FINAL REPORT - International Joint Commission

In terms of the coastal interests, the benefits of Plan A + are realized primarily through a gain in the area of
shoreline protection maintenance. Although the benefits are relatively small, Plan A + is the only plan that
achieves a gain in terms of shore protection benefits relative to 1958-DD on Lake Ontario. This is likely
attributable to the tightly regimented range that Plan A + tries to maintain. This range reduces the amount
of downcutting that occurs during low water level periods and yet tries to keep the Lake low enough to
prevent overtopping. Interestingly, this tight range, which tends to have a slightly higher average than
1958-DD, does not slow erosion of unprotected properties.
FINAL REPORT
The increases in damages resulting from Plan B + are likely attributable to the broader range of levels allowed
by the Plan, which provides more opportunity for both downcutting and overtopping. Plan D + does not
differ greatly from 1958-DD.
Table 9 shows the shore protection maintenance benefits under Plan A + to be fairly equally distributed
around the Lake. The disbenefits of Plan B + affect all counties around the lake, but are worse on the south
shore. Plan D + provides a mix of small gains and losses around the lake, which probably indicates that it
is so similar to 1958-DD that it is difficult to distinguish them.
Table 9: Shore Protection Maintenance, by Lake Ontario County, based on the Stochastic
Supply Simulation (average annual values (in million U.S. dollars) discounted at 4% over
30-year period)
In summary, Plan A + is the best of the candidate plans for shoreline interests on Lake Ontario. Its gains
come from benefits associated with the shore protection maintenance performance indicator. However,
Plan A + also causes erosion to happen more quickly than 1958-DD and is similar to Plan B + in that respect.
Plan A + also causes increased flooding downstream, as does Plan B + . Plan D + is slightly worse for shore
protection maintenance than 1958-DD but, overall, does not cause significant harm to shoreline interests
on the Lake or upper river relative to 1958-DD. Plan D + is the only plan that provides coastal benefits on
the lower river relative to 1958-DD.
Options for Managing Lake Ontario and St. Lawrence River Water Levels and Flows
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