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
Table 4-3 - Best Predictor Variables
Best Models Chosen (Seasonal Fitting)
Event Duration Deer Lake
St John’s
A
5 min PxT T
10 min T PxT
15 min PxT PxT
30 min PxT PxT
1 h PxT PxT
2 h PxT PxT
6 h PxT P
12 h P P
24 h P P
T = Average Monthly Temperature
P = Total Monthly Precipitation
PxT = Product of P and T
4.6 Developing Projected Precipitation Intensity Values
The projected values of precipitation intensity, which make up the IDF curve, were
developed using three applications of the ―delta‖ method (Hamlet and Lettenmaier,
1999; Miller, et al., 2003). In this application, the delta approach is preferred over using
climate projections directly, because the delta method reduces the bias inherent in
climate simulations. In the delta method, climate projections are used to estimate the
change in climate variables and this change is then used to adjust the observed record.
The projected change is determined for each climate projection by comparing the
climate condition during the overlap period from the climate condition at some future
point in time. The overlap period is the period of time where the model simulation
overlaps the observed climate. In the projections used in this work, the overlap period
is 1950 through 1999. In this work, the climate condition during the overlap period is
represented as the average for the period 1950 through 1999, and the climate condition
at the future point in time is represented as a 30-year average centered on that point in
time. The projected IDF curves were based on three future time periods, 2020, 2050
and 2080. The method for adjusting climate variables is illustrated in Figure 4-1.
AMEC Environment & Infrastructure 23