Report of Research, Field Investigation and Survey of Robert D ...

Values are given monthly, and for purposes of continuity I have assumed the most likely
interpretation of the ‘annual average elevation’ to be during June of the year, once the spring
freshet has passed. At Paragraph 5.1, I indicated 4 years for which elevations would be of
interest. Of these, 1823 pre-dates the NOAA data, and I have relied on the elevation determined
by D. Lambden. The remaining elevations are taken from the NOAA document and corrected to
CGVD28, since this is the datum provided by our GPS observations, as discussed at paragraph
5.3. Since Collingwood is located 26km from, and directly across Nottawasaga Bay from the
project area, I used the IGLD1985 to CGVD28 correction of 0.052m for Collingwood. As noted
in the Stewart Table, IGLD1985 - correction = CGVD28.
Average Elevations for Critical Years in Chronology of Wimblewood Beach
Year Water Elevation (IGLD1985) Water Elevation (CGVD28)
1823 175.9 175.85
1891 176.73 176.68
1920 176.70 176.65
1929 177.13 177.08
6.5.5 Historical Lake Huron Water Level Data produced by Canadian Hydrographic Service
(CHS) (Tab 43)
This document is similar to the NOAA document above, but from a Canadian source.
Unfortunately, these records only go back as far as 1918. As with the NOAA records, elevations
are referred to IGLD1985. The values are monthly means for Lakes Michigan and Huron, and
are the average of readings from gauging stations located at Thessalon, Tobermory, Milwaukee,
Ludington, Mackinaw City and Harbour Beach. For comparison and validation of the NOAA
elevations, the CHS elevations for June, 1920 is 176.73 and for June, 1929 is 177.15. These
values agree within a worst case of 0.03m, which I would consider well within ‘background
noise’ for all of the other factors, such as storm surge.
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