Water Stewardship Information Sources

Citation BGC Engineering. 2009. Climate Change (2050) Adjusted IDF Curves: Metro Vancouver Climate Stations. Prepared for Metro Vancouver.
Organization Metro Vancouver
URL http://www.metrovancouver.org/services/liquid-waste/LiquidWastePublications/ClimateChange2050AdjustedIDFCurves2009.pdf
Abstract/Description or Keywords This study provides adjusted Intensity Duration Frequency curves for ten Metro Vancouver
climate stations that consider changes in winter precipitation intensity for the 2050 time
horizon (2040’s-2070’s) due to predicted effects of global warming. These adjusted curves
form a useful step towards estimating changes in design runoff events used in a variety of
applications, including the planning and design of water and wastewater management
infrastructure.
Predicted changes in future rainfall amount were based on two model runs of the Canadian
Regional Climate Model (CRCM), using the A2 emission scenario for the 2050 horizon. The
A2 scenario, which uses very conservative (high) emission assumptions, suggests that
monthly fall and winter precipitation in the Metro Vancouver area will increase in magnitude
by 10% to 21% by approximately the 2050’s. Herein, the more conservative 21% value was
used for analysis and presentation of results.
Predicted changes in future rainfall intensity were obtained by identifying a statistical
relationship between rainfall amount and intensity for existing data, and then using this
relation to estimate future rainfall intensity based on a 21% increase in rainfall amount. The
estimated fractional changes in rainfall intensity were used to adjust IDF values. Results
suggest that the frequency of extreme rainfall intensity events will significantly increase, with
forecasted 50 year rainfall intensities approximately equal to or greater than the current 100
year rainfall intensity at most stations.
This study is exploratory in nature as it is limited to a single time horizon, one emission
scenario, and two model runs of the CRCM that are based on the same Global Circulation
Model (GCM). Of the over fifty Metro Vancouver rain gauges in Metro Vancouver, ten
gauges were selected for analysis that are active stations with the most complete data
record. In a subsequent study, it may be possible to add additional stations if they also show
a statistically significant historical relationship between rainfall amount and intensity and if
existing analogue precipitation data be transcribed into digital format. Further work is
required to address these limitations, quantify uncertainties and to establish regional IDF
curves for various zones within the Metro Vancouver area.
Information Type report
Regional Watershed Lower Fraser
Sub-watershed if known
Aquifer #
Comments
Project status complete
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