M. J. Anderson, D. A. F. Kiddle, & T. M. Logan

This report was first published in the November 2020 University of Canterbury Civil and Natural Resources Engineering Research Conference.

Summary

Although local communities urgently need to build their resilience to natural hazards, very few analytical tools exist to support them in doing so. Existing methods for evaluating resilience rely on discipline-specific approaches in either infrastructure or community capacity. While these methods have merit, a systems approach is required to quantify & operationalize resilience within our urban environments. To enable urban planners and local governments to do this, we have developed a computational approach to assess the resilience of a city’s access by simulating the effects of inundation and liquefaction scenarios on the transport network and amenities. We illustrate our approach by applying it to three cities: Ōtautahi (Aotearoa), Seattle and Houston (USA), identifying communities within these cities whose access to essential services is threatened by natural hazards.

This tool enables local and national governments to build equity and resilience by doing the following:

  • Aid investment prioritization to maximize access equity and performance within pre & post hazard scenarios
  • Aid disaster response preparedness
  • Identify critical nodes within amenity networks (food resources, health care, etc.)
  • Identify critical links within the transport network
  • Identify vulnerable geographic areas and demographic groups

Implementation

Ōtautahi Christchurch

Map: Access to supermarkets

Use the slide bar to see how the disruptions to the transport and service networks affect people’s access in the wake of a multi-hazard earthquake-induced tsunami event.

Isolated Residents: 48,000

Note: This is a hypothetical worst-case scenario superimposing local liquefaction data and far-sourced tsunami data. This has been used purely to demonstrate the ability to simulate multi-hazard events.

Graph: Empirical Cumulative Distribution Function (ECDF)

Use the slide bar to view the quantified change in access performance and equity.

  • Any point along the curved line represents the % of residents (y-axis) within X km of a supermarket (x-axis). The earlier the curve reaches 100%, the better performing the access is.
  • The vertical line is an equally distributed equivalent (EDE) which represents the mean distance of the population, penalized by the inequality within the distribution.

Seattle, USA

Map: Access to medical clinics

Use the slide bar to see how the disruptions to the transport and service networks affect people’s access in the wake of an earthquake causing liquefaction damage.

Isolated Residents: 5000

Graph: Empirical Cumulative Distribution Function (ECDF)

Use the slide bar to view the quantified change in access performance and equity.

  • Any point along the curved line represents the % of residents (y-axis) within X km of a supermarket (x-axis). The earlier the curve reaches 100%, the better performing the access is.
  • The vertical line is an equally distributed equivalent (EDE) which represents the mean distance of the population, penalized by the inequality within the distribution.

Houston, USA

Map: Access to primary school education

Use the slide bar to see how the disruptions to the transport and service networks affect people’s access in the wake of a hurricane causing inundation/flooding damage.

Isolated Residents: 225,000

Graph: Empirical Cumulative Distribution Function (ECDF)

Use the slide bar to view the quantified change in access performance and equity.

  • Any point along the curved line represents the % of residents (y-axis) within X km of a supermarket (x-axis). The earlier the curve reaches 100%, the better performing the access is.
  • The vertical line is an equally distributed equivalent (EDE) which represents the mean distance of the population, penalized by the inequality within the distribution.

Access & Isolation Equity

A resilient city is more than one with robust infrastructure; it also needs to have healthy and socially cohesive communities to ensure that it can respond to and adapt following hazard events. A city’s access to essential services is a reliable indicator of resilience. However, good access alone is not sufficient for resilience; the access must also be equitable between different demographic groups if we are to build community cohesion. Our tool not only quantifies the resilience of access, but it also enables users to investigate whether this access has any inequities between different demographic groups – we encourage this to be explored within the graphing function of our previously linked interactive web app. This ensures urban planners can consider the equity of access to amenities such as health care, education, and other necessities.

 

 

 

During each of the 1,000-10,000 hazard simulations run on the cities of Houston, Seattle, and Christchurch, select groups of residents were deemed isolated from certain amenities. In the case of Houston, in over 90% of the simulations, the same 200,000 residents were unable to access a supermarket due to the damage to local roads. It is vital that the representation of demographic groups is not unevenly distributed within the isolated populations. Our approach gives users the ability to evaluate this too, this can be seen for Christchurch in the figure (left). 

 

Any demographic groups above the datum line are disproportionally represented within the isolated population. In the case of Christchurch, we see that higher-earning areas are more likely to become isolated when a tsunami and earthquake event occurs. This is very likely due to higher-income areas residing around coastal areas (e.g. Sumner) which are more exposed to these hazards than other areas.

Impact & Development

The goal of this framework is to help communities build resilience and make better decisions around adaptation pathways. Engagement with local councils within Aotearoa has indicated the potential use for this tool in:

  • Pre and post-disaster investment prioritization
  • Vulnerability assessments
  • Community engagement
  • Policy analysis

This tool will continue to be developed to increase the utility for urban planners and decision-makers so they can better quantify and build community resilience. Likely features include:

  • Disaster Response Preparedness: Evaluate access resilience of the full city from emergency services to aid investment prioritization to ensure emergency services are not isolated from the rest of the city in the wake of a disaster.

 

  • Interdependent Infrastructure: Incorporate and model the dependence of amenities on three waters and electricity infrastructure to increase the accuracy of the operability assessment. Cascading failures could also be analyzed.

 

  • Equitable Recovery Optimisation: Evaluate access over time in a post hazard scenario by incorporating recovery simulations. These simulations will highlight the improvement possible with the use of an equitable optimization algorithm vs an uninformed recovery process.

 

  • Community Engagement & Preparedness: Utilising this as a community engagement tool by adding a property search function, allowing members of the public to discover their access resilience to services, what hazards their house area is exposed to. This could allow councils to improve individual household preparedness if residents are already aware of the possible scenarios during a large hazard event.