FINAL REPORT - International Joint Commission

FINAL REPORT
Figure 36: Net economic benefits over the 101-year historical sequence for Plan D + at
Lac St. Louis
In summary, Plan A + provides the greatest economic benefits for recreational boaters, both upstream and
downstream. Plan D + provides benefits to downstream recreational boaters and no major losses to
Lake Ontario boaters, except during occasional low supply conditions (e.g., every 25 years). Plan B + does
not hurt downstream boaters, but it does have negative benefits for Lake Ontario and boaters in the
Thousand Islands area because it is associated with a greater range in levels and therefore more periods
of low levels outside the desired range for boaters. Nonetheless, many upper St. Lawrence River boaters
have expressed their pleasure at the fact that Plan B + generally allows for an extended boating season because
it shifts the peak to a point earlier in the spring and does not allow levels to drop as low in the fall.
Coastal
In understanding the results of a plan in terms of coastal interests, it is first important to keep in mind the
key findings of the Coastal Technical Work Group outlined in the previous chapter. The coastal results
focus on three key performance indicators: flooding, erosion and shore protection maintenance. For all
three of these indicators, on Lake Ontario, the biggest issue is the timing of the high levels. When high
levels coincide with the storm season in late fall and early spring, the greatest damage can occur. On the
lower St. Lawrence River, the biggest issue is flooding and there is very little difference between plans in
terms of erosion and shore protection, largely because the lower river is not as susceptible to large windgenerated
waves.
Note that erosion and shore protection maintenance are the only economic performance indicators to have
serial dependence, and their damages cannot be avoided, only delayed. The best way to assess the plans,
therefore, is to determine which one delays or postpones these damages to a later time. The damages are
then discounted to a present value. In this case, the results of the stochastic runs become very important
and are the best indication of potential impacts that are not a function of the historical supplies.
Flooding
While there are over 7,600 property parcels, with a total building and contents value of about $1.3 billion,
that are 3 metres (9.8 ft) or less in elevation above chart datum (74.15 m or 243.29 ft.), all plans try to
keep levels below 76.2 metres (250 ft). At this level, there are about 3,000 vulnerable property parcels,
with a total value of about $571 million U.S. Plan 1958-DD has significantly reduced flooding on Lake
Ontario compared with the unregulated regime. Expected average annual flood damages under 1958-DD
are about $170,000 U.S. Plan A + is the only plan to have small benefits in terms of Lake Ontario flooding,
relative to 1958-DD, because of less frequent very high lake levels. Plan B + and D + have some small
64 Options for Managing Lake Ontario and St. Lawrence River Water Levels and Flows