Surveying Climate Hazards in Canada's National Capital Region - Impacts on Built and Planned Infrastructure in a Changing Climate

Changes in climate, as reflected by both increasing frequency and intensity of extreme weather events, are expected to induce a wide range of potentially costly and disruptive impacts to services and operations reliant upon critical public assets. To address the potential challenges induced by shifts and changes to climate and extreme weather events, a pilot project to assess the climate change vulnerabilities for real property assets in Canada's National Capital Area (NCA) was undertaken over the 2018-2019 period. This study focused on climate hazards responsible for inducing building and engineering impacts by applying thresholds that correspond to infrastructure codes and standards. The climate parameters analysed represented key relevant hazards and impact-based thresholds for the NCA and reflect the consideration and inclusion of multiple asset categories (e.g. buildings, bridges, central heating plants) and subcategories (e.g. buildings of significantly different vintage and construction). The specific climate parameters and thresholds analysed in the project were selected following a review of previous reports, studies, climate vulnerability and risk assessments (e.g. Engineers Canada PIEVC Climate Vulnerability assessments), codes and standards literature, building condition reports, and additional documents from the National Capital Area and similar municipalities.

This assessment considered two future emissions scenarios representing a mid-range greenhouse gas (GHG) mitigation reduction strategy (representative concentration pathway (RCP), RCP 4.5) and a “business-as-usual” case (RCP8.5). The two cases were completed for three future time periods – the 2030s (2021-2050), 2050s (2041-2070), and 2080s (2071-2100) – using the 1981-2010 period as the historical reference baseline. To complete the assessment, RSI evaluated future climate projections using the ensemble mean of the 37 Coupled Model Intercomparison Project Phase 5 (CMIP5) global climate models (GCMs), the suite of models that contributed results to the IPCC Fifth Assessment (AR5). To calculate variables using the CMIP5 projections, a methodological procedure called the “Delta Approach” was used to derive localized climate change projections. To develop baseline climate conditions and projections, climate stations at the Ottawa International Airport, Ottawa CDA, and Angers, QC within the National Capital Area, were used. For parameters that are not well handled by climate modeling at any temporal or spatial resolution (e.g., events such as tornadoes and hail), the application of skilled professional judgement was applied to multiple sources of information, including a review of specialized studies, literature, and climate analogues to establish likely future projections for the NCA.

Results from the projection of climate parameters will be presented as part of this presentation. In general, projections for temperature-related parameters show increases in maximum temperature, cooling degree days, and overall mean winter temperatures by the end of the 21^st century, while decreases are shown in the number of cold days and heating-related parameters for the NCA. Projections of precipitation-related parameters show increases in design storm intensity, rain-on-snow events, and overall annual precipitation amount. Snowfall events and snow load amounts are expected to remain nearly constant even in a warming climate due to the likelihood of cold-air outbreaks remaining nearly the same as current conditions, and the mean overall winter temperature remaining below zero even under the most aggressive warming scenario. However, the frequency of riverine flooding due to snowmelt and spring runoff is projected to decrease as less overall snowpack is expected by the end of the century.