Flood Risk and Vulnerability Analysis Project - Atlantic Climate ...

Development of Projected Intensity-Duration-Frequency Curves
for Corner Brook and Goulds/Petty Harbour, Newfoundland May 16, 2012
3.0 TIME FRAMES
Time frames adopted for this work are summarized in Table 3-1.
Table 3-1 - Project Time Frames
Description
Time Frame
Climate simulation overlap period 1950-1999
Climate simulation projection period 2000-2099
2020 projection averaging period 2005-2034
2050 projection averaging period 2035-2064
2080 projection averaging period 2065-2094
4.0 APPROACH
4.1 Candidate Approaches
The Canadian Standards Association (CSA) has published the Technical Guide,
Development interpretation and use of rainfall intensity-duration-frequency information:
Guideline for Canadian water resources practitioners (Technical Guide) (CSA, 2010),
which provides background about the methodologies used to develop IDF curves based
on current climate, and a discussion about methodologies that are potentially applicable
to the development of IDF curves that reflect projected future climate conditions.
Appendix 8 of the Technical Guide provides a review of several approaches that, at the
time it was compiled, had been applied to estimate the sensitivity of extreme
precipitation to projected climate change. For detail on the available methods, the
reader is directed to the Technical Guide and the references therein. The methods are
summarized below in several categories:
Extrapolation of trends. Linear regression is applied to observed historical data to
characterize the trend in short-term precipitation extremes and these statistical
models are then used to extend the trend to future periods.
Direct interpretation of GCM output. GCMs provide output at a daily time step and at
a grid scale that can range from about 1 to 4 degrees (approximately 100 to 400 km
on a side at the equator, with the longitudinal dimension decreasing with increasing
latitude). Some studies (e.g. Kharin et al, 2007) have used daily GCM output to
characterize daily precipitation extremes. These methods cannot directly address
time steps shorter than the time step of the GCM.
Direct interpretation of Regional Climate Model Output. Regional climate models
(RCMs) use a finer grid scale than is used by a GCM (e.g. 25 km for an RCM versus
100-400 km for a GCM). Because RCMs are usually ―nested‖, that is, their spatial
AMEC Environment & Infrastructure 17