Climate projections have demonstrated increasing costs and risks under plausible future climate change scenarios. Future climate conditions within RROIT are based upon the Clausius-Clapeyron relation — a theoretical relationship between air temperature and the amount of water the air could potentially hold —which indicates that an increase in air temperature of 1°C corresponds to an increase of approximately 7% in rainfall amounts. Accordingly, future storm return periods in RROIT are adjusted using a regionalized approach, whereby IDF station data with 30+ years of records are analyzed for future time horizons using the Clausius-Clapeyron adjustment. The temperature change applied in the Clausius-Clapeyron adjustment was the projected increase in annual daily maximum air temperature for the future time periods of 2050 and 2080. Projected temperatures are based on the average output of 37 Global Climate Models (GCMs) within the CMIP5 ensemble. Consistent with a precautionary approach for estimating risk, the tool uses RCP 8.5 (high emissions) as a default scenario. Outputs of RROIT include flood risk area maps that highlight buildings and infrastructure at risk for flooding under the current climate-based storm events, including the 2-, 5-, 10-, 25-, 50-, and 100-year return period. The RROIT methodology used for riverine surface flooding utilizes flood elevations for different flood frequencies to estimate damages, which are adjusted for climate change under future climate scenarios. Such information allows for the monetary quantification of structure and content damage in private and public infrastructure flooding. RROIT provides the business case for investing in infrastructure and natural assets while presenting the financial assessment and return on investment to support decisions.
In 2018, with funding from National Disaster Mitigation Program (NDMP), Canadian Mortgage and Housing (CMHC), RBC Nature Tech, Neptis Foundation, Peel Region and Member Municipalities, Credit Valley Conservation (CVC), and Risk Sciences International (RSI) developed the Risk and Return on Investment Tool (RROIT) to help municipalities, property owners and financial investors make evidence-based, cost-effective decisions to reduce flood and erosion risks. RROIT is a multi-flood hazard tool aimed at reducing risks under existing and future climate scenarios. Along with aiding decision-makers in understanding the financial implications of extreme events associated with climate change, RROIT can also help meet the requirements of Canadian government funding programs, for which Infrastructure Canada’s “Climate Lens” is required for approval. RROIT has been piloted in five municipalities across Canada to demonstrate that combining management options can simultaneously retain stormwater runoff, reduce damages, and provide co-benefits, such as improving water quality. RROIT can present quantitative costs from a risk assessment regardless of whether neighbourhoods, municipalities, and regions are data rich or lack quantitative models. Some of the financial analysis and management options RROIT can apply to riverine flooding, erosion, urban flooding, and basement flooding. Results produced from using RROIT can be presented in the form of flood risk maps, summary graphs, and tables that reflect the event-based economic impact of flooding and erosion. The tool also has the ability to compare the costs of grey, green, and natural assets. By using RROIT, local governments can inform significant processes, such as infrastructure master planning, watershed planning, asset management, and the identification of critical infrastructure.