Tidal Range

at the

Bear River Railway Bridge

Digby County, Nova Scotia




The tidal range – the vertical difference between the sea surface levels at two consecutive tidal extremes (low to next high or high to next low) – is of interest to anyone working on the water around the Bay of Fundy.  In this project, the removal of a major bridge structure located near to the mouth of a river subject to the full tidal range in the Annapolis Basin, an arm of the Bay of Fundy, the demolition contractor must pay close attention to the tides, and must plan the work each day to fit with the time of low and high tide.  Fortunately, there are reliable tidal prediction services readily available on the Internet, that can provide accurate predictions for the times of the low and high tides on any chosen day for years in advance.

For this contractor, the times of low and high tides are the main item of interest, but also there are significant variations in the tidal range that may at times affect the work.  This note addresses the variations in tidal range that occur in the Annapolis Basin from day to day within each month.

Within each month, the tidal range at this location varies from a minimum of about 15 feet to a maximum of about 25 feet.

At the Bear River bridge location in January 2012, the tides were as follows:


Minimum tidal range
about fifteen feet
date time height time height range
2012 Jan 2
Monday
12:02 2.0 m
6.6 feet
18:13 6.8 m
22.3 feet
4.78 m
15.7 feet
2012 Jan 3
Tuesday
13:01 2.1 m
6.9 feet
19:13 6.7 m
22.0 feet
4.60 m
15.1 feet
2012 Jan 4
Wednesday
13:58 2.0 m
6.6 feet
20:10 6.8 m
22.3 feet
4.78 m
15.7 feet


Maximum tidal range
about twenty five feet
date time height time height range
2012 Jan 11
Wednesday
12:44 8.3 m
27.2 feet
19:01 0.8 m
2.6 feet
7.50 m
24.6 feet
2012 Jan 12
Thursday
13:27 8.3 m
27.2 feet
19:43 0.7 m
2.3 feet
7.59 m
24.9 feet
2012 Jan 13
Friday
14:13 8.3 m
27.2 feet
20:29 0.8 m
2.6 feet
7.50 m
24.6 feet

Note: The above figures account for the astronomical tides only – the tidal effects due to astronomical influences and ignoring all meterological effects such as wind and barometric pressure. Tides produced by astronomical influences can be predicted with great accuracy years, even centuries in advance, but meterological influences on tides cannot be predicted with any confidence more than two or three days in advance.  However, at this location (everywhere in the Bay of Fundy) astronomical effects are the primary factors determining tide levels, with meterological effects being a distant second – except for the rare times when an intense storm (exceptionally low barometric pressure) happens to coincide with an astronomical circumstance known as a Perigean Syzygy.




Go To:   Photographs of the Bear River bridge
    http://ns1758.ca/rail/dar-bridge-bearriv.html

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    http://ns1758.ca/rail/dar-bridge-sissiboo.html

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    http://ns1758.ca/rail/railways.html

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First uploaded to the WWW:   2011 December 29
Latest update:   2012 May 22