Climate Change Analysis – Durham Road

Like many areas in North America, the Regional Municipality of Durham in Ontario has seen more frequent rain events and their consequences on their infrastructure. This impact has been especially true for some of the region’s larger, more significant roads.

The Region tasked a team comprising of GEI, the Climate Risk Institute (CRI) and the Toronto and Region Conservation Authority (TRCA) to help examine which roads are most vulnerable to flooding to better understand how to prepare for more frequent, intense, and longer-lasting rain events.

On this project, however, the definition of vulnerability extended beyond simply infrastructure risk. Durham Region also wanted the effort to include a look at the impacts of climate change from a socio-economic perspective and consider nearby populations and community hubs that could potentially be more affected by these severe weather events.

To begin, the team completed a climate change analysis and flood vulnerability assessment on Durham’s transportation network across the region. A significant portion of this work included the integration of future climate data and information.

The integration considered future climate data around storms, factoring in a “shift” of the annual exceedance probability (AEP) given the impact of climate change. AEP refers to the probability of a given event occurring in any given year, expressed as a percentage (e.g., a 1% chance to occur in any one year is a 1% AEP, or a 100-year event). The team’s recommendations approached the return periods (storm events) from a shifting perspective of likelihood of multiple design storms rather than projecting the future amount of extreme rainfall.

This risk-scoring approach was used to understand how critical a particular road is and whether it is at risk of current and future flooding. This indicator-based approach reviewed the following:

  • Functional classification of roads
  • Average annual daily traffic
  • Goods movement routes
  • Degree of redundancy
  • Proximity to sensitive receptors
  • Social equity and justice
  • Evacuation and disaster recovery – proximity to nuclear hazards
  • Designated transit routes

To compliment this process, the team reviewed neighbourhood health data provided by the region. This information helped add a socio-economic lens to the risk-scoring. Social equity considerations have become an important component when planning for climate change, as vulnerable populations are experiencing the impacts disproportionately.

This work is being used by the Region to inform asset management and disaster route planning, and in prioritizing future investments to increase climate change resilience. The Region continues to work with GEI on flooding and climate resilience efforts and is now undertaking an urban flooding assessment to identify “hot spot” areas of potential flood risk.

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Road closed sign on flooded road

Key Challenges

The team completed a climate change analysis and flood vulnerability assessment, including the integration of future climate and community health data. Future climate data factored in a shift of the annual exceedance probability given the impact of climate change. Additional socio-economic data considered nearby populations and community hubs potentially more affected by severe weather events.

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