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

extreme will be considered. Areas that may be affected will be identified and, where possible,
some quantification will be attempted.
Winter Rains
Results from modeling of future trends to late century indicate more marked increases in
winter temperatures and precipitation (Bruce, 2011). Rain is usually a key flood inducer
but often works in concert with other factors or events. While it is not possible to deal
with all possibilities and all peculiar local effects, several scenarios arise:
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Abundant winter rain combined with an intense and sudden warming affecting an
area with significant snow cover. The rain combined with rapidly melting snow can
exceed an areas ability to channel water off. The western and eastern parts of the
Newfoundland are likely to be affected by different aspects of this issue. The west
coast of Newfoundland is more likely to be susceptible to a heavy snow melt given
the typically abundant winter snow packs in this region whereas the east coast is
more likely to be afflicted by frequent heavy precipitation events given the its location
relative to the Atlantic storm track ;
Abundant winter rains combined with an intense and sudden warming that would
swell rivers and break up winter ice. Such a rapid break-up can cause ice jams
which effectively dam water from escaping and cause water accumulation upstream
leading to floods. A most noteworthy such event occurred at Badger in February,
2003. The flooding was followed by a return to very cold temperatures (-20 ºC)
which froze the floodwaters encasing cars and homes in ice and keeping many of
Badger‟s 1,100 residents homeless for several weeks;
Abundant winter rains falling on frozen ground which has a seriously compromised
ability to absorb water. This would occur when an intense winter rain storm or a
series of smaller ones arrive at the end of a prolonged cold period. An example of
this occurred in Ontario in 1980 when a 5 year rainfall fell on frozen ground in the
Ganaraska River watershed resulting in the highest documented flood on record.
The island of Newfoundland is rendered especially vulnerable given the relatively
thin soils and therefore the poor soil storage capacity;
A key feature of these scenarios, abundant precipitation from synoptic scale
phenomena, is likely well captured by GCMs and IDF curves. Another key ingredient in
several of the above winter rain scenarios is a sudden and marked warming. Modeling
also shows greater increases in winter temperatures but does not characterize them
further. More marked temperature swings, including more frequent sudden winter
warming events, going forward into this century, will likely be one of the mechanisms
leading to increased winter temperatures. The potential for flooding events of these
types to increase in frequency through this century is to be expected. They will affect
especially the Western and Central WRMD regions.
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