In 2003 a Draft Stormwater Management Plan was submitted by CBCL Limited for consideration by the Town of Stratford. At a meeting on October 29th 2009, the Town indicated that it had considered the alternatives presented in the 2003 report and expressed a desire to adopt a stormwater management plan consistent with a goal of sustainable development. Then in 2010, CBCL Limited conducted this study to assess the effects of climate change on rainfall intensity and the impact of these projected changes on the Stormwater Management Plan. The overall plan for the study included the following main tasks:
- Import the USEPA SWMM5 model developed in the original study in 2003 and updated in the 2010 Study into the Stormnet computer model owned by the Province;
- Re‐run the updated models for a range of design rainfall events based on predicted increases in peak intensities related to climate change; and
- Use this data to update the figures and tables from the 2010 study report that are associated with the Town’s selected approach to stormwater management and are impacted by changes in rainfall intensity.
The study assessed the impacts of changing climatic conditions for 3 future periods centred on the years: 2020, 2050 and 2080 and for return periods of 10, 25, 50 and 100 years. The Climate Change Coordinator for the department reviewed the data prepared by Environment Canada and with assistance from the Canadian Climate Change Scenarios Network (CCCSN www.cccsn.ca), performed model validation for several global Climate Change models. Observed climatic data for the period of 1961‐1990 was input to 30 models and the resulting average rainfall was compared to the records at the Charlottetown Airport station. The assessment of potential changes in rainfall resulting from climate change indicates that rainfall intensities will likely increase. Whether intensities of all durations will increase to the same degree, the magnitude of the increases and the timing of the increases are uncertain. Please refer to the assessment report for a completed detailed description of the methodology used to design and rainfall intensities. It is expected that higher rainfall intensities will result in higher peak runoff flows in the drainage systems from existing development and future development of currently undeveloped land as well as redevelopment of existing developed lands.