Finding opportunity in adaptation

Our climate is changing. How we approach and adapt to the meet the unpredictable is a key focus for WSP.

What we know is that effective adaptation requires an understanding of how risks interact as a starting point. Decisions should be based on careful consideration of the cross-cutting nature of risks, and the trade-offs between the actions that we take.

Here we look at how climate change is reshaping the New Zealand summer, the tools we’re using to predict the impact it will have and the opportunities it presents – if we’re prepared to change our mindset.

In recent summers, we’ve experienced storms of varying magnitudes, and this is just a taste of things to come. In our changing climate, we anticipate more frequent and extreme weather events; WSP are helping our clients understand the pace of change and its consequences.

Climate change industry practice in New Zealand, both scientific and planning, refers to flooding with ‘deep uncertainty’. However, there is a great deal of information that we can gather and interpret to better understand the risks.

Over the last few years thinking has shifted from dealing reactively with an emergency response, to acknowledging the need to take a pro-active planning approach.

Preparedness relies on understanding the risk of flooding and using this to make operational decisions; planning for an emergency response, allowing for recovery and repair, and developing a strategy to deal with future events. To address this, we use tools to understand the likelihood of a flood event and predict the performance of existing infrastructure under that inundation or erosion.

Computational modelling of flood and erosion is rapidly developing. We can now model fluvial (from rivers), pluvial (from stormwater systems), coastal inundation, dam/stopbank breach and groundwater flooding. These models can predict the depth, extent, velocity and duration of the inundations that result from a range of storms. These can be singular predictions, or combined effects of rainfall, wind, wave action and storm surge. With this information, outputs can be tailored.

We apply hydrological and geomorphological understanding with published climate science to develop a range of input parameters and statistical analysis to understand a range of different magnitude historic and future storm events. We can also identify extreme parameters to stress test existing or proposed infrastructure across a range of scenarios.

Recently we’ve developed probabilistic models for erosion risk that can test sensitivity to a range of uncertainties in the base model. This produces suites of output files that provide more than just a line on a plan. A visual representation of a range of future scenarios can provide more information on which to base strategic and operational decisions.

Once the likelihood of a range of future events is determined, we can better understand the likely performance of existing (or proposed) infrastructure. At the moment, this management of flood risk isn’t well understood or practiced in New Zealand, but it’s critical.

We’ve interpreted flooding in the following ways:

Emergency management decision making – assessment of the risk posed from waves coming over the top of a breakwater, causing a danger to the public safety (pedestrians and vehicles). Assessment of the loading on, and likely stability of, infrastructure adjacent to the coast.

Maintenance required post event – likely damage to infrastructure during a flood event (including movement of rocks within the revetment, undermining concrete structures, scour to vegetated slopes). Effect of exposure to saltwater (corrosion issues) or inundation with floodwater
(repair/clean-up costs, disruption to service for electrical equipment). Consideration of water quality associated with potentially contaminated stormwater.

Strategic decision making – Assessment of the financial damages of flooding including disruption, clean-up and repair costs. Combination of the likelihood and consequence to assist development of a business case for risk management investment.

Granted, there is uncertainty associated with climate change, but we aren’t powerless. There’s a lot we can do to help understand the likelihood and consequence of flooding which can be used to make informed decisions.

Matt Balkham is Head of Water Resources and Flood Risk Management. He looks after WSP’s stormwater, flood risk management and coastal risk management business.