When Christchurch City Council began work on the Avon Precinct Project – an ambitious and high-priority component of the city’s post-quake rebuild – they wanted to understand the likely consequences for the CBD during a once-in-a-hundred-year flood of the Avon River.
“We needed to know if it would make good economic sense to build flood protection measures into the precinct project at the outset,” says Graham Harrington, Senior Surface Water Planner,“and, if so, how they could be incorporated into the landscaping.”
And they needed to know fast.
Harrington turned to RiskScape, a software solution developed by NIWA and GNS Science that provides easy-tointerpret analysis of the risks, and physical, economic and social impacts, from a range of natural hazards.
Visit the RiskScape website
RiskScape incorporates data and knowledge about a community – topography, roads, utilities, building designs, land uses and social characteristics – to create a detailed geographical inventory of the area. When hazards of different magnitudes and return periods – like a oncein- a-hundred-year flood – are superimposed, RiskScape estimates likely damage, replacement costs, casualties, economic losses, infrastructure and business disruption, as well as the total number of people affected.
“RiskScape was ideal for us because it already includes property valuations, and has been customised to New Zealand conditions,” says Harrington. “It gave us a rapid assessment and enabled us to make informed decisions about the project.”
RiskScape confirmed that incorporating flood defences into the project would be difficult to justify economically. “Instead,” says Harrington, “all new central city developments and re-developments will be located out of the predicted reach of the flooding. This will minimise potential damage costs, while avoiding initial capital and ongoing maintenance expenses and other impacts on the river landscape and precinct amenities.”
Cantabrians need no reminding of New Zealand’s vulnerability to natural hazards. But other areas of the country are just as susceptible: floods, windstorms, volcanic eruptions, earthquakes and tsunamis are a fact of life for Kiwis, and to build resilient communities, planners and managers must prepare for them.
That’s why NIWA and GNS Science, working within the Natural Hazards Platform, are extending RiskScape’s modelling capabilities. Says NIWA’s RiskScape Manager and Hydrodynamicist Dr Graeme Smart: “The software currently models earthquakes, river flooding, tsunamis, volcanic ash fall, windstorms and coastal storm-tide inundation. Now we’re looking to add landslides, volcanic lahars and pyroclastic flows, snowstorms and climate change effects.
RiskScape users are encouraged to supplement national datasets with as much local information as they can lay their hands on: a key to the tool’s effectiveness.
“The more – and more accurate – the local data, the better the result,” says Smart. “Detailed information about assets at risk is particularly important.”
Cost-benefit analyses of disaster mitigation measures, he adds, are complex, “because you need to know the damage costs your planned protection measures will avert. RiskScape evaluates the potential costs of future disasters, and delivers results at a fine scale.”
Potential damage to buildings, for example, can be calculated right down to individual structures.
RiskScape’s outputs can be tailored to a wide range of analytical and reporting requirements. Options include hazard and hazard-impact maps, shape files, PDF reports, summary tables and KML files that can be displayed in Google Earth.
The software is currently available to government and academic users, and NIWA aims for future wider release. A comprehensive user guide and dedicated website (www. riskscape.org.nz) provide support, important system information and updates.
