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

flooding in parts of Newfoundland and Labrador. It is based on due consideration of the
preceding sections of this report which deal primarily with average conditions but also some
analysis of the key climate and extreme weather drivers, literature reviews and internet
searches on this subject, and consultations with a number of weather and other professionals
who have lived in Newfoundland at least several decades.
It is appreciated that others have attempted to quantify more precisely the return periods for
precipitation events of various intensities. Earlier in this section, IDF curves were updated for at
least one site within each WRMD region. These curves capture the character of precipitation at
a specific location based on the past long record of precipitation intensity observations.
Updating these frequently is crucially important in an era of changing climate.
Others (Lines et al, 2008; AMEC, on-going flood mapping project for Goulds/Petty Harbour and
Corner Brook) have developed approaches to project IDF curves forward in time, thus
producing forecast IDF curves for a specific period some decades into the future. However, the
main inputs into the process are outputs from GCM runs. As Lines points out, those are very
coarse models, grid spacing of 300 X 400 kms, and are not suitable when studying impacts on
much smaller areas, 100 square kilometres or less. This gives rise to downscaling and
statistical approaches to refine coarse GCM outputs at higher resolution over a limited domain.
As was explained earlier, these approaches start with GCM outputs and a finer surface mask to
run regional models on a finer scale over a smaller domain. These approaches remain largely
dependent on the quality of the coarse GCM outputs.
Unfortunately coarse GCMs cannot be expected to capture well meteorological phenomena on
smaller scales than the synoptic scale. Meso-scale phenomena such as hurricanes will be
poorly resolved. Regional models with a domain size corresponding to Newfoundland and
Labrador would be unable to capture a meso-scale phenomena, i.e., a hurricane, generated
thousands of kilometres away in the equatorial Atlantic. Since these phenomena are
responsible for some of the most extreme weather in this case, these approaches would miss
the precipitation maxima likely with such events in the future.
When one considers flooding specifically, combinations of factors coming together need to be
considered together. An updated or forecast IDF accounts only for the new water from
precipitation. This is especially worrisome for Newfoundland which has a concentration of its
communities along the coasts. Those communities would be subject to sea level rise and both
ocean surge and waves as well as abundant precipitation from massive storms. Conditions
could be rendered yet more dire if such storms also coincide with high tides.
A number of weather phenomena or scenarios will be considered in turn. They will be briefly
introduced, similar recent events will be discussed, and some features that could render them
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