary statistics for these variables, including distribution plots such as histograms, and probability and cumulative distribution functions
- maps of the spatial distribution of these variables around New Zealand.
WASP builds on guidance previously published by the Ministry for the Environment.
Its development was funded by the Foundation for Research, Science and Technology (now the Ministry for Business, Innovation and Employment).