I was looking through the Cruising Almanac included in the March edition of 'Practical Boat Owner' and trying to imagine Spring Tides with a range of 20-30 ft. and the attendant currents, when I realised that our own tidal characteristics could be of interest to British members.

The South Australian coastline includes two large gulfs; the largest is Spencer Gulf, approx. 150 N. Miles long, and 70 N. Miles wide at the Southern end where it opens onto the Southern Ocean. It is up to 30 fathoms deep and contains many of the grain ports such as Port Victoria and Wallaroo, which marked the starting points of the great sailing ship grain races to England and Europe early in the Century.

The smaller gulf of St. Vincent is 90 N. Miles long and 35 N. Miles wide, with depths of up to 20 fathoms. Its opening to the Ocean is partially blocked by Kangaroo Island, 70 miles long and 25 miles wide. The Western passage, Investigator Strait, opens out below Spencer Gulf, and the South Eastern Backstairs passage, about 8 N. Miles wide, shows the highest tidal currents on the charts of 3 Knots during Spring Tides. Adelaide, the capital of South Australia, with a population of just under 1 million, stretches for about 25 miles along the Eastern shore of St. Vincent's Gulf.

The charts for St. Vincent's Gulf show a tidal range of 2 ft. 3 ins. at Neaps and 5 ft. 3 ins. at springs, with an extreme range at the solstices of 8 ft. 5 ins. The local rule of thumb within the gulf is to allow for a maximum tidal current of 1 knot per 3 ft. of range. The tide simply floods northwards up the gulf and ebbs southwards. None of this information is unusual and probably only evokes a comment of 'Lucky sods'. However, the gulfs share one other tidal trick with the Gulf of Mexico and some areas of the North African Coast, and that is the 'Dodge' and 'Double Dodge' tide!

Dodge tides must not be confused with Neap tides, but occur five or six times each year when one or two tides are completely missed, or dodged. The level of water in the two gulfs falls to the mean level and then remains stationary for a period of 12 to 18 hours before recommencing the normal tidal pattern. As you can imagine, the problems of navigation are greatly simplified and crossing bars and entering rivers becomes a doddle. The only disadvantage is that all the species of fish go 'off the bite’, so you must leave your lines packed away for the day.

So, in South Australia on certain days each year, "Waiting for the Tide" takes on a whole new meaning! Good Sailing!