Figure 1 : Generic framework for climate change risk assessments, with specific examples in the context of stormwater system design and planning

Text description of figure

This figure provides a decision-tree in the form of a flow-chart, showing the logical steps in a generic framework for climate change risk assessments. The chart includes specific considerations in the context of stormwater system design and planning. The generic decision steps are from the Quality Planning Guidance Note on Effects of Climate Change under the Resource Management Act (www.qp.org.nz).

The steps are:

Step 1: Establish the context of the activity, plan or hazard to be considered.

For stormwater system design it may be useful to consider:

• performance expectation
• assets in catchment area
• planning horizon: Lifetime and flexibility of future upgrades
• state of existing system, other risks from sea-level inundation, land-use change.

Step 2: Is this activity, plan or hazard sensitive to climate, and might this be magnified by climate change? For stormwater, consider the effect of changes in:

• heavy rainfall
• mean rainfall
• average temperature.

If No to Step 2, then:

No further analysis required. Regular review is recommended in the case of planning and hazard management

If Yes to Step 2, then:

Step 3: Identify the relevant climate factors. Develop preliminary scenarios of how these factors and any relevant socio-economic conditions may change in your area. Consider both upper and lower ranges for climate change effects. Undertake an initial screening assessment of likely impacts. Over the planning horizon, considerations relevant to stormwater systems would include:

• changes in housing and infrastructure development
• changing value of assets
• changes in land-use that influence run-off
• climate changes.

Obtain initial estimate of change in heavy rainfall. Use standard modelling tools to estimate the effects of those changes on system performance.

Step 4: Does the screening assessment suggest significant impacts and/or inadequate information?

(Note that the answer will depend on a combination of performance expectations, socioeconomic changes and climate changes)

If No, then:

No further analysis required. Regular review recommended in the case of planning and hazard management

If Yes, then:

Step 5: Undertake a detailed quantitative analysis. For stormwater the options include:

• dynamic time series modelling
• regional atmosphere models.

Then:

Step 6: Evaluate risks and priorities and prioritise these against other risks and opportunities.

(This may involve a cost-benefit analysis, consideration of adaptation options such as soft or hard upgrades and the ability to undertake upgrades later, and the uncertainty of projections)

Step 7: Use results in decisions about the activity, plan or hazard. Carry information forward into other relevant council activities and plans.

(At this point you will consider community consultation and the link with broader development plans and expectations.)